The Nature of Nutrients

It sounds like a simple question of logic. If bones require calcium, then people who eat a lot of calcium-rich dairy products should have extra-strong bones, right? So why are hip fractures uncommon in Singapore, where adults don't drink milk, while they soar in dairy-loving Scandinavia? "Countries with higher calcium intakes have the highest fracture rates, not the lowest," says Dr. Walter Willett, chair of nutrition at the Harvard School of Public Health. It's the Calcium Conundrum.

Scientists have identified nearly 40 vitamins and minerals that the body needs for various tasks, from shoring up bones to bolstering the immune system and repairing cellular damage. But as the Calcium Conundrum suggests, they work more subtly than drugs. Instead of delivering predictable effects at particular doses, they team up in complex ways that we're just beginning to understand. Forgo your daily orange for a vitamin C pill, and you will miss out on other compounds that protect the heart, fight cancer and combat infections. "You can't just pop vitamin E over hot-fudge sundaes and expect to get any benefit," says nutritionist Alice Lichtenstein at Tufts University.

But don't mistake the subtlety of these compounds for a lack of power. Exciting new findings are pouring out of the nation's research labs, linking long-neglected nutrients to everything from brain function to cancer risk. And it's increasingly clear that, despite our abundant food supply, we're still getting too little of some crucial vitamins and minerals. Here are some of the latest insights on how eating well can help us live well--and target some of our most common dietary deficiencies.

CALCIUM as it turns out, this mineral really is critical to bone strength. But as scientists are now learning, it doesn't work by itself. Healthy bones require a mix of calcium, phosphorus and magnesium. They also need adequate protein to form their basic framework, vitamin K to maintain structural proteins and two other bone strengtheners that we're probably even shorter on than calcium: vitamin D (for calcium absorption) and exercise (to stimulate bone-building cells). Put it all together, and one potential explanation for the calcium paradox jumps out. Though doctors say genetic differences are partly responsible, vitamin D levels must be playing a role too. If you consider that we get most of our vitamin D from sunshine striking the skin, it's logical that people who live near the sun-drenched equator absorb their calcium better and suffer fewer bone fractures.

But calcium does more than build strong bones. It is crucial for transmit-ting nerve impulses and maintaining a regular heartbeat. It stimulates hormone secretions and activates enzymes. It may even help protect against colon cancer. And most people could stand to consume more. "Only half of Americans are getting the required amount," says Dr. Felicia Cosman of the National Osteoporosis Foundation. Recommended intake is 1,000 milligrams a day for adults--1,200 for women older than 50 and 1,300 for teens.

VITAMIN D when epidemiologists Cedric and Frank Garland began mapping the incidence of colon cancer in the United States back in the 1970s, they noted a curious pattern. People in the South were half as likely to die of the disease as those in the Northeast. Could the reason be the sunshine vitamin--D? Since then the research has grown, linking vitamin D with lower risks of not just colon cancer but also breast, prostate and ovarian cancers. That's not all. People with higher levels of D are less likely to suffer autoimmune diseases, including type 1 diabetes and multiple sclerosis. They may even have less heart disease and better lung function. "I'm not an alternative-medicine nut who says one nutrient is good for everything," says biochemist Reinhold Vieth at the University of Toronto. "But vitamin D might be."

It clearly does far more than aid calcium absorption. Vitamin D helps mobilize and modulate the immune system--which explains its effect on autoimmune diseases. Biochemical studies suggest that it helps keep cells from becoming malignant--and when cells do go bad, it encourages them to self-destruct. Scientists suspect the vitamin has still other functions. "Tissues throughout the body have receptors for vitamin D," says Dr. Michael Holick of Boston University. "Why would they be there if they had no purpose?"

Just how much vitamin D we need is a matter of debate. The government recommends 200 to 600 international units a day, but a growing scientific consensus says that's too low. In a paper last month, the Garlands wrote that 1,000 units a day could cut colon cancer in half and reduce the rates of breast and ovarian cancer by 25 percent. Holick has stirred the ire of his fellow dermatologists by suggesting that the best source in the summer is five to 10 minutes of sunshine on the arms and legs two to three times a week, without sunblock. But in the winter, the sun's oblique rays are not strong enough in many countries to stimulate D production. For help, turn to supplements of vitamin D3, fatty fish and fortified foods, including milk and certain brands of orange juice and soy milk.

OMEGA-3 FATTY ACIDS In 2001 a series of ads appeared in Boston newspapers. "Are you extremely moody? Do you often feel out of control? Are your relationships painful and difficult?" The ads came from Harvard psychologist Mary Zanarini, one of the nation's leading researchers in borderline personality disorder. She was seeking volunteers to test a potential treatment for the ailment--a fish-oil component called EPA.

Fish oil? As medical treatments go, it may sound more like snake oil. But a growing body of research suggests the omega-3 fatty acids in fish oil benefit not just the heart but also a range of psychiatric and neurological problems, from bipolar disorder and schizophrenia to depression, ADHD, Alzheimer's and, yes, borderline personality disorder. The brain is an astonishing 60 percent fat, and it needs omega-3s for optimal function. Studies suggest they help build cell membranes, boost levels of the brain chemical serotonin and increase the number of connections between neurons. "It's like neuronal fertilizer," says Dr. Joseph Hibbeln, a psychiatrist at the National Institutes of Health. "Brain cells given omega-3s grow more synapses."

Omega-3s may even be good for bone. Nutritionist Bruce Watkins at Purdue University has found that they stimulate bone-building cells in the periosteum, the membrane that covers the long bones. --"It's the part that hurts when you bang your shin," says Watkins. "I call it 'the brain of the bone' because it contains a lot of nerve tissue and controls a lot of bone metabolism." Nourish it with omega-3s, he advises, because its bone-building cells lay down the protein matrix on which calcium and other minerals are deposited.

Where can you find omega-3s? Food contains two basic varieties--the short-chain version (called ALA) found in walnuts, flaxseed, canola oil and leafy greens, and the long-chain versions (EPA and DHA) in seafood and omega-3-enriched eggs. The long-chain forms appear to have the greatest benefits, particularly for the brain. The American Heart Association also recommends eating fatty fish at least twice a week for the prevention of heart disease. For patients who already have heart trouble, it prescribes one gram of EPA and DHA a day, from fatty fish or supplements.

CHROMIUM unless dietary trends do an abrupt about-face, the world is heading for a dramatic increase in type 2 diabetes. According to the World Health Organization, the global caseload will more than double by 2025--to 300 million, up from 143 million in 1997. Want to avoid becoming a statistic? A good place to start is reducing your intake of white flour and sugar. But emerging evidence suggests you should also consider boosting your chromium.

Why? Scientists have long known that chromium is involved in sugar metabolism. Whenever your body mobilizes stored glucose, it requires chromium to do that. Now research is showing that the mineral may help diabetic and pre-diabetic patients boost their insulin sensitivity by increasing both the number of insulin receptors on cells and the activity of those receptors. "In almost every study where we gave chromium, we got better control of glucose with less insulin," says biochemist Richard Anderson at the USDA's Human Nutrition Research Center in Beltsville, Maryland.

Since we need only trace amounts of chromium, it should be easy to get enough from the diet. Yet research suggests that many of us are falling short--perhaps because we're eating so many refined carbohydrates. So try consuming more chromium-boosting broccoli, apples and other produce while cutting down on chromium-depleting sugar. As a fallback, consider a supplement of chromium picolinate. (Multivitamins contain chromium, but in a less absorbable form.) The current recommendation is 25 to 35 micrograms a day, but trials have used 200 or more.

POTASSIUM potassium gets almost no press, yet it's remarkably effective at lowering blood pressure--and even a 1 to 2 percent reduction translates into a reduced risk of strokes. Potassium also helps prevent kidney stones and heart arrhythmias. It even appears to benefit bones by neutralizing acids in the bloodstream that leach calcium from bone deposits. "Unless you have kidney disease, potassium is one of those things, like love and money, that you just can't get too much of," says University of Mississippi physiologist David B. Young.

The current guidelines call for 4,700 milligrams a day, but most people don't even get close. It's not that hard. A single cup of sweet potato has 950 milligrams. Four figs boast 540; a cup of cantaloupe, 500, and a glass of OJ, 450. "If you can consume 8,000 milligrams a day in your diet--the level we evolved to eat--chances are you'll get everything else you need, too," says Dr. Steven Pratt of San Diego's Scripps Memorial Hospital. That would include fiber and thousands of beneficial plant chemicals, such as the cancer-fighting compounds in broccoli.

In the end, there are few shortcuts to optimal health. Much as we would like to rely on pills, fitness requires regular exercise and a healthy diet--one that's rich in fruits, vegetables and whole grains, along with smaller amounts of fish, nuts and dairy. "The amazing thing is, the same dietary pattern helps everything from cancer to heart disease and diabetes," says Lichtenstein. There's no conundrum there. Bring on the vegetables.