EAT YOUR EGGS

In 1929, researchers tested a variety of foods for vitamin D content and found the second most potent source of vitamin D was egg yolk. The book describes studies in which Hess both cured and prevented rickets in rats by giving them egg yolks. He also gave prophylactic treatment to 12 infants to forestall development of rickets in the winter months, which his experience had taught him to expect in the great majority of bottle-fed infants. He gave them one egg yolk added to their regular formula starting in December. None of the 12 developed rickets in March as expected and, unlike prior years, blood phosphates remained stable at summer values.

About this same time, Johns Hopkins University investigators cured seven African-American children of rickets, in most cases severe, by adding one or two eggs daily to their diet of milk and cereal.

Like the vitamin D in cod liver oil, the amount of vitamin D in egg yolks also varies. Researchers in Kansas looked at four groups of hens: one group got sunlight in the yard plus 30 minutes under a quartz mercury vapor lamp producing UV-B light; another got sunlight through glass plus 30 minutes under the lamp; the third group got sunlight alone; and the fourth group got sunlight under glass alone. Eggs from hens under glass produced rickets in rats. Those with considerable UV-B prevented rickets completely and those with less (no lamp) caused the development of slight rickets. Only the sunlight plus lamp completely prevented rickets, showing that the natural UV-B in Kansas did not provide sufficient light for optimal vitamin D. Giving cod liver oil to the chickens had the same effect as exposure to UV-B light. Cod liver oil as two percent of the ration increased levels of vitamin D in the egg yolks fivefold.
The surprising conclusion is that chickens should either be given sunlamp treatment or cod liver oil. Poultrymen and consumers alike need to recognize that the axiom "an egg is an egg" is a mistaken one. Rather, "an inadequate ration may yield impoverished eggs as well as animals." The authors suggest that eggs be graded by vitamin content. What a concept! Too bad no one listened. What would they think of our so-called "organic" eggs from hens raised in barns, never exposed to light and given "all-vegetarian" feed?

MEET MRS. MELLANBY

The most fascinating part of this little book is the chapter describing the experiments done in England by a Mrs. May Mellanby. Her husband, Dr. E. Mellanby, was the author of over 400 studies and the first to control rickets with diet. Cod liver oil had been used for centuries as a remedy but the specific application to rickets was first demonstrated by Dr. Mellanby. (Control of rickets using UV-B light was demonstrated almost simultaneously by investigators at Columbia and Johns Hopkins University in 1921.) In his research into rickets in dogs, he discovered the mineral-blocking effect of phytic acid in grains and legumes. Dr. Mellanby demonstrated that diets containing high levels of cereals, especially oatmeal, and lacking vitamin D, are the most effective producers of rickets. If vitamin D is inadequate there is poor tooth development, but Mrs. Mellanby then went on to prove that no matter how much cereal is fed, if vitamin D is adequate tooth formation is normal. Mrs. Mellanby believed that as cereals increase in the diet, vitamin D must also be increased to offset their anticalcifying effects--think of the implications of this research on today's baby-feeding habits, where infants are given cereals as their first food but denied egg yolks until they are one year old!

Mrs. Mellanby also determined that vitamin D must be present from conception in order for proper tooth formation to occur. If vitamin D is absent during the early gestational period, the enamel cannot form properly, and it cannot be repaired by giving vitamin D later.

In her initial studies Mrs. Mellanby used dogs as the source of data but she later examined more than one thousand "baby" teeth from children. She divided these teeth into four categories--normal, hypoplastic (slightly underdeveloped), moderately underdeveloped and grossly underdeveloped. Only 149, or about 14 percent, of the total 1,036 were sound. About one-quarter were slightly underdeveloped, but nearly two-thirds were moderately or grossly underdeveloped.

It is more difficult to examine teeth in place, but of 266 adult teeth examined by Mrs. Mellanby, not one was sound. The teeth were extracted only for purposes of straightening the teeth, which means that they were erupting in a jaw that was underdeveloped. Thus, children with narrow faces most likely have underdeveloped teeth. Tooth structure and later decay are directly related. Prevention of cavities must start in the womb.

CURING CAVITIES

A final plum from this most fruitful book regards secondary dentine. Secondary dentine, a less well-organized form of tubular dentine, is produced throughout life as a patching material where cavities have begun, where the overlying enamel has been worn away, and within the pulp chamber as part of the aging process. Sometimes when cavities occur, production of secondary dentine can "heal" the decayed spot or rebuild portions of the tooth that have worn away. If vitamin D is adequate, secondary dentine will be well calcified. If vitamin D is lacking, dentine will be of poor quality or not present at all.

There is some evidence that the mineralization of dentine may depend on calcium derived from saliva rather than blood; in other words, it is deposited from the exterior rather than the interior of the tooth. The book describes studies by Dr. C. L. Pattison who, working with Mrs. Mellanby, determined that the calcium content of saliva doubled or even tripled when the diet contained adequate vitamin D from cod liver oil.