Calcium is the basic building block of bone, but bones need a great many other nutrients in order to stay strong.
Calcium absorption requires vitamin D. If you don’t get enough D, calcium provides much less benefit. In fact, research suggests that the more vitamin D you get, the less calcium you need. We recommend 800 to 1,000 IU for most people, which usually requires a supplement, since the vitamin is found in few foods. If a test reveals that your level of D is very low and/or you have osteoporosis, you may need higher intakes. Though the skin makes the vitamin in response to sun, you shouldn’t rely on this, since D production can vary widely, depending on many factors, and since sun exposure can cause skin cancer.
This is needed for bones to synthesize proteins involved in calcium utilization. Many studies have found that people who consume the most vitamin K from food have higher bone mineral density and reduced risk of osteoporosis. Research on supplements has been less consistent. Still, a 2009 review in Nutrition Research found that high doses of K (at least 200 micrograms) improve bone quality and reduce fracture risk in older women. While it’s too early to recommend supplements, it’s a good idea to get more vitamin K from food—notably from broccoli, spinach, kale and other leafy green vegetables. Vitamin K can interfere with the anticoagulant warfarin (Coumadin), so if you take this drug, talk to your doctor about how much K is safe to consume.
Working with calcium and vitamin D, magnesium helps form and maintain bones. People with high magnesium intakes tend to have greater bone density. It’s not known if supplements make a difference. While a magnesium deficiency can impair the body’s use of calcium and vitamin D, doubling or tripling the recommended magnesium intake (320 milligrams a day for women, 420 for men) does not increase calcium absorption.
Other key nutrients for bone health
Phosphorus, potassium, fluoride, iron, zinc, copper, silicon, manganese, boron, vitamin C and strontium are bone-friendly elements. You need some vitamin A for healthy bones, but too much (more than about 6,000 IU a day from food and supplements) can cause bone loss. Substances in soy (isoflavones), fish (omega-3 fats) and tea (flavonoids) have been linked to bone health, but research has been inconsistent. A high sodium intake causes calcium to be leached from bones.
Where can you find bone-healthy nutrients?
Choose a diet rich in vegetables (especially dark leafy greens), fruits and whole grains, plus dairy products and fortified cereals. And consider taking a vitamin D supplement.