VitaMins Health: Vitamin D: The “sunshine” vitamin

Blame it on the sunshine

As discussed in our recent VitaMins health: getting clued up on flu, we see significantly more people die during the winter months than at other times in the year. The effect of winter on our health extends beyond the immediate impact on mortality. For example, when we find ourselves once again waking up, going to work and leaving the office in dark, many people are hit with seasonal affective disorder (SAD). Studies show that almost a third of Brits and a fifth of Canadians and Americans suffer what is otherwise known as “winter depression”, and the main theory is that a lack of sunlight might stop a part of the brain called the hypothalamus from working properly.

There are also potentially long-term health implications of a lack of sunlight. While we get most of the essential nutrients required to be healthy from a balanced diet, vitamin D is the one exception with 90% of our intake coming from sunlight. Dietary sources of vitamin D include oily fish, eggs and fortified foods, but there is a concern that we cannot maintain sufficient vitamin D levels from these sources alone. With reduced sunlight hours being compounded by indoor lifestyles, medical professionals believe that many people are becoming vitamin D deficient during the winter months.

Although there isn’t a consensus on what constitutes vitamin D deficiency, the Institute of Medicine define a sufficient level to be a serum 25-hydroxyvitamin D value of 50-125 nmol/L. They report that 33% of the US population have levels below this and Statistics Canada state that 32% of Canadians were below the cut off. A cross-sectional National Diet and Nutrition Survey revealed that 39.3% of UK white 19-64 year olds have levels below 25 nmol/L in the winter. People with darker skin, for example those of African, African-Caribbean or south Asian background, need even more sunlight to generate enough Vitamin D. As a result, these people may be particularly at risk, as are people who aren’t often outdoors, those in institutions such as nursing homes or those who regularly cover up most of their skin when outdoors.

What’s it for?

To keep bones, teeth and muscles healthy the body requires sufficient levels of calcium and phosphate. Vitamin D is needed to absorb and regulate the amounts of these nutrients in the body. A lack of vitamin D is the most common cause of the bone disease osteomalacia, or rickets when in children, which is a softening of the bones due to impaired bone metabolism. Vitamin D deficiency is also one of the main lifestyle risk factors for osteoporosis, a bone disease characterized by a low bone mass, known as “the silent thief” as bone loss occurs without symptoms until the bone breaks.

While research is still in early days, there have been studies suggesting that vitamin D might have protective benefits against heart failure, diabetes, cancer, respiratory tract infections, autoimmune disease and even hair loss.

Future of supplements

Vitamin D supplements are one of the only supplements that medical professionals consistently advise us to take. The UK department of health recommends that children up to the age of 4 should be given a daily supplement containing 10 micrograms of vitamin D unless they are already using instant formula which is already fortified with vitamin D. They also recommend adults take a 10 microgram vitamin D supplement if they aren’t often outdoors or if they cover up their skin when outdoors and state that everyone should consider taking supplements during the autumn or winter. The organisation Osteoporosis Canada advises year-round vitamin D supplementation for all Canadian adults.

Not everyone agrees on supplements though and some people believe them to be a waste of money and potentially harmful. With regards to vitamin D, excess levels may increase the risk of kidney stones and unlike vitamin D produced in the skin, which is biologically regulated, there is the potential that vitamin D from supplements could build up to high level. Tim Spector, Professor of Genetic Epidemiology at King’s College London takes a sceptical view of supplements stating that “we should trust that thousands of years of evolution would cope with a natural drop in vitamin D levels in winter without us snapping our limbs.”

That being said, we are now spending much more time indoors than our ancestors ever did and, with life expectancy increasing, are we giving “the silent thief” more time to cause damage? With an aging population, it might be time to start increasing awareness of the potential risks of vitamin D deficiency to help prevent bone weakening diseases and extend the independent lifespan of the elderly.