What These Changes Mean for Nutrition

From the nutritional point of view, it is important that figures on food consumption be translated into terms of calories, protein, minerals, and vitamins. The figures indicate the extent to which available food supplies, if equitably distributed, would provide for the nutritional needs of the population. They show how shifts in consumption have altered the nutritive value of the national diet over the years.

Calories. There has been little change in the calories provided by the per capita food supply between 1909 and 1945, except that during the depression years in the 1930's calorie averages were rather low. The lowest figure, 3,170 calories for each person a day, occurred in 1935. At that time the purchasing power of many families was low and the drought of 1934 brought smaller supplies of some foods. But even this level is higher than the prewar consumption in most countries.

All foods contribute some calories to the diet. Therefore a study of the proportion of the total calories coming from different groups of food is one way of seeing the effect of shifts in consumption over a period of years. The upward trends in consumption of milk, of citrus fruit and tomatoes, and of green and yellow vegetables are reflected in their contribution of calories. Likewise the downward trends in consumption of grain products and of potatoes are clearly apparent.

Protein. The amount of protein in the per capita food supply declined slightly from 1909 to the middle 1930's, a result of lowered consumption of grain products and meats. Since 1935, the year of the lowest average, the protein content of the diet has increased because of higher consumption of milk, of meat, poultry and fish, and of dry beans, peas, and nuts.

Fat. The amount of fat, visible plus invisible, in the over-all food supply has been increasing, partly because of larger supplies of fats as such and partly because of increased consumption of milk.

Calcium. Probably the most striking trend in the nutritive value of the national diet is the increase in calcium that has occurred during the 37 years of this series-1909 to 1945. This trend parallels closely the increase in milk consumption, since from two-thirds to three-fourths of the calcium in the diet has come from milk. For no other food is there so direct a relationship between its consumption and the average quantity of a single nutrient in our diet.

Iron. Trends in the iron content of the national diet reflect changes in consumption of grain products and meats, which together furnish nearly half of the total iron. Because the consumption of both of these groups declined between 1909 and 1935, per capita supplies of iron decreased also. There was little change during the 1930's, but a marked increase occurred after 1941 when meat consumption went up, and especially after flour and bread began to be enriched with iron and some of the vitamins.

Thiamine (Vitamin B,). Nearly a third of the thiamine in the food supply comes from meat. Pork is an especially rich source. Trends in the thiamine content of the diet follow very closely the trends in meat consumption. Whole-grain cereals are excellent sources of thiamine but most of the grains used in this country during the period were highly refined. Therefore, this food group contributed only about a fourth or less of the total thiamine. The enrichment of flour and bread introduced during the war had by 1944 brought up the thiamine contribution from grain products to about a third of the total. As a result of this program the average thiamine content of the per capita food supply in 1943, 1944, and 1945 is estimated to be about one-fourth higher than it would have, been without enrichment.

Riboflavin (Vitamin G). This vitamin is often too low in American diets. Nearly half of the total quantity in the food supply comes from milk and from 15 to 20 percent from the meat, poultry, and fish group-The average amount of riboflavin in the diet showed little change between 1909 and 1939 or 1940 when the gradual increase in milk consumption was partly offset by a decline in meat. Between 1940 and 1945, however, the riboflavin in the diet increased almost one-third following the rapid rise in milk consumption, the enrichment of grain products, and some increase in meat consumption.

Niacin. The amounts of niacin available for consumption throughout the years of this study have followed the same trend as protein, iron, and thiamine. Since nearly half of the total comes from meat, the average quantities decreased from 1909 to the late 1930's; they increased during the war years because of greater supplies of meat, poultry, and fish and the enrichment of grain products.

Vitamin A value. The increase in consumption of green and yellow vegetables is one reason for the larger amounts of vitamin A available, especially from 1941 to 1945. More whole milk, also a source of vitamin A, was consumed and victory gardens supplemented market supplies of vegetables.

Ascorbic acid (Vitamin C). Nearly all the ascorbic acid in the diet comes from vegetables and fruit. Therefore, any changes in consumption of these foods are reflected in ascorbic acid values. From 1909 to the middle 1930's, there was a slow upward trend in vitamin C values. From then on, however, the increase was spectacular. A large part of this increase came from the larger quantities of citrus fruit and tomatoes; part of it came also from green and yellow vegetables.