You may know vitamin D, often referred to as the “sunshine vitamin,” because of its role in helping to maintain strong bones. But did you know that it plays a role in immunity, brain and fetal development and heart function as well? Vitamin D has anti-inflammatory properties, preventing the release of pro-inflammatory mediators by blood cells. Have you had your vitamin D levels checked in the past year? If not, I encourage you to do so.
Vitamin D is often called the sunshine vitamin because our bodies can synthesize it through sunlight exposure to our skin.
Vitamin D was discovered in the early 1900s in western Europe, as researchers were trying to find a cure for a condition called rickets, where children’s bones become extremely soft and children are knock-kneed. Luckily, rickets and the adult version, osteomalacia, are uncommon in the US today. The Institute of Medicine, which sets the recommended daily intakes for vitamins and minerals to avoid deficiency disease among the US population, recommends a vitamin D intake of 400IU for infants, 600IU for children and most adults, and 800IU for those over age 71. This level is set to prevent rickets and osteomalacia across the population. But is this level sufficient to prevent other conditions?
Vitamin D deficiency, as measured by blood levels, has become more common in recent years. Is it because we wear more sunscreen, our bodies have a reduced ability to create vitamin D through our skin as we age, a population increase in obesity is affecting absorption, that we aren’t eating enough foods with vitamin D, or perhaps another reason?
While not definitive, epidemiological studies have demonstrated a correlation between vitamin D and autoimmune disease, where low blood levels of vitamin D are associated with autoimmune diseases like Hashimoto’s thyroiditis (autoimmune hypothyroid), Type 1 Diabetes Mellitus, multiple sclerosis (MS), rheumatoid arthritis (RA), and inflammatory bowel disease (IBD), to name a few. Given that autoimmune disease is rapidly rising, this is clearly an area for further research.*
What is an appropriate blood level? Most US labs set the reference range for normal vitamin D blood levels at 30-100 ng/mL, though many experts and research supports levels of 50-80 ng/mL. Levels over 100 ng/mL can be cause for concern.
So, what should you do?
- Get your vitamin D levels checked at least once a year!
- If your levels are below 50 ng/mL, supplement and/or increase your dietary intake of vitamin D-rich foods
- Spend some time outside every day. It’s not only good for making vitamin D; research shows it improves mood and overall health too!
If you are looking to increase your dietary intake of vitamin D, you’ll want to focus on fish oils, fatty fish, egg yolk, fortified milk and juice and fortified cereals. The best dietary sources are cod liver oil (1 Tablespoon = 1300IU), swordfish (3oz.= 550IU) and sockeye salmon (3 oz = 450 IU). Note: Milk in the Unites States is fortified with 100IU per cup, but foods made from milk, like yogurt and cheese, are usually not fortified.
In terms of supplements: For your average adult, taking a supplement of 1000IU in the form of D3 is appropriate, especially during the winter and spring months when our stores may be lower because of decreased sunlight exposure in the fall and winter. There’s no need to megadose, as this is a fat-soluble vitamin. Of course, getting your doctor to check your vitamin D levels is always the best strategy because you can then fine-tune your supplement dose. The current tolerable upper limit intake as established by the Institute of Medicine is 4000IU/day, though some practitioners recommend higher doses to those who are deficient.
Additional Resource: National Institutes of Health, Office of Dietary Supplements. Vitamin D Fact Sheet
*The National Institutes of Health estimates that 23.5 million Americans currently have an autoimmune disease. To put that in perspective: cancer affects 9 million and heart disease, 22 million.
The advice provided herein is general advice and does not take into account individual health conditions, medications and other supplements. If you are pregnant or are a parent to an infant, there are additional considerations not contained in this post. Before starting any supplements, I highly recommend speaking to your doctor, Registered Dietitian or licensed nutritionist.