Standing outside 15 minutes a day three times a week lets the skin produce enough vitamin D most of the year. But workaholism and legitimate fear of skin cancer--sunscreen blocks D production--limit how much Americans produce even in summer. Winter sunlight is not intense enough at most U.S. latitudes to produce any vitamin D, which is why it is now time to switch over to cod liver oil. Ideally you should get your vitamin D level tested. This is a very simple non-fasting blood test that can be done at most commercial labs. At this time of year I have many people taking 10,000 units of vitamin D, in addition to cod liver oil, to get their levels back up. Please note that this type of dose should only be used with blood monitoring, as vitamin D toxicity is not easily treated.
NewsDay October 27, 2003
ABC News October 28, 2003