Calcium and Weight Loss: What the Research Says (and What It Means for Your Bones)

In short: Back in the early 2000s, a few studies suggested that getting more calcium could speed up fat loss. Larger reviews of the research since then have found that calcium supplements don’t help with weight loss. Calcium is still essential for your bones, but more isn’t always better, and food is usually the best place to get it.

An earlier version of this article said that calcium “may increase weight loss.” That was a fair reading of the research in 2013, but the evidence on calcium and weight loss has moved on. Here’s what current studies show about calcium, body weight and bone health, and how much calcium you actually need.

What does calcium do in the body?

Calcium is the most abundant mineral in your body. More than 99% of it is stored in your bones and teeth, where it gives them strength and structure. The small amount in your blood and tissues helps your muscles contract, your nerves send signals and your blood clot [1].

Your body needs vitamin D to absorb calcium properly from your gut [1]. Vitamin K also plays a part in building bone (see our post on vitamin K and bone loss).

Where the calcium and weight loss idea came from

The theory started with lab and animal research. When you eat very little calcium, your body makes more of the active form of vitamin D (called calcitriol) to hold on to the calcium it has. In mice, this seemed to push fat cells to store more fat and break down less of it. Eating more calcium appeared to reverse this, and calcium-fed mice lost more fat while dieting [2].

Two early human studies got a lot of attention:

• A small 24-week trial of 32 adults with obesity who were all cutting about 500 calories a day. The low-calcium group lost 6.4% of their body weight, the calcium supplement group lost 8.6%, and the high-dairy group lost 10.9% [2]. With only about 10 people per group, though, a few individuals could sway the results a lot.
• A re-analysis of five older calcium studies in 780 women, originally designed to look at bones, not weight. Four of the five were observational, which means they spotted a link between lower calcium intake and higher body weight but couldn’t show that calcium caused the difference. The authors estimated that calcium intake explained only about 3% of the differences in body weight between women [3].

These findings were interesting enough to launch many more trials. The results of those bigger studies are what matter most today.

What larger studies show about calcium and weight loss

When researchers pool the results of many randomized controlled trials (studies where people are randomly assigned to calcium or a comparison group), the effect mostly disappears.

A 2006 review combined 13 trials and found no link between taking calcium supplements or eating more dairy and losing weight, once differences in people’s starting weights were taken into account [4].

A larger 2015 meta-analysis (a study that combines the results of many trials) included 41 trials with more than 4,800 people [5]. It found that:

• Taking about 900 mg a day of extra calcium as supplements didn’t change body weight or body fat compared with control groups.
• Eating more dairy didn’t change body weight either.
• In people who were also on a calorie-reduced diet, eating about three servings of dairy a day was linked to losing roughly 1 kg (about 2 lb) more body fat over around four months. The authors called this “an indication,” not proof, and it only applied to dairy foods, not supplements.

The authors concluded that increasing calcium through supplements or dairy “is not an effective weight reduction strategy in adults” [5]. The US National Institutes of Health (NIH) Office of Dietary Supplements also describes the evidence as mixed and notes that calcium supplements don’t appear to affect body weight or body fat [1].

So if you’re working on your weight, calcium pills aren’t likely to make a noticeable difference. What you eat overall and how active you are matter far more. Our article on energy homeostasis explains how your body balances the energy you eat with the energy you use.

Calcium and bone health: what the evidence says now

Calcium’s role in bones is real, but the benefit of taking extra calcium is smaller than once thought.

Bone density. Bone mineral density (BMD) is a measure of how much mineral is packed into your bones. A 2015 review of 59 trials in adults over 50 found that getting more calcium, from food or supplements, raised BMD by about 1–2%. That increase happened in the first year and didn’t keep growing after that. The authors concluded it was unlikely to meaningfully reduce fracture risk [6].

Fractures. A companion review found that how much calcium people get from their diet isn’t linked to their risk of breaking a bone. In supplement trials, there was a small reduction in fractures overall, but the highest-quality trials showed no clear benefit at any site [7].

The largest single trial, part of the Women’s Health Initiative, followed 36,282 postmenopausal women for about seven years. Those taking 1,000 mg of calcium plus 400 IU of vitamin D a day had about 1% higher hip bone density, but no significant drop in hip fractures. They also had a 17% higher risk of kidney stones [8].

Based on evidence like this, the US Preventive Services Task Force (an independent panel of health experts) recommends against daily supplements of 1,000 mg or less of calcium with 400 IU or less of vitamin D to prevent fractures in postmenopausal women living at home who don’t have osteoporosis. It found too little evidence to make a call for men, younger women or higher doses [9]. This advice doesn’t apply to people who already have osteoporosis, low vitamin D or a history of fractures, who may be advised to take calcium by their doctor.

How much calcium do you need?

The NIH recommends the following daily amounts for adults [1]:

• Ages 19–50: 1,000 mg
• Ages 51–70: 1,000 mg for men, 1,200 mg for women
• Over 70: 1,200 mg

The upper limit (the most you should get from food and supplements combined) is 2,500 mg a day for adults up to 50 and 2,000 mg a day from age 51 [1].

Many people can reach their target through food. Good sources include milk, yogurt, cheese, canned fish with soft bones (like sardines and salmon), calcium-set tofu, fortified plant milks, kale and broccoli. Dairy also comes with protein and other nutrients; our post on milk after workouts looks at that side of things.

Calcium supplement side effects and safety

Calcium at recommended amounts is generally safe, but supplements do have some downsides:

• Digestive issues: gas, bloating and constipation are the most common complaints [1].
• Kidney stones: calcium supplements, especially with vitamin D, have been linked to a higher risk of kidney stones [1, 8].
• Heart health: a 2010 meta-analysis found that calcium supplements taken without vitamin D were linked to about a 27–31% higher risk of heart attack [10]. A later review of trials and long-term observational studies found that calcium intake within the upper limit wasn’t linked to heart disease in healthy adults [11]. The question isn’t fully settled, which is one more reason to favor food sources and avoid going over the recommended amount.

If you do take a supplement, your body absorbs calcium best in doses of 500 mg or less at a time. Calcium carbonate is best taken with food, while calcium citrate can be taken with or without food [1]. Calcium can also interact with some medicines, so check with your doctor or pharmacist first.

The bottom line on calcium and weight loss

The early excitement about calcium and weight loss hasn’t held up. Larger studies show calcium supplements don’t help you lose weight or body fat, and the possible small benefit from dairy during dieting is uncertain. Calcium is still important for healthy bones, but extra supplements give only a small boost in bone density and don’t clearly prevent fractures in healthy people. For most adults, aiming to meet the recommended intake through food is the simplest, best-supported approach.

This article is for general information only and isn’t medical advice. Talk to your doctor or another qualified health professional before starting a new supplement. See our medical disclaimer.

References

1. National Institutes of Health, Office of Dietary Supplements. Calcium: Fact Sheet for Health Professionals.
2. Zemel MB, Thompson W, Milstead A, Morris K, Campbell P. Calcium and dairy acceleration of weight and fat loss during energy restriction in obese adults. Obesity Research. 2004;12(4):582-590.
3. Davies KM, Heaney RP, Recker RR, et al. Calcium intake and body weight. Journal of Clinical Endocrinology & Metabolism. 2000;85(12):4635-4638.
4. Trowman R, Dumville JC, Hahn S, Torgerson DJ. A systematic review of the effects of calcium supplementation on body weight. British Journal of Nutrition. 2006;95(6):1033-1038.
5. Booth AO, Huggins CE, Wattanapenpaiboon N, Nowson CA. Effect of increasing dietary calcium through supplements and dairy food on body weight and body composition: a meta-analysis of randomised controlled trials. British Journal of Nutrition. 2015;114(7):1013-1025.
6. Tai V, Leung W, Grey A, Reid IR, Bolland MJ. Calcium intake and bone mineral density: systematic review and meta-analysis. BMJ. 2015;351:h4183.
7. Bolland MJ, Leung W, Tai V, et al. Calcium intake and risk of fracture: systematic review. BMJ. 2015;351:h4580.
8. Jackson RD, LaCroix AZ, Gass M, et al. Calcium plus vitamin D supplementation and the risk of fractures. New England Journal of Medicine. 2006;354(7):669-683.
9. US Preventive Services Task Force; Grossman DC, Curry SJ, Owens DK, et al. Vitamin D, calcium, or combined supplementation for the primary prevention of fractures in community-dwelling adults: US Preventive Services Task Force recommendation statement. JAMA. 2018;319(15):1592-1599.
10. Bolland MJ, Avenell A, Baron JA, et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ. 2010;341:c3691.
11. Chung M, Tang AM, Fu Z, Wang DD, Newberry SJ. Calcium intake and cardiovascular disease risk: an updated systematic review and meta-analysis. Annals of Internal Medicine. 2016;165(12):856-866.