At one time, scientists believed vitamin D was only important for bone health. Years ago, kids often took a spoonful of cod liver oil to ensure they were getting enough vitamin D. Without it, they could develop a bone disfiguring disease called rickets.
These days, we know vitamin D plays a role in healthy immune function and likely has other benefits as well. For example, some preliminary studies show vitamin D helps prevent certain forms of cancer, protects against some autoimmune diseases and aids in weight control. Some research even shows it improves sports performance. Still, there’s a lot we don’t know about vitamin D.
What is clear is that many people don’t get enough vitamin D. A 2011 study carried out by the National Center for Health Data statistics showed that almost a third of people have vitamin D levels that are borderline low or are frankly deficient. In some parts of the world, the vitamin D deficiency disease, rickets, is making a comeback in kids. Why is it that so many people have low levels of vitamin D? Let’s look at some of the factors that can impact your vitamin D level.
Where You Live
The best source of vitamin D is sunlight. When the sun’s rays hit your skin, your skin forms vitamin D precursors. These precursors are, in turn, activated by your liver and kidneys to form the active form of vitamin D. Unfortunately, most foods contain little or no vitamin D with the exception of vitamin D-rich mushrooms, fatty fish, and foods that are fortified with vitamin D. If your skin never saw the light of day, you’d more than likely experience a serious vitamin D deficiency.
If you live at a high latitude, for example, the northern part of the United States, you get little direct sunlight during the late fall and early winter, unless, of course, you spend your winters in Florida. As you get closer to the equator, your skin gets more direct sunlight and vitamin D deficiency becomes less common. That’s why if you live at a high latitude, consider getting your vitamin D level checked. The symptoms of vitamin D deficiency can be vague and non-specific, including fatigue or muscle aches. Some people blame it on not getting enough sleep or stress when they’re actually D deficient.
How Much Pigment You Have in Your Skin
The pigment that gives your skin and hair color is called melanin. It turns out that melanin has a strong affinity for the ultraviolet rays that stimulate skin vitamin D production. If you have a lot of melanin in your skin, it soaks up these rays, leaving less available for making vitamin D. So, if you have a darker skin pigment, due to more melanin, you need more sun exposure than someone with light skin to keep your vitamin D levels in an optimal range.
Does sunscreen make it harder for your body to make vitamin D? It’s not clear. Most people, when they put on sunscreen, don’t apply enough to completely block ultraviolet light. Yet wearing a sunscreen does reduce the amount of ultraviolet light your skin gets and that means fewer vitamins D precursors. The key is to balance the risk of skin cancer and premature skin aging with the risk of vitamin D deficiency. Balancing the two can be challenging. That’s why a growing number of people take a vitamin D supplement.
Your Body Weight
A number of studies link being overweight or obese with a low vitamin D level. The question is whether being overweight triggers a drop in vitamin D or whether a low vitamin D level plays a role in weight gain. In one study, researchers found people who weighed more were genetically at higher risk for vitamin D deficiency. Whether it’s genes or another factor, the bottom line is people who have a high level of body fat need more vitamin D than those who are of normal weight.
How Old You Are
As you age, your body becomes less efficient at making vitamin D even when you expose your skin to the sun. Vitamin D precursors made on the skin have to be processed by the liver and kidneys to be activated. The liver and kidneys of people over 60 are less proficient at doing this, especially if they have poor kidney or liver function. Plus, intestinal absorption of the vitamin D you get through diet goes down. In the elderly, low levels of vitamin D can cause muscle weakness and an increased risk of falls.
How Healthy Your Gut Is
You absorb the vitamin D you get through diet through your small intestines. If you have absorption issues or a disease like celiac disease or inflammatory bowel disease, your small intestines can’t absorb vitamin D as well as a normal, healthy gut can. What’s more interesting is a study showing participants who took a probiotic supplement had 25% higher vitamin D levels relative to those who didn’t. So, gut bacteria may influence the absorption of vitamin D – another reason to cultivate healthy gut bacteria by eating fermented foods.
If you live in an area with polluted air, your risk of vitamin D deficiency is higher than if you live in an area where pollution is less of a problem. That’s because particulate matter in the area scatters ultraviolet light so that less of the light you need to make vitamin D reaches your skin. You can’t control the pollution in your area but you can get your vitamin D level checked so you know where you stand.
The Bottom Line
Now you know what increases your risk for vitamin D deficiency. Even if you don’t have these risk factors, monitor your vitamin D level with a blood test every year or two to make sure you have enough of this essential vitamin that you need for more than just bone health.