Calcium supplements have limited benefits for bone health and may carry a risk of side effects

Osteoporosis and bone fractures are associated with many complications and premature death, especially among older adults. Millions of people therefore take calcium supplements, vitamin D, or a combination of both to support bone health. But according to a new meta-analysis published in The British Medical Journal, these supplements provide little or no benefit. The findings also suggest that high levels of calcium in the blood from various supplements may increase the risk of atherosclerosis, blood clots, and cellular stress. It is therefore important to recognize that bone health also involves magnesium and vitamin K2, which help remove calcium from the bloodstream and deposit it in the bones.

About one in three people age 65 and older experience at least one fall each year. Many of these falls result in bone fractures, pain, surgery, loss of independence, and placement in a nursing home. Hip fractures are themselves associated with serious complications, and 20 to 30 percent of patients die within the first year. As the number of older adults continues to grow, the need to prevent falls and the resulting bone fractures is therefore an increasing global health concern.
Bones contain a significant amount of calcium, and vitamin D plays a role in calcium absorption. For this reason, millions of people have been given these two nutrients for decades—as standalone supplements or in combination—to improve bone health. Nevertheless, several previous studies have questioned their effectiveness, and the researchers behind the new meta-analysis wanted to investigate this relationship further.
The meta-analysis included 69 randomized controlled trials with more than 150,000 participants in total. Most of the participants (87%) lived at home and were not at high risk of falls or bone fractures. By examining the studies and accounting for various types of systematic errors (bias), the researchers compared the effects of calcium supplements, vitamin D supplements, a combination of both, or placebo on reducing the number of falls and resulting bone fractures.
Overall, the meta-analysis revealed that calcium, vitamin D, or a combination of both had little or no effect on preventing falls and resulting bone fractures.
According to the researchers, health authorities should therefore introduce new guidelines for calcium and vitamin D supplementation. The researchers also point out that exercise and strength training are important for both bones and muscles, which act as a cushion in the event of a fall.
The new study was published in The British Medical Journal and is consistent with previous studies that we have discussed on this website.

Note: Calcium supplements may increase the risk of atherosclerosis and blood clots

Blood calcium levels should be tightly regulated, and the large daily calcium supplements (800–1,000 mg) prescribed to older adults may often do more harm than good. This is because these calcium supplements cause blood calcium levels to rise sharply over the following eight hours. Over time, this may contribute to atherosclerosis and high blood pressure. This is among the findings of a previous review article published in Current Osteoporosis Reports. According to the researchers behind this review, the official calcium recommendations in the United States and Europe are also set too high due to misleading studies. In addition, many people get substantial amounts of calcium from dairy products, which may further affect the balance of calcium in the blood.
It is also well established that cells in nervous tissue and other soft tissues should contain very little calcium. If these cells take up too much calcium, they can become overactivated, potentially triggering cramps, inflammatory conditions, oxidative stress, and cell death.

Greater focus on adequate vitamin D, magnesium, and vitamin K2 for bone health

As mentioned, vitamin D plays a role in the absorption of calcium from the intestines. Several studies show that vitamin D supplementation is relevant in cases of widespread deficiency and that many people need more vitamin D than the official recommendations if blood levels are to be optimized.
Magnesium also plays a crucial role in the body's distribution of calcium. This is because magnesium acts as a kind of gatekeeper in cell membranes, ensuring that most calcium is transported into the bones while cells in nervous tissue and other soft tissues remain almost calcium-free. Therefore, calcium supplements should never be taken without combining them with magnesium.
In addition, vitamin K2 plays a role in the formation of a protein (matrix Gla protein) that removes calcium from the bloodstream, as well as another protein (osteocalcin) that strengthens bone tissue.
In this way, magnesium and vitamin K2 contribute both to strengthening bones and to counteracting atherosclerosis.
According to another study from 2025 (Qifei He et al., 2025) concerning vitamins, older patients who have suffered hip fractures are particularly likely to be deficient in vitamin D, vitamin K, vitamin A, and folic acid (folate/vitamin B9).

As this shows, bone health involves much more than calcium.

This is because magnesium, vitamin D, vitamin K2, and other vitamins play different roles in calcium absorption, the body's distribution of calcium, and a wide range of enzymatic processes involved in bone formation and bone density.

References:

Oliver Massé et al. Calcium, vitamin D, or combined supplementation to prevent fractures and falls: systematic review and meta-analysis. BMJ 2026

Ian R Reid. Calcium Supplementation – Efficacy and safety. Current Osteoporosis Reports 2025

Andrea Rosanoff et al. Essential Nutrient Interactions: Does Low or Suboptimal Magnesium Interact with Vitamin D and/or Calcium Status. Advances in Nutrition 2016

Qifei He et al. Association between vitamin levels and geriatric hip fractures: A cross-sectional study. Frontiers in Nutrition 2025