Scientific Update

Popular wisdom and a number of studies have found that calcium supplements can slow bone loss in adults. Does this slowing of bone loss reduce fractures due to osteoporosis? Researchers studied close to 78,000 women and 43,000 men to see if higher intakes of calcium-rich foods during the adult years could reduce their risk of fractures.^1,2

The women were first studied for 12 years beginning when they were aged 34 through 59 years; men were studied for eight years starting when they were 40-75 years old. None of the women had ever used calcium supplements. Both groups reported what they were eating at several times in the study as well as reporting any fractures of the forearm or the hip from low to moderate trauma (like slipping or falling from a low height). This type of fracture was considered to be due in part to weakened bones.

No evidence was found that higher intakes of cow's milk or calcium from food sources (women) or from food and supplements (men) reduced the risk of fracture. These results remained unchanged when they were adjusted for other factors like menopausal status, use of estrogen, and caffeine consumption. This study raises important questions. Is it possible that calcium intake actually has little impact on the risk of bone fracture in adults? Perhaps, but many study subjects were relatively young for having hip fractures. Bess Dawson-Hughes and colleagues found that when subjects 65 years and older were given supplements of calcium and vitamin D for three years, their incidence of fracture decreased.³ This suggests that there may be some benefit to increased calcium and vitamin D in older adults.

What about calcium from non-dairy sources? The women's study found that women using greater amounts of calcium from dairy foods had a modestly increased risk of hip fracture compared to women having the same level of calcium intake from non-dairy sources. This was apparently not due to the protein content of dairy products. Look for much more work in this area of research.

Breast Cancer and Dietary Fat

Some epidemiological studies have suggested that the intake of total fat has little effect on the risk of breast cancer. A recent study suggests a possible explanation for these findings. Researchers from Sweden and the U.S. studied more than 61,000 Swedish women aged 40 to 76 years. They determined what the subjects were eating at the beginning of the study and followed them for an average of four years to see which women developed breast cancer.

The researchers found that increased consumption of monounsaturated fat was associated with a decreased risk of developing breast cancer. Increased use of polyunsaturated fat was associated with an increased risk of breast cancer. Saturated fat use was not associated with breast cancer. Foods high in monounsaturated fats include olive oil and canola oil; foods high in polyunsaturated fats include safflower oil, soybean oil, corn oil, and sunflower oil.

These results could explain why total fat intake has often not been associated with the risk of breast cancer, since often women whose diets are high in monounsaturated fat also have diets high in polyunsaturated fat. The effects of the two kinds of fat then cancel each other out unless statistical methods to adjust for these effects are used, as was done in this study. What are the implications of this study for vegetarian women? While total fat intake does not appear to be associated with increased risk of breast cancer, it is associated with risk of heart disease; so some limitation of dietary fat is still recommended. The results of this study will need to be supported by other research, but they do suggest that use of monounsaturated fats may be more protective against breast cancer than use of polyunsaturated fats.