Osteoporosis, Rickets, Hip fractures
What Most People Don’t Know About Vitamin DBy Dr. Gifford Jones
It’s a rare person who hasn’t some knowledge of vitamin C and E. But vitamin D is the poor cousin. Most people couldn’t fill a postage stamp with what they know about this vitamin. Like other vitamins it has a vital role. And today there’s much interest in it’s involvement in the prevention and treatment of osteoporosis.
Early in the 1900’s researchers discovered that a deficiency of vitamin D caused rickets. This is a childhood disease in which bones fail to develop normally. The result is bowlegs and knock-knees.
The use of vitamin D-fortified milk virtually eliminated rickets in North America. However, some people may still not be getting enough of this vitamin.
We obtain vitamin D from foods and sunlight. Napoleon Bonaparte, brooding in exile on the island of St. Helena, reflected, “Were I to choose religion, I would probably become a worshipper of the sun. It gives life and fertility to all things. It is the true God of the earth”.
Napoleon had no idea then that much of the vitamin D produced by the body starts with the sun. When we’re exposed to ultraviolet rays (UV) a chemical in the skin is changed into an inactive form of vitamin D.
Inactive vitamin D is also present in several foods such as milk, eggs, butter, salmon, herring, mackerel and some breakfast cereals.
The inactive form of vitamin D is transported to the liver. Here it undergoes a second change and the kidneys changes it into the active form the body needs.
Active vitamin D carries out several functions. One step is to enhance the absorption of calcium from the intestines. Another is to help deposit calcium in bones and teeth.
Reports from around the world show that some people still lack adequate amounts of vitamin D. This is amazing since only 15 minutes of direct sun exposure to the face arms and hands three times a week manufactures enough vitamin D.
But getting sunlight isn’t easy if you’re elderly and the streets icy. Or the streets are not safe for walking.
In 1990 a study revealed that 80 percent of people ages 66 to 99 in Boston had decreased stores of vitamin D during the winter. They were spending less time outdoors and heavy clothes protected them from the sun.
In France women in nursing homes or apartments were often found to be consuming inadequate amounts of dairy products. Moreover in France dairy products are not fortified with vitamin D.
French researchers gave these women 800 international units of D along with 1200 milligrams of calcium a day. They discovered during an 18 month period a 43 percent decrease in the number of hip fractures!
We forget that there are times when some populations do not receive the benefit of sunlight. During northern winter months, sunlight is filtered at a more oblique angle through the atmospheric ozone layer. This decreases the ultra-violet radiation that reaches the earth’s surface.
At a latitude above 42 degrees north, vitamin D production in people’s skin ceases from October to the end of February. And that latitude includes all of Canada!
There’s another problem. As we age our body becomes less efficient. In this case the body makes decreased amounts of vitamin D from UV rays.
Illness also plays a role. Liver or kidney disease decreases the ability to change inactive vitamin D into the active form. Bowel problems may also make absorption of vitamin D more difficult. And certain medicines such as Dilantin used in treating epilepsy and irregular heart rhythms can increase the risk of vitamin D deficiency.
What should consumers do? We know that too much sunlight can cause skin malignancy. But a little bit of sunlight goes a long way. The vitamin D you manufacture in the summer is stored in the liver to use during winter months.
You don’t need a sunscreen for 15 minutes in the sun. But use one for longer periods. Sunlight penetrates loosely woven materials like rayon and silk. But not dense materials such as wool or denim. And UV rays won’t pass through ordinary glass windows.
Drink your milk. The recommended daily allowance is two cups of milk to provide the necessary amount of vitamin D for adults.
But for menopausal women and men over 55 years of age there’s increased bone loss and greater need of calcium and Vitamin D. Studies show taking 400 IU of vitamin D, twice the RDA, along with calcium helps to decrease bone loss. But don’t overdose with Vitamin D. Excessive amounts cause nausea, irritability and the formation of calcium deposits in kidneys and lungs.(1) Reader Feedback | Email Article | Email Us | Print friendly
Dr. Gifford Jones Bio
|Dr. Gifford Jones Most recent columns
W. Gifford-Jones M.D is the pen name of Dr. Ken Walker graduate of The Harvard Medical School. He’s been a ship’s surgeon, hotel physician and family doctor and later trained in surgery at McGill in Montreal, University of Rochester N.Y. and Harvard. His medical column is published by 60 Canadian newspapers and several in the U.S. He is the author of seven books. Dr. Walker has a medical practice in Toronto. His Web site is: http://www.mydoctor.ca/gifford-jones