When I talk to clients about their supplement lineup, I frequently get comments like, “I know I should be taking a calcium supplement but I’m not yet” or “well, there are the obvious ones, like calcium.” And to some extent, they’re right – calcium is very important. But the current research on calcium supplements might surprise you – and leads me to recommend against most traditional calcium supplements. In this post, I’ll cover all about calcium supplements – from why calcium is important in the body, to whether or not calcium supplements actually work, to the risks of calcium supplements, to how to get calcium from your food, and more.
Why Calcium is Important in the Body
When you think of calcium, you probably think of bones, and you’re not wrong! 99% of the calcium stored in the body is in the skeletal system. Calcium is essential for strong, resilient bones and healthy teeth. But did you know that calcium also plays a role in regulating the secretion of some hormones, transmitting nerve impulses, helping blood clot and muscles contract, and even keeping your heart beating at a normal rhythm?
Our bodies are constantly regulating the amount of calcium in the blood. If there’s not enough calcium in the blood, a hormone called parathyroid hormone stimulates our bones to break down ever so slightly to release some of their calcium into the blood and normalize blood levels. This, over time, causes weakening of the bones, leading to osteopenia and osteoporosis. (Parathyroid also helps us absorb more calcium and causes our kidneys to excrete less calcium, so it’s really trying to help us here!)
For most people to maintain adequate calcium levels in their blood without causing bone degradation, consuming around 1,000 mg of calcium per day is required. So, doesn’t it sound easy to get that from a supplement?
Do calcium supplements work?
Not so fast on the supplements. It sounds like an easy way to get in our needed calcium, but in practice, results are not as convincing. Here are a few interesting notes:
- Most meta-analyses (these are “studies of studies,” so they’re combining lots of large data sets) show little to no correlation between calcium supplements and risk of fractures. This one concludes, “Evidence that calcium supplements prevent fractures is weak and inconsistent.”
- This article, a debate article contrasting the points of view of encouraging and discouraging calcium supplementation, does suggest that calcium supplementation with vitamin D can reduce fracture risk, but that given the potential risks (which we’ll discuss below), concludes that “calcium supplements should not be suggested in patients with a normal calcium intake.” The opposing viewpoint concludes that “any benefit in preventing fractures is at best very small, if there is any at all, and that any such benefit is outweighed by the small risk of serious adverse events.”
- Ian Reid, Professor of Medicine and Endocrinology at the University of Auckland, suggests in his research that while calcium supplements do tend to raise blood calcium levels, they don’t prevent fractures. He says, “recent meta-analyses suggest no significant prevention of fractures. In sum, there is little substantive evidence of benefit to bone health from the use of calcium supplements.”
- This Harvard Medical School article says, “there’s little evidence that high intake has more than a marginal effect on bone density and fracture prevention … exercise and reversing vitamin D deficiency are not promoted enough and are more important for bone health.”
- Shockingly enough, this study found that women whose calcium intake was the highest (both from food and supplements) had no reduction in overall fracture risk, but an even higher than normal risk of hip fractures
- Erin Michos, MD, MHS , associate director of preventive cardiology for the Ciccarone Center for the Prevention of Heart Disease, says: “The truth is, the research is inconclusive. But there is a growing body of evidence that suggests no health benefit, or even worse, that calcium supplements may be harmful.”
What do we learn from that? While some studies do show benefit in preventing fractures to those taking calcium supplements, the data is limited and inconclusive. So the supplements are not really giving us the benefit we expected.
What are the potential dangers of calcium supplements?
I referenced dangers and risks above, which is likely confusing. Wait … you mean that taking a calcium supplement might actually be detrimental? Let me explain what the research shows with another few notes:
- The most commonly cited risk is that calcium supplements come in a format that cannot be readily absorbed by the body (usually calcium carbonate, coming from ground limestone). When the body receives lots of calcium that it cannot absorb into skeletal tissue, it tries to “deposit” the calcium elsewhere, and this can lead to calcification of arteries, which can then lead to heart issues.
- A study done by Dr. Erin Michos, cited above, found that “[calcium] supplement users showed a 22 percent increased likelihood of having their coronary artery calcium scores rise higher than zero over [a] decade, indicating development of heart disease.” She and her co-researchers did NOT find this risk in people who had high intake of calcium from diet; the risk only increased with calcium supplementation.
- And to the Johns Hopkins publication, which states that “recent studies have linked calcium supplements with an increased risk of colon polyps (small growths in the large intestine that can become cancerous) and kidney stones, which are hard masses usually formed in the kidneys from an accumulation of calcium and other substances.” This article also recognizes the risk of calcium buildup in the heart’s arteries resulting from calcium supplementation.
- And then back to Professor Reid, who concludes after his research that the “likelihood that calcium supplement use increases cardiovascular events, kidney stones, gastrointestinal symptoms, and admissions to hospital with acute gastrointestinal problems. Thus, the balance of risk and benefit seems to be consistently negative.”
- This meta-analysis concludes that calcium is helpful, but given the potential risks for cardiovascular disease, GI disease, and kidney disease, the authors recommend proceeding with caution and considering each individual’s risks when it comes to calcium supplementation.
- Finally, this study concluded that, for women who have had strokes, the risk of dementia was seven times higher among women who took calcium supplements than it was among those who didn’t.
If I’m not going to supplement, how do I get calcium from food?
OK, so we’ve determined that calcium is helpful (or at least, we think it’s helpful), but that most traditional supplements come with some risk. So, without a supplement, is it possible to get enough calcium from food?
Yes, it’s definitely possible to get enough calcium from food. For starters, what is enough? Most recommendations are around 1,000 mg per day for women up to 50 and men up to 70, increasing to 1,200 mg / day thereafter.
Here are several ways to get calcium from foods:
- Leafy greens have abundant calcium! One cup of cooked broccoli has 180 mg of calcium; other greens like kale, collard greens, and Brussels sprouts also contain abundant calcium. And most research shows that the calcium from leafy greens is far more bioavailable than that from dairy, which we’ll discuss below.
- Beans of all kinds also contain very bioavailable calcium. In fact, tofu (made from soybeans) can have up to 750 mg in just 4 oz of firm tofu!
- Sardines have wonderful calcium since you’re eating the bones of the fish. 3 ounces of sardines contain about 370 mg calcium.
- Nuts and seeds, particularly almonds and sesame seeds, contain lots of calcium – up to 280 mg per single ounce of sesame seeds!
- One cup of figs contains 300 mg of calcium!
- Dairy is, of course, the most commonly cited source of calcium, and one cup of yogurt has about 450 mg calcium, while one cup of milk has about 300 mg calcium. If you tolerate dairy, and try to prioritize the best quality possible, then this can be a great option! But if you don’t tolerate dairy or are looking to reduce inflammation, don’t worry – you can get adequate calcium with all the above options. Here’s more on dairy.
What can I do to ensure healthy bones aside from eating calcium rich foods?
- If you’re going to take a supplement, I highly recommend choosing one made from whole foods. The research has been done on the most common calcium supplements, which as I mentioned, are not absorbable by the body. However, good quality, whole foods-based calcium supplements contain several cofactors, like vitamin K, magnesium, and vitamin D, which all help the body process calcium appropriately and can prevent buildup. While I haven’t seen studies that use participants on whole foods-based calcium supplements, I strongly suspect that the results would be more favorable than the existing studies! I have commonly recommended this one but there are several good brands available.
- Remember that movement is CRITICAL for bone health! Johns Hopkins states that women who sit for 9 or more hours daily are 50% more likely to suffer from a hip fracture than those who move more! Weight-bearing exercise, like walking, running, jumping, and strength training, are wonderful for bones.
- Reduce inflammatory foods, sugar, sodas, wheat, coffee, and more. These leach calcium from your bones and require even more calcium to be consumed. If you really want to dive into details, I recommend this podcast episode.
A few caveats…
First, nothing on The Lyons’ Share website, podcast, or other material should ever be taken as medical advice. If your doctor or other practitioner has suggested a calcium supplement, I recommend discussing this with that person rather than stopping on your own. Also, the field of nutrition is constantly evolving. I find it exciting when studies (like all those cited above) conflict and lead to confusing outcomes – that means we’re still in the process of learning! I always do my best to stay on top of the research, and I will always update blog posts with new information if better, more updated research emerges. In the meantime, keep learning, and keep doing your best – that’s all we can ask of ourselves!
Now it’s your turn … Did you know this about calcium? What is most surprising to you?