Many segments of the U.S. population fall short of meeting their calcium requirements and there is an increasing concern that this will lead to a rise in the number of major chronic diseases, such as osteoporosis, hypertension, and some cancers, among others. The role of calcium in preventing these diseases has been well established. To help solve the calcium crisis, a wide variety of calcium-fortified foods and beverages are becoming available. Both the level of calcium added and the specific foods and beverages fortified with calcium are arbitrary. Orange juice, juice drinks, cereals, waffles, snack foods, candy, water, and dairy foods are among some of the foods fortified with calcium. In many cases, relatively high levels of calcium are added. This has led to the question of whether calcium fortification has gone too far.

What are the functions of calcium?

Calcium is essential to:

• maintaining total body health,
• normal growth and development,
• keeping your bones and teeth strong over your lifetime (they contain 99% of the body’s calcium, the remaining 1% is in blood),
• ensuring the proper functioning of muscles and nerves,
• keeping the heart beating,
• helping blood clotting and regulating blood pressure,
• metabolising iron,
• the action of a number of hormones (particularly those associated with the thyroid and parathyroid glands),
• cell structure, and
• absorbing vitamin B12.

Calcium deficiency is usually due to an inadequate intake of calcium. When blood calcium levels drop too low, the vital mineral is ‘borrowed’ from the bones. It is returned to the bones from calcium supplied through the diet. If an individual’s diet is low in calcium, there may not be sufficient amounts of calcium available in the blood to be returned to the bones to maintain strong bones and total body health.

What are the problems with calcium-fortified foods?

Although there is a need to have an adequate amount of calcium in the diet concerns have been expressed about the large number of calcium-fortified foods and beverages available. These concerns include the following:

• The use of calcium-fortified foods does not correct the poor dietary patterns of food selection, which are largely responsible for Americans’ low calcium intake. Many calcium-fortified foods and beverages such as juices, spreads/margarines, snack foods, and water are not nutritionally equivalent to foods, which are naturally rich in calcium. Also, some people may mistakenly believe that intake of calcium-fortified foods ensures a nutritionally adequate diet.
• The increased availability of calcium-fortified foods, many of which contain high levels of calcium, makes it relatively easy to exceed the safety limit or the ‘Tolerable Upper Intake Level’ of 2,500 mg calcium/day. This is particularly true for groups not actually at risk for calcium deficiency, such as adolescent and young adult males. These groups already meet or are close to meeting their calcium requirements.

• Other concerns associated with some calcium-fortified foods and beverages relate to:

• The unknown level of calcium bioavailability (that is, the amount of calcium, from the fortified food, that the body is able to use). Factors that facilitate the absorption of calcium include:

- vitamin D and Vitamin K,- sufficient hydrochloric acid in the stomach,

- small amounts of fat (high fat reduces the availability of calcium),

- exercise,

- magnesium, and

- hormones, including the parathyroid and estrogen hormones.

• If these factors are themselves deficient then the calcium will not be absorbed and will not be available for use by the body.

• Increasing calcium but not magnesium intakes, has caused a nationwide imbalance in optimal calcium to magnesium ratios. Research studies have shown that animals fed diets deficient in magnesium develop skeletal abnormalities, including osteoporosis. When calcium in the body is too high compared to magnesium, excess calcium may be deposited in the soft tissues. This may result in calcium deposits in places such as the kidneys, the arteries and the heart.

• Excessively high intakes of calcium can interfere with the absorption of zinc, magnesium, iron, phosphorus and other nutrients. An increased intake of calcium in the diet increases requirements for magnesium, another mineral important for bone health.

Food, especially food naturally containing calcium, is the first priority in meeting calcium needs. Foods naturally containing calcium provide many other essential nutrients, as well as possibly other health-promoting components, in addition to calcium. Food sources of calcium are leafy green vegetables, root vegetable, salmon, nuts, tofu and broccoli.

For individuals who, for one reason or another, are unable to eat calcium rich food, calcium-fortified foods and/or calcium supplements in a balanced formula can be consumed to achieve adequate calcium intake. However, these are considered a supplement to and not a substitute for, foods naturally containing calcium. When calcium supplements are taken it is also important to ensure that the calcium is in balance with the other nutrients that are required by the body for the calcium to do its work.

What are adequate intakes of calcium?

Adequate Intakes (AIs) for calcium are:

500 mg for children aged 1 to 3 years,

800 mg for children aged 4 to 8 years,

1,300 mg for adolescents aged 9 to 18 years,

1,000 mg for adults aged 19 to 50 years, and

1,200 mg for adults aged 51 years and older.

The Recommended Daily Allowances (RDA) are lower than the AIs but many health professionals do not see the RDAs as being sufficient for maintaining health and wellbeing.

Signs of calcium toxicity can include: confusion, slow or irregular heartbeat, bone or muscle pain, nausea and vomiting.

Conclusion

Calcium is an important mineral for health. It is involved in many functions in the body and there is no doubt that many Americans are not getting enough calcium in their diets. The fortification of foods and beverages with calcium is an attempt to increase calcium intake, however this is a simplistic response to a complex problem and may actually lead to more harm than good. In order for a calcium supplement to work the calcium needs to be in balance with the other nutrients need by the body. This balance is not provided by the simple addition of calcium to food.

References

Institute of Medicine, Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. 1997, Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. National Academy Press.

U.S. Department of Health and Human Services. 2000, Healthy People 2010. (Conference Edition in Two Volumes).Washington, D.C..

U.S. Department of Agriculture, Agricultural Research Service, Food Surveys Research Group. 1996, Pyramid Servings Data. Results from USDA’s 1994-96 Continuing Survey of Food Intakes by Individuals.

Weaver, C.M. 2001, In Bowman, B.A., and R.M. Russell, (Eds). Present Knowledge in Nutrition. 8th edition. ILSI Press.