PHILADELPHIA — In the wake of the mixed results from the most ambitious, definitive study of postmenopausal women's health ever conducted, what's a woman to do?

That's the question now that the federally funded Women's Health Initiative has wrapped up. It took 15 years, $725 million, 40 medical centers, and the steadfast participation of 161,000 American women ages 50 to 79.

The WHI set out to test strategies touted as ways women could ward off cancer, heart disease, osteoporosis and Alzheimer's disease — "the major causes of death, disability and frailty in older women of all races." Could hormone supplements fight these chronic diseases? Could a low-fat diet rich in fruits and vegetables? Could calcium and Vitamin D pills?

The WHI's hormone trials, which began reporting results in 2002, shattered conventional wisdom, reversed doctors' advice, and turned off the flow from cash-cow hormone products. The results of the diet and calcium/Vitamin D trials, published this month, are also surprising and controversial.

Still, translating the WHI into helpful advice is tough because the results are complex and reveal more about what doesn't work than what does. The bottom line:

Estrogen-progestin hormone therapy raised the risk of breast cancer, heart attack, stroke, dangerous blood clots, dementia, and incontinence, while cutting the risk of hip fracture and colon cancer.

Estrogen alone — only for those who have had a hysterectomy — had no significant effect on the risk of heart disease, colon cancer, dementia and breast cancer, but raised the risk of stroke and blood clots in leg veins. It cut hip-fracture risk.

A reduced-fat diet rich in fruits and vegetables had no significant effect on the risk of breast cancer or heart disease. It reduced the chance of developing polyps, a precursor of colon cancer, but did not reduce colon cancer.

Calcium/Vitamin D supplements had no effect on colon-cancer risk. It increased hip-bone density, but had no impact on hip fractures.

"The media like to boil down a complicated thing to a sound bite," says Marcia Stefanick, a Stanford University obstetrician-gynecologist and WHI researcher. Scientists "don't know how to do sound bites. It's been frustrating for us and confusing for women."

While the WHI results are sure to be dissected and debated for years, some lessons and recommendations are already clear, researchers and participants agree. Among the messages:

Don't rely on circumstantial evidence. Before the WHI, studies of women's health habits consistently found that those who took hormones had less heart disease and lived longer than women who opted not to.

These "observational" studies were bolstered by other circumstantial evidence. For example, unlike men, women rarely suffer heart attacks before age 50, when their estrogen plummets.

The problem was, hormones weren't making women healthier — rather, healthier women were taking hormones. They avoided such no-nos as smoking, drinking and getting fat.

In 1991, the government finally agreed to do what no one had done before: test the mantra with a "clinical trial." The WHI randomly assigned 27,300 healthy postmenopausal volunteers to take hormones or not, then followed them to see whether it helped their hearts, or other organs.

The rest is medical history.

As for diet and calcium/Vitamin D, the WHI does not have such clear advice because the results of these trials were "disappointing," as many WHI researchers put it.

That doesn't mean women should ignore current dietary and calcium recommendations. It's just that the benefits of avoiding fat and boosting calcium by 1,000 milligrams a day were so modest that they could be due to chance — they were "not statistically significant."