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FROM THE EDITORS

Building blocks of bone


Robert D. Sheeler, M.D.
Medical Editor, Mayo Clinic Health Letter


It's hard to keep all the balls in the air when you're juggling everything you're supposed to be doing to maintain good bone health. I find in clinical practice that doctors may provide too much advice sometimes and people may lose track of one or two factors that are critical to the success of building and maintaining bone.

If you can keep things simple, you'll have a better chance of reaching your goals. I consider three elements are necessary if you want to build a strong foundation for bone health: calcium, vitamin D and exercise. You may come across various, conflicting levels of calcium and vitamin D intake recommended by different agencies and organizations. Here are the levels that I try to get for myself. They're also what I tell my family to achieve:

  1. Adequate calcium intake — Aim for 1500 milligrams (mg) per day. Don't count on more than 500 mg of calcium at any one time because that's the most your body can absorb in a single dose. As a supplement, I prefer calcium citrate, as it has been proven to help bone density, it's well absorbed and well tolerated by most people, and the citrate may help to prevent kidney stones. See the tables below that list common dietary sources of calcium and describe different calcium supplements.  I hope they may be of help to you.
     
  2. Adequate vitamin D — Aim for 800-1000 units per day. Vitamin D increases calcium absorption in your body. If you don't get enough vitamin D, the calcium level in your bloodstream drops. You can take vitamin D along with a calcium citrate supplement. Taking two tablets twice daily will give you 800 units of vitamin D. People may get a little bit more vitamin D from sun exposure but too many spend too much time indoors or live too far north to count on sunshine to meet their vitamin D needs. Plus, damaging sun exposure can increase your risk of skin cancer. Vitamin D toxicity is not likely to occur if daily doses are under 2000 units per day.
     
  3. Weight-bearing exercise — Aim for 35 minutes per day. Exercise that causes your lower extremities to bear the weight of your body is the kind of activity that helps preserve and maintain bone density. Walking is an excellent choice because it's the best-tolerated exercise that most people can do on a long-term basis. Higher impact activities such as running, using stair machines and participating in sports like basketball and racquetball can build even stronger bones, but there's the trade-off of increased risk of orthopedic injury that may limit your ability to participate on an ongoing basis. The highest bone density I have ever seen was in a middle-aged woman who rollerbladed every day for 2 to 3 hours. Her cardiovascular health was also amazing.

You might try keeping a log for a week to see how much calcium and vitamin D you get on a regular basis. Then plan to take supplements, if you need to, based on those amounts. If you know the numbers well, you can add up how much you have gotten though the day and then top off your requirements with a supplement in the evening — providing you're within 500 mg of your 1500 mg target level for calcium, since 500 mg is as much as you can absorb at once.

Something else that gets people in trouble is thinking that they don't need to follow these rules if they're on a medication for osteoporosis. In fact, think of osteoporosis medicine as better concrete for bone building. You still need bricks (calcium and vitamin D) to form a solid structure and exercise as a stimulus, telling your body where the bone should be built.

Common dietary sources of calcium

Food

Amount

Calories

Calcium (mg)

Milk, low-fat (1%)

1 cup

100

290

Milk, skim (fat-free)

1 cup

85

305

Yogurt, plain, low-fat

1 cup

155

450

Yogurt, fruited, low-fat

1 cup

245

340

Swiss cheese

1 ounce

110

225

Cheddar cheese

1 ounce

115

205

Mozzarella cheese, part-skim

1 ounce

70

220

Cottage cheese, low-fat (1%)

1 cup

165

140

Sardines, canned, with bones

3 ounces

175

325

Salmon, sockeye, canned, with bones

3 ounces

140

190

Orange juice, calcium-fortified

1 cup

110

350

Orange

1 large

85

75

Papaya

1 medium

120

75

Rhubarb, cooked and sweetened

½ cup

140

175

Spinach, fresh, cooked

½ cup

20

120

Beans, baked

½ cup

135

65

Broccoli, fresh, cooked

½ cup

25

30

Carrots, raw or cooked

½ cup

25

20

Pizza, with cheese

1 slice

270

190

Tomato soup, with milk

1 cup

160

160

Soy milk, calcium fortified

1 cup

100

370

Tofu, prepared with calcium

½ cup

95

435

Almonds, oil roasted (about 22 whole)

1 ounce

170

80

Peanuts, oil roasted (about 32 whole)

1 ounce

165

25

Source: USDA Nutrient Database

 

Common calcium supplements

Calcium carbonate

This type of calcium supplement is the least expensive and most commonly used calcium supplement. It's absorbed best when taken with meals, but it may cause constipation.

Calcium citrate

This type of calcium supplement is the most easily absorbed, is less likely to cause abdominal discomfort and doesn't have to be taken with meals.

Calcium phosphate

This type of calcium supplement is the least likely to cause constipation.


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