According to the Harvard School of Public Health – ‘If you live north of the line connecting San Francisco to Philadelphia and Athens to Beijing, odds are that you don’t get enough vitamin D. African-Americans and others with dark skin, as well as older individuals, tend to have much lower levels of vitamin D, as do people who are overweight or obese. Being “D-ficient” may increase the risk of a host of chronic diseases, such as osteoporosis, heart disease, some cancers, and multiple sclerosis, as well as infectious diseases, such as tuberculosis and even the seasonal flu. Several studies link low vitamin D levels with an increased risk of fractures in older adults, and they suggest that vitamin D supplementation may prevent such fractures—as long as it is taken in a high enough dose. A summary of the evidence comes from a combined analysis of 12 fracture prevention trials that included more than 40,000 elderly people, most of them women. Researchers found that high intakes of vitamin D supplements—of about 800 IU per day—reduced hip and non-spine fractures by 20 percent, while lower intakes (400 IU or less) failed to offer any fracture prevention benefit.
Vitamin D may also help increase muscle strength, which in turn helps to prevent falls, a common problem that leads to substantial disability and death in older people. Once again, vitamin D dose matters: A combined analysis of multiple studies found that taking 700 to 1,000 IU of vitamin D per day lowered the risk of falls by 19 percent, but taking 200 to 600 IU per day did not offer any such protection.
The heart is basically a large muscle, and like skeletal muscle, it has receptors for vitamin D. So perhaps it’s no surprise that studies are finding vitamin D deficiency may be linked to heart disease. The Health Professional Follow-Up Study checked the vitamin D blood levels in nearly 50,000 men who were healthy, and then followed them for 10 years. They found that men who were deficient in vitamin D were twice as likely to have a heart attack as men who had adequate levels of vitamin D. Other studies have found that low vitamin D levels were associated with higher risk of heart failure, sudden cardiac death, stroke, overall cardiovascular disease, and cardiovascular death. How exactly might vitamin D help prevent heart disease? There’s evidence that vitamin D plays a role in controlling blood pressure and preventing artery damage, and this may explain these findings.
Dozens of studies suggest an association between low vitamin D levels and increased risks of colon and other cancers. The evidence is strongest for colorectal cancer, with most (but not all) observational studies finding that the lower the vitamin D levels, the higher the risk of this disease. Vitamin D levels may also predict cancer survival, but evidence for this is still limited. Yet finding such associations does not necessarily mean that taking vitamin D supplements will lower cancer risk.
Multiple sclerosis (MS) rates are much higher far north (or far south) of the equator than in sunnier climes, and researchers suspect that chronic vitamin D deficiencies may be one reason why. One prospective study to look at this question found that among white men and women, those with the highest vitamin D blood levels had a 62 percent lower risk of developing MS than those with the lowest vitamin D levels. The study didn’t find this effect among black men and women, most likely because there were fewer black study participants and most of them had low vitamin D levels, making it harder to find any link between vitamin D and MS if one exists.
The flu virus wreaks the most havoc in the winter, abating in the summer months. This seasonality led a British doctor to hypothesize that a sunlight-related “seasonal stimulus” triggered influenza outbreaks. More than 20 years after this initial hypothesis, several scientists published a paper suggesting that vitamin D may be the seasonal stimulus. Among the evidence they cite: Vitamin D levels are lowest in the winter months. The active form of vitamin D tempers the inflammatory response of some white blood cells, while it also boosts immune cell’s production of microbe fighting proteins. Children who have vitamin D-deficiency rickets are more likely to get respiratory infections, while children exposed to sunlight seem to have fewer respiratory infections. Adults who have low vitamin D levels are more likely to report having had a recent cough, cold, or upper respiratory tract infection.
For most people, the best way to get enough vitamin D is taking a supplement, but the level in most multivitamins (400 IU) is too low. Encouragingly, some manufacturers have begun adding 800 or 1,000 IU of vitamin D to their standard multivitamin preparations. If the multivitamin you take does not have 1,000 IU of vitamin D, you may want to consider adding a separate vitamin D supplement, especially if you don’t spend much time in the sun.’
It is important to know your blood level of vitamin D – most researchers agree it should be 30 ng/ml or above. Talk to your healthcare provider. Knowing your level will enable you to take the correct dose of vitamin D.
Daily Probiotic – In my last column I wrote about the benefits of probiotic supplements. It is posted on this blog. Here are two supplements that are easy to obtain and are of high quality; each pill contains 5 billion or more of the most helpful bacteria for your gut: Jarro-Dophilus and Floragen3. Keep your probiotic refrigerated – not frozen – and take one daily with water on an empty stomach first thing in the morning. It is helpful to use a probiotic daily, rather than intermittently if you have a digestive upset or need an antibiotic. Foods containing helpful probiotics include plain yogurt, kefir, and many fermented foods.
Sadja Greenwood, MD. MPH stay tuned for another easy resolution.