When we think about the warmer weather, we often think of vitamin D – the sunshine vitamin! Vitamin D is a key nutrient that has gained popularity over the last ten years due to its potential benefits on the brain, immune system, and prevention of autoimmune disease. Many of these benefits are linked to the health of our gastrointestinal system, as this nutrient plays a role in supporting several elements of the gut.
So how does the sunshine vitamin work?
When our skin is exposed to sunlight, UV rays activate a process where cholesterol is converted to vitamin D through the liver and kidneys. While the sun is an excellent way to obtain adequate vitamin D, there are some challenges in relying on this method. Unfortunately, from October until May, the sun is not strong enough in the northern latitude of the US to produce vitamin D through our skin (not to mention, we are indoors for most of the winter months). It’s also important to know that sunscreen, clothing, and exposure to the sun behind glass will block vitamin D production in the skin by up to 90%. For all of these reasons, it has become popular to take vitamin D supplements in addition to relying on sunlight.
How does vitamin D support the gut?
When it comes to the gut, vitamin D plays a role in supporting several mechanisms. First, it has been shown to help support a healthy gut lining, which plays a role in improving the immune system and preventing autoimmune reactions in the body. Deficiencies in vitamin D have also been linked to the development of Irritable Bowel Syndrome (IBS) and Inflammatory Bowel Disease (IBD) ( Tangestani et al., 2021 ).
In addition to supporting the gut-immune response, vitamin D has also been found to affect the gut microbiome. One meta-analysis showed that higher dietary Vitamin D intake was associated with shifts in microbial colonies and increased levels of certain probiotic bacteria, like Bifidobacterium ( Bellerba et al., 2021 ). Another review showed a possible benefit of co-supplementation of vitamin D and probiotics in improving overall gut health and function ( Abboud et al., 2020).
Only a handful of foods contain vitamin D, which is another reason why supplementation has become helpful in obtaining adequate levels. These foods include:
Wild-caught fish (salmon, halibut, sardines)
Mushrooms (must be grown in UV light)
Fortified foods (dairy, plant milk)
Should you be taking a supplement?
Because vitamin D can be toxic at high levels of supplementation, I always recommend talking to your healthcare provider to have your vitamin D levels measured first. Understanding if you are deficient or sufficient can help you decide the appropriate dosage. However, there’s no harm in consuming more vitamin D-rich foods in your regular diet. And when it comes to sun exposure, 10-15 minutes per day on your hands and face should be enough to maximize your body’s production. Just make sure to wear sunscreen during long periods of exposure and chat with your doctor about your risk for sun exposure.