The Role of Calcium and Vitamin D in Osteoporosis Prevention

Calcium and Vitamin D are Needed for Strong Bones

The foods we eat contain a variety of vitamins, minerals and other important nutrients that help keep our bodies healthy. Two nutrients in particular — calcium and vitamin D — are needed for strong bones.

The Role of Vitamin D

Vitamin D is needed for the body to absorb calcium. Without enough vitamin D, we can’t form enough of the hormone calcitriol (known as the “active vitamin D”), causing insufficient calcium absorption from the diet.

In this situation, the body must take its calcium from its stores in the skeleton, which weakens existing bone and prevents the formation of strong, new bone.

You can get vitamin D safely in two ways: through the skin and from the diet.

Vitamin D is formed naturally in the body after exposure to sunlight. Fifteen minutes in the sun is plenty of time to manufacture and store all of the vitamin D you need. Experts recommend a daily intake of between 400 and 800 International Units (IU) of vitamin D, which also can be obtained from supplements or vitamin D-rich foods such as egg yolks, saltwater fish and liver. Do not take more than 800 IU per day unless prescribed by your doctor since massive doses up to and over 5,000 IU of vitamin D may be harmful.

The Role of Calcium

Calcium is needed for our heart, muscles and nerves to function properly and for blood to clot. Inadequate calcium significantly contributes to the development of osteoporosis.

Many published studies show that low calcium intake throughout life is associated with low bone mass and high fracture rates. National nutrition surveys have shown that many women and young girls consume less than half the amount of calcium recommended to grow and maintain healthy bones.

However, calcium alone cannot prevent osteoporosis and is not a substitute for medication that may be needed to curb excessive bone loss.

Recommended Calcium Intakes

Amount of daily recommended calcium by age, from The National Academy of Sciences (1997):


  • Birth - 6 months = 210 mg
  • 6 months - 1 year = 270 mg

Children/Young Adults:

  • 1 - 3 years = 500 mg
  • 4 - 8 years = 800 mg
  • 9 - 18 years = 1,300 mg

Adult Women and Men:

  • 19 - 50 years = 1,000 mg
  • 50 + years = 1,200 mg

Pregnant or Lactating:

  • 18 years or younger = 1,300 mg
  • 19 - 50 years = 1,000 mg

Calcium Culprits: Protein and Sodium

While a balanced diet aids calcium absorption, high levels of protein and sodium (salt) in the diet also are thought to increase calcium excretion through the kidneys. Excessive amounts of these substances should be avoided, especially in those who have low calcium intake.

Lactose Intolerance

Lactose intolerance also can lead to inadequate calcium intake. Those who are lactose intolerant have insufficient amounts of the enzyme lactase that is needed to break down the lactose found in dairy products. In order to include dairy products in the diet, dairy foods can be taken in small quantities or treated with lactase drops, or lactase can be taken as pills. There are even some milk products on the market that already have been treated with lactase.

Calcium Supplements

If you have trouble getting enough calcium in your diet, you may need to take a calcium supplement.

The amount of calcium you will need from a supplement depends on how much calcium you obtain from food sources. There are several different calcium compounds from which to choose, such as calcium carbonate and calcium citrate, among others.

It is necessary for the calcium tablet to disintegrate in order to be absorbed by the body. If you are unsure whether a tablet will break down, you can test how well it disintegrates by placing it in six ounces of vinegar or warm water, stirring occasionally for 30 minutes. If the tablet has not almost completely disintegrated in this time, it probably will not do so in your stomach.

All calcium supplements are better absorbed when taken in small doses (500 mg or less) several times throughout the day. In many individuals, calcium supplements are better absorbed when taken with food.

A Complete Osteoporosis Program

Remember, a calcium-rich diet is only one part of an osteoporosis prevention or treatment program. Like exercise, getting enough calcium is a strategy that helps strengthen bones at any age. But these approaches may not be enough to stop bone loss caused by lifestyle, medications or menopause.

It is important to speak to your doctor to determine the need for an osteoporosis medication in addition to diet and exercise.

Source: NIH ORBD ~ NRC, Calcium & Vitamin D: Important at Every Age, Rev. 2/2003

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