Many health professionals are skeptical about the value of supplements. They often advise their patients to eat a well-balanced diet and skip vitamin and mineral pills.
The exception has been calcium, sometimes with vitamin D. For decades, doctors have advised women (and some men) to take calcium supplements to ward off osteoporosis. There was even some preliminary data suggesting that extra calcium might reduce the risk of colorectal cancers (Cochrane Database of Systematic Reviews, Jan. 23, 2008).
After further study, however, the idea that calcium could prevent either osteoporosis or colon cancer has not held up. A recent meta-analysis published in JAMA did not find evidence that calcium supplements reduce the risk of hip fractures (JAMA, Dec. 26, 2017).
Now the notion that calcium protects against colon polyps also has been upended. A gold-standard, randomized controlled trial of more than 2,000 people has just been published (Gut, March 1, 2018).
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This study included more than 2,000 middle-aged Americans at high risk of polyps because they had already had one or more discovered during a colonoscopy. These volunteers were randomly assigned to take 1,200 mg of calcium, 1,000 IU of vitamin D-3, both or neither for at least three years. Then they had another colonoscopy to look for polyps. At that point, the scientists saw no effect.
The investigators also collected data on polyps found after the treatment had stopped. That is when they discovered that the supplements increased the likelihood of precancerous polyps. Calcium alone raised the risk 2.65 times, while calcium with vitamin D made people 3.8 times more likely to develop polyps six to eight years after starting supplementation.
The authors of the study point out that both women and smokers were at higher risk of polyps when they took supplemental calcium. As a result, doctors might want to change their advice. It no longer seems prudent to urge women to take extra calcium and vitamin D “just in case.” Those who have already had a polyp and those who smoke may need to be particularly cautious about taking such supplements.
In addition, there has been great uncertainty about whether calcium pills are safe for the heart and arteries. The Nurses’ Health Study, with 74,245 women observed over 24 years, did not find any risk (Osteoporosis International, August 2014). However, data from the Women’s Health Initiative indicate a modest cardiovascular risk associated with calcium supplements with or without vitamin D (BMJ, April 19, 2011).
What does this mean for ordinary people? It suggests that calcium supplements are not a great backup plan to make up for inadequate dietary intake. Instead, people may need to concentrate on getting calcium from their food choices.
While everyone knows that milk is a good source of calcium, many older people don’t drink milk. They might consider yogurt, mozzarella or Cheddar cheese, or they might turn to tofu, turnip greens, collards, kale or bok choy. Canned salmon or sardines, with the bones, also are good food sources of calcium and provide some vitamin D. Soybeans, white beans, sesame seeds and almonds can help supply dietary calcium, as well.
With careful attention to menu planning, people can be confident that they are getting the calcium they need. They won’t have to run even modest risks of colon polyps or calcified plaque from taking calcium pills.
Joe Graedon is a pharmacologist. Teresa Graedon holds a doctorate in medical anthropology and is a nutrition expert. Their syndicated radio show can be heard on public radio. In their column, Joe and Teresa Graedon answer letters from readers. Write to them in care of King Features, 628 Virginia Drive, Orlando, FL 32803, or email them via their website: www.PeoplesPharmacy.com.