Supplements for Bone Health, Graded

Quick answer

Calcium and vitamin D have the best-documented roles in bone, and both entries are graded moderate. Adults need 1,000 to 1,200 mg of calcium and 15 to 20 mcg (600 to 800 IU) of vitamin D a day from all sources. Magnesium and vitamin K have graded entries too, but trials of extra amounts are mixed.^1,2

Key facts

About 98% of the body's calcium is in the skeleton, which also acts as the reserve that keeps blood calcium steady.¹
A meta-analysis of 51 trials in 12,257 people over 50 found bone density 0.7% to 1.8% higher with calcium, and the authors judged the gain too small to be likely to matter clinically.³
In VITAL, 2,000 IU of vitamin D a day for about five years gave no added benefit for bones in 25,871 adults who mostly had adequate levels.⁴
Most trials of vitamin D for bone also gave calcium, so the effect of each is hard to separate.²
The body absorbs calcium best in amounts of 500 mg or less at a time.^1,5

What the evidence shows

Five graded entries qualify for bone: two for calcium and one each for vitamin D, magnesium and vitamin K. Most describe an established role of the nutrient. Where trials of extra amounts exist, the entry says what they found.

Needed to build and maintain bones and teeth*^1,5

Moderate evidence

A long-established role of the mineral, described by NIH. About 98% of the body's calcium sits in the skeleton, and the recommended amounts for adults were set at the intake needed to maintain bone. The skeleton is also the reserve the body draws on to keep blood calcium steady, so a shortfall shows up in bone over years rather than in a blood test.

Amount studied: Recommended intake: 1,000 mg a day for most adults, 1,200 mg for women over 50 and everyone over 70

Produces small gains in bone mineral density in adults over 50*^1,3,6

Moderate evidence

A meta-analysis of 51 randomized trials of calcium supplements in 12,257 people over 50 found bone density 0.7% to 1.8% higher at five skeletal sites, with similar gains from extra dietary calcium. The gain appeared within a year and did not grow after that; it was similar with or without vitamin D and at higher or lower doses, and the authors judged it too small to be likely to matter clinically. In the Women's Health Initiative, 1,000 mg of calcium with vitamin D a day left hip bone density 1.06% higher after about 7 years.

Amount studied: Calcium supplements from under 500 mg to over 1,000 mg a day, with or without vitamin D, for one to several years

Helps the body absorb calcium and maintain normal bones*^2,4,7

Moderate evidence

This is vitamin D's best-established role and the basis of official intake recommendations. It matters most when intake and sun exposure are low. In adults who mostly had adequate levels already, extra vitamin D gave no added benefit for bones: VITAL tested 2,000 IU a day in 25,871 people for about five years and found no difference from placebo.

Amount studied: The recommended 15 to 20 mcg (600 to 800 IU) a day from all sources; VITAL tested 2,000 IU a day on top of diet

Contributes to the normal structure of bone*^8,9

Moderate evidence

A long-established role of the mineral, described by NIH: half or more of the body's magnesium is held in bone, where it is part of the bone's structure and takes part in bone formation. This is a role of the nutrient. NIH describes the trials of whether extra magnesium changes bone density as few and small, and says more research is needed.

Amount studied: Recommended daily intake from food and supplements

Contributes to the maintenance of normal bones*^10,11

Moderate evidence

Vitamin K is needed to activate osteocalcin, a protein in bone, and NIH reports that the European Food Safety Authority found a cause and effect relationship between dietary vitamin K and the maintenance of normal bone. Supplements beyond a normal intake are another matter: trials are mixed, a 2019 review of 36 randomized trials found no clear effect on bone mineral density in women after menopause once lower quality trials were set aside, and the FDA has not authorized a health claim for vitamin K in the US.

Amount studied: Adequate intake of 90 to 120 mcg a day from food; supplement trials used from 180 mcg of MK-7 to 45 mg of MK-4 a day

How much adults need

Recommended daily amounts for adults, from all sources^1,2,5,8,10
Nutrient	Recommended per day
Calcium	1,000 mg, rising to 1,200 mg for women from 51 and men from 71
Vitamin D	15 mcg (600 IU) from 19 to 70, 20 mcg (800 IU) from 71
Magnesium	400 to 420 mg for men, 310 to 320 mg for women
Vitamin K	120 mcg for men, 90 mcg for women (adequate intake)

The body absorbs calcium best in amounts of 500 mg or less at a time. Someone taking 1,000 mg a day from supplements does better with two smaller doses than one large one.^1,5

Calcium supplements are generally absorbed better when taken with food, whatever the form and even in people with low stomach acid.¹

Vitamin D is fat soluble, so it is best absorbed with a meal or snack that includes some fat. Some is absorbed even without fat.^2,12

Food first

Dairy foods supply most of the calcium in American diets, but they are not the only source.^1,5

Eight ounces of plain low-fat yogurt has about 415 mg of calcium, a cup of nonfat milk 299 mg, 3 ounces of canned sardines with bones 325 mg, and half a cup of firm tofu made with calcium sulfate 253 mg.¹

Canned sardines and salmon with the bones, kale, broccoli and Chinese cabbage also provide calcium, and many fruit juices, soy and almond drinks, tofu and cereals have calcium added.^1,5

Fortified foods provide most of the vitamin D in American diets. Almost all US milk is fortified with about 3 mcg (120 IU) a cup, and many plant milks, breakfast cereals and some brands of orange juice, yogurt and margarine have vitamin D added. Cheese and ice cream are usually not fortified.^2,12

Green leafy vegetables are the richest sources of K1. Half a cup of boiled frozen collards has 530 mcg, a cup of raw spinach 145 mcg, a cup of raw kale 113 mcg and half a cup of boiled broccoli 110 mcg.¹⁰

Legumes, nuts, seeds, whole grains and green leafy vegetables such as spinach provide magnesium, as do fortified breakfast cereals, milk and yogurt.⁹

Upper limits and who should ask first

The upper limit for calcium from food and supplements combined is 2,500 mg a day for adults aged 19 to 50 and 2,000 mg from age 51. For children aged 9 to 18 it is 3,000 mg.^1,5

The upper limit for adults and children aged 9 and over is 100 mcg (4,000 IU) a day from all sources, including during pregnancy and breastfeeding. It is 25 mcg (1,000 IU) for babies up to 6 months, 38 mcg (1,500 IU) from 7 to 12 months, 63 mcg (2,500 IU) at ages 1 to 3 and 75 mcg (3,000 IU) at ages 4 to 8. Signs of toxicity are unlikely below 250 mcg (10,000 IU) a day, but NIH notes that even intakes below the upper limit might cause harm over time.^2,12

The upper limit for magnesium from supplements and medicines is 350 mg a day for adults. It does not count magnesium in food and drinks.^8,9

No upper limit has been set for vitamin K, because of its low potential for harm: the expert panel that sets intakes found no reported adverse effects from vitamin K in food or supplements in people or animals. This does not apply to anyone taking warfarin or a similar blood thinner.^10,13

Taking calcium with vitamin D can raise the chance of kidney stones. In the Women's Health Initiative, 36,282 women after menopause given 1,000 mg of calcium and 400 IU of vitamin D a day had 17% more kidney stones over 7 years than those on placebo.²

You take levothyroxine, a quinolone or tetracycline antibiotic, a bisphosphonate, dolutegravir or lithium. Calcium can interact with them.
You have had kidney stones, have kidney disease or have high blood calcium.
You take warfarin or another blood thinner. Vitamin K changes how these medicines work.
You take a diuretic or a medicine for acid reflux, which magnesium can interact with.
You already take a multivitamin, calcium with vitamin D, cod liver oil or prescription vitamin D.

Questions people ask

How much calcium should I take from a supplement?

Count your food first. The body absorbs calcium best in amounts of 500 mg or less at a time, and calcium supplements commonly contain 500 or 600 mg.^1,5

Do I need vitamin D with calcium?

The body needs vitamin D to absorb calcium through the main active route in the gut. Most trials gave both together, so the effect of each is hard to separate.^1,2,5

Does extra magnesium or vitamin K change bone density?

NIH describes the trials of extra magnesium as few and small. For vitamin K, a 2019 review of 36 trials found no clear effect on bone mineral density in women after menopause once lower quality trials were set aside.^8,11

Can calcium and vitamin D cause kidney stones?

In the Women's Health Initiative, 36,282 women after menopause given 1,000 mg of calcium and 400 IU of vitamin D a day had 17% more kidney stones over 7 years than those on placebo. Ask your doctor first if you have had kidney stones.²

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*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.