Skin color adapts to sunlight intensities which produce vitamin D or ultraviolet light damage to folic acid. Now researchers at the University of Leeds suggest that people with very pale skin may be unable to spend enough time in the sun to make the amount of vitamin D the body needs -- while also avoiding sunburn.
Europeans typically tend to be pale, have lighter colored hair, and a range of eye colors. Some recent genetic studies suggest that until recently, Europeans may have been dark-skinned.
The reason this is interesting is that there has been some debate as to when Europeans became so pale. Some have argued that it happened about 40,000 years ago when people from Africa swept into Europe. Others have argued that it wasn't until farming took a hold that pale skin became common.
The difference between the two theories has to do with vitamin D and where prehistoric people could get it. There are two general sources for vitamin D--sunlight and diet.
We know that a farmer's diet does not have enough vitamin D meaning that people in farming-based societies need to get a lot of it from the sun. We also know there is not enough sunlight in Northern Europe for dark skinned people to get enough vitamin D. So farming based societies that live in Northern Europe need to have lighter skin.
But farming didn't really take a hold in Europe until 6,000 or 8,000 years ago. So what about the 30,000 or 35,000 years that people lived in Europe before farming? If there was enough vitamin D in their diet, then there would have been no need for pale skin. Recent genetic work suggests that the diet of these hunter-gatherers may have had plenty of vitamin D.
Regardless of their origins, pale populations have multiplied and have migrated across the earth, many times to geographic regions which are to their disadvantage. Researchers have noted that sunlight and supplements are not the only factors that can determine the level of vitamin D in a person's body.
Lighter skin color allows deeper penetration by UV-B rays, which decreases the amount of sunlight exposure needed for adequate vitamin D production. If you have darker skin, it's harder for UV-B rays to penetrate your skin and create vitamin D, which means that you need greater exposure to sunlight than someone with lighter skin.
Some inherited differences in the way people's bodies process vitamin D into the active form also have a strong effect on people's vitamin D levels.
The most recent study defined the optimal amount of vitamin D required by the body as at least 60nmol/L. However at present there is no universally agreed standard definition of an optimal level of vitamin D.
What we do know is that low levels of vitamin D have been correlated with high incidences of cancer, heart disease, autoimmune disorders, poorly functioning immune systems, and musculoskeletal disorders.
Some 600,000 cases of breast and colorectal cancers could be prevented each year if vitamin D levels among populations worldwide were increased, according to previous research. And that's just counting the death toll for two types of cancer.
Professor Julia Newton-Bishop, lead author of the study based in the Cancer Research UK Centre at the University of Leeds, said: "Fair-skinned individuals who burn easily are not able to make enough vitamin D from sunlight and so may need to take vitamin D supplements.
"This should be considered for fair-skinned people living in a mild climate like the UK."
Researchers took the vitamin D levels of around 1,200 people and found that around 730 people had a sub-optimal level. Those with fair-skin had significantly lower levels. Researchers chose 60nmol/L as the optimal vitamin D level in part because there is evidence that levels lower than this may be linked to greater risk of heart disease and poorer survival from breast cancer.
A consensus between health charities including Cancer Research UK says that levels below 25nmol/L are vitamin D deficient which means that these levels are associated with poor bone health. But some researchers consider that higher levels, around 60nmol/l, may be desirable for optimal health effects.
Sara Hiom, director of health information at Cancer Research UK, said: "We must be careful about raising the definition of deficiency or sufficiency to higher levels until we have more results from trials showing that maintaining such levels has clear health benefits and no health risks.
"Vitamin D status is potentially one of the most powerful selective pressures on the genome in relatively recent times.Our study appears to support this interpretation and it may be we have not had enough time to make all the adaptations we have needed to cope with our northern circumstances," said Professor George Ebers, from the Action Medical Research Professor of Clinical Neurology, in reference to skin shade and sunlight exposure ratios.
Optimizing Your Vitamin D
The best way to optimize your vitamin D is through safe sun exposure, or alternatively using a safe tanning bed. It is frequently possible to generate about 20,000 units of vitamin D by exposing your skin to the sun.
However, if you do not have access to regular sun exposure on a large portion of your bare skin, a vitamin D3 supplement may be necessary.
Based on the most recent research, the current recommendation for dosage is 35 IU's of vitamin D per pound of body weight.
So for a child weighing 40 pounds, the recommended average dose would be 1,400 IU's daily, and for a 170-pound adult, the dose would be nearly 6,000 IU's.
However, it's important to realize that vitamin D requirements are highly individual, as your vitamin D status is dependent on numerous factors, such as the color of your skin, your location, and how much sunshine you're exposed to on a regular basis.
So, although these recommendations may put you closer to the ballpark of what most people likely need, it is simply impossible to make a blanket recommendation that will cover everyone's needs.
The only way to determine the correct dose is to get your blood tested since there are so many variables that influence your vitamin D status.
Getting the correct test is the first step in this process, as there are TWO vitamin D tests currently being offered: 1,25(OH)D, and 25(OH)D.
The correct test your doctor needs to order is 25(OH)D, also called 25-hydroxyvitamin D, which is the better marker of overall D status. This is the marker that is most strongly associated with overall health.
Next, the “normal” 25-hydroxyvitamin D lab range is between 20-56 ng/ml. As you can see in the chart below, this conventional range is really a sign of deficiency, and is too broad to be ideal.
In fact, your vitamin D level should never be below 32 ng/ml, and any levels below 20 ng/ml are considered serious deficiency states, increasing your risk of as many as 16 different cancers and autoimmune diseases like multiple sclerosis and rheumatoid arthritis, just to name a few.
The OPTIMAL value that you're looking for is 50-65 ng/ml.
This range applies for everyone; children, adolescents, adults and seniors.
These ranges are based on healthy people in tropical or subtropical parts of the world, where they are receiving healthy sun exposures. It seems more than reasonable to assume that these values are in fact reflective of an optimal human requirement.