To protect your bones you do need calcium in your diet, but you also need to keep calcium in your bones.
How to get Calcium into your bones
Greens, beans, or fortified foods.
The most healthful calcium sources are green leafy vegetables and legumes, or "greens and beans" for short. Broccoli, Brussels sprouts, collards, kale, mustard greens, Swiss chard, and other greens are loaded with highly absorbable calcium and a host of other healthful nutrients. The exception is spinach, which contains a large amount of calcium but tends to hold onto it very tenaciously, so that you will absorb less of it.
Beans are humble foods, and you might not know that they are loaded with calcium. There is more than 100 milligrams of calcium in a plate of baked beans. If you prefer chickpeas, tofu, or other bean or bean products, you will find plenty of calcium there, as well. These foods also contain magnesium, which your body uses along with calcium to build bones.
If you are looking for a very concentrated calcium source, calcium-fortified orange or apple juices contain 300 milligrams or more of calcium per cup in a highly absorbable form. Many people prefer calcium supplements, which are now widely available.
Dairy products do contain calcium, but it is accompanied by animal proteins, lactose sugar, animal growth factors, occasional drugs and contaminants, and a substantial amount of fat and cholesterol in all but the defatted versions.
Exercise, so calcium has somewhere to go.
Exercise is important for many reasons, including keeping bones strong. Active people tend to keep calcium in their bones, while sedentary people lose calcium.
Vitamin D from the sun, or supplements
Vitamin D controls your body's use of calcium. About 15 minutes of sunlight on your skin each day normally produces all the vitamin D you need. If you get little or no sun exposure, you can get vitamin D from any multiple vitamin. The Recommended Dietary Allowance is 600 IU (5 micrograms) per day. Vitamin D is often added to milk, but the amount added is not always well controlled.
How to Keep It There
It's not enough to get calcium into your bones. What is really critical is keeping it there. Here's how:
Reduce calcium losses by avoiding excess salt.
Calcium in bones tends to dissolve into the bloodstream, then pass through the kidneys into the urine. Sodium (salt) in the foods you eat can greatly increase calcium loss through the kidneys.If you reduce your sodium intake to one to two grams per day, you will hold onto calcium better. To do that, avoid salty snack foods and canned goods with added sodium, and keep salt use low on the stove and at the table.
Get your protein from plants, not animal products.
Animal protein in fish, poultry, red meat, eggs, and dairy products tends to leach calcium from the bones and encourages its passage into the urine. Plant protein in beans, grains, and vegetables does not appear to have this effect.
Smokers lose calcium, too. A study of identical twins showed that, if one twin had been a long-term smoker and the other had not, the smoker had more than a 40 percent higher risk of a fracture.
American recommendations for calcium intake are high, partly because the meat, salt, tobacco, and physical inactivity of American life leads to overly rapid and unnatural loss of calcium through the kidneys. By controlling these basic factors, you can have an enormous influence on whether calcium stays in your bones or drains out of your body.
Did you know?
Most humans have some degree of lactose intolerance. For them, eating or drinking dairy products causes problems like cramping, bloating, gas, and diarrhea. These symptoms can range from mild to severe. Certain groups are much more likely to have lactose intolerance. For example, 90 percent of Asians, at least 70 percent of blacks and First Nations, and approximately 50 percent of Hispanics, Jews and people from Southern India are lactose intolerant, compared to only about 15 percent of people of Northern European descent. To suggest that dairy is a necessary part of our diet is to ignore that most humans are unable to digest it and cannot possibly require it to have a healthy life. More on food equity here.