High intake of dairy products linked with increase in Prostate Cancer Risk

13/12/05 In a combined analysis of 10 published studies, men with the highest intake of dairy products and calcium were more likely to develop prostate cancer than men with the lowest intakes. These results were published in the Journal of the National Cancer Institute.

The prostate is a gland of the male reproductive system. It produces some of the fluid that transports sperm during ejaculation. After skin cancer, prostate cancer is the most common form of cancer diagnosed in men.

Calcium is a nutrient that has been linked with a decreased risk of osteoporosis, hypertension, and colorectal cancer. Some studies, however, have suggested that high calcium intake may increase the risk of prostate cancer.

The reason for a link between high calcium intake and prostate cancer is unclear, but could potentially involve suppression of plasma 1,25-dihydroxyvitamin D3 (the active form of vitamin D; thought to play role in the control of prostate cell growth and differentiation) or elevation of plasma levels of insulin-like growth factor-I (a hormone associated with an increased risk of prostate cancer).

To evaluate the link between dairy products, calcium, and risk of prostate cancer, researchers combined information from 10 published that addressed this question. All studies were prospective (meaning that subjects were enrolled and exposure information was collected before the men developed cancer). This type of study design minimizes some types of bias.

The studies were conducted in the U.S. or Europe and were published between 1984 and 2005. Information about consumption of dairy products and calcium was collected by questionnaires completed by the study subjects.

Data from the 10 studies suggest a modestly increased risk of prostate cancer among men with the highest intake of dairy products or calcium:
- Men with the highest intake of dairy products were 11% more likely to develop prostate cancer than men with the lowest intake.
- Men with the highest intake of calcium were 39% more likely to develop prostate cancer than men with the lowest intake.
- A trend between increasing intake and increasing risk of prostate cancer was observed for both dairy products and calcium.

The researchers conclude that “High intake of dairy products and calcium may be associated with an increased risk of prostate cancer, although the increase appears to be small.”

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