Vitamin D is already well known for its benefits in building healthy bones. A new study supports the idea that it also may reduce cancer risk as well as breast cancer mortality, especially in women with a lower body mass index. 

Breast cancer remains the most common cancer in women worldwide and is the leading cause of death from cancer in women. Reproductive risk factors such as early onset of puberty, late menopause, later age at first pregnancy, never having been pregnant, obesity, and a family history have all been shown to be associated with breast cancer development. The role of vitamin D concentration in the development of breast cancer, however, continues to be debated.

This study involving more than 600 Brazilian women suggests that vitamin D may reduce cancer risk by inhibiting cell proliferation. Study results appear in the article "Low pretreatment serum concentration of vitamin D at breast cancer diagnosis in postmenopausal women."

Researchers involved in the study concluded that postmenopausal women had an increased risk of vitamin D deficiency at the time of their breast cancer diagnoses, associated with higher rates of obesity, than women of the same age group without cancer. Similar studies also have previously demonstrated a relationship between vitamin D and breast cancer mortality. Women in the highest quartile of vitamin D concentrations, in fact, had a 50% lower death rate from breast cancer than those in the lower quartile, suggesting that vitamin D levels should be restored to a normal range in all women with breast cancer.

"Although published literature is inconsistent about the benefits of vitamin D levels and breast cancer, this study and others suggest that higher levels of vitamin D in the body are associated with lowered breast cancer risk," says Dr. JoAnn Pinkerton, executive director of NAMS. "Vitamin D may play a role in controlling breast cancer cells or stopping them from growing. Vitamin D comes from direct sunlight exposure, vitamin D3 supplements, or foods rich in vitamin D."

The amount of physical activity that women undertake is not linked to their risk of early menopause, according to the largest study ever to investigate this question.

Until now, there have been conflicting findings about the relation between physical activity and menopause, with some studies suggesting that women who are very physically active may be at lower risk of a menopause before the age of 45, while others have found evidence of the opposite effect.

However, the study that is published in Human Reproduction [1], one of the world's leading reproductive medicine journals, has analysed data from 107,275 women, who were followed prospectively from the time they joined the Nurses' Health Study II in 1989 until 2011, and found no association between physical activity at any age and early natural menopause.

Dr Elizabeth Bertone-Johnson, Professor of Epidemiology at the University of Massachusetts, USA, who directed the research, said: "Our study provides considerable information in helping us understand the relationship between activity and timing of menopause; this is because of its size, its focus on early menopause specifically, and because of its prospective design, which limited the likelihood of bias and allowed us to look at physical activity at different time periods.

"Several previous well-designed studies have found suggestions that more physical activity is associated with older age at menopause, but even in those studies the size of the effect was very small. Our results, in conjunction with other studies, provides substantial evidence that physical activity is not importantly associated with early menopause."

Female US registered nurses aged 25-42 were enrolled in the Nurses' Health Study II in 1989 and they completed questionnaires about lifestyles and medical conditions every two years thereafter. They were asked about the time they spent in recreational physical activities such as walking, running, cycling, racquet sports, swimming laps, aerobic activities, yoga, weight training and high intensity activities such as lawn mowing. The researchers also collected information on factors such as race, ethnicity, age, education, height, the age when the women had their first periods, whether or not they had been pregnant and how often, use of oral contraceptives and hormone therapy, whether or not they smoked, weight and body mass index (BMI), diet and use of dietary supplements.

In order to assess the frequency, duration and intensity of the activities, the researchers multiplied the hours per week of each activity by its metabolic equivalent (MET) score to create total MET hours per week. One MET equals one kilogram calorie per kilogram per hour (kcal/kg/h), which is the amount of energy expended by sitting quietly for an hour.

During the 20 years of follow-up, 2786 women experienced natural menopause before the age of 45. The researchers found no significant difference in the risk of early menopause between, for instance, women reporting less than three MET hours a week of physical activity and women reporting 42 or more hours a week (the equivalent to four or more hours of running or eight or more hours of brisk walking per week). The amount of physical activity that the women reported in their teenage years was also unrelated to the risk of early menopause.