One of the clear results Lady May Mellanby’s extensive research on dental decay is what she referred to as “the cereal effect”. Poorly mineralized teeth and tooth decay were more prevalent in both children and animals who consumed the greatest amount of cereal grains.
In diets that were deficient in vitamin D, puppies that were fed oatmeal as part of their diet developed the most defective teeth (poorly formed and poorly mineralized enamel and dentin). Those receiving received white rice and white flour developed the best mineralized teeth. Whole wheat flour was worse for teeth than white flour. Lady Mellanby showed that it was the amount of wheat germ in the flour that affected tooth development and calcification. The anticalcifying agent in cereal grains could be largely, though not completely, countered with adequate intake of vitamin D.
In the diet trials with children, Lady Mellanby varied vitamin D, calcium and cereal content, and found the best results with those children who consumed a cereal-free diet, rich in vitamin D and calcium. In these children almost no new cavities developed, and pre-existing cavities showed extensive hardening and healing. This is in contrast to the children following vitamin D and calcium poor diets that contained extra servings of oatmeal. Those children showed decreasing dental health with development of new cavities and no hardening or healing of existing cavities.
So what is the anticalcifying agent present in the cereal grains? It was suspected, and later proved, to be phytic acid, or phytate, which is found naturally in nuts, seeds, and grains. White rice and white flour have generally low levels of phytate, while whole wheat flour and oatmeal have higher levels. When ingested, phytate can chemically bind in the gut with calcium and other minerals such as magnesium, iron and zinc, making them unavailable for absorption. The minerals are excreted with the undigested fiber. The effect of consuming fiber-rich cereal grains is the same as reducing the dietary intake of calcium and other minerals.
In Hawaii during the 1920’s rampant early childhood decay in the children of plantation workers was eliminated when traditional taro and sweet potatoes were substituted for the rice and bread that made up much of their diet. Taro and sweet potatoes are low in phytate.
We are all encouraged to consume more healthy, whole-grained, fiber-rich foods. However, as Professor Harold Sandstead writes in 1992:
…it appears that some health promoters who suggest that US adults should consume 30-35 g dietary fiber daily have not done their homework or have simply ignored the carefully done research on this topic. They appear to be unaware of the effects of phytate on mineral retention and the fact that many of the commonly consumed sources of fiber are rich in phytate, or to have been mislead by reports…[that] conclude that foods rich in fiber and phytate do not impair retention of essential minerals.”
Fortunately, for those who prefer to consume cereal grains, nuts and seeds the phytate content can be reduced by soaking, fermentation or longer rise times in breadmaking. Nourishing Traditions by Sally Fallon provides an excellent introduction to this with recipes and directions.