Case Study: Whole Grains, Starch, and Dysentery

Currently, the scientific consensus supports consumption of whole grains, whereas throughout human history since farming began, until the 20th century, the preference has been for processed grains that have had their hulls (bran) and sometimes also their germ removed. Paleo Diet proponents argue that the hulls contain the phytates that interfere with digestion, and also that a starch based diet is unnatural (wasn't possible before agriculture). On the other hand, scientific studies demonstrate that many east Asians have evolved additional starch–digestion genes since they began farming. Nutrition scientists argue that our modern diet lacks fiber, which whole grains provide. Others counter that oat fiber is the only grain fiber shown to be beneficial to human digestion.

In poor countries, most mortality occurs in infants and small children. While the official cause of death may vary, typically an important factor is dysentery. A strong case can be made that dysentery is the number one killer of humans, and has been for a long time (perhaps since agriculture began). Before farming, when humans were more mobile, they would have been much less likely to pollute their drinking water. Moreover, low population densities probably would have constrained the development of dysentery-causing organisms.

What does a mother in a poor country feed to a small child with dysentery? Starch, the purer the better. Fiber only exacerbates the symptoms. This may in part explain the preference for white rice, white flour, etc., in traditional diets. Such foods would have fewer vitamins and minerals than whole grains, but these nutrients are supplied primarily by other foods – fruits, vegetables, meat, and fish.

This example illustrates once again that there are likely genetic differences in our ability to utilize different foods, but also that the conditions under which traditional diets developed are not identical to the situation in which we find ourselves in the developed world today. Dysentery is not a serious problem in the US. Perhaps whole grains are more beneficial to us than they would be to residents of poor nations. On the other hand, evidence that whole grain fiber (except for oats) is beneficial is essentially absent, while the extra vitamins and minerals in whole grains are trivial for anyone consuming other foods which we can access in abundance in our supermarkets.