The Nature of Nutrients

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.