If you're concerned about your health, chances are you're feeling confused of late—especially if you're a woman. In the wake of findings in 2002 that had even the experts flip-flopping over hormone-replacement therapy (HRT), two more major studies have questioned the value of widely recommended measures targeting women: calcium pills and vitamin D to prevent broken bones, and low-fat diets to ward off heart disease and breast and colon cancer.

But don't throw up your hands just yet and go whole hog, so to speak, on a steady diet of cheeseburgers, chips, and cream puffs. Nobody is suggesting that diet makes no difference, not even the study's authors. In fact, as well as prompting renewed examination of near-religious beliefs about nutrition and health, the findings have sparked a debate about how far rules can be stretched when it comes to measuring results.

The studies in question were part of the U.S. Women's Health Initiative, which was also responsible for the controversial HRT findings. The research on low-fat diets, which included 49,000 women from ages 50 to 79, demonstrated that overall, after eight years, these diets had no effect on the rates of breast cancers, strokes, heart attacks, or colon cancer. The calcium-and–vitamin D study of 36,000 women found that taking supplements for seven years did not prevent broken bones or colorectal cancer, but did produce a one-percent increase in bone density in the hip.

Yet in the February 19, 2006, issue of the New York Times, Dr. Jacques Rossouw, project officer for WHI, advised women on low-fat diets to persist and urged women whose fat intake is high to bring it down. As for calcium and vitamin D, Rossouw said the study results had enough hints of benefit that women who don't get sufficient calcium in their diet should take supplements.

That certainly seems at odds with the study findings, but it depends on how you interpret the data. According to standard research methodology, the difference in results between two comparison groups (see sidebar) has to be a certain size to be statistically significant. The dietary-fat study found a nine-percent reduction in breast-cancer risk in the low-fat-diet group, whereas 10 percent would have been meaningful. Rossouw said if the study had gone on longer, its results might well have become significant.

Statistical interpretations aside, the study had other limitations. There wasn't enough variation in fat intake between the comparison groups, points out Dr. Greg Hislop, a senior epidemiologist at the BC Cancer Agency. “Everyone was eating similarly,” he said during a telephone interview with the Georgia Straight. “And there was no follow-up to ensure adherence to the diet.” In fact, participants were supposed to cut their fat to 20 percent of their daily calories, but on average they only got to 29 percent.

The calcium study, too, had pitfalls, according to Diana Steele (right), a registered dietitian with Vancouver company Eating for Energy. “If not controlling for type of supplement and quantity, or whether the participants smoked or drank, which inhibits the absorption of calcium, the results are not conclusive,” she said by phone.

Steele continues to urge her clients, particularly those over 50, to get up to 1,500 milligrams of calcium a day. Because supplements need to be taken together with vitamin D to ensure proper absorption, she suggests that for maximum effect, people try to get their daily dose of calcium from foods. Milk, fortified soy and rice beverages, dark-green leafy veggies, canned salmon with the bone in, sesame seeds, and yogurt are all good sources of the bone-building micro-nutrient.

So don't give up on the salads and supplements yet. But allow for the odd side of fries or helping of doughnuts. Because in the end, the only firm conclusion one can draw from these studies is that staying on a diet is never easy.