For years we've been told by governments and health organizations to drink milk to build strong bones and keep them healthy as we age. Health Canada, for instance, recommends consuming milk (or fortified soy beverages) every day to get essential nutrients, particularly calcium, for bone health.
Consuming enough calcium from foods such as milk is thought to protect us from osteoporosis, a bone-thinning disease that increases the risk of fractures, especially of the hip, spine, wrist and shoulder. (Ninety-nine per cent of the body's calcium is housed in our bones.) If your diet lacks calcium, the mineral will be moved from your bones to your bloodstream, where it's needed to conduct nerve impulses, contract muscles and assist in blood clotting. Weakened bones are susceptible to fractures.
Findings from large studies, however, have questioned the ability of milk to prevent osteoporotic fractures. Most have failed to find an association between milk consumption and reduced hip fracture risk.
A review of 52 studies – including only two randomized controlled trials – published on Sept. 29 in the British Medical Journal found no evidence that increasing calcium intake from foods reduced fracture risk. Daily recommended calcium intakes, based on bone health, are 1,000 mg for adults ages 19 to 50, 1,200 mg for women older than 50 and 1,200 mg for men older than 70.
Some research findings also hint that drinking a lot of milk can increase the risk of health problems, including prostate and ovarian cancers and bone fractures. Keep in mind, though, the vast majority of these studies are observational in nature and don't prove causality. Whether milk, the nutrients it contains or other lifestyle factors are to blame isn't clear. Still, their findings may leave some people wondering whether milk is the best way to get their daily calcium.
Milk and dairy products are convenient ways to get calcium – you don't have to give them up – but they are only one of many sources.
You'll find calcium in cooked leafy green vegetables such as kale, collard greens, rapini and bok choy. Spinach and Swiss chard are high in calcium but they also contain oxalates, natural compounds that bind to calcium, making the mineral less available to the body. Other good calcium sources include fortified non-dairy milks (e.g., soy, almond, rice, cashew), soybeans, firm tofu, navy beans, pinto beans, almonds, almond butter, tahini and blackstrap molasses.
It requires more than calcium, however, to maintain strong bones throughout life.
Vitamin D helps the body absorb calcium from the intestines. Vitamin K, found mainly in green leafy vegetables, stimulates the production of proteins that strengthen bone.
Magnesium, plentiful in legumes, nuts, seeds and whole grains, is needed to synthesize hormones involved in calcium balance. Phosphorus, a mineral in dairy products, grains and protein-rich foods, works closely with calcium to form hydroxyapatite, the structural component of bones (and teeth).
Protein, too, is required for building and repairing strong bone tissue. Eating enough protein also helps preserve muscle mass, which is important for mobility and preventing falls.
Including soy in your diet may also benefit bones. Soybeans contain isoflavones, phytochemicals shown to delay bone loss in women.
It's not only women who need to eat foods rich in bone-building nutrients. According to Osteoporosis Canada, at least one in five men will suffer from an osteoporotic fracture during their lifetime. (The same holds true for one in three women.)
Whether or not you are at high risk for osteoporosis, it's never too soon to take dietary action against the disease. The bone loss that can lead to osteoporosis can occur well before you're 50.
Six must-have foods for bone health
When it comes to building strong bones, calcium and vitamin D are key players. But other nutrients are needed, too, including vitamin K, magnesium, phosphorus and protein. The following six foods are true multitaskers when it comes to delivering bone-beneficial nutrients.
Canned sockeye salmon: Salmon, especially sockeye, is one of the few foods that offers a generous amount of vitamin D, a nutrient that helps the body absorb calcium from foods and supplements.
Eighty-five grams (3 ounces) of canned sockeye salmon serves up 730 international units (IU), a little more than Health Canada recommends for children at the age of 1 to adults at the age of 70 (600 IU). (Older adults are advised to get 800 IU a day.) In addition to eating salmon, take a vitamin D supplement (400 to 1,000 IU) year round.
Canned salmon delivers other bone-friendly nutrients, too: 85 g (with bones) provides 17.5 g protein, 200 mg calcium and 277 mg phosphorus.
Collard greens: This leafy green vegetable is a good source of calcium, offering 134 mg per 1/2 cup cooked. You'll get more calcium if you eat your greens cooked rather than raw since heat releases some of the calcium bound to natural compounds called oxalates.
Collard greens are also an exceptional source of bone-building vitamin K (386 micrograms per 1/2 cup). Studies have linked higher intakes of vitamin K to a lower risk of hip fracture in men and women and higher bone density in women. Research suggests it takes about 200 mcg of vitamin K a day to protect bones, an amount higher than the official daily-recommended intakes (90 mcg for women and 120 mcg for men).
Pumpkin seeds: Their claim to fame is magnesium, a mineral that helps balance calcium in the blood and contributes to healthy bone structure. Some studies have tied higher dietary magnesium intakes to higher bone densities in women and men.
One 1/4 cup of pumpkin seeds supplies a generous 162 mg of magnesium, 40 per cent to 50 per cent of a day's worth. (Men need 420 mg of magnesium daily; women require 320 mg.) One 1/4 cup of pumpkin seeds also provides half a day's worth of phosphorus (370 mg) and three grams of protein.
Soybeans: A 3/4 cup serving of cooked soybeans delivers 24 g of protein, 131 mg of calcium and more than one-quarter of a day's worth of magnesium (111 mg). Soybeans are also one of the best sources of isoflavones, natural plant compounds found, in many studies, to slow down bone loss in peri- and postmenopausal women.
Research suggests a daily intake of 80 mg to 90 mg of isoflavones is needed to improve bone mineral density. (One 3/4 cup serving of soybeans contains 84 mg.)
Edamame, young green soybeans, is also a good source of protein (16.5 g per three-quarters of a cup), calcium (195 mg), magnesium (81 mg) and, to a lesser extent, isoflavones (24 mg).
Greek yogurt: Made from milk, Greek yogurt is, of course, an excellent source of calcium (so is regular yogurt). A 3/4 cup serving of plain Greek yogurt contains, on average, 200 mg of the mineral. (Some brands supply half a day's worth of calcium – 500 mg – in one serving.)
But when it comes to bone health, plain Greek yogurt has an edge over its regular counterpart thanks to its hefty protein content: 18 g per 3/4 of a cup versus regular yogurt's 9 g. Greek (and regular) yogurt also offers a generous amount of phosphorus and some magnesium.
Tahini: Made from ground roasted sesame seeds, tahini is a decent source of calcium, offering 128 mg per two tablespoons. Along with calcium, two tablespoons of tahini also provides 5 g of protein, 28 mg of magnesium and 220 mg of phosphorus (adults need 700 mg of phosphorus a day).
For a change from peanut or almond butter, spread tahini on whole grain toast, crackers and apple slices or add it to smoothies and protein shakes.
Leslie Beck, a registered dietitian, is based at the Medisys clinic in Toronto.
How much calcium do I need?
The recommended daily amount of calcium you need (in milligrams) depends on your age.
Children, 1 to 3 years: 700
Children, 4 to 8 years: 1,000
Children and teens, 9 to 18 years: 1,300
Adults, 19 to 50 years: 1,000
Women, 51+ years: 1,200
Men, 71+ years: 1,200
Source: U.S. Institute of Medicine