Nutrition and aging.

We're all getting older. But do we have to feel old? Or can good nution keep us functioning like 20-year-olds? (Okay, 30-year-olds.)

In 1977, Congress decided that it was time to find out. It established the U.S. Department of Agriculture's Human Nutrition Research Center on Aging at Tufts University.

More than a decade later, researchers at the Center have found some answers to questions about nutrients and aging. This month, NAH's Bonnie Liebman interviewed four of the researchers by telephone.

GASTROINTESTINAL TRACT 

Q: How does age change the GI tract?

A: One common condition is atrophic gastritis, or the inability to secrete sufficient stomach acid to kill bacteria. So ingested bacteria are no longer killed and they reside in the stomach and the upper most part of the small bowel. It affects about 20 percent of people aged 60 to 69 and 40 percent of people over 80.

Q: What harm does it do?

A: People aren't sick with it. But we've found that bacteria interfere with the absorption of vitamin B-12. If you put these people on antibiotics to reduce the numbers of bacteria, their B-12 absorption returns to normal.

The answer isn't to treat people with antibiotics, but to see if these people need to ingest more vitamin B-12 to overcome the bacterial binding.

Q: What happens if you're deficient?

A: A deficiency of B-12 that isn't severe enough to show up in the blood can be associated with psychiatric dementias. A number of elderly people may be written off as victims of Alzheimer's or senile dementia. They are not oriented to time or place; they don't recognize people. A deficiency can also cause neurological symptoms, such as tingling or abnormal gait.

But these people go back to normal with vitamin B-12. I worry that a large population of older people in nursing homes and at home are not functioning well, and they're not being picked up.

Q: If your uncle had dementia, would you give him B-12?

A: First, I'd check his blood B-12 level. If it were high-normal, I wouldn't worry about it. If it were low-normal, I'd have an assay done for homocysteine and methyl, which build up in the tissues and blood when there isn't enough B-12. The problem is that most hospital laboratories aren't set up to measure them. It costs about $150.

Or, I'd give him standard 1000 microgram injections of B-12 for several months and check his neurological progress.

Q: Why not B-12 supplements?

A: The crystalline form is absorbed well, but I'd hate to make a general recommendation, because you might miss people with pernicious anemia, who can't absorb any form of vitamin B-12 from the GI tract.

Q: Does B-12 deficiency have other dangers?

A: High homocysteine levels are also linked epidemiologically to cardiovascufar disease. We don't know if homocysteine is toxic, but children who are born with high levels because of a genetic defect the very early of heart attacks and strokes.

Q: Are older people worse at absorbing other nutrients?

A: Surveys show over and over again that older people are deficient in vitamin B-6. It's been blamed on low intake, but B-6 is ubiquitous in the diet, so we guessed that it was probably a change in the absorption or utilization, and sure enough, it took about 20 percent more B-6 to bring levels up to normal in depleted older people than in depleted younger people.

So the present RDA [Recommended Dietary Allowance], which is the same for people over and under age 51, is insufficient, and that might have a big impact on programs like Meals on Wheels.

Q: Are other RDAs too low for older people?

A: The present RDA for riboflavin is lower for people aged 51 and older because it's linked to decreased calorie intake. But we just found that older people need as much as younger people.

The main source of riboflavin is milk, which is also a good source of protein, calcium, and vitamin D. But riboflavin is easily destroyed when the milk is packaged in plastic containers, particularly when it's sitting under bright lights in the store. Cardboard containers are more likely to preserve the riboflavin.

Q: Are any RDAs too high for older people?

A: Vitamin A may be too high. I'm concerned about older people taking vitamin A supplements over long periods of time. In one study, high blood levels of vitamin A esters were related to higher levels of transaminases in the blood. Those enzymes are a measure of liver damage. The levels were all still in the normal range, but that study followed people for only three years. We don't know what happens if people take vitamin A from age 60 on.

Q: Why are older people at risk?

A: Their livers are less able to clear the vitamin from the body. If you give people in their 70s the same dose as people in their 40s, the older group gets higher blood levels.

Q: Should older people avoid vitamin-A supplements?

A: Unless they have bizarre eating habits-such as eating liver every day--it's probably safe to take the USRDA, which is 5,000 International Units (IU). In contrast, there is no toxic potential for betacarotene, which the body can convert-- although inefficiently--to vitamin A.

Q: Do you recommend other supplements for older people?

A: If they're worried for any reason or if their diet is not varied or if they're on medications that reduce their appetite, yes. I used to be against supplements because people could use them as an excuse for poor dietary habits. But I'm quite convinced that non-milk-drinkers need a vitamin-D supplement, and many people don't get enough folate or vitamin B-12. So I tell my patients, and my parents, to take a supplement with no more than the USRDA.

Q: Do you take supplements yourself?.

A: No. I'm not old yet. I do take betacarotene because of its anti-cancer potential.

BONES

Q: Do older bones have different nutrient needs?

A: We've studied calcium in women aged 50 to 70. Within the first five years of menopause they were resistant to benefit. But women six years or more past menopause were responsive.

Q: How was there "response"?

A: If they were eating 400 milligrams or less of calcium a day--that's half the RDA---and we increased their intake to the RDA, they had a reduction in the rate of bone loss from the spine, hip, and forearm. According to a national survey, half of postmenopausal women consume less than 475 mg of calcium.

Q: Have you studied men and premenopausal women?

A: No, hut there's not a lot of bone loss going on in those people, so the benefit is probably not as great.

Q: Are other nutrients critical for older bones?

A: We're trying to see if vitamin D insufficiency contributes to bone loss. Vitamin D works by helping the body absorb calcium. In the calcium trial, we saw that postmenopausal women with low intakes of vitamin D had higher parathyroid hormone (PTH) levels in the winter.

Q: How does that harm their bones?

A: PTH draws on calcium reserves in the bone to keep blood calcium in the normal range. So as PTH rises, more calcium is taken out of the bones.

We put all of our postmenopausal women on 400-milligram calcium supplements, and randomly assigned half to a placebo and half to 400 IU of vitamin D a day. In the winter, women in both groups lost bone from the spine, but the vitamin-D group lost half as much and showed an overall benefit.

Q: Don't we get vitamin D from sunshine?

A: At our latitude here in Boston--42 degrees north--winter sunshine isn't effective in stimulating vitamin-D production in the skin. Between October and March, the angle of the earth is such that the ultraviolet UV-B rays don't reach our skin. So we're totally dependent on dietary vitamin D.

Q: Does being older make it worse?

A: Yes. Older people are less mobile, so they're outside less. Even in the summer, they have lower blood levels of vitamin D. And levels are very low in nursing home residents.

Also, the skin gets less efficient at synthesizing vitamin D as we age. The concentration of compounds that are turned into vitamin D is lower. But we need relatively little, so it's hard to tell how important that is.

And at least one study says that older people don't absorb vitamin D as well from food, but the details haven't been worked out. Considering all of these factors, older people are more likely to be deficient in vitamin D.

Q: Do you recommend supplements?

A: you can meet your calcium and vitamin

D requirements by drinking four glasses of skim milk a day.

Q: What about non-milk-drinkers?

A: I use supplements if necessary to raise vitamin-D levels to the midpoint of the normal range in my patients in the bone clinic. But I'm not willing to make recommendations beyond that.

VISION

Q: How does vision decline with age?

A: The two major problems are cataracts and age-related degeneration of the macula, which involves damage to the retina. Cataracts that are severe enough to interfere with vision occur in about 5 percent of people aged 55 to 64, 18 percent of people 65 to 74, and 49 percent of people 74 and older. Essentially, everyone gets them if they live long enough.

Macular degeneration occurs in approximately six percent of persons over 65 years of age.

Q: Is there any treatment?

A : A lens with a cataract can be surgically removed from the diseased eye and replaced with a plastic lens implant. It's effective, but it's also costly, and people have to go through the discomfort of having poor vision for years before the cataract becomes severe enough to remove.

There is no real treatment for retinal damage. It is the most common cause of blindness in older Americans.

Q: How about prevention?

A: There is no known way to prevent either disorder. But more evidence is accumulating that both can be delayed, especially cataracts, with antioxidants: the carotenoids and vitamins C and E.

Q: What kind of evidence?

A: Like old metal pipes that become rusty, or oxidized, the lens is damaged by light and oxygen, possibly in combination. But the lenses of animals fed high-vitamin-C diets are protected.

In humans, it's hard to find two studies that say the same thing, but most show that the higher the antioxidant intake, the lower the risk of cataracts.

Q: Is there a level above which you get no additional protection?

A: Yes. I think that for vitamin C it's less than 500 milligrams per day. For vitamin E and carotenoids, we don't know. And for macular degeneration, the evidence is even less clear.

Q: What foods or supplements do you recommend?

A: A prudent diet rich in fruits and vegetables, and if one wants to take a supplement, that's not a silly idea. I'm reluctant to say how much of what until we have the results of the intervention trials that are currently under way.

Q: What do you take?

A: I take 500 mg of vitamin C, 400 IU of vitamin E, and 10,000 IU of beta-carotene.

It can't hurt, though it may not help because my diet is pretty good anyway.

IMMUNE SYSTEM

Q: Does immune function decline with age?

A: Yes. The major change is that the action of T-cell lymphocytes goes down, starting at about age 20. T-cells defend against virus and tumor cells and provide help for other white blood cells to fight against bacterial invasions.

Q: Can certain nutrients slow the decline?

A: We've found that vitamin E--800 IU a day--enhances the immune response in older people. But we don't know if you need 800 IU. We're trying to find the lowest level that works. And we're studying other antioxidants. So far we've seen an improvement in the immune system of animals given glutathione, an antioxidant made by the body. We're testing beta-carotene in humans, but we don't have results yet.

Q: Why should antioxidants help?

A: The cells of the immune system have a high content of polyunsaturated fatty acids in their membrane, or outer wall, and these fats are susceptible to oxidation. The membrane is crucial for immune response. It recognizes and binds foreign compounds, and is the vehicle through which ceils of the immune system communicate with each other.

Q: Do other nutrients affect immune cells?

A: Yes. Proteins, vitamins, minerals, and fats. For example, fish oil seems to decrease the immune response in older subjects. We've been feeding older people 2.4 grams a day of omega-3 fatty acids. The fish oil may be acting as a pro-oxidant or may be affecting their immune systems through some other mechanism. We don't know.

Q: So should fish oil-takers take antioxidants?

A: Yes. If you want to take fish oil, you should get one with vitamin E.

Q: Should people take supplements?

A: Use of some supplements by some population groups might be appropriate, but we don't know enough to recommend a specific level of vitamin E supplementation. Until we do, people should eat a balanced diet that includes fruits and vegetables that contain antioxidant nutrients.

Q: What future studies are planned?

A: We've seen improvements in the immune system as measured by blood tests. The next question is, does it translate into increased resistance to disease? We know it does in animals, but we need field trials in humans.