How vitamin D savvy are you? Most importantly, are you getting enough of this vitamin that your body requires for optimal health? Vitamin D is often referred to as the “sunshine vitamin” since the best source is sun exposure. When you expose bare skin to the sun, ultraviolet light activates vitamin D precursors on your skin. Once galvanized the altered vitamin D precursors travel to the kidneys and liver where they are further activated to a form your body can use. It’s a sequence of events that help you maintain a sufficient vitamin D level.
What’s so special about vitamin D? Vitamin D behaves more like a hormone than a vitamin. For one, you need it to absorb calcium from your digestive tract and for your kidneys to reabsorb it rather than excrete it all into your urine. However, you need calcium not just for bone health but on a minute-by-minute basis for muscle contractions, a normal heartbeat, blood clotting, and more. But, vitamin D also plays a vital role in immune function, both in keeping your immune system primed to fight infection and by helping to tame tissue-damaging inflammation.
In addition, some studies link low vitamin D with a higher risk of cardiovascular disease, cancer of the colon, depression, cognitive decline, and type 2 diabetes. Note that this is an association, it doesn’t show causation. Still, it’s something we should be aware of.
Vitamin D Gene Expression
Did you know almost every cell in the human body has receptors for vitamin D? This shows how important vitamin D is to overall health. In fact, the active form of vitamin D binds to these receptors, and by doing so, impacts the expression of a variety of genes.
One concern is that people get enough vitamin D to maintain health. But, we now know that a significant percentage of the population has low or sub-optimal levels of vitamin D. There’s also controversy as to what the optimal level of vitamin D actually is and having more of it offers health benefits.
How much vitamin D is TOO much? For example, some athletes take high dose supplements because vitamin D plays a role in muscle function. People who are deficient in vitamin D may have muscle weakness. But, does consuming more really offer benefits? It likely depends on whether you’re deficient in vitamin D.
Health care professionals measure vitamin D level with a blood test called a 25-hydroxy vitamin D blood test. Based on guidelines set by the Institute of Medicine, these values represent levels of sufficiency or insufficiency:
Deficient: Levels less than 12 ng/ml (30 nmol/l)
Insufficient: Levels between 12–20 ng/ml (30–50 nmol/l)
Sufficient: Levels between 20–50 ng/ml (50–125 nmol/l)
High: Levels greater than 50 ng/ml (125 nmol/l)
So, you should aim for a blood level, as determined by a 25-hydroxy vitamin D blood test of at least 20 ng/ml or 50 ng/ml. But is this ideal? In the past, some experts have pointed out that 20 ng/ml, although within the guidelines, is too low for optimal health. In fact, studies suggest a level of at least 30 ng/ml is better in terms of lowering health risks.
However, a very high level has drawbacks as well. At levels above 200 ng/ml, vitamin D can cause toxicity. Vitamin D is a fat-soluble vitamin, so rather than being eliminated through the urine, like water-soluble vitamins, it’s stored in fat tissue. A very high vitamin D level can lead to an elevated calcium level and, in extreme cases, even kidney failure. Paradoxically, it an also trigger bone loss.
However, most people won’t reach this level unless they’re taking high doses of supplemental vitamin D, greater than 10,000 IU per day. You won’t develop vitamin D toxicity from sun exposure. But even a level below the toxicity level may have risks. Some studies suggest that levels above 30 ng/ml are linked with a higher risk of some cancers, greater risk of cardiovascular death, and higher, overall mortality.
How to Make Sure You’re Vitamin D Level is Okay
Since whole foods, with the exception of eggs, salmon, and specially treated mushrooms, are low in vitamin D, sunlight exposure is the best way to ensure you’re getting enough. The problem is most people spend the majority of the day indoors where they aren’t exposing their skin to ultraviolet light. That’s why it’s a good idea for everyone to get a vitamin D level to avoid the risks of being vitamin D deficient. Certain factors increase the risk of having a low vitamin D level. These include:
· Having darkly pigmented skin
· Being overweight or obese
· Living in an area of the country that gets little direct sunlight
· Being past the age of 65
· Taking certain medications
· Having conditions that reduce absorption of vitamin D from the digestive tract.
· Spending little time outdoors or wearing a sunscreen
If any of these apply to you, talk to your physician about checking a vitamin D level. In fact, it’s a good idea to check your vitamin D level regardless, so you know where you stand. At the very least, your level should be above 20 ng/ml, but, ideally, you should have a level around 30 ng/ml, but not much higher. It’s possible that higher levels may be beneficial for people with certain health problems, such as multiple sclerosis and other autoimmune diseases, but more research is needed to determine what level is safe and optimal for good health. There’s still a lot we don’t know about the benefits vs. risks of having a vitamin D level much above 50 ng/ml.
The Bottom Line
Talk to your physician about your vitamin D status. If you’ve never checked a level, now would be a good time to start monitoring it, especially if you have risk factors for vitamin D deficiency. There’s growing evidence that vitamin D is important for more than bone health. So, we need to be aware of our level and take steps to make sure we’re not deficient.
National Institutes of Health. “Vitamin D”
Sports Med. 2018; 48(Suppl 1): 3–16.
MedLine Plus. “Vitamin D Test”