My dislike of many starchy carbs like bread, potato, rice, pasta and breakfast cereals is based on a body of evidence which suggests that the gluts of insulin their eating induces can speed our path to conditions such as obesity and type 2 diabetes. And, despite all this talk about their ‘nutritious’ nature, the fact remains that they leave a lot to be desired on this front too.
I most recently covered the hazards of consuming too may blood sugar and insulin disruptive carbs in by blog post of 28th November. Specifically, I focused here on two studies which found links between high glycaemic index (GI)/glycaemic load (GL) diets and an increased risk of type 2 diabetes. The post which followed this focused on a study which found that a low GI diet, compared to a high GI diet, brought benefits for health quite quickly.
After this particular post a commenter sprung to the defense of high GI foods, claiming that the fact that the Japanese eat a lot of rice (a high GI food) and are healthy proves that high GI foods cannot be bad for us.
I thought I’d write about this today because this comment came in over the weekend and I hear similar lines of argument quite a lot. The question usually goes along the lines of: “If starchy foods are so bad, how come the Mediterranean/Chinese/French diet which is full of pasta/rice/French bread is so healthy?�
Firstly, I think that we sometimes have a very stereotypical image of some traditional diets. The French do eat French bread, but most of their diet is actually made up of quite natural, unprocessed foods. The same is true of the Italians, who when they eat pasta, actually tend to eat it as a starter rather than a main course. And while the Chinese do eat rice, again, they eat a lot of other foods too including vegetables, fish and meat. I can’t find any good data on the overall GI/GL of the diets of these or other nations. If we had some, maybe we’d see that the stereotypical view we have of their diets is far from accurate.
But even if these nations do eat a stack of starch and at the same time enjoy good health and longevity, what would this tell us? The fact is health and longevity are the products of many, many different factors. Some negative influences may be ‘offset’ by more positive ones. So, for instance, perhaps rice does make up a fair proportion of the Chinese diet, but maybe the Chinese are generally an active bunch, and this may be helping to protect against any damage that rice might reek in the body.
When examining the effects food (or anything else) has on health, it’s important to isolate the factor you want to assess and, as much as possible, keep everything else the same. one way of doing this is to look within a population, and see what relationship there is, in this case, between the GI/GL of the diet and health. When such studies are done, there is quite compelling evidence which demonstrates that we eat a high GI/GL diet at our peril. The post of 28th November alone highlights two studies which support this concept.
Turning our attention back to the Japanese for a moment, does the evidence show that rice is as benign a food as some would have us believe? Well, rather predictably, the answer is no. Earlier this year saw the publication of a study in the European Journal of Clinical Nutrition which looked at the relationship between GI and GL and body mass index (BMI) in Japanese women aged 18-20 [1]. The study found that higher GI and GL diets were associated with higher BMI. The differences in BMI were small (but statistically significant), but then again, young Japanese ladies do tend to be on the slim side. Further evidence for the not-so-benign nature of starch in the Japanese diets comes from a study which found the consumption of a high GI diet to be associated with adverse effects on risk markers for cardiovascular disease such as blood fat and insulin levels [2].
Pointing to the Japanese diet as proof of one’s ideological standpoint is not scientific, and is essentially not much more scientifically rigorous than claiming that because your grandpa Joe smoked and lived to be 100, smoking cannot be harmful to health. Come to think of it, Japanese men smoke a lot, but it hasn’t stopped them having one of the best life expectancies in the World…
References:
1. Murakami K, et al. Dietary fiber intake, dietary glycemic index and load, and body mass index: a cross-sectional study of 3931 Japanese women aged 18-20 years.
Eur J Clin Nutr. 2007;61(8):986-95
2. Amano Y, et al. Correlation between dietary glycemic index and cardiovascular disease risk factors among Japanese women. Eur J Clin Nutr. 2004;58(11):1472-8.
