How much calcium do you really need?

How much calcium per day is recommended? Like many women, you may have memorized the minimum daily calcium requirement - 1,000 milligrams (mg) a day for women ages 50 and younger and 1,200 mg for women over 50 - and followed it faithfully in an effort to preserve your bones.

Some other countries have similar calcium intake recommendations: Canada's are the same as those in the United States. Australia, New Zealand, and Germany recommend 1,000 mg/day for all women. However, some countries have lower goals: for example, the United Kingdom recommends 700 mg/day, and Japan 650 mg to 800 mg/day.

Why is calcium important?

Adequate calcium is necessary for good health, and not just because it's a major component of our bones. It also plays a vital role in keeping our organs and skeletal muscles working properly. The body gets the calcium it needs for basic functions by releasing the calcium stored in our bones into the blood through bone remodeling - the process by which bone is constantly broken down and rebuilt.

Because bone density drops when bone breakdown outpaces bone formation, scientists reasoned that maintaining an adequate level of calcium in the blood could keep the body from drawing it out of the bones. In the late 1970s, a couple of brief studies indicated that consuming 1,200 mg of calcium a day could preserve a postmenopausal woman's calcium balance.

Based on those studies, in 1997 a panel of the Institute of Medicine (now the National Academies of Sciences, Engineering, and Medicine) raised the recommendation for calcium intake from 800 mg to 1,200 mg a day for women over 50. However, the recommendation was based on calcium balance studies that lasted just a few weeks. In fact, calcium balance should be determined over a much longer period. Moreover, there isn't sufficient evidence that consuming that much calcium actually prevents fractures. Nonetheless, the recommendation has been carried forward since then.

Researching calcium supplements

In the past two decades, several clinical trials involving thousands of postmenopausal women have sought to determine how calcium intake affects the risk of fractures. In each study, women were randomly assigned to one of two groups - one to receive calcium and supplements of vitamin D (to aid calcium absorption) and the other to get placebo pills.

Overall, these major trials did not find that calcium supplements helped to reduce fracture risk.

Some recent research has shown mixed results. For example, a 2025 analysis of 23 studies involving more than 70,000 older adults found a 7% reduction in overall fracture risk, but no protection specifically for hip fractures or spinal fractures.

The U.S. Preventive Services Task Force is an independent volunteer panel of experts that makes evidence-based recommendations. This task force is currently reviewing the evidence on calcium and vitamin D supplementation in older people. The panel's draft statement declares there is not enough evidence to make recommendations on calcium supplementation, and that overall, the evidence for calcium plus vitamin D supplementation does not show a decreased risk of falls, fractures, or mortality.

The downside of calcium supplements

Studies also have revealed a couple of downsides to high levels of calcium supplementation, but not to calcium obtained through a regular diet.

An increased risk of kidney stones. Clinical trials and studies suggest that high doses of calcium supplements may increase the risk of kidney stones. On the other hand, high levels of dietary calcium are thought to offer some protection against kidney stones. Supplements, especially if taken between meals, may promote stone formation by increasing the amount of calcium that is eliminated in the urine.

An increased risk of heart attack. Analyses of clinical trials suggest that the risk of heart attack may increase by 10% to 20% with calcium supplementation, but not with dietary calcium intake.

Mortality risks? Long-term follow-up data on participants in the Women's Health Initiative showed that women taking calcium and vitamin D supplements had a 6% higher risk of cardiovascular-related death - but also a 7% lower risk of cancer-related death.

Vitamin D is important, too

Vitamin D is also essential for healthy bones. In fact, the daily vitamin D requirement was first introduced to help prevent rickets - a condition in which developing bones are soft and can become bowed - in children.

Vitamin D is made in the skin through exposure to ultraviolet radiation in sunlight. However, the amount produced varies widely from person to person. People with darker skin produce less vitamin D than lighter-skinned people, and in all populations, the skin's ability to convert sunlight to vitamin D declines with age. Plus, if you follow the advice to reduce your risk of skin cancer by keeping covered and wearing sunscreen, you're also cutting your vitamin D production.

Such variability has made it difficult for researchers to tell how much vitamin D people make in addition to the amount they consume in supplements. Evidence from studies that have measured blood levels of vitamin D indicates that levels in the high-normal range are optimal for building bone. However, taking too much vitamin D can be dangerous.

So how much calcium do you really need?

One thing the studies have taught us is that both calcium and vitamin D are essential in building bone. If you can get at least 700 mg of calcium from food, that should be enough. But if you're not sure, check with your primary care provider before reaching for a calcium supplement.

However, getting enough vitamin D from sunlight and dietary sources can be challenging. Some foods are fortified with vitamin D, so check product nutrition labels.

If you're taking a vitamin D supplement, you probably don't need more than 15 mcg to 20 mcg (600 IU to 800 IU) per day. Some people may need a higher dose, but unless your medical team recommends it, avoid taking more than 100 mcg (4,000 IU) per day.

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