In departing from food customs there is a natural timidity lest the new
food shall in some way be less healthful than the old. Recent scientific
researches have revealed a hitherto unsuspected property in butter, a
discovery which has aroused some concern as to whether we can safely
substitute other fats for it. Young animals fed on a diet of highly
purified food materials in which lard is the only kind of fat may seem
fairly well but do not grow normally, while those fed the same diet in
every respect except that the lard is replaced by butter grow as young
animals should and are more resistant to disease. Study of other food fats
shows that they may be divided into two groups, one with this growth
promoting property and one without it. In general, the vegetable oils do
not have it, while butter and beef oil do; on the other hand, lard does
not have it, while the oil from corn does. Careful analysis of the
situation has shown that a fat-soluble vitamine is present which can in
the laboratory be separated from the fat. This same vitamine is present in
a variety of food materials--in whole milk, in egg yolks, in leaves of
plants--but we have not studied it long enough to know just how much
spinach we can substitute for a tablespoonful of butter so far as the
vitamine is concerned. We must await further investigations. But we may
rest assured that with a fairly liberal amount of milk and some green
vegetables, possibly some beef fat, we need not fear any disastrous
consequences from the substitution of some other fat for butter. Where the
diet is limited and the entire quantity of fat is not very large, it seems
prudent to select oleomargarine made largely from beef oil and, where
circumstances permit its use without the sacrifice of any other dietary
essential, to use butter in the diet of growing children unless they get a
full quart of milk apiece a day.

Changing our food customs is difficult because it means also changing our