Smart Choices: Getting enough vitamin D?
Published 12:00 am, Wednesday, August 11, 2010
Vitamins don't usually make the news, but right now in the world of nutrition, vitamin D is getting a lot of ink.
And with good reason: New research shows lifestyle changes have taken us to the point where half of the population isn't getting enough of the so-called sunshine vitamin, a deficiency that has important implications for fighting disease, keeping newborn babies healthy and making sure we do everything we can for the physical and mental well-being of the elderly.
Unlike other vitamins, vitamin D is absorbed primarily from exposure to the sun rather than from what we eat.
With each generation, we've lived less outdoors and more indoors. When we are in the sun, we're conditioned to use sunscreen to block ultraviolet rays that can damage our skin.
Adults and children have become more sedentary, jobs have moved inside, and television and other media have reduced our open-air activities.
“I became interested in vitamin D research when I learned so many people had a deficiency,” said Kendra Glassman, registered dietitian at Audie Murphy VA Hospital in San Antonio. “I started testing all my patients in the intensive care unit.”
Glassman found that 98 percent of her patients had hypovitaminosis D, or deficient levels of the vitamin.
“All but two were above the threshold, but still considered low,” reported Glassman, who starts patients on a supplement regimen to correct the deficiency.
Vitamin D strengthens bones by speeding the absorption of calcium, but research also shows that it works to prevent high blood pressure, autoimmune diseases and some cancers.
I exercise regularly outdoors, but I also use sunscreen, so I decided to get myself tested.
I was surprised to receive a “low-normal range” result. My physician recommended an over-the-counter calcium and vitamin D supplement.
Given the plentiful supply of the sun's ultraviolet B rays, or UVB, that triggers vitamin D production in the skin, it's surprising that so many people fail to get the daily minimum requirement.
The skin can synthesize the vitamin in as little as 10 minutes of sun exposure, depending on the season, whether the sky is clear, time of day, latitude, skin pigmentation and sunscreen use.
Good food sources of the fat-soluble vitamin include salmon, tuna and mackerel. Smaller amounts are found in beef liver, egg yolks and cheese.
Many foods are fortified with the vitamin, including milk, boxed cereals and some brands of yogurt, orange juice, soy drinks and margarine.
Some medical researchers are so convinced by the new research they are taking vitamin D supplements in excess of the currently established upper-level intake.
Time will tell if the research is overstated or if an increase in the daily recommended intake is merited.
Many multivitamins and calcium supplements contain vitamin D in an “adequate intake” amount, which vary according to age. From birth to age 50 we require 200 International Units per day. That figure doubles to 400 IU for people ages 51 to 70 and increases to 600 IU for people older than 70.
Does your diet and lifestyle provide you with sufficient vitamin D? Find out by asking your physician to test your levels.
There's a good chance you're not getting enough vitamin D. If not, supplements may be the most sensible course of action.
Siobhan Walsh is a registered dietitian. Her Smart Choices column appears every other Sunday in Taste.
E-mail her at firstname.lastname@example.org.