Although calcium is essential for bone health and may play a role in protecting against colorectal cancer, the study provides more evidence that absorbing too much calcium, particularly through dietary supplements, can be harmful.
The daily recommendation for calcium is about 1,000m a day. Researchers determine that elevated risks occur when the daily absorption exceeds 2,000mg a day.
"It may be possible in the future to personalize prevention using this type of genetic knowledge," said Gary Schwartz, an associate professor of cancer biology, urology and public-health sciences at Wake Forest Baptist and co-author of the study.
More than 240,000 men in the U.S. are diagnosed annually with prostate cancer, with about 33,720 dying from the disease, according to the National Cancer Institute. Only lung cancer kills more American men.
According to the Prostate Cancer Foundation, there are no proven strategies for preventing the disease. However, changes in diet and lifestyle have been shown to reduce the risk of the disease progressing.
The study by Wake Forest Baptist and the University of Southern California represents a follow-up on recent Wake Forest Baptist research that found a prostate-cancer risk with high levels of calcium in blood and high serum calcium levels.
Researchers specifically focused on black men because much of the data on the diet-cancer link comes from studies of white men.
Researchers studied 783 black men living in the San Francisco and Los Angeles areas, 533 of which were diagnosed with prostate cancer. Researchers studied the effects of genotype, calcium intake and diet-gene interactions.
The men who reported the highest intake of calcium were two times more likely to have localized and advanced prostate cancer than those who reported the lowest.
Another pivotal determination is that men with a genotype associated with poor calcium absorption were 59% less likely to have been diagnosed with advanced prostate cancer than men who genetically were the best absorbers of calcium.
Schwartz said further study of men of other races is needed to confirm the findings. The latest study offers a better understanding of why calcium in diet may increase the risk for prostate cancer and who is at increased risk, Schwartz said.
That includes determining which individuals would benefit from modification to their daily calcium intake, such as taking fewer antacid tablets and watching how much dairy, fish, nuts and vegetables they consume.
For example, an 8oz glass of 2% milk has 297mg of calcium, eight ounces of plain low-fat yogurt has 400mg and an ounce of cheddar cheese has 204mg.
Whether a product is calcium fortified can have a big impact – 8oz of calcium-fortified orange juice has 300mg of calcium, while unfortified orange juice has 22mg.
"It's very easy to overstep the high level of daily calcium intake, so being aware of how well your body absorbs calcium is important," Schwartz said.
The study can be found on the website of the Journal of Bone and Mineral Research. The final study results will be in its January print edition.
From the September 28, 2011, Prepared Foods' Daily News.