The best sources of this growth-promoting dietary essential, fat-soluble A, are whole milk, cream, butter fat, egg yolk fat, and some products of the plant kingdom, as the leaves of plants and certain roots. Such foods as bolted (white) flour, degerminated corn meal, polished rice, starch, glucose, and the sugars from milk, cane, and beet, are mentioned by authorities as especially poor in fat-soluble vitamine.
A lesson taught by experiences during the late war, was the importance of certain amounts of fat in the human dietary ; as in those countries where milk, butter, and fats generally were unobtainable, the people became singularly susceptible to contagion. Tuberculosis, for instance, became a veritable epidemic when the fat supply was cut too low. Whether tuberculosis does not follow a deficiency of fat-soluble vitamine, rather than a general deficiency of fats, is a question that is still undetermined.
Whether an abundance of olive oil, cottonseed oil, or other vegetable fats, or lard, which do not contain fat-soluble vitamine, will provide against the incursions of tuberculosis, or if such fats as milk, cream, butter fat, and egg yolk fat, which contain of at-soluble vitamine, are absolutely necessary as a protective against disease, is a proposition that still awaits final solution.
The facts cited by recent investigators seem to agree that fat-soluble vitamine need not be sought solely in foods known to be rich in fats. Of the various plant structures, the leaves are the richest in fat-soluble vitamine. Some roots are next, and lastly cereal grains. Clover, alfalfa, spinach, Swiss chard, and lettuce contain the fat-soluble vitamine in similar magnitude; and of these, lettuce has the least.
Writing on the subject of “Fat Soluble as Nutritave Factors in Plant Tissues,” Osborne and Mendel’ say: “o.1 gm. of alfalfa, clover, timothy, and spinach evidently furnishes relatively at least as much of this vitamine as does o.1 gm. of butter fat. These vegetable products may in fact contain more than butter fat.” This agrees with the work of Hindhede, 6 whose results with young men correspond with observations on laboratory animals. He has contended that fat is not required in the diet of adults if an amount of fresh fruits and vegetables sufficient to supply the vitamines is eaten daily.
Steenbock and Boutwell 7 demonstrated that fat-soluble vitamines are present also in some roots, and in cucurbitous vegetables (pumpkin and squash). They found the carrot and the yellow sweet potato to contain so much of the fat-soluble vitamine that, as a source of this dietary essential, they must be classed with leafy vegetables.
They found the yellow maize (corn) to be comparatively rich in this growth-promoting vitamine, as when animals were dependent on it for their fat-soluble vitamine, the results were good, and sometimes, even if not in most cases, normal. On the other hand, white maize, in every case where experimental animals were de-pendent on it for their fat-soluble vitamine, proved to be an absolute nutritional failure.
A lack of this essential constituent in the diet results first in a failure of growth and maintenance of life. Second, there is oft-occurring inflammation of the eyes, or xerophthalmia, and malnutrition of the skin, as indicated by encrustation of the ears, and sores on the body generally.