Food & Diet

  • Multivitamins, yay or nay?

    Multivitamin supplements were first made available in the 1940s, and since it's conception, it has grown into a multi-billion dollar industry. People spend over $5 billion US per year on purchasing multivitamins in the United Sates alone and in Australia, it's estimated that over 19% of the population take some kind of multivitamin supplementation, shelling out around half a billion dollars per year. Many people are firm believers in taking multivitamins, claiming that they are the magical bullet, or a long term health insurance policy to help you live longer and healthier; on the other hand, I have seen people, including health professionals blatantly dismiss any potential benefits of multivitamins, claiming that "it doesn't work". So do multivitamins work? By "work" if you mean whether the multivitamins from a pill can get into your body after ingestion then the answer is a big YES. Will your body benefit from taking vitamins on top of your meals, well that depends. In this article, we will explore the truths and myths of multivitamin supplements, we will look at whether taking multivitamins can improve your daily nutritional intake, whether they can prevent diseases, improve sports performance, are they really safe for general consumption, and who should or should not take them. So here is what the latest research has to say.

    Multivitamin supplements and daily nutritional intake

    Many take multivitamin supplements because they believe that they can help them to achieve the recommended levels of daily nutritional intake, which could not be met by eating food alone. It's like a nutritional insurance policy. While it is true that using multivitamin supplements can improve a person's nutritional intake, it is also a double-edged sword. Depending on the content and the composition of the particular multivitamin product, and the diet of the consumer, it also increases the likelihood of consuming too much of nutrients, to above the upper level of intake (the highest average daily intake level without adverse effects), which in turn, can cause health complications.

    A study investigating the effects of taking multivitamin supplements in the US found that, multivitamin supplementation can increase the prevalence of nutritional adequacy in both men and women. The greatest improvements in intake were vitamin E, zinc and vitamin A. However, taking multivitamins also increased the prevalence of excess nutritional intake for vitamin A, iron, zinc and niacin (Murphy et al. 2007, American Journal of Clinical Nutrition). The researchers concluded that multivitamins should be formulated better in accordance with specific demography of people in order to address nutritional inadequacy associated with a particular diet and reduce the chance of excessive dosing.

    It has been shown that excessive nutrient intakes are more commonly associated with multivitamin users in comparison to those who take single vitamin supplements (Rock 2007, American Journal of Clinical Nutrition). That is not really surprising as each person is different, with a different nutritional requirement, whereas multivitamin supplements are usually one size fits all. Even with the specialized formulas, such as those made specifically for women or elderlies, they are still not personalized enough to take into account your normal diet, age, weight and height. It also seems like the younger we are, the easier it is for us to exceed the tolerable upper intake limit from multivitamins. Studies showed that over half of the multivitamin users below the age of 13 exceeded the upper intake limit for folic acid whereas approximately 5% of the multivitamin users over the age of 50 exceeded their limit (National Institute of Health 2013).

    Effects of taking excessive amount of vitamins and minerals

    I'm sure you've heard of the saying "you cannot overdose on vitamins as the body will get rid of the excess through urine". Well that is only partially true. It is correct that most water-soluble vitamins are not stored in the body but that doesn't mean you can assume excess intake is safe. In addition, excess amount of certain water-soluble vitamins can be quite harmful. Excess intake (above the upper level of intake of 2000mg/day) of vitamin C, an antioxidant for example, can have oxidative effect to make it a pro-oxidant; moreover, excess intake of vitamin C can cause oxalate crystalisation, which can lead to kidney stones (Worblewski 2005, Polskie Towarzystwo Lekarskie). Another example is massive and prolonged ingestion of vitamin B6 at 10 grams a day for 5 years can cause sensory and motor neuropathy (nerve disorders) (Morra et al 1993, Functional Neurology). These are just examples of what prolonged, excess intake of vitamins can do, so just remember, even with the water soluble can be harmful at excess levels, don't over dose.

    Now let's have a look at fat soluble vitamins, vitamins A, D, E and K. Unlike water-soluble vitamins, fat-soluble vitamins dissolve in fat and stored in the body and can accumulate to dangerous levels over time. Vitamin toxicity can occur from long-term excessive over intake of fat-soluble vitamins, which can have dangerous health complications. However, due to the relatively "moderate" content of over the counter multivitamins, vitamin toxicity is unlikely to occur from normal consumption, unless of course, you decided to abuse it. The level of vitamin A has been shown to be among the most improved following multivitamin intake, which caused percentage of people exceed the upper level of intake. Excessive intake of vitamin A during pregnancy has been shown to increase the chance of birth defects (Institute of Medicine 2001). The consequences of excessive intake of fat-soluble vitamins can be quite serious and be potentially life threatening.

    Many multivitamin supplements also contain minerals, such as iron, calcium, zinc and copper. While the minerals are certainly essential for the function of the body, excess intake can also cause serious health complications. Excess iron can cause liver damage (Swanson CA 2003, Alcohol); excess copper can cause neuronal toxicity (Brewer 2012, Biofactors) and excess zinc, even at a level close to the upper limit of the upper level of intake can interfere with the utilization of copper and iron and adverse affect HDL cholesterol concentrations (Fosmire 1990, American Journal of Clinical Nutrition).

    So the message I'm trying to get across is that, all vitamins and minerals are essential for the function of the body, the supplementation of these nutrients is okay if you knew that you are not getting enough from the food or being diagnosed with deficiencies. However, make sure to read the content of the supplement packaging and chose a product that contains nothing at a concentration close or higher to the recommended dietary intake or adequate intake values. Pay special attention to the vitamin A and iron content, as most people get enough of them already from food, they are the easy ones to overdose.

    Can take multivitamins help to prevent diseases?

    That is a tricky question. If you have some form of deficiency then the answer is probably yes. If you are already getting enough nutrients from your normal diet, then as we discussed above, excess intake doesn't really do your body any good. Two randomized trials investigated the disease-prevention effect of multivitamin supplements in over 300,000 women aged between 45-79 over an 8-11 year period found multivitamin supplementation does not reduce the chance of chronic diseases, cancer and mortality (Neuhouser et al. 2009, Archives of Internal Medicine; Park et al. 2011, American Journal of Epidermiology).

    On the other hand, independent studies have yielded completely contradictory results. Studies found multivitamin supplementation may increase the chance of breast cancer in Swedish women but have a reduced chance of heart attack. On the contrary, an American study showed the use of multivitamin supplements can in fact reduce the chance of breast cancer in women, however, taking HIGH LEVELS of multivitamins long term may increase the chance of prostate cancer in men (National Institute of Health 2013). The use of multivitamins has also been shown to reduce blood pressure in over-weight Chinese women (Wang et al. 2009, Asia Pacific Journal of Clinical Nutrition).

    It is difficult to obtain accurate data from small independent studies, as there are just way too many variables at play that could skew the results. Results from randomized trials are said to be relatively more accurate, however, not many trials have been conducted to study the effects of multivitamin supplements. A trial investigated whether multivitamin supplementation can prevent chronic disease in men aged over 50 over an 11.2 year period and found multivitamin supplementation did not reduce the risk of chronic diseases, however, it did reduce the risk of cancer by 8% (Gaziano et al. 2012, JAMA).

    Other randomized trials have also concluded that the use of multivitamin supplementation can significantly reduce the chance of cancer and all-cause mortality in men but not women. Moreover, it can significantly reduce age related eye diseases in both men and women. Other trials have found multivitamin supplementation can reduce fasting blood glucose levels, however, it does not reduce the risk of diabetes in 50-71 year old adults (National Institute of Health 2013). The supplementation of folic acid containing multivitamins can significantly reduce the occurrence and recurrence of neuron tube defects (Czeizel AE 2011, Annals of Nutrition and Metabolism).

    Experts in the field have concluded that there are realty no concrete evidence support nor against the use of multivitamins (Due to contradictory results). But they won't recommend it anyway due to the possible safety concerns. People with a healthier lifestyle tend to take more multivitamins, and because everyone's diet is different, plus there are so many different varieties of multivitamins available, it is difficult to standardize the studies and trials. Moreover, the parameters and time frames used by each study/trial is limited, thus the full effect of multivitamin supplementation cannot be investigated. Due to the above factors, no study can really make a cause-effect claim regarding to multivitamins.

    Multivitamins are not medicines, they merely provide nutrients that we should obtain enough from food, drinks and our surrounding environments. Too much or too little nutrients will affect the optimal function of the body, thus gulping down the vitamin pills will not make you more super human than your body's own natural capabilities under optimal conditions. Do not believe the over-hypes surrounding multivitamin supplements, yes they will probably make you feel and function better if you are not getting enough nutrients from the food you eat. However, if your nutritional status is adequate, multivitamin supplements will not make it "more adequate", instead, you will just run a higher chance of overdosing yourself, which can be potentially harmful.

    Multivitamins and sport performance

    Can taking multivitamins improve sports performance? Well, it's has been establish that deficiency in vitamin C can reduce aerobic power but does not decrease endurance capability. Supplementation of multivitamins to athletics with a normal vitamin balance does not improve their performance (American Dietetic Association et al. 2009, Medicine and Science in Sports and Exercise). The supplementation of antioxidants did not reduce exercise induced oxidative stress (Ferrer et al. 2009, International Journal of Sports Nutrition and Exercise Metabolism). However, athletic with known deficiencies or on a poor diet can use supplements to improve their nutritional status, which will in turn help with performance and recovery.

    So is it safe to take multivitamins?

    We just spent paragraphs discussing the pros and cons of multivitamins. One may ask, if there are so many bad effects of excessive intake of vitamins and minerals, is it still safe to take them? To answer this question, I will need to first clarify that most studies and trials were conducted under very specific conditions on a very specific groups of subjects. Some studies used ultra-high dose of multivitamins most of us don't get exposed to. To us average people, the current recommendation by the National Institute of Health of America is that taking basic multivitamins that provides approximating recommended intakes should pose no safety risks to healthy people. However, if you are taking additional nutritional supplements, or fortified foods (with extra vitamins/minerals such as vitamin water), then you will run a higher risk of excess intake of certain nutrients at level above the upper level of intake, which consequently increases the possibility of adverse effects.

    Who should or shouldn't take vitamin supplements?

    Basic over the counter multivitamins should be safe for the consumption of healthy people. If you are on a special diet and/or do not eat balanced meals on a regular basis, then multivitamin supplementation might be beneficial. In addition, components of multivitamin supplements can be beneficial to certain population groups. The most obvious one would be people with vitamin and/or mineral deficiencies. Based on the results of some of the studies investigating effects of multivitamin supplements, around 25% of the subjects tested had some sort of nutritional deficiency in America (Murphy et al. 2007, American Journal of Clinical Nutrition). In Australia, it was suggested that over 1/3 of the adult population have vitamin D deficiency, and over 73% of adults have vitamin D levels that are considered below the optimal for musculoskeletal health, which is a key factor for falls and fractures in the elderly (Daly et al. 2012, Clinical Endocrinology). Vitamin supplementation in these people may be beneficial. However, it is unlikely for a person to be deficient to all vitamins and minerals and thus taking multivitamins might be a bit of overkill. Supplementation of a single vitamin/mineral is sufficient.

    It was suggested that supplementation of vitamin D and calcium in post-menopausal women can increase bone mineral density and prevent fracture; supplementation of synthetic folic acid (400mg/day) can reduce the chance of neural tube defects in newborns; vegans and people over the age of 50 are recommended to take vitamin B12 supplements as they are less able or like to absorb it from food; it's recommended that breastfed or partially breastfed infants should receive 400IU/day vitamin D shortly after birth until they are weaned; similarly, vitamin D supplementation is also recommended for non-breastfed infants if they drink less than 1000mL/day of vitamin D fortified formula. Please consult a healthcare professional if you think you belong to one of the groups of people above and want to take nutritional supplements.

    Who shouldn't take vitamin supplements?

    One man's best friend is another man's poison. This phrase is so very true here. There are particular groups of people who should really pay extra attention on what's in your supplements, as taking the wrong thing can really have detrimental effects on your health.

    • Smokers, ex-smokers and asbestos exposed persons: beware of vitamin A and beta-carotene! Smokers took supplements that contain beta-carotene (20mg/day, maximum recommended dietary intake is 6mg/day) had an 18% higher chance of lung cancer after 5-8 years (New England Journal of Medicine 1994). Smokers, ex-smokers and asbestos exposed persons who took 30mg/day of beta-carotene and 25,000IU/day of vitamin A (recommended dietary intake 2300-3000IU) had a 28% higher chance of getting lung cancer (Omenn et al. 1996, New England Journal of Medicine).
    • Pregnant women: excess amount of vitamin A intake can increase the chance of birth defects in infants.
    • Adult male, post-menopausal women and children under of age of 6: should avoid taking multivitamins containing the adequate intake level of iron unless you are being diagnosed with iron deficiency or inadequacy in order to avoid iron poisoning.
    • People who are on anti-blood clotting medications: please consult your healthcare professional before taking any supplements containing vitamin K, as vitamin K is involved in blood clotting and would reduce the efficacy of your medications.

    How should I choose multivitamin supplements?

    Ideally, it would be nice to know your nutritional status before choosing a multivitamin product. The most common method for testing nutritional status is through blood tests, sounds simple but it is also insensitive and inaccurate for many nutrients. The reason for that is nutrients are usually stored at specific sites in the body and on the other hand, blood samples are usually not representative of the sites. You could have normal blood tests results even if you are deficient (such as zinc), or a mildly abnormal result that doesn't actually mean much clinically (such as vitamin B6). To obtain more accurate results, tests have been developed to measure nutrient at the sites they act. However, it is cost and time consuming for a normal healthy person to do these tests just for the purpose of choosing multivitamins.

    The following recommendations may be helpful as a general rule of thumb for multivitamin shopping. Remember, if you suspect that you are sick, always consult a healthcare profession before drugging yourself up. For general multivitamin shopping, one should always choose a product that's specifically made for your gender, age and special requirements (ie. pregnancy or post-menopausal). Avoid high levels of vitamin A and beta-carotene if you are smoker or ex-smoker. Men should also choose multivitamins contain little or no iron. Do not use products that contain nutrients exceed their recommended dietary intake values.

    Final word

    The human body is extremely complex, vitamins and minerals, albeit essential, are only a small part of our building blocks. Multivitamins may be helpful in maintaining the optimal levels of nutrients in the human body, but it is by no means a replacement for your normal diet. Excess intake of nutrients from supplements can be more harmful to your body than not taking any supplements at all. In a world of fast foods, many do consume insufficient nutrient-dense foods and beverages. Vitamin supplements may have its place in the current society. But remember, nothing beats a good balanced meal and a healthy lifestyle.

  • High Carb or High Fat Diet?

    While you need your whole grains for health and energy, is it causing trouble when it comes to trimming down? This is how you can adjust your diet for optimal Fat and Carb intake.

    Fats and carbohydrates are two of the 3 macronutrients. The third is protein. Since most readers already know that they need plenty of protein to recover and build muscle, we'll focus on the role that Carbs and Fats plays in your performance.

    How to Balance your Carbs

    Carbohydrates are viewed as fuel. Without them, you'd be sluggish and tired during workouts. We all need some carbohydrates, the question is how much. During all phases of training, with the exception of your last bit of cutting, you'll need more carbs rather than less.

    Focus on getting 4 to 7 grams of carbohydrates per kg of bodyweight. You're looking at between 1400 and 2000 Calories. This should be enough to help fuel workouts, feed your brain and muscles, and get your recovering adequately. Focus on whole grains like brown rice and steel cut oats, and lower GI fruits. These will not spike insulin levels and they'll leave you satisfied for longer since they digest slowly.


    Fats; you need -em even if you hate -em!

    Our own body fat is not an indication of how much fat we eat. Unhealthy fats, such as trans-fats and saturated fats do not mix well with a carb diet, however, and can lead to several other health problems. Unhealthy fats are implicated as a cause in many cardiovascular health problems; it is best for them to be consumed infrequently. On the other hand, healthy fats should be consumed several times per day!

    Healthy fats from nuts, seeds, fish, eggs, and plants such as avocado, olive and coconut are very necessary!

    These fats are responsible for many functions, including being the only source of energy for certain functions. In addition to this, the nervous system relies heavily on fats, as does the digestive system. Some micronutrients are fat soluble, requiring a healthy fatty diet to metabolise them.

    Besides playing a role in energy production and digestion, fats also help to break down and metabolize our own stored body fat. Though it seems odd, you need to consume more fat to help get rid of your own fat for good! Eating these fats triggers fat-burning enzymes called ketones. Ketones help to metabolise stored fat for energy.

    As it were, you need your worst enemy more than you realise! As mentioned earlier, this really only counts for the healthier fats, not saturated fats!

    How much Fat do you need?

    A healthy male athlete can have as little as 4% body fat. A healthy female athlete can have as little as 12%. When it comes to eating fats, you should be eating them every day in small doses. You don't need a lot of benefit from them.

    Eggs for breakfast, a midmorning snack of nuts, and a second snack or meal later in the day containing any form of fats or oils is ideal.

    Hope that answers your questions re. high carb or high fat diet. If you do have further questions, please use the QnA Section and one of our experts will endeavour to answer you asap.


  • Glycemic index, its perks, and limitations

    The glycemic index or GI is the measurement of the blood sugar level increase in response to consuming carbohydrates (usually 50 grams) contained in foods. The value of GI is relative to that of pure glucose, which has a GI of 100. It is acknowledged that a GI of 70 or above is considered as high, a GI of 56 - 69 is medium, and a GI of 55 or less is considered as low. Foods with a higher GI number will induce a greater and more rapid the blood sugar response after ingestion; and conversely, food with a low GI will induce a more slow and steady glucose release.

    The concept of GI was initially introduced by Jenkins et al. in 1981, originally designed as a food guide for people with diabetes. Due to the importance of carbohydrates and sugar in body's metabolism and function, GI has since been widely adapted by the non-diabetic population as a guide to optimize diet and performance. Here we have a brief look at the role of GI control in weight management, exercise and limitations of using GI as a sole measure for blood sugar control.

    Effects of GI on weight management and health

    It is estimated that there are over 1 billion overweight adults in the world and 300 million of those are obese. It has been proposed that the population's increased consumption in high energy, high fat and high sugar diet coupled with low physical activity are the main causes of overweight (Lopes da Silva and de Càssia Gonçalves Alfenas, 2011, Nutrición Hospitalaria). Being the main energy course of human diet, the amount of carbohydrates ingested thus has a significant influence on human health.

    GI links to obesity and other health problems

    There is evidence suggesting that low GI diets may be protective against the development and obesity of related disease such as type 2 diabetes and coronary heart diseases (Barclay et al. 2008, Amercian Journal of Clinical Nutrition). Low GI diets have been linked with improved BMI (Ma et al. 2005, American Journal of Epidemiology). High GI diets have been linked with increased body fat mass, body weight and waist circumference in women over a 6-year period, but not in men (Bare-Bruun at al. 2006, American Journal of Clinical Nutrition). A diet based on high carbohydrates, low GI foods has been found to reduce the sugar and insulin hike post-eating without increasing LDL-cholesterol (the bad cholesterol) or serum triglycerides (level of fat in blood) (Brand-Miller et al. 2009, Journal of the American College of Nutrition). Low GI diets have been found to be more effective in promoting weight loss in children and adolescents than low fat diets (Esfahani et al 2011, IUBMB Life). A meta-analysis concluded that (after analysed 6 trials) strict low GI diets resulted in significant reduction in weight, total fat mass, and BMI compared to people with normal diets (neither high GI nor low GI) in adolescent and adults (Thomas et al. 2007, Cochrane Database of Systematic Reviews). Another meta-analysis study compared results from 23 studies and found that low GI diets can effective induce weight loss (Livesey 2008 et al. 2008, American Journal of Clinical Nutrition).

    There has been inconclusive evidence showing that low GI diets may reduce the risk of various cancers, such as breast cancer, prostate cancer, colon cancer and pancreatic cancer, however, the results of various studies are inconsistent and as such this is an area warrants further scientific investigation (Esfahani et al. 2009, Journal of the American College of Nutrition). Nevertheless, there is overwhelming evidence to show that low GI diets are effective in weight management and can reduce the risk of type 2 diabetes, coronary heart disease and possibly a range of other health related complications such as cancer.

    GI is affected by combining different types of food

    GI provides values for individual foods. However, when a food is included into a meal, the GI of the meal will not be the same as the GI of the individual food. Contents from other co-ingested food, such as protein, fat, soluble dietary fiber and even acidic compounds will have an influence on the glucose and insulin response to the meal as a whole (Bornet 2007, Apetite). It is generally agreed that the GI of a meal should be the calculated by the GI of individual food weighed by their percentage of carbohydrate contribution to the entire meal. Thus the overall GI of a meal can be reduced (without being unhealthy) by incorporating foods contain high levels of dietary fiber.

    GI and exercise

    The manipulation of GI for optimizing exercise performance and post-exercise recovery is an exciting new area of research in sports nutrition. However, studies to date yielded mixed results on whether GI manipulation can actually enhance performance. More research into the effects of GI on exercise is clearly required. Therefore, it is important to look at the findings of these studies in a critical manner. Here we present to you some of the recent findings regarding to GI manipulation and exercise.

    Effects of GI on exercise and recovery

    It has been found that the ingestion of carbohydrate before and during a workout can improve performance. For details of this please refer to the article "Are sports drinks beneficial during workouts?" from the previous issue. While a small number of studies suggested that eating low GI foods before an exercise is beneficial, as the more sustained release of glucose can maintain the energy levels of athletes during the session, the majority of the studies concluded that GI of the ingested meals before exercise has no impact on performance (Donaldson et al. 2010, International Journal of Sports Nutrition and Exercise Metabolism). It is worth noting that a portion of the small number of studies where a pre-exercise low GI meal did enhance performance, the subjects were conducting workouts at lower intensities (3 out of 4 such studies showed improvement). The catch is that this improvement of performance would diminish if the intensity was maxed at any time during the exercise (Mondazzi and Arcelli 2008, Journal of American College of Nutrition). Therefore, to benefit from a low GI pre-exercise meal from a performance point of view, one has to maintain a consistently low intensity performance throughout the entire course of the workout.

    On the other hand, there's good evidence suggesting that consuming pre-exercise low GI foods can prevent hypoglycemia (low blood sugar levels) that are usually experienced towards the end of prolongs exercise, as compared to consuming high GI pre-exercise foods. Preliminary research also showed that consuming low GI foods before exercise can induce greater plasma free fatty acids levels in comparison to consuming high GI foods. Free fatty acids are used as energy fuel and can be oxidized by the muscle during exercise, therefore support better energy metabolism. Even though the performance enhancing property of a low GI pre-exercise meal is highly questionable, there is enough evidence to show that low GI foods can at least enhance energy metabolism and thus can be deemed as more beneficial in comparison to high GI foods as pre-exercise meals.

    Effects of GI on post exercise recovery

    In contrast, it's almost universally agreed that high GI foods/meals can increase muscle glycogen resynthesis, replenish glucose storage after a workout session. It has been shown in one study that the increase in muscle glycogen concentrate from the end of exercise to end of 24 hour recovery period was 50% greater in people consumed high GI foods in comparison to those who had low GI foods (Burke et al. 1993, Journal of Applied Physiology). Consuming high GI foods after a workout can speed up immediate post-exercise recovery.

    The limitations of GI and glycemic load

    Many manufacturers advertise their food as having a "low GI" and this may have created misconceptions in the public that low GI = healthy. Well, here is something for you to think about: a super supreme pizza from a popular fast food franchise has a GI of 36, whereas green peas have a GI of 51; here is another one, the GI of premium full cream vanilla ice cream is 38, and the GI of grapes is 59; and there is one more, the GI of watermelon is 71, whereas the GI of microwave chicken nuggets is 46. In each case, the junk food wins the low GI contest hands down compared to natural fruits and vegies. But would you really honestly think a super supreme pizza is healthier than fresh green peas? Our examples show that lower GI doesn't necessary mean healthier, what is it then?

    GI is originally created as a simple tool to measure of how quickly the blood sugar level would rise after consuming 50 grams of pure carbohydrate equivalent from a specific food. And that is that, it doesn't measure fat content, or calories, or additives, it is only an index to predict sugar levels in blood in response to consuming carbohydrates. This means that food contains pure trans fat (no carbohydrates) would probably have a GI of close to 0, and trans fat is certainly not healthy. On top of that, GI doesn't tell you how much carbohydrate there is in a specific type of food either, and this is the real limitation of using GI as a sole gauge of sugar control. As we stated before, GI is established by measuring the change in blood glucose levels after consuming 50 grams of carbohydrates. Now, carrots and super supreme pizzas have a similar GI, however, it would require a lot of carrots to equate 50 grams of carbs and it is unlikely for anyone to eat that many carrots in one serving. This means the carbs in carrots would have a much-reduced effect on blood sugar in real life situations than the published GI. In contrast, pizzas contain a much higher percentage of carbs and it would not take much to consume the 50-gram portion. You see the problem? It is okay to compare GI of similar types of foods. But comparing GI dissimilar foods without knowing their carbohydrate content can be very misleading, it's like comparing the weight of people without knowing their heights and gender. People in the profession realized this limitation of GI and hence another form of measurement was developed, this is called glycemic load, GL.

    GL combines GI and the amount of carbohydrates contained in a serving of a particular food, gives a much fuller picture on how foods can affect our blood sugar. A GL of less than 10 is considered as low, 11-19 is considered as medium and 20 or more is considered as high. Watermelon has a GI of 71, that is quite high, but as it only contains around 5% carbs, that gives each serving (120g) a GL of 4, which is low. In contrast, even though s super supreme pizza has a much lower GI compared to the watermelon, each serving (100g, just under 2 slices) would yield a much higher GL of 9, that's not too bad actually, considering how unhealthy we think fast food pizzas are.

    This brings me to the final point that I want to make: both GI and GL are measurements of the effects of carbohydrate on blood sugar ONLY, and they can only measure foods that contain carbs. Pure fat without any carbs would have a GI and GL of both 0, but it is by no means healthier than fruits and vegies with much higher GI/GL. Two slices of super supreme pizza may have a GI and GL in the relatively lower range, but it also contains quite a bit of fat and is quite high in calories, both are not accounted for in the GI and GL measurements. That being said, GL is a more sensible way of measuring how carbohydrates in a particular food can affect blood sugar levels compares to GI, and should be used in conjunction with other criteria to assess the quality of a particular food.

    The infamous last words
    The GI/GL are nifty tools to predict blood sugar response after ingesting food. They can be used to optimize diet in order to achieve a better health. Use it wisely, don't abuse it.

  • Biological clocks, circadian rhythm and weight control

    Many associate weight gain with eating high fat, high calorie food, and a lack of exercise. Recent advances in medicine discovered that there is another important factor, possibly more important than the type of food you eat, which could affect the body's weight. That is our own biological clock. Most of us know that the "biological clock" is important in regulating the daily functions of our bodies, what we don't realize, is just how important this clock really is; and the fact that the "biological clock" is actually an intricate network of "clocks", which are made up by a group of molecules that is present in nearly all cells throughout our bodies. This means almost every single cell in our body has its own clock. All these clocks are controlled, synchronised and coordinated by a master clock in the hypothalamus of the brain called suprachiasmatic nucleus pacemaker neurons. The biological clock influences almost all physiology and behavior in humans, such as sleep-wake cycles, cardiovascular activities, endocrine system that controls the body's metabolisms and hormone levels, kidney activities, and gastrointestinal and liver functions. In addition, the biological clock has been linked directly to lipid (fat) metabolism (Froy 2010, Endocrine Reviews). The disruption/alteration of these clocks will have implications on the gastrointestinal and metabolic functions of the body and consequently influence our food digestion, processing and absorption that are essential for maintaining a healthy body weight and personal well-being.

    The regulation of our master clock is based on the 24-hour light and dark cycle where our earth rotates along its axis. As such, the principle signal for the regulation of our master clock is light, which then sends output signals to the clocks in other cells of the rest of the body to synchronize their functions. This system allows the body to produce optimal functions at optimal times within a 24-hour day. However, unlike the master clock in the brain, the individual clocks in our tissues can also be affected and reset by stimuli other than light, such as eating times. As a result, this can create time "misalignment" between individual clocks in our body and the mater clock in the brain.

    Circadian rhythm is the daily physiological and behavior patterns driven by our biological clocks. Part of its functions is metabolizing food and nutrients and managing energy input and expenditure, hence maintaining optimal body weight. This rhythm can be disrupted by our own voluntary behaviors, such as irregular eating habits or working irregular shifts, outside the control of the master clock in our brain. When time misalignment occurs between different parts of the body, the balance of the body's energetics and metabolism will be disturbed, and potentially serious health related issues would follow, including obesity and diabetes (Wong et al. 2007, PNAS; Scott et al, 2008, International Journal of Obesity), which in turn will affect circadian rhythm, creating a vicious circle.

    Ok, until now I have emphasized enough about the importance of our biological clocks and circadian rhythm in maintaining a healthy body weight, and probably scared enough people about the potential metabolic and weight management complications associated with the disruption of this rhythm. The reality is, we live in a highly stressful and demanding society, it is almost impossible for an average Joe like you and me, to plan our lives based on our innate rhythms and clocks. We need to work with other people's schedules, we have responsibilities on our shoulders and deadlines to meet, all at the expense of our circadian rhythm. But remember, at the end of the day, we neglected one thing that is the most precious to us, our own health. Although it is unrealistic to plan our daily lives fully based on our own exact circadian rhythms, partly because even with all the advanced medical technologies at hand, we are still not sure what the precise rhythm for each organ is, we could follow some general principles, which would put us more or less on the ball park.

    Evidence has indicated that there is a direct link between the fluctuation of the body temperature of a mammal throughout a day (yes, the body temperature of warm blooded mammals fluctuates) and circadian rhythm (Buhr et al. 2012, Science). By looking at a graph of an average person's body temperature cycle, it is not hard to figure our how we should plan our daily activities. The body temperature is an indication of metabolic rate, and it is at the lowest at around 6am each day and gradually increases as the day goes on. There is a little dip in temperature at around 1pm, which is why many of us feel tired and sleepy at around that time. Body temperature reaches its highest level at around 6pm and then it's all downhill from there, until reaching the lowest point at 6am, the cycle is complete.

    circadian-rhythmResults from numerous studies unanimously concluded that the time one eats and the time one sleeps are two important daily rituals that help to manage body weight and BMI, more so than the amount of calories contained in the food. Our body functions according to the 24-hour light-dark cycle. At light we eat; at dark we sleep.

    Since we first came to existence, our body is designed to fast overnight and only eat during the day. This practice follows our natural circadian rhythm and allows our organs and tissues to properly rest and recover from a day's activities. However, we now live a very different lifestyle compared to what we are evolved as humans to live. This disrupts the metabolic pathways controlled by our natural circadian rhythm, and some speculate that it is one of the main causes of the current obesity epidemic in many first world countries.

    It has been shown that eating at night is less satisfying than eating in the morning, which results in over-eating (de Castro, 2004, Journal of Nutrition). Nighttime eating can result in higher fatty acid uptake and triglyceride storage in scientific studies conducted in animals (Bray and Young, 2007, Obesity Review). A more recent study also found that mice eating during a restricted 8-hour period are significantly leaner and healthier than those consumed the same amount of calories but were allowed to eat freely throughout the day, regardless of the content and quality of the diet (Hatori et al. 2012, Cell Metabolism). This suggests that having a high fat diet is not the main culprit for weight gain. The time which people eat their meals can have a bigger impact on body weight and metabolic functions. If the Hatori study is applicable in humans, by consuming food frequently only during the 8 hour day period and fast at night, we will cure obesity, regardless of what type of food we eat. How about that?

    Another important aspect of maintaining correct circadian rhythm is sleep. Sleep depreciation, short sleep and poor sleep quality have been associated with diabetes, higher BMI, metabolic syndrome, increased appetite and obesity (Huang et al. 2011, Journal of Clinical Investigations). People who habitually sleep less than 6 hours or over 9 hours per night have an in crease risk of developing type 2 diabetes and impaired glucose tolerance (Gottlieb et al. 2005, Archives of Internal Medicine). The duration of wakefulness at times when one should be sleeping is directly related to BMI and waist to hip ratio independent of age, sex and physical activity (van Amelscoort et al. 1999, International Journal of Obesity Related Metabolic Disorders). So if you want to be lean, make sure to sleep 7-8 hours a day, can't be that hard!

    It is true that many of the studies mentioned above were conducted using animals not humans. However, the biological clock is present in all living things on earth, even in plants. Its function to regulate the body's physiology and behavior based on the 24-hour earth cycle is shared across species. Therefore, it is reasonable to assume that findings from animal studies can be translated into humans, possibly with small variations of course.

    Even though living a balanced life based on the biological clock and circadian rhythm has been described in alternative medicine for centuries, it is still a relatively new field in modern western medicine and science. Modern technologies however, provided concrete scientific evidence linking the biological clock with the well-being of the body as well as obesity. Thus by adapting eating/sleeping habit with this rhythm, one can maximize the body's potential, and subsequently improves its well-being.

    An adaptation of the appropriate eating/sleeping pattern for obtaining the ultimate lean body based on the circadian rhythm should look something simple like this: eat regularly during the day, have more food in the morning and gradually decrease the amount as the day goes by; try not to eat at night if you can help it and make sure to get 7-8 hours of sleep per night. Sounds simple, right? Of course, each person is different. This is just a basic framework that can be modified based on one's own personal circumstances. The important thing is that you know the science behind it.

    Researching and writing this article made me realize just how in-one we are with our surrounding environments, the earth and even the universe. We function by the basic rules of nature, regardless of how superior we think we are compare to other organisms on earth. We all want to be healthy and feel good about ourselves. We pursue that by taking the best supplements, go through the tedious exercise regimes, eat some of the most ridiculous foods. They do work, however, we forgot the most basic and important factor, the rhythm of ourselves. Play by rule of nature and you will live a healthy and feel-good life.

  • Aspartame

    Aspartame (additive no. 951) is a non-nutritious, low calorie artificial sweetener used in over 6000 food products. It is commonly found in diet sodas, Equal®, sweetened low fat yogurt, sugar free deserts, some condiments, certain sweets and sugar-free gums. The use of aspartame is approved by the US (FDA), European Union (EFSA) and Australia/New Zealand (FSANZ) food safety authorities and is considered safe for human consumption by over 90 countries in the world (Acceptable daily intake at up to 40mg/kg/day of body weight as of 2006).

    A survey conducted by the Cancer Council of Australia in 2003 found that most Australians consume 6-15% of the established acceptable daily intake of aspartame per day, which was well below the level where adverse health effect could occur. To put this into perspective, Diet Coke contains around 0.52mg/mL of aspartame. This means, a 60kg person would need to drink around 4.6L of Diet Coke per day to reach the upper limit of the acceptable daily intake for aspartame. If you prefer Coke Zero, which contains approximately 0.24mg/mL aspartame, then one 60kg will have to drink 10L of that stuff a day to be considered unsafe. That is quite a lot of liquid and it's very unlikely for anyone to consume that much fluid in a day.

    What was generally agreed on by most food safety governing bodies, is that aspartame, even though can be damaging to human health when consumed in high doses, is safe for normal human consumption as the average aspartame ingested daily per person falls well within the upper limit of its acceptable daily intake quantity. That sounds quite harmless, I mean, too much of anything can be damaging to health, even drinking too much water can cause hypernatremia (water intoxication) and may potentially lead to death, no kidding. So where did all these controversies surrounding aspartame come from?

    Historically, there has always been controversy surrounding the use of aspartame, the head of FDA was fired in 1981, allegedly after refusing to approve the legalization of aspartame (Cancer Council of Western Australia, 2010, accessed on 10th December 2012). Since the legalization of aspartame, there have been a number of reviews by food safety authorities over the safety of its consumption, and each time the reviewing organization maintained the position that aspartame is safe for human consumption.

    The most recent controversy over the safety of aspartame consumption that lead to a new round of reviewing and re-evaluation appeared to sprung from 2 independent studies published in 2010. One study investigated the long-term carcinogenic (cancer causing) effects of aspartame in mice (Soffritti et al. 2010, American Journal of Industrial Nutrition) and concluded that the life-long consumption of aspartame can result in liver and lung cancers in the mice tested. The other study analysed 59,334 Danish pregnant women and made the association between artificially sweetened soft drink intake and the increased risk for preterm delivery (Halldorsson et al. 2010, American Journal of Clinical Nutrition). In response, the EFSA conducted scientific evaluations on the above 2 studies and released its statement on February 2011. In the statement, EFTA pointed out the fatal experimental design flaws of both studies mentioned above, and rightfully concluded that neither provide sufficient evidence to demonstrate that aspartame is carcinogenic or can increase the risk of preterm delivery. Based on available scientific evidence at the time, the EFTA stated that aspartame is safe for human consumption.

    A number of studies regarding to the safety of consuming aspartame has been published since EFTA statement on February 2011. Below are snippets of some of the scientific literatures available since 2011 regarding the safety of aspartame:

    • It was found that the consumption of equal or greater than 1 daily serving of diet soda can slightly increase the risk of non-Hodgkin lymphoma and multiple myeloma in men but not in women compared to those compared to caloric sugar-sweetened soda, the author concluded that the study results indicated the "possibility" of a detrimental effect of aspartame on the risk of cancers tested (Schernhammer et al, 2012, American Journal of Nutrition).
    • A study found that the long-term consumption of aspartame can lead to an imbalance of antioxidants and pro-oxidant status in the brain in rats (Abhilash et al, 2012, Drug and Chemical Toxicology).
    • Chronic exposure of aspartame can result in detectable methanol in blood and subsequently induces oxidative stress in rat brains (Iyyaswamy and Rathinasamy 2012, Journal of Biosciences).
    • A medical case report found that the consumption of aspartame caused systemic allergic dermatitis in a 37 year old woman (Veien and Lomholt 2012, Contact Dermatitis).

    Sound scary isn't it? Well only if the results of the studies are scientifically sound. Perhaps in response to the new studies emerged describing the possible adverse effects of consuming aspartame, on May 2011, EFTA was asked by the European Commission to conduct a full re-evaluation on the safety of aspartame. On June 2011, EFTA launched a public call for scientific data on aspartame and the re-evaluation is expected to be completed on May 2013.

    Many consume artificially sweetened food and drinks as part of their weight management regime. The intake of aspartame in place of caloric sugar does not cause weight loss if a person consumes the same amount of calories. Interestingly, it has been found that consuming aspartame without knowing can lead to reduced total calorie intake whereas knowingly ingesting aspartame can increase overall energy intake (Yang 2010, Yale Journal of Biology and Medicine). So if you want to lose weight, either ingest aspartame in place of caloric sugar without knowing it, or just simply eat healthy and restrict your overall daily energy intake. The long-term effect of artificial sweeteners on children and adolescents is unknown and its potential role in weight management in relatively unclear (Foreyt et al. 2012, The Journal of Nutrition). Additionally the American Heart Foundation and American Diabetes Foundation also issued a statement stating that there are insufficient data indicating that the use of artificial sweeteners in place of caloric sweeteners "reduced added sugars or carbohydrate intakes, or benefit appetite, energy balance, body weight, or cardiometabolic risk factors" (Gardner et al. 2012, Circulation). Thus, I suggest you to exercise caution when using artificial sweeteners such as aspartame as part of your weight management regime, until more concrete scientific data on the safety and efficacy of these sweeteners are available.

    So what's my position on aspartame? Well, I myself am guilty of consuming decent quantities of diet soda each week. After researching for this article, the can of diet soda that usually sits on the side of my computer when I'm having the writer's block was replaced by a glass of spring water. I am eager to see the final results of the EFTA re-evaluation and their soon-to-be updated recommendations regarding to aspartame consumption. Until then, I will be on an aspartame elimination diet.

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