At 57, Tina Turner posed for pantyhose ads. Whether or not she's gone under the knife, you can't chalk it all up to plastic surgery. There's been a remarkable revolution in our ideas about aging. Many Americans are exuding tremendous vitality at a time of life that would have been unimaginable to their grandparents. In fact, most of us hit our stride at an age that would astonish previous generations.

Scientists have also learned that age is not just measures by the calendar. It's now know that the most feared part of aging - that dreaded slide into frailty and dependence - has more to do with biology than chronology. And your biology, in turn, is shaped both by your genetic makeup, which you cannot control, and your lifestyle, which you definitely can.

"You can influence and control your biological age by the way you conduct your life. You can add years to your active life with the right kinds of habits," says Irwin H. Rosenberg, MD. Especially your eating habits.

News From the Epicenter of Aging

Dr. Rosenberg should know. He's the director of the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) at Tufts University in Boston. The center - one of six research institutes sponsored by the United States Department of Agriculture - is the only one devoted exclusively to studying the links between nutrition and aging.

Since research on aging began in earnest in the 1980s, some of the most significant findings in the field have come out of here. Granted, they haven't discovered Ponce de Leon's dream: a wellspring of eternal youth. But they have come to an important conclusion: All of our various body parts and biological processes don't age in the same way. Rejuvenation then comes from drinking from not one Fountain of Youth, in a sense, but many fountains.

Now, seven years later, Dr. Rosenberg has more good news. The latest research seems to be uncovering two important new biomarkers: 1.) our brains, and 2.) our immune systems. Eating the right foods may help us to keep our minds clear, quick, and sharp and help to fight off disease for a long, long time.

Brain Power Forever

Last year's headlines brought news of a previously unknown risk factor for heart disease: homocysteine. This amino acids, when present in the blood at elevated levels, is suspected of damaging artery linings, making them more susceptible to artherosclerosis. Because of that, homocysteine may be a trigger that causes 10% to 15% of all heart attacks.

What you may not have read is this: High homocysteine levels may affect your brain as well as your heart.

It's been known for some time that arteries occluded by cholesterol can lead to strokes, and that strokes, large or small, result in cell damage that affects normal brain function. (It also affects speech, gait, and memory, depending on where in the brain the stroke occurred.) It's also known that the B vitamins play an important role in nervous system function. When the human brain sputters along without adequate amounts of B vitamins, disorders like depression and dementia may be the unfortunate result.

But are there subtler forms of nutritional deficiencies that may not result in such outward, obvious signs? Does nutrition influence cognitive function in normally healthy people? Those are the key questions, and the scientists here are beginning to tease out some answers. The first puzzle piece was picked up in the early 1990s, when a team of HNRCA researchers, led by Dr. Rosenberg, looked at the 1,041 surviving elderly people from the famous Framinham Heart Study. They found an association between high homocysteine levels and gunked-up carotids-the arteries on either side of your neck that carry oxygen to the brain. So it's entirely possible that the brain cells of people with high homocysteine levels are not getting an ample supply of nutrients.

Then researchers Karen Riggs, PhD, and Avron Spior III, PhD, added another finding. When they gave 70 elderly veterans a battery of cognitive tests, they saw an association between low levels of vitamin B6 and folate and high levels of homocysteine in the blood - and poor performance on a test called spatial copying, in which the men were asked to copy geometric figures like circle and cubes. "The subjects with the highest homocysteine concentrations performed on average like patients with mild Alzheimer's disease," they wrote (American Journal of Clinical Nutrition, March 1996).

The next step in the research will be to conduct MRI scans on people with high homocysteine levels and poor cognitive test scores to see whether, basically, they suffer from blobs of dead brain cells. "We know there's something happening in the brain, but we don't know what the homocysteine is actually doing," says Dr. Riggs. "We'll have to find out what's happening at the levels of the brain cell to tie together these two findings."

The science here may be confusing, but at least it boils down to some easy nutrition advice. Homocysteine levels are kept in check by adequate amounts of vitamins B6, B12, and folate in your daily diet. Aim for the Daily Values: 2 milligrams (mg) of B6, 0.4 mg of folate, and 6 micrograms of B12. To get what you need, make foods rich is these vitamins a part of your healthy diet and, as Prevention recommends, consider taking a multivitamin to make up for any shortfall.

"Cognition is a particularly complex area," says Dr. Riggs about her chosen field. But it can yield tantalizing evidence - like the findings contained in a chart taped to her office door. At first glance, the chart, obscurely titled "Survival by Quartile of Gs," means nothing. All is shows is three downward-trending lines. But to Dr. Riggs, it means plenty; The three lines represent the death rates of men who took part in a veterans' study back in the 1960s. It shows that the men who were the fastest at taking various perceptual and motor speed tests (such as plugging pegs into holes) are the most likely to be alive today,: 88% of them in fact. Whereas, of the men who were in the slowest fourth of the group 29 years ago, only 52% are alive today.

"Whatever was affecting their brain function was starting to show up 30 years ago," Dr. Riggs observes. Could it be that degenerative diseases sneak up in a doctor's diagnosis of heart disease or high blood pressure? That's a lifetime of scientific inquiry, right there.

Super Immunity Plan

One of the 16 laboratories at the center is the Nutritional Immunology Laboratory. This is where Simin Nibkin Meydani, DVM, PhD, investigates the role of nutrients in boosting the immune system - the body's natural line of defense against viruses, bacteria, and tumors. The problem is, the whole system gets out of whack with age. "It actually becomes dysregulated," says Dr. Meydani. When that happens, we have less resistance to disease.

Like most scientists, Dr. Meydani has spent years finding out what doesn't work; a recent study of black currant seed oil, for instance, found no immune boosting effect. But she is excited about her current work on a more commonly known nutrient: vitamin E.

Vitamin E is necessary to the body, although cases of deficiency are rare in Western cultures because we get it in our high-fat diets. Nonetheless, for decades, some people have consumed supplemental amounts in the form of vitamin E capsules, cased on their own hunches rather than any clinical scientific evidence, which was virtually nonexistent.

Then, in the 1980s, scientists realized the key role played by vitamin E as an antioxidant. It soaks up free radicals, which are produced by the interaction of oxygen and fats in the body. In doing so, it protects the cells of the immune system from damage. Now that the mechanism is understood, says Dr. Meydani, "It makes sense why vitamin E would enhance the immune system." (It's also possible that vitamin E protects artery walls from getting gunked up with cholesterol.)

Dr. Meydani had two major studies published in 1997. In one study of 88 elderly people, those who took vitamin E for four months showed greater immune system response, as measured by antibodies in the blood, than those who received only a placebo. (The optimum level was 200 IU per day; many times above what is possible to get from food.) (Journal of the American Medical Association, May 7, 1997.) A second study, in which old mice were given megadoses of vitamin E, showed that the daily supplement offered some protection against an influenza virus. Notably, this study was the first in which "a higher than adequate intake of a nutrient has demonstrated a beneficial effect on influenza in animals" (Journal of Infectious Diseases, July 1997).

So Dr. Meydani appears to be one study away from saying conclusively that vitamin E supplements - beyond what you'd get from a healthy diet - do indeed enhance the older person's resistance to infectious disease. And that one study is under way. It involves 634 residents of nursing homes in the Boston area. It will test the effects of vitamin E supplementation on flu infections. Final results are three to four years away. In the meantime, Prevention recommends a supplement of 100 to 400 IU of vitamin E per day.

Secrets of age-stopping

Nutrition science moves forward by little steps that add together to develop a picture," says Dr. Rosenberg. Here are some components of the big picture as they have begun to emerge.