The warmth and brightness of the weekend sun got me thinking about Vitamin D for this week’s Insight. What’s the relationship between this vitamin and sunlight? Why has this nutrient been added to one of our most widely consumed beverages? Let’s bone up on this subject in the paragraphs to follow.
We know that Vitamin D is essential for healthy bones and teeth and regulates the level of calcium in our blood. It also appears to have an essential role in muscle function and in maintaining healthy immune systems. Along these lines, we now have clear evidence that Vitamin D can help to prevent colon cancer and may do the same for breast and prostate cancers. Whether it has any role in the treatment of certain cancers is the subject of ongoing research.
With only 10–15 minutes of sunshine per day, the body can manufacture all the Vitamin D that a person needs. The ultraviolet rays hitting the skin create a chemical reaction that allows this production to occur. Additionally, Vitamin D is found naturally in only fish and fish-liver oils, and to a lesser degree in eggs. Vitamin D is not inactivated by cooking. And, as I mentioned initially, much of our milk is now fortified with Vitamin D as well. So, if you’re healthy, eat a balanced diet, and get outside in the sunshine at least 1.5 to 2 hours a week, you should be getting all the Vitamin D your body needs. Darkly pigmented individuals and people rarely exposed to sunlight are less efficient at manufacturing Vitamin D. Vegans lack the dietary sources, and alcoholism reduces the body’s ability to absorb Vitamin D.
The daily amount of vitamin D needed is defined in several different ways. In the United States, Recommended Daily Allowances or RDAs have become the most common standards to define the amounts of vitamins and minerals necessary for adequate nutrition in healthy folks. RDAs for a given nutrient can vary depending on a person’s age, sex, and physical condition (e.g. Pregnancy or kidney disease). For adolescents and adults, 5–10 micrograms/day(200–400 IUs or International Units) are the RDA, with the amount increasing to 10 micrograms/day for pregnant and breast-feeding women. Older adults generally have the RDA at the higher end (8-10 mcg/day or 400–600 IUs) since our bodies become less efficient in manufacturing the Vitamin as we age. Remember, this total includes both what we consume in our diets and what we take as supplements. Unless specifically instructed by your doctor, you should not exceed the RDA for Vitamin D since it can accumulate in your body and generate harmful health effects as a result.
Just so you’ll know how unpleasant Vitamin D toxicity can be, here’s a listing of the potential/probable symptoms as your body accumulates excess levels. First, you’ll likely have anorexia, nausea and vomiting. . .followed shortly by weakness, nervousness, hypertension, constipation, itching, and excessive and frequent urination. Kidney function becomes impaired, and ultimately, abnormal calcium deposits develop in various organs and body tissues, especially the kidneys. Abnormalities in your urinalysis and high serum levels of calcium will give clues to your physician for appropriate diagnosis. And remember, misguided use of megavitamins can generate all of the above problems if Vitamin D is allowed to accumulate to high levels. So, if you’re one of the folks who gulps handfuls of vitamins and supplements daily in the quest for eternal exuberance, remember to check the levels of fat soluble vitamins in your regimens. Vomiting, uncontrolled scratching and urination, and calcified kidneys hardly make one exuberant. . .or even fun to hang around with for that matter!
Severe Vitamin D deficiency seems to be rare in the United States these days, though in the past, it was more evident, and caused rickets, a disease in which a child’s bones did not form properly. However, Massachusetts General Hospital conducted a study in its clinic population during 1994 and found 57% of the patients to be Vitamin D deficient, 22 % severely so. Decreased exposure to sunlight because of the more severe northern winters was cited as one factor in these results, but the study did generate concern that Vitamin D deficiency might be generally more common than expected in modern American. If this is the case, then it is obviously being both underdiagnosed and undertreated.
I guess I’ve milked this topic enough! So get a little sunshine in your life, eat your fish, and drink fortified skim milk if you don’t suffer from the nuisance of lactose-intolerance. Do supplement with Vitamin D liquids and capsules if you need additional amounts for various health reasons, but remember there are consequences if you exceed what your body can handle! No bones about it, if you stay within the guidelines, you’ll help to maintain your health in a most D‘lightfulWay!
Stephen L. Hines, M.D.
April 2001
