In response to the idea that high glycemic foods can cause insulin resistance, what would be your response to people like Dr. John McDougall that claim there are plenty or cultures in Asia who live on diets consisting of high glycemic foods such as potatoes and rice but have little to no rates of diabetes or other chronic illnesses?
Here’s a link to his article http://www.drmcdougall.com/misc/2006nl/july/glycemic.htm.
Pedro Bastos Response:
I believe that not all people will develop insulin resistance on a high glycemic load diet and not all people will see the same improve their body composition and/or insulin sensitivity on a low glycemic load diet. It appears to be dependant on your genotype. We have some examples of that: for instance, the aborigines don’t tolerate a high carb diet very well and the Kitava do better. But don’t forget that low glycemic load doesn’t automatically mean very low carb and high carb or normal carb doesn’t necessarily mean high glycemic load, as the glycemic load depends on the amount of carbs on a given serving of a certain food and the Glycemic Index of that food, so saying that the Asians eat a high glycemic load diet may not necessarily be true.
Another possibility that some people will develop insulin resistance on a high glycemic load diet (and some will not) is that a deprived fetal environment (which normally, but not always, leads to an underweight baby) may lead to a specific metabolic programming that has been called the trify phenotype, which means that these babies will develop various diseases of civilization when exposed to the postnatal environment (western diet and sedentary lifestyle) that is characteristic for affluent societies and of rapidly developing countries.
What I mean here is that depending on your genotype and/or epigenotype you may or may be not react adversely to a high carb diet. Moreover, there are also various variables that need to be considered when we want to know why certain populations suffer more from the diseases of insulin resistance, such as (among many other variables):
- Exercise (it has a huge impact on insulin sensitivity and sarcopenia, a typical consequence of inactivity), leads to insulin resistance and an increased risk of the metabolic syndrome).
- Vitamin D and/or ultraviolet exposure (for instance, in Kitava they don’t suffer from Vitamin D deficiency, whereas in the western world many of us do and there is evidence linking Vit D deficiency to an increased risk of Type 2 Diabetes and the Metabolic Syndrome, among various other diseases).
- Magnesium deficiency is strongly associated to an increased risk of the Metabolic Syndrome and Cardiovascular diseases. Presumably this wasn’t a problem for our ancestrors and to many non-westernized populations, but it is a huge problem in the US.
- Fructose intake – although our ancestors and many non-westernized populations around the world eat fruit, which is a source of fructose, fruit also has Vitamin C (which counteracts some of the adverse effects of fructose) and they don’t eat as much fructose as the Americans do, because HFCS has been added to many foods and because of the American eating habits (I’m Portuguese and I always am amazed when I go to the US and see what the people eat and the amount of sodas they drink and the amount of obese people I see there). In Dr. Cordain’s papers and in his lectures (I attended several) he mentions fructose as a cause of elevated uric acid and insulin resistance. And we have a spreadsheet with the fructose content of various foods for those who need to cut back on fructose intake (those who are already insulin resistant or have elevated blood uric acid levels and/or have been eating a very high fructose diet, which upregulates certain enzymes that need to be downregulated in order to reverse the effects of this high fructose intake and the only way to do it is by eating a very low fructose diet for a few weeks, before resuming a normal fructose diet (whose main sources are mainly fruit).
- Bioactive peptides and antinutrients in Neolithic foods (see Dr. Cordain’s scientific paper on cereal grains here and Dr. Staffan Lindeberg’s research team paper on lectins and leptin resistance (link below).
- Visceral fat – cytokines derived from visceral adipose tissue will cause insulin resistance.
- Sleep deprivation – it may set off a hormonal cascade that may ultimately result in insulin resistance and Obesity.
- Etc, etc…
We have to realize that many Americans have already the signs and symptoms of the Metabolic Syndrome and/or Type 2 Diabetes insulin resistance and many more have some degree of insulin resistance and for these people a low glycemic load diet may be very beneficial. But, as you may infer from our newsletters and from Dr. Cordain books and scientific papers, eating a low GL diet it is not enough and it is only a characteristic of the many general universal characteristics of pre-agricultural diets that Dr. Cordain and his research team have been deciphering over the past 15 to 20 years. AS so, if one wants to achieved optimal health, he shouldn’t focus only on one dietary characteristic, but on all of them plus the lifestyle that presumably shaped our genome during the Pliocene and Pleistocene (exercise, sun exposure or vitamin D supplementation + sleep + stress management + avoidance of environmental toxins).
All this sheds light on why some Asian populations live on a high carb diet, but do not develop the Metabolic Syndrome. Perhaps because they don’t overeat (remember that caloric restriction is the only proven way to increased longevity in many animal models and presumably one of the main reasons why you have so many centenarians in Okinawa), they don’t eat much fructose, they exercise, they don’t suffer from Vitamin D deficiency (and perhaps also magnesium deficiency), have “normal” sleeping patterns, etc, etc, etc.
Nevertheless, I would like to mention that apparently healthy people from India (living in India and eating their traditional vegetarian diet) have more visceral fat than healthy Caucasians and are more prone to Type 2 Diabetes and other diseases associated with the Metabolic Syndrome.
Finally, even in healthy people with no signs or genetic predisposition for insulin resistance, a high glycemic load diet may not be ideally, as it will increase glycolysis and it will decrease beta-oxidation (aging is associated with an increased glycolysis and decreased beta-oxidation and one of the mechanisms why caloric restriction increases longevity is believed to be a decrease in glycolysis and in increase in beta-oxidation). Moreover, it may increase inflammation (see link to paper) and, it may also cause several hormonal disturbances (elevated IGF-1 and androgens and decreased Sex Hormone Binding Globulin and IGFBP-3), which then increase our risk for various diseases.
I hope this helps.
Pedro Bastos, MA MS Ph.D. candidate in Medical Sciences at Lund University, Sweden; International College of Human Nutrition and Functional Medicine
For more information, please view some of our published research.