Vitamin D: What It Is & Why It's Important
Winter is coming, or if you live in Alaska like me, it's already here. Depending on where you live, you may or may not be aware of the importance of vitamin D. In the last few years, vitamin D has been a hot topic in the medical community and it is becoming more obvious how important it is for everyone to make sure they are getting enough.
Most people probably associate vitamin D with strong bones, but it does so much more than that. It is responsible for many processes in the body including the balance of calcium and phosphate (important for bone health), immune function, cancer prevention, cardiovascular health, and regulating inflammation (this article and this article talk about those things more in depth).
Most people are deficient in vitamin D and since it's involved in so many important processes in the body, that's kind of a big deal. It's such a big deal that I ask almost every patient that I see if they are taking vitamin D.
What is vitamin D and where can I get it?
Vitamin D is actually a hormone, not a vitamin. Because of this vitamin D is not found in very many foods, and probably none that you are actually interested in eating - fish livers are the most dense source but it is also present in the flesh of fatty fish (salmon, tuna, and mackerel). Because it is not a true vitamin (it's a hormone), your body can produce it when exposed to sunlight. However, the vitamin D that your body creates from sunlight must undergo several chemical processes before it is able to be used by your body.
In addition to fish, vitamin D is also found in eggs and grassfed dairy products, but in much lower levels that what is found naturally in fish (less than 50%). It is also important to note that if the animal that the eggs or dairy came from did not spend time outside, there will be almost no vitamin D present as sun exposure is critical to its production in animals as well. Many foods are also supplemented with vitamin d (orange juice, conventional milk, and cereals), but I do not recommend consuming those as they are not otherwise nutritionally dense and take away from your overall health.
The best way to get vitamin D is through sun exposure, but your ability to make it depends on where you live. Living in Alaska, we need to supplement year round because even in the summer months we are unable to make enough to keep us from dropping to dangerously low levels in the winter. Anyone living North of a line drawn between San Francisco, CA and Richmond, VA is at risk for winter time vitamin D deficiency if you rely on the sun as your main source. Anyone living North of Seattle is at risk for year round deficiency due to the half-life of vitamin D being about 3 weeks.
Relying on dietary sources alone is not sufficient (unless you like cod liver oil), but if you live in a place where "your shadow is longer than you are tall (an indicator of the oblique angle of the sun), you are not making much vitamin D," according to the Vitamin D council.
Risks of vitamin D deficiency
It is estimated that least 75% of Americans are deficient in vitamin D. Signs of deficiency can range anywhere from achy bones, and fatigue to depression and stomach issues. However, many people may not notice any symptoms at all but are unknowingly putting themselves at risk for a number of illnesses which have all been linked to deficiency, some of which include:
- Cardiovascular Disease
- Autoimmune Diseases
- Type 2 Diabetes
- Chronic Inflammation
- Cholesterol Dysregulation
- Cancers including: colon, breast, ovarian, melanoma and prostate
True vitamin D deficiency in children causes a disease called rickets and a disease called osteomalacia in adults. These are both relatively uncommon in the US due to the presence of fortified foods as well as current recommendations for supplementation of breastfed babies.
Vitamin D supplementation
The best way to determine if you are deficient in vitamin D is to get a blood test. Unfortunately there is no consensus on what optimal vitamin D levels are. The Institute of Medicine says that 20 ng/mL is sufficient for most individuals, but other experts say that upwards of 30 ng/mL is idea.
Vitamin D supplementation is a complex issue. Depending on the color of your skin (darker skinned individuals have a lower rate of synthesis from sun exposure) and where you live, you needs might be different. Also, since vitamin D is a fat soluble vitamin, if you have more fat mass you'll need a higher dose. In general 600 - 1000 IUs is a good place to start for supplementation. You can adjust as needed based on your lab results.
The best way to ensure that you are not deficient in vitamin D is to have your levels checked by your healthcare provider and work with your healthcare provider to supplement as needed.