Macronutrients

How do the elderly handle macronutrients -- fat, protein, carbohydrate? Surprisingly, we have found that, unlike our rat studies, where we have noted diminished pancreatic function with aging, fat malabsorption does not increase with age. Though pancreatic function does decline in the human with age, it remains far in excess of what is needed to digest normal amounts of dietary fat, at least up to 100 g/day. However, at an unnaturally high fat diet, the older person starts excreting increased amounts of fecal fat whereas the young person will not change the percentage of fat in their feces.

The older person can handle normal protein diets just as well as the young person. On an unusually high protein diet, such as 1.5 g/kg/day, the older person does, in fact, begin to excrete more protein (as measured by fecal nitrogen) than does the younger person.

As for carbohydrate, the situation is confusing because good detailed studies have not been carried out. Breath hydrogen can rise, after a carbohydrate meal, because of exposure of the carbohydrate to colonic bacteria. The rise may be attributable to carbohydrate malabsorption but could be explained by the common condition in the elderly of atrophic gastritis which would cause higher amounts of benign bacteria (i.e., swallowed bacteria) to reside in the small intestine.

As we age, there is, on average, a predictable decrease in lean body mass of unknown etiology, primarily skeletal muscle, occurring even if we continue to eat adequately. The decreasing muscle mass contributes to impairment in functionality and undermines the ability to carry out independent tasks necessary to carry on daily living, making the elderly person more susceptible to serious falls. Several studies, using exogenous growth hormone, produced demonstrable increases in lean mass as well as a small but significant increase in skeletal mass. But this is not an appropriate public health response to sarcopenia because of growth hormone's cost and side effects. Instead, we emphasize less technological, but equally effective, strength training exercises. Even the oldest of the old, people in their 90s, can respond to modest exercise programs that provide just as much increase in lean mass as growth hormone and just as much improvement in strength and subsequent protection from falls. Moreover, the exercise program also improves mood for these people (i.e., less depression). The exercise program can benefit debilitated nursing home patients, as well as individuals with a variety of degenerative diseases, including rheumatoid arthritis.

Micronutrients

The older person has an increased vitamin D requirement because (1) decreased exposure to sunlight reduces Vitamin D synthesis, (2) their skin is, compared to a child's, 40% as efficient in Vitamin D synthesis and (3) their kidney is less responsive to converting the inactive form of vitamin D to the active hormonal form, 1,25 dihydroxy vitamin D.

Low dietary intakes present a problem for almost all micronutrients because older people are not taking in as much food as younger people. Though this caloric reduction is appropriate, since activity is lower, it can result in very low levels of vitamins and minerals. The recommended adequate vitamin D intake in a person more than seventy years old was raised recently from 200 to 600 IU per day, which cannot be achieved by food alone. Vitamin D supplementation is almost mandatory. The calcium recommendation has been increased from 1000-1200 mg/day, obtained by drinking or eating the equivalent of three servings of calcium-rich dairy products per day or 8 ozs. of calcium fortified orange juice three times per day. The elderly person is often unable or unwilling to take in these foods, thus, the issue of calcium supplementation for an older person should also be on the physician's mind.

Vitamin B12, when it is bound to food, is not absorbed efficiently in many elderly people due to atrophic gastritis, estimated to affect between 10-30% of the U.S. population over the age of 60. Therefore, many elderly people need to ingest the B12 either in a vitamin supplement or in the form of a fortified cereal. For other vitamins and minerals, we are less certain, although there does appear to be a slightly increased need for vitamin B6 in the older person as compared to the younger person, which is reflected in the new Recommended Dietary Allowances (RDAs). Folate's RDA has been raised not only for elderly adults but also for younger adults, so the level is back to 400 ug/day. Relevant to the elderly is the issue of homocysteine, a sulfur containing amino acid whose blood concentration rises with mild folate depletion. Although controversial, it appears that elevations in homocysteine are an independent risk factor for myocardial infarctions, peripheral vascular disease, as well as cerebrovascular diseases. Folate's other potential benefit is protection against cancer, primarily colorectal cancer. Iincreasing folate up to about 1 mg/day seems to have a protective effect against the development of this common cancer. It is best not to recommend a total daily intake of folate over 1 mg at this point, otherwise there's a risk of either disguising or exacerbating covert B12 deficiency.

The situation for Vitamin A is somewhat different. Vitamin A enters the body in two forms: preformed (from meat and dairy products) and as carotenes from fruits and vegetables. The tolerance of an older person for preformed vitamin A seems to be less than for the younger person because the older person is less able to clear vitamin A from the circulation and put it into storage. As a result, vitamin A, circulating in the blood as retinyl esters, the esterified form of retinol, can build up in the blood and actually be converted to "toxic" compounds. An older person should not take a vitamin supplement that contains more than Vitamin A's RDA. This is particularly important since it appears that there is a thin margin of safety in using vitamin A for the older person. Recently, it has been shown that even taking in twice the RDA of vitamin A can result in increased bone demineralization, exactly what we are trying to fight against by recommending higher levels of vitamin D and calcium in the diet.

The issue of vitamin E supplementation in elderly people remains controversial. There are two potential benefits: fewer cardiovascular events and an improvement in the immune system of the elderly. Results from the large CHAOS trial indicated a reduction in cardiovascular events with 400 mg of vitamin E daily. Studies clearly demonstrate that one can boost the somewhat impaired cellular immune response in the elderly by giving doses of vitamin E at these levels. We recommend supplementation of 200-400 mg of vitamin E/day, although the evidence supporting the beneficial effects of such supplementation is tenuous.

There is one note of caution from a Finnish study, which showed that Vitamin E had no effect in lowering cancer risk and that beta carotene actually increased lung cancer risk among smokers. Though high fruit and vegetable diets are definitely correlated with lower risk of cancers at almost any site you wish to look at, a little beta-carotene, in the form of what is contained in the diet, may be good, while a high supplementary dose may produce unexpected harmful effects. It is generally recommended that people do not take beta carotene supplements at this time.

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