Researchers at the University of Copenhagen have just published an important paper - explaining the mechanisms by which vitamin D helps our immune systems fight off viral and bacterial infections. T cells, the cells that detect and kill foreign pathogens must be triggered into action by vitamin D. When the T cell meets a clump of bacteria or viruses, it extends a signaling device - an antenna - known as a vitamin D receptor. If it finds enough vitamin D in the blood, it is transformed into a ‘killer’ cell that will attack and destroy all cells carrying traces of a foreign pathogen, or into a ‘helper’ call that assist the immune system in acquiring ‘memory’. This memory enables the immune system to recognize the pathogen at the next encounter and launch an enhanced response. If vitamin D blood levels are low, T cells are less likely to be transformed into killer or helper cells.
Prior studies have shown that people with higher blood levels of vitamin D are less likely to get respiratory infections. The Copenhagen group has found a mechanism that may explain this. Many local residents suffered from prolonged colds and coughs this winter – getting adequate D is good preventive medicine and may help from now on..
We are heading into summer and the sun is back – so you can get D from safe sun exposure as well as from pills. While the majority of dermatologists discourage exposing skin to sunlight without sunscreen of 15 spf or higher, a few say that 10 minutes a day of exposure of the arms, legs and back is safe and can result in good levels of vitamin D being formed. Avoid sun exposure on your face by wearing sunscreen and a hat, because of skin damage and wrinkles. Get a blood level of 25 hydroxy vitamin D at the clinic, and aim for 35-40 ng/ml by taking vitamin D3 pills as well as safe sun exposure. Most doctors are now suggesting 1000-2000 IU of D daily in pill form.
A recent study from the University of South Carolina, funded by the National Institutes of Health, showed that pregnant women who took 4000 IU of vitamin D daily, starting at three months of pregnancy, had half the usual risk of premature delivery and ‘small for dates’ babies, and a 25% lower risk of respiratory infections, vaginal infections and gum problems. The pregnant women also had less diabetes, high blood pressure and ‘eclampsia’ - a dangerous complication. The university is now studying extra vitamin D for nursing mothers. (If you are pregnant or nursing, check with your doctor!)
In a previous column on chocolate, I wrote that chocolate increases the amount of nitric oxide (NO) in the body. . NO is a gaseous ‘signaling molecule’ that crosses membranes and freely diffuses between cells. It signals the muscular coating around arteries to relax, thus improving blood flow and lowering blood pressure. Another protective effect of NO is its inhibition of blood clotting and the adhesion of white blood cells to the lining of blood vessels. These findings tie in with a joint Swedish-US study that showed that heart attack patients who had eaten chocolate at least twice a week during the year before their attack were 66% less likely to die at that time from cardiac causes. Over the following 8 years, the risk of cardiac mortality went down as chocolate consumption went up – there was a 44% reduction of risk associated with eating chocolate up to once a week. The authors of this study cautioned that chocolate is not a health food, being high in sugars and fats. However, there are healthy ways to eat it. Buy unsweetened cocoa powder (Green and Black is organic and fair trade) and put it in a shake, sweetened with a date or two, pomegranate concentrate, banana, xylitol or stevia. Mash a banana and some peanut butter, add unsweetened cocoa powder, and eat it right away, or put it on toast.
Here’s another benefit – researchers at the University of Barcelona put 47 men and women (age 55 and older) on diets including 1/4th cup unsweetened cocoa powder and skim milk , to be taken twice a day, and found, after a month, that those who drank cocoa had lower levels of inflammatory markers associated with heart disease, and significantly higher HDL cholesterol (the good kind). People sensitive to caffeine should be careful with these amounts of cocoa, as they give a stimulant effect.
Dear readers – I hope your spirits are rising with the sun and the wonderful green plants in your gardens and all around you.
Sadja Greenwood, MD,MPH - back issues at on this blog. Leave me a message!