This limited investigation shows that the diet of some miners differs substantially from that of the general population, in that the vitamin A intake is high.
This high intake, which in view of the nature of their work is of considerable theoretical importance, appears to be to some extent conditioned by their manner of working, and therefore less susceptible than might have been anticipated to changes in income.
The largest single source of vitamin A is the butter eaten by the men, which varies from ½ to 1 lb., the higher figure being the more frequent and probably the more representative. The large consumption of butter is associated with a large consumption of bread and, except in certain individuals, probably does not vary greatly from person to person, or from season to season.
The next most important source of vitamin A is liver, but great differences occurred in its intake. Its great value as a food, which could be readily admitted into his dietary, has as yet barely been appreciated by the average miner.
The addition of further quantities of vitamin A to the diet, in the shape of Prepalin, occasioned no discomfort, but produced no material improvement in the miners' power of dark adaptation.
The excellent health of the group of miners investigated and freedom from nystagmus or other defects of vision appears to be good reasons for endeavouring to maintain in the miner a relatively high daily intake of 6000–7000 units of vitamin A.