However, higher vitamin D levels were associated with a decreased risk of colorectal cancer death.

Several epidemiological studies have supported the hypothesis that that vitamin D can reduce cancer mortality by decreasing cancer incidence or improving survival. Animal and cell studies suggest that vitamin D may reduce tumor growth and induce cancer cell death. Diet and exposure to sunlight are the major sources of vitamin D.

D. Michal Freedman, Ph.D., of the National Cancer Institute in Bethesda, Md., and colleagues analyzed data from the third national Health and Nutrition Examination Survey to examine the relationship between levels of circulating vitamin D in the blood and cancer mortality in a group of 16,818 participants aged 17 and older.

After about a decade of follow-up, 536 participants had died of cancer. Cancer mortality was not related to the level of circulating vitamin D for the overall group, nor was it related when the researchers looked at the data by sex, race, or age. But higher levels of vitamin D (80 nmol/L or more) were associated with a 72 percent reduced risk of colorectal cancer mortality, compared with lower levels (less than 50 nmol/L).

To our knowledge, this study is the first to examine the relationship between measured serum vitamin D levels and cancer mortality for selected site and for all sites combined, the authors write.

In an accompanying editorial, Cindy Davis, Ph.D., and Johanna Dwyer, D.Sc. of the National Institutes of Health in Bethesda, Md., discuss the complicated relationship between nutrients, like vitamin D, and cancer. They suggest that not enough is known about the benefits and limitations of vitamin D to use it for the prevention of disease or death.

These findings must be put into the context of total diet and lifestyle. There are many risk factors other than diet for colorectal cancer, and there are many possible dietary risk factors other than vitamin D that have been linked to cancer risk, the editorialists write.

jncicancerspectrum.oupjournals/

The ratio of mono-unsaturated to trans fats in diet Protein consumption (derived from animals or vegetables) Carbohydrates consumption (including fiber intake and dietary glycemic index) Dairy consumption (low- and high-fat dairy) Iron consumption Multivitamin use Body mass index (BMI, weight in kilograms divided by the square of height in meters) Physical activity

The researchers assigned a "fertility diet" score of one to five points. The higher the score, the lower the risk of infertility associated with ovulatory disorders.

The women with the highest fertility diet scores ate less trans fat and sugar from carbohydrates, consumed more protein from vegetables than from animals, ate more fiber and iron, took more multivitamins, had a lower BMI, exercised for longer periods of time each day, and, surprisingly, consumed more high-fat dairy products and less low-fat dairy products. The relationship between a higher "fertility diet" score and lesser risk for infertility was similar for different subgroups of women regardless of age and whether or not they had been pregnant in the past.

Said Chavarro, "We analyzed what happens if you follow one, two, three, four, or more different factors. What we found was that, as women started following more of these recommendations, their risk of infertility dropped substantially for every one of the dietary and lifestyle strategies undertaken. In fact, we found a sixfold difference in ovulatory infertility risk between women following five or more low-risk dietary and lifestyle habits and those following none."

hsph.harvard/