Nutritional Needs After 25

PEARL SWANSON.

MANY of us are aware of the changes in appearance, mental outlook, and body functions that occur as we pass from youth into middle age and then into old age.

Behind the outer changes we see in people as they grow older are changes in the body and in its workings. We know now that some of the adverse changes are due not to aging as such but to impaired nutrition of body cells so they cannot do the job they have to do.

We have to think therefore of an adult's nutrition in terms of the past, the present, and the future. His nutritional state at any specific age reflects his current food practices and all his previous dietary history. Poor eating habits in early life leave their imprints some correctable, some non-correctable in later years.

And, conversely, the nutritional state at any one interval foretells what kind of individual a person will be, nutritionally speaking, 10 or 25 or 40 years hence.

A good diet throughout one's life consequently is an insurance that carries many benefits. Good eating habits in early life will bring us a vigorous maturity. A continuance of them will extend our years of usefulness and delay and, in some instances, even prevent the appearance of many of the so-called characteristics of old age.

The older a person grows, the longer and more complex is his dietary history. The variations in nutritional status and dietary needs of a group of adults thus are bound to be greater than corresponding variations in a group of young people. Recommendations for the food needs of this age group must be pointed especially to the needs of individuals.

The same nutritional principles that describe adequate diets for earlier periods of life apply to the diets of adults. Even though the adult has grown up matured his basic food supply still must provide all the nutrients necessary for maintaining body structure and for operating its machinery.

The difference between these processes in the mature and the young person is largely one of intensity. Preserving the integrity of body tissue replaces the more active processes of growth and maintenance characteristic of youth. Some metabolic activities are slowed, and food needs decrease. There may be less demand for nutrients used in the manufacture of important substances in the body that control and regulate metabolism.

The adult's diet nevertheless must still supply all the energy-producing foods, the protein-rich foods, and the vitamin- and mineral-carrying foods.

The approximate amounts of food energy and nutrients essential to adult well-being in the United States have been estimated by the National Academy of Sciences-National Research Council for persons of different ages and activity. The recommendations apply to the needs of groups of people and take into account the variations among people in any group. They are generally higher than average requirements, for they include a margin of safety.

For that reason we must use these dietary allowances carefully when we try to assess an individual's nutrition. A diet pattern that provides over a period of time a substantially lower amount of any nutrient than recommended, however, is likely to be inadequate for many individuals.

ESTIMATES of how well people are eating are based on knowledge of what they are eating. This information has been obtained from surveys of food intakes of various groups of adults.

A food survey is a research device designed to get a comprehensive picture of what a number of persons, typical of a special group, eat.

Sometimes they were interviewed by the investigator and reported the kind and quantity of food they had eaten during the 24-hour period just preceding the interview. Sometimes the individuals kept records of the food they ate for a week or 10 days. Sometimes they weighed all food they ate for a definite period. Or again, they provided information in terms of a "diet history," in which the investigator established the kind and amounts of food customarily eaten over a period of time.

The data describing the food intakes of individuals participating in a survey are averaged, and mean figures are obtained of the amounts of food eaten and the nutrients supplied by the day's diet. A mean value always represents a central tendency and is made up of many values, some of which are high, some are low, and many are intermediate.

The results of eight surveys some statewide in scope, others representative of specific groups in which about 5 thousand persons in various parts of the United States cooperated afford a base for estimating the quality of diets chosen by adults. Mean values for food energy and the various nutrients furnished by the diets of men and women living in different places are remarkably similar, however, when the activity, sex, and age of the persons are taken into account.

In general, men choose diets that furnish nutrients (with the possible exception of calories) in amounts close to the recommended allowances of the National Research Council. The mean nutritive value of men's diets is higher than that of women's diets. All surveys reveal that mean values for calories and calcium fall short of the allowances in diets commonly chosen by women.

Mean data, however, because they are based on a collection of high, low, and middle values, may hide important facts and fail to disclose the real issue in this instance, the number of people having poor diets. Estimates of the proportions of dietaries with specific nutrients lower than the recommended allowances may serve as a first approximation of the extent to which people choose inadequate diets. Data from a survey of food intakes of women in the North Central States in 1948 illustrate this point.

In the five States represented in the survey (2,085 women), the percentages of diets that provided less than the recommended allowances for calories, protein, calcium, ascorbic acid (vitamin C), and vitamin A were 75, 45, 80, 60, and 70, respectively.

The definition of the recommended allowances, however, does not permit us to assume that all individuals whose food contains less than 100 percent of the allowance of any nutrient are eating inadequate diets.

Nutritionists differ in what they consider poor diets. Some feel that the diets that furnish less than three-fourths of a recommended allowance may be very close to inadequacy. Others evaluate them in terms of two-thirds of the recommendations, or even one-half. In the north-central survey, nutritionists used 8o percent of the recommended allowances as the criterion.

On that basis they found that the diets of 68 percent of the 1,072 women interviewed in Iowa furnished less than 80 percent of the recommended daily allowance for calcium. The average daily calcium value of their diets was only 0.32 gram of calcium. The allowance is 0.8 gram a day.

The mean value for the protein content of the diets reported by the women appeared adequate but we found that 29 percent of the diets provided less than 80 percent of the recommended allowance. The women whose diets fell in this group were getting an average of only 33 grams of protein a day.

Similar figures for ascorbic acid were 49 percent and 30 milligrams, respectively; for vitamin A, 63 percent and 2,350 I.U. (International Units).

Data from the other surveys, analyzed in a similar fashion, yield approximately the same figures. They show that the nutrients in which the largest percentage of diets of men and women are likely to be deficient in respect to the allowances are calcium, vitamin A, and ascorbic acid. Thiamine, or riboflavin, or iron may be poorly represented among the diets of some groups. Another analysis, based on a survey in Iowa, suggests that even in this land of plenty a large segment of our adult population may be undernourished, and thousands and thousands of individuals both men and women, but especially women are short changing themselves by eating inadequate diets.

We estimated, for example, that in Iowa in 1948 about 388 thousand women were choosing diets providing less than 0.6 gram of calcium; 129,500 were getting less than 45 grams of protein daily; 333 thousand had less than 55 milligrams of ascorbic acid; and 530 thousand had less than 4 thousand I.U. of vitamin A a day.

The general nature of the inadequacies points up some of the nutritional problems of adults. The more important relate to the energy, protein, calcium, and vitamin requirements.

THE ENERGY VALUE of the food we eat determines to a large extent the good we derive from it.

The diet must provide calories to support the work that the heart and other organs in our bodies always are doing. It also must provide energy for all the chemical reactions going on in our tissues continuously. The number of calories needed for these jobs determines the basal metabolic requirement.

In addition, food also must supply enough energy to cover the calories expended in customary work and play.

A phrase I like very much has been used to describe these needs "the calorie cost of life." This cost varies from person to person and is determined by age, body size, sex, physical activity, and specific dynamic action of food eaten.

How much energy do diets customarily eaten by men and women in our country provide?

The mean energy values of the diets chosen by men in the eight surveys range from 2,600 to 3,400 Calories a day. These intakes are close to the recommended allowances.

The recommendation for a moderately active woman 45 years old weighing 128 pounds is 2,200 Calories. A definitely low caloric value is one of the most striking features of the diets of women. The diets of women under age 70 average about I,700 1,800 Calories a day.

Energy values of this order are of real concern to the nutritionist. Are the low-calorie diets of women associated with a state of undernutrition?

This possibility is suggested by the observation that the diets of many women in some groups, in the neighborhood of 45 percent provide less than two-thirds of the recommended energy allowance. The energy intakes, therefore, in many instances may be only slightly greater than the basal energy requirement, which constitutes one-half to two-thirds of the total need. Daily energy intakes of 1,500 Calories scarcely can cover the basal metabolism and the activities of the day.

That many women may be reducing their calories by too wide a margin is indicated by their comments when they try to tell you how they feel: "I tire so easily." "I am tired all the time." "I have no pep." "I have many headaches."