Prostate Cancer & Calcium Concerns

Question:

My husband has prostate cancer. I recently read that a high calcium intake may cause prostate cancer. How high is too high? Should I be restricting his calcium intake?

Answer:

What is the connection between calcium and prostate cancer risk?

Dozens of research studies have looked at potential connections between calcium and prostate cancer risk. Unfortunately, this research presents a very mixed picture. Some studies suggest that too much calcium can increase prostate cancer risk. Yet other research does not show this connection.

The picture also is unclear because most of the calcium in the American diet comes from dairy foods, such as milk, yogurt, and cheese. It is possible that calcium itself is not a problem, but something about dairy foods increases prostate cancer risk. Further, taking into account the type of dairy food is important. Perhaps certain types of dairy foods increase prostate cancer risk while others do not.

Calcium supplements

One double-blind, placebo-controlled clinical trial—considered the gold standard of medical research—randomly assigned 672 men to receive either 3 grams of calcium carbonate, or a placebo pill (no calcium), daily for four years. This clinical trial originally was designed to study the effect of calcium supplements on risk of developing colorectal adenomas, which are growths in the colon and rectum that if left untreated, can develop into cancer.

The men in the group were followed for an average of 10.3 years, and other new cancers, including prostate cancer were studied as well. The study authors found no significant differences in prostate cancer risk between the calcium supplemented and the placebo groups. In other words, taking calcium supplements daily for four years did not increase or decrease prostate cancer risk.

Dairy, dietary calcium (from food) and prostate cancer risk

Dairy foods are the major source of calcium in the “average” American diet, so it’s important to try to sort out if dairy, calcium, neither, or both are linked with prostate cancer risk. Some studies on dairy products and prostate cancer risk suggest that compared with men eating very little dairy, men who eat more than three to five dairy servings per day have a higher risk of prostate cancer. However, other studies do not show this link.

In several of the studies that have shown a link between dairy and prostate cancer, low-fat dairy seems to be more of a problem than high fat dairy: high fat dairy products, such as whole milk and cheese are not associated with increased prostate cancer risk, but low-fat products are.

How much dairy or calcium is too much?

Other than the calcium supplement clinical trial, the dozens of other studies on dairy foods, calcium, and prostate cancer risk are observational, and cannot prove cause and effect. For this reason, it’s difficult to come up with an exact calcium or dairy intake that is “safe” vs. “unsafe,” in terms of prostate cancer risk.

However, when researchers have found an increased risk of prostate cancer associated with dairy foods or dietary calcium (food sources), the results suggest that more than three to five servings of dairy per day may be a problem. This suggests that moderate dairy intake—up to three servings per day—is not associated with increased prostate cancer risk.

This is good news: men who are concerned about prostate cancer, but who enjoy dairy, likely do not need to eliminate it from their diets completely to address prostate cancer risk.  Sticking to three or fewer servings of dairy per day is a reasonable goal based on the available research evidence.

To summarize

The one clinical trial on calcium supplements did not show that calcium increases prostate cancer risk. The dozens of observational studies on dairy foods, dietary calcium, and prostate cancer risk paint a mixed picture. However, it appears that eating moderate amounts of dairy (three or fewer servings per day) and/or dietary calcium are not associated with increased prostate cancer risk.

Getting enough calcium, without overdoing it

Calcium is important to health. Not getting enough calcium can increase the risk of osteoporosis, even among men. Further, for men with prostate cancer, some treatments can increase the risk of bone loss and fractures, so trying to completely avoid calcium is not a good idea.

Getting enough calcium without overdoing it is the goal. The recommended calcium intake for men up to 70 years of age is 1,000 mg per day. For men over 70 years, the recommended intake is 1,200 mg of calcium per day. Talk to a registered dietitian for advice on how to meet these calcium goals.

For many men, diet alone will provide enough calcium. One serving of dairy, such as eight ounces of yogurt or milk, provides between 300 and 400 mg of calcium. This means that if you eat three servings dairy every day, you probably do not need calcium supplements. Calcium can also be found in non-dairy foods, such as fortified milk substitutes (soy, almond, or rice milk), and fortified juices, cereals, and bread products.

If you don’t eat dairy, it’s likely that a combination of food and supplements will best help you get enough calcium. This means that you’ll get some of your calcium from food, and some from supplements. It does not mean that you need to take 1,000 or 1,200 mg of calcium from pills. If you do this, you probably will end up getting too much calcium, because you are still getting some from the foods you eat.

Green leafy vegetables provide between 25 and 100 mg of calcium per serving, so while these foods are a good source of calcium, you’d need to eat a lot of them to meet your entire recommended dietary intake.

Also pay attention to which foods are calcium-fortified. If you eat a lot of calcium-fortified foods, you may not need supplements either, even if you don’t eat dairy products.

Again, be sure to talk to a registered dietitian for advice on how to meet your calcium goals. If you are being treated for prostate cancer and bone health is a concern, work with both your doctor and your dietitian to determine how much calcium you need every day.

 

The original question and answer were generously donated by Diana Dyer, MS, RD a cancer survivor, registered dietitian, organic garlic farmer, and the author of "A Dietitian's Cancer Story: Information & Inspiration for Recovery & Healing from a 3-time Cancer Survivor.

Question and Answer updated by Suzanne Dixon, MPH, MS, RD on behalf of the ON DPG

 

References:

  1. Aslam R, Neubauer S. Dairy foods, milk, calcium, and risk of prostate cancer. Oncology Nutrition Connection 2013; 21(1): 1, 3-10. Accessed January 2, 2014. http://dpgstorage-prd.s3.amazonaws.com/ondpg/documents/daa1c27f6308967a/winter_2013.pdf.
  2. Baron JA, Beach M, Wallace K, Grau MV, Sandler RS, Mandel JS, Heber D, Greenberg ER. Risk of prostate cancer in a randomized clinical trial of calcium supplementation. Cancer Epidemiol Biomarkers Prev. 2005;14(3):586-9.
  3. National Institutes of Health. Office of Dietary Supplements. Dietary Supplement Fact Sheet: Calcium. Accessed January 2, 2014. http://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/.

 

 

Page Updated: February 2014