A very large study of over 20,885 men was published in American Journal of Clinical Nutrition; Dec 22 2008 that showed that eating dairy products often may be a risk factor for prostate cancer and advanced prostate cancer.

Lead researcher, Edward L Giovannucci, at the Harvard Medical School showed that men who consumed more than 2.5 servings of dairy products daily were 34 percent more likely to be diagnosed with prostate cancer than those who consumed less than 0.5 servings.

The study was a pat of the Physicians’ Health Study, a cohort of male US physicians that were followed over an eleven year time period. Over te eleven years 1,012 were diagnosed with prostate cancer.

The study design estimated dairy calcium intake on the basis of consumption of 5 dairy products including cold breakfast cereal, whole milk, and skim milk, cheese and ice cream. These 5 dairy products were the main sources of dietary calcium for the study population.

The researchers found each additional 500 mg of calcium from dairy products per day was associated with a 16 percent increase in the risk of prostate cancer. The association was similar even intake of other foods such as chicken, fish, and eggs was considered.

They also found that when the 5 dairy foods were considered individually, skim milk was significantly positively as it related to prostate cancer and men who consumed one or more servings per day. These higher consumers were 32 percent more likely to have prostate cancer than those who did not consume any dairy products.

Skim milk accounted for 48 percent of total dairy product intake and 57 percent of the total dairy calcium intake.

Men who had the highest intake of dairy products were 38 and 42 percent more likely to have advanced and non- advanced prostate cancer

respectively than those who had the lowest intake. Similarly men who had the highest intake of calcium from dairy products were 30 and 47 percent more likely to be diagnosed with advanced and nonadvanced prostate cancer respectively than those who had the lowest intake.

The researchers believe that calcium is the key element that mediated that association between intake of dairy products and prostate cancer risk. They found the association of calcium intake from dairy products with prostate cancer risk was virtually the same as the one of dairy products, that is, those who had greater than 600 mg calcium per day were 32 percent more likely to develop prostate cancer than those who had only less than 150 mg per day.

They also felt that the effect of calcium on the prostate cancer is mediated by its effect on the production of 1, 25-dihydroxyvitamin D3, the most potent form of vitamin D in the body. Vitamine D has been found to protect against more than at least 17 types of cancer at high serum concentrations. They proposed that high intake of calcium suppressed the production of 1, 25-dihydorxyvitamin D3, raising the prostate cancer risk.

They found that after adjustment for age, body mass index, and smoking status, dairy calcium intake was significantly inverse associated with 1, 25-dihydroxyvitamin D3 concentrations. Each 300-mg increase in total daily intake from dairy products, 1, 25-dihydroxyvitamin D3 declined 2 pmol/L or 1.02 pg/mL.

Men who consumed more than 600 mg calcium per day from skim milk had a lower 1,25-dihydroxyvitamin D3 level than those who had less than 150 mg calcium from skim milk, 71 pmol/L (30.06 pg/mL) versus 85 pmol/L (35.64 pg/mL).

Calcium from skim milk was also significantly inversely associated with serum concentrations of 1, 25-dihdyroxyvitamin D3. But skim milk calcium was not correlated with serum concentration of 25(OH)D, which the researchers said was understandable because most 25(OH)D is derived from sun exposure.

The researchers said in their report that twelve of 14 prior epidemiologic studies showed that highest intake of dairy products was associated with a 1.5 to 2.5 times higher risk of prostate cancer compared to those who had the lowest intake.

At least two studies, according to the authors, have suggested that dietary calcium could affect prostate cancer risk by down-regulating the production of 1, 25-dihydroxyvitamin D3, a hormone believed to protect against prostate cancer.

The take home message is simple. Stop consuming, or at least limit, your diary consumption. If you do use milk do not use skim milk. Talk with your doctor and ask if you should supplement your vitamin D consumption. Ask your doctor to run a vitamin D screen at the time you have your next blood test.

Joel T Nowak MA, MSW