Good reasons for taking vitamin D

~ March 25, 2008

BY DR. DAVID WONG
The Prince Edward Island Guardian
www.theguardian.pe.ca

Question: I am the mother of three lovely children. When our third child was born six weeks ago, our family doctor told me that I should give him vitamin D everyday because I am breast-feeding him.

I breast-fed our two older children but I never gave them any vitamin D, and they are perfectly fine. I wonder whether I should follow our doctor’s suggestion.

Answer: Your doctor is correct, you should give him vitamin D 400 international units (IU) a day because you are breast-feeding him. Recent research shows that many children and adults in Canada are not getting enough Vitamin D, and this can affect our health.

Vitamin D is normally produced in our skin when it is exposed to ultraviolet light rays from the sun. If a white-skinned person in a bathing suit is exposed to summer sun around noon time for 15 to 20 minutes, about 10,000 IU of vitamin D will be produced by the skin. However, if a dark-skinned person is exposed to the sun in the same way, only about 2,000 IU of vitamin D is being produced.

Melanin, a dark pigment present in the skin, blocks the ultraviolet rays. As a result, less vitamin D is produced. In the same way, if we put on sunscreen lotion or wear long-sleeve shirts and long pants to prevent sunburn, the amount of vitamin D produced in the skin also decreases.

Vitamin D is best known for the growth and development of bones in children. The importance of vitamin D was first discovered in England in the mid-17th century. Physicians at that time saw young children with bone deformities they called rickets. They recognized rickets was most common during winter months and they suspected a link between rickets and exposure to sunlight.

Over time, cod-liver oil was found to be effective in the prevention and treatment of rickets. As a result, vitamin D was discovered and was shown to be important for calcium absorption from the intestines and deposition in the bones.

Because of the importance of vitamin D in the prevention and treatment of rickets, all cow’s milk (except yogurt drinks), soy milk and some orange juice sold in North America are fortified with vitamin D. For a long time, many people, including physicians, thought that these measures had eradicated rickets completely.

In 1984, several Canadian researchers reported 16 Inuit infants living in high Arctic coastal communities with vitamin D deficiency rickets. This report rekindled interest in vitamin D and the fact that rickets still occurs in spite of years of fortification of cow’s milk and other products.

In 2007, another group of researchers reported a two-year study which identified 104 children across Canada with rickets due to a lack of vitamin D in their diet. Most of these children lived in the far north, many were breast-fed and had no vitamin D supplement given to them. Their mothers also lacked vitamin D because of limited exposure to the sun and did not have enough vitamin D from their diet or supplementation during pregnancy and while they were nursing.

These findings highlighted the importance of lack of sun exposure for Canadians, especially during the fall and winter months, and a deficiency of vitamin D in the body. Unless the diet is rich in vitamin D, supplementation is necessary to prevent a vitamin D deficiency state.

Aboriginals have changed their diet in recent years. They used to hunt and fish and stay active outdoors much of the time. Their source of food used to have good amount of vitamin D. However, with a more westernized diet, their intake of vitamin D has decreased.

Although breast milk is the most natural and nutritious food for babies, it does not contain enough vitamin D unless the mother’s vitamin D level is high, either from lots of sun exposure or taking significant amount of vitamin D (from food or supplements, or both) during pregnancy and breast-feeding.

Because of these findings, the Canadian Paediatric Society now recommends that all breast-fed babies should be supplemented with 400 IU of vitamin D everyday during the first year of life.

For those who live in areas further north than approximately Edmonton, Alta., the amount of vitamin D required from all sources should be increased to 800 IU per day between October and April.

It is also recommended that pregnant and breast-feeding women should receive 2,000 IU of vitamin D a day. This recommendation is based on the lack of sunshine in Canada, as well as the importance of vitamin D in the development of bones and other organs in babies before and after birth.

Recent research also suggests vitamin D is important for most parts of the body, not only for bones. All chemicals interact with cells in the body through receptors, which are like doors that allow chemicals to enter cells. Most cells in the body have vitamin D receptors, which means that vitamin D is important in the function of most cells in the body.

A number of medical conditions have been linked to a lack of vitamin D. These include osteoporosis, asthma, rheumatoid arthritis, multiple sclerosis (MS), inflammatory bowel diseases (Crohn’s disease and colitis), diabetes, disturbed muscle function, tuberculosis and several types of cancer. Many of these diseases are much more common in countries like Canada and northern Europe.

Because of recent research findings, the Canadian Cancer Society recently recommended that all white adults take 1,000 IU of vitamin D a day in fall and winter, while non-whites should take this amount year-round.

Most multivitamin pills only have 400 IU of Vitamin D, although 1,000 IU vitamins D pills are becoming more available recently.

Although vitamin D is very important for the body in many ways, we still don’t know what is the maximum safe dose that one can take.

More does not necessary mean better or safe. Excessive amount of vitamin D can increase calcium level in the blood and cause calcium deposits in places where it shouldn’t happen.

Until research can answer some of these questions, the safest way is to follow the recommendations of these professional societies. In the meantime, it likely won’t hurt for you to get some natural vitamin D on a sunny day, although this has to be balanced with danger of sunburn and long-term risk of skin cancer.

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Dr. David Wong is a consultant pediatrician in Summerside and president of the Community Paediatric Section of the Canadian Paediatric Society. His column is in The Guardian every four weeks. You can find his previous columns at www.askdrwong.ca. If you have a question for Dr. Wong, mail it to: Ask Dr. Wong, P.O. Box 21018, Summerside, P.E.I., C1N 6A1.