Calcium and Vitamin D
Dynamic duo for health

Susie Langley, RD

The link between calcium, vitamin D and preventing osteoporosis is widely recognized, but both of these nutrients play other important roles in the body. 

Emerging evidence is prompting nutrition experts to reconsider the present daily requirements for vitamin D. It now appears that D may enhance immunity and help prevent some cancers. Researchers at Emory University in Atlanta and Harvard University in Boston are predicting that improving vitamin D status might ward off up to half of all breast cancers and two thirds of colorectal cancers diagnosed in the U.S. Vitamin D receptors in skeletal muscle may be involved in the prevention and treatment of multiple sclerosis; receptors in the brain may play a role the treatment of neurological diseases such as Alzheimer’s and Parkinson’s.

Endocrinologist Dr. Michael Holick, a professor of medicine at Boston University, believes that vitamin D deficiency is reaching epidemic proportions. Mounting evidence implicates D deficiency in an increased risk for type 1 diabetes, rheumatoid arthritis, hypertension, multiple sclerosis, psoriasis, heart disease and certain cancers. Holick advises having your vitamin D status checked at your yearly physical.

A deficiency of vitamin D causes the softening of the bones known in children as rickets, and this appears to be on the rise. A recent study found 104 cases of rickets in Canadian children. In adults the condition is called osteomalacia and it carries an increased risk of osteoporosis and fractures. In the past, rickets were eradicated by sun exposure and vitamin D–fortified milk. D is called the sunshine vitamin because the body makes it from a cholesterol-like substance when skin is exposed to solar ultraviolet rays.

As many as 80% of older women worldwide may have low blood levels of vitamin D. Studies done at Cornell University Medical School in New York found that only 10% of women had normal blood levels of vitamin D, compared with 40% of men. Canadians are considered at higher risk for D deficiency because of our northern latitude and low sun exposure during the winter months.

As for calcium, besides keeping teeth and bones healthy, this crucial mineral plays an important role in muscle contraction, conduction of nerve signals and healthy blood pressure levels. It is important for normal blood clotting and may also help prevent colon cancer. But calcium can’t do its famous bone-building act without its partner, vitamin D, which signals the intestines to absorb more calcium.

It is important to maintain adequate calcium and vitamin D at all ages. Many experts recommend an intake of 1,000 international units (IU) daily. New guidelines coming in 2010 may go as high as 1,000 to 2,000 IU a day with an upper tolerable limit of 10,000 IU.

Recommended daily intakes

— Dietary Reference Intakes (National Academies Press, 2006)

Getting more calcium and D

Drink lower-fat milk products or alternative beverages such as soy drinks fortified with vitamin D. An eight-ounce (250-millilitre) serving equals 100 international units (IU) of vitamin D and 300 milligrams of calcium. Boost calcium intake with calcium-fortified tofu and orange juice, dark green leafy vegetables, legumes, nuts and seeds.  

Eat one or more servings per week of fatty fish such as salmon, rainbow trout, Arctic char, mackerel, sardines, anchovies or tuna. A three-ounce (90-gram) serving equals 200 to 600 IU of vitamin D. Liver, egg yolk and lean beef are other good sources.

Take a daily multivitamin with 400 IU of vitamin D. Check the label to make sure it contains the active form, vitamin D₃ (cholecalciferol), not vitamin D₂, known as ergocalciferol.

If your multivitamin does not meet recommended levels for your age group, take a daily calcium and vitamin D supplement, especially during the winter months. (See “Recommended  Daily Intakes,”. You can also visit http://books.nap.edu/html/dri_calcium/tables.html.)

Ask your doctor if you should take a daily vitamin D supplement or a supplement of fish-liver oil, but do not exceed 2,000 IU of vitamin D a day.

Allow your face, arms and hands a few minutes of unprotected daily sun exposure.