Vitamin D

Vitamin D doesn’t get a lot of respect. Oh, sure, we need this nutrient to build strong bones. But what else has vitamin D done for us lately? Well, word has it that the sunshine vitamin is looking for a little respect.

A long list of research initiatives has linked vitamin D deficiency with conditions as diverse as osteoporosis, multiple sclerosis, cancer, and diabetes. These links are a wake-up call for Canadians, one of the most at-risk populations for vitamin-D deficiency. Most Canadians need to supplement with vitamin D due to our low levels of sunlight in winter.

Sunny D

With the exception of fish liver oils and enriched food products, few significant dietary sources of vitamin D are available. Therefore exposure to sunlight is key to metabolizing healthy levels of vitamin D.

Sunlight reacts with a derivative of cholesterol in our skin to form vitamin D, or more specifically, vitamin D3 (cholecalciferol), which in turn is converted into its active hormone form, calcitriol.

Calcitriol, also called hormone D, actively participates in the absorption of calcium in the intestines. It also maintains calcium and phosphorus levels in the blood. Most important, calcitriol aids in cell differentiation and the expression of several types of white blood cells, including monocytes, and activates B and T cells.

Boning Up

Profound vitamin-D deficiency gives rise to conditions characterized by malformed, weak, thin, and brittle bones in both children and adults. Further, individuals who suffer from the bone loss of osteoporosis typically have low levels of vitamin D.

The results of a study of 548 patients 60 years of age or older who were admitted at South Glasgow University Hospital in Scotland for nonvertebral fractures, showed that 97 percent of the patients had vitamin D levels below normal. This result is to be expected given vitamin D’s role in calcium absorption and regulation.

Builds Immunity

A large-scale study reported in the January 2004 issue of the journal Neurology involved 187,563 participants and found that women whose daily vitamin D intake was equal to or higher than 400 IU had a 40 percent lower risk of developing multiple sclerosis (MS) than women with lower intakes. In addition, lower levels of sunlight in northern countries such as Canada lead to lower levels of vitamin D in the population and correspondingly higher MS rates.

A Finnish study following more than 12,000 babies born in 1966 revealed that those who were given the recommended amounts of vitamin D supplement had an 80 percent reduced risk of developing type 1 diabetes. Further, vitamin-D deficiency has been shown to impair insulin synthesis and secretion in humans, underlying a possible link to the onset of type 2 diabetes.

Cancer Prevention

Vitamin D has been the subject of numerous cancer prevention studies. A recent report in the Journal of the National Cancer Institute suggested that vitamin supplementation could reduce cancer-related deaths in men by as much as 30 percent annually.

Apart from helping to prevent cancer and autoimmune diseases, vitamin-D deficiency also contributes to inflammatory diseases, including inflammatory bowel disease, skin conditions, and childhood asthma.

As a population living in a colder, northern climate that requires we wear heavier clothing, Canadians should supplement with vitamin D in order to prevent the health consequences of vitamin-D deficiencies.

Daily Recommended Vitamin D Intake

• Birth to 50 years 200 IU
• 51 to 70 years 400 IU
• Over 70 years 600 to 800 IU

At-risk Canadians

Although breastfed babies receive many nutrients, breast milk is deficient in vitamin D. Combined with the trend toward reduced sun exposure and the use of sunblock on infants and children, and breastfed children may be at greater risk of vitamin-D deficiency. Health Canada recommends that breastfed children receive 400 IU of vitamin D daily.

Falls and fractures are a major health risk for the elderly. Muscle weakness resulting from vitamin-D deficiency is a contributing factor to falls. In one study, incidence of falls was almost halved among elderly participants who took 800 IU of vitamin D daily with calcium
compared with calcium alone.