Why take a drug, herb or any other supplement? It’s usually because we believe the substance will do something desirable, and that we’re doing more good than harm. To be truly rational we’d carefully evaluate the expected risks and benefits, estimate the overall odds of a good outcome, and then make a decision that would weigh these factors against any costs (if relevant) to make a conclusion about value for money. But having the best available information at the time we make a decision can still mean decisions turn out to be bad ones: It can be that all relevant data isn’t made available, or it can be that new, unexpected information emerges later to change our evaluation. (Donald Rumsfeld might call them “known unknowns.”)
As unknowns become knowns, risk and benefit perspectives change. Clinical trials give a hint, but don’t tell the full safety and efficacy story. Over time, and with wider use, the true risk-benefit perspective becomes more clear, especially when large databases can be used to study effects in large populations. Epidemiology can be a powerful tool for finding unexpected consequences of treatments. But epidemiologic studies can also frustrate because they rarely determine causal relationships. That’s why I’ve been following the evolving evidence about calcium supplements with interest. Calcium supplements are taken by almost 1 in 5 women, second only to multivitamins as the most popular supplement. When you look at all supplements that contain calcium, a remarkable 43% of the (U.S.) population consumes a supplement with calcium as an ingredient. As a single-ingredient supplement, calcium is almost always taken for bone health, based on continued public health messages that our dietary intake is likely insufficient, putting women (rarely men) at risk of osteoporosis and subsequent fractures. This messaging is backed by a number of studies that have concluded that calcium supplements can reduce bone loss and the risk of fractures. Calcium has an impressive health halo, and supplement marketers and pharmaceutical companies have responded. There are pills, liquids, and even tasty chewy caramel squares embedded with calcium. It’s also fortified in foods like orange juice. Supplements are often taken as “insurance” against perceived or real dietary shortfalls, and it’s easy and convenient to take a calcium supplement daily, often driven by the perception that more is better. Few may think that there is any risk to calcium supplements. But there are now multiple safety signals that these products do have risks. And that’s cause for concern. (more…)
Calcium is good for us, right? Milk products are great sources of calcium, and we’re told to emphasize milk products in our diets. Don’t (or can’t) eat enough dairy? Calcium supplements are very popular, especially among women seeking to minimize their risk of osteoporosis. Osteoporosis prevention and treatment guidelines recommend calcium and vitamin D as an important measure in preserving bone density and reducing the risk of fractures. For those who don’t like dairy products, even products like orange juice and Vitamin Water are fortified with calcium. The general perception seemed to be that calcium consumption was a good thing – the more, the better. Until recently. (more…)
A Walmart ad in my local newspaper trumpets “75% of all Americans don’t get enough Vitamin D” and offers to sell me Maximum Strength Vitamin D3, 5000 IU capsules to “promote bone, colon and breast health.” Meanwhile, the Institute of Medicine (IOM) tells me that “the majority of Americans and Canadians are receiving adequate amounts of … vitamin D” and that no one should take more than 4000 IU a day. Apparently Walmart and the IOM aren’t talking to each other.
The media have been giving the impression that vitamin D is a new wonder drug. They have told us that we aren’t getting enough sunlight, that a large percentage of us suffer from vitamin D deficiency, and that low levels of vitamin D are associated with cancer, multiple sclerosis, peripheral vascular disease, diabetes, rheumatoid arthritis, Parkinson’s and Alzheimer’s disease, and other conditions. Low levels of vitamin D have been linked to higher overall mortality (but so have high levels of vitamin D!). The anti-vaccine folks have been telling us (without any controlled studies) that vitamin D supplements are better than vaccines for preventing influenza. There’s no good evidence that raising vitamin D levels with supplements actually prevents any of these conditions, but many people think it should, and doctors have increasingly been measuring blood levels and prescribing high dose supplements. Is this just another passing fad like the enthusiasm for vitamin C, or are we belatedly recognizing a serious deficiency problem?
I’ve had a lot of inquiries about “is this information trustworthy?” and “how much vitamin D should I be taking?” I’ve been telling people that I didn’t know, that recent findings will soon result in new recommendations, and I’ve been eagerly awaiting the new guidelines. Now we have them, thanks to the IOM. They are not what most of us anticipated. Since so many doctors had been advocating higher levels to prevent things like cancer, I thought official recommended intake levels would go up; instead, they went down.