For many integrative health practitioners, coaches, and DIY health enthusiasts, increasing vitamin D status is a first-line treatment for improving overall health and wellness, including mental health, nutrition, metabolic health, and gut health imbalances.
Simply raising this one little fat-soluble vitamin (or some might say hormone) can take a person from debilitating illness to getting back on the road to wellness. It’s not a cure-all, but it does seem to have a remarkable impact on mental acuity, energy, mood, and more.
Today we want to focus specifically on the link between vitamin D and gut health, and how you can increase your absorption of vitamin D supplementation by improving your gut health. Because you’re only as healthy as the nutrients you absorb!
The relationship between vitamin D and gut health
After years of research, we know that raising vitamin D to therapeutic levels can have a profound effect on gut health. A study on 80 women with vitamin D deficiency but otherwise healthy found that vitamin D supplementation significantly increased microbiome diversity. Increased microbial diversity in the gut may affect the individual by improving the inflammatory response and regulating the immune system. 
Vitamin D supplementation has also been shown to improve inflammatory bowel disease outcomes, particularly lowering inflammation in Crohn’s disease patients. Vitamin D has been shown to reduce intestinal permeability and modify the immune response in the gut, encouraging healing of the gut lining. 
You might think that vitamin D needs to be ingested to affect the gut environment, but that’s not necessarily the case.
Getting vitamin D from the sun vs. supplements
Our best natural source of vitamin D is not ingested at all; it comes from sunlight. Well, we don’t exactly get it from the sun itself: when sunlight hits our skin, cholesterol molecules there absorb the UVB rays and kick off a conversion process that turns inactive D2 into active vitamin D3.
Research has shown that vitamin D produced from sunlight in our skin lasts 2-3 times longer in circulation than vitamin D ingested orally. Plus, 100% of vitamin D produced in the skin is bound to the vitamin D binding protein and used in our cells. Ingested orally, only 60% is bound to the protein, so vitamin D absorbed through the skin via sunlight is much more efficient. 
This is also why constantly using sunscreen can lower your vitamin D synthesis and absorption from sunlight. Since sunscreen blocks UVB rays, the conversion process from D2 to D3 can not take place. An SPF 30 sunscreen reduces the skin’s ability to produce active vitamin D by 95-98%! 
While UV light has been linked to premature aging and skin cancer, it may be much, much more harmful to avoid sunlight as often as we do in our society. A study on 30,000 Swedish women found that those who avoided the sun had a 2x increased risk of all-cause mortality versus those who were exposed to sunlight regularly. That’s right: their risk of death from all causes was doubled. So, we might all be better off getting a little more sun exposure in our lives, as long as we’re not getting sunburns every day. 
Bypassing the gut
Getting your vitamin D through the sun, besides being more efficient, means that you can bypass absorption through the gut, where your body has to work a lot harder to extract nutrients from food and supplements.
On the other hand, many of us don’t spend the kind of time in the sun that our ancestors did, and those who live farther from the equator naturally get less and lower quality sun exposure, especially during the winter months. So there is still a good argument for supplementing vitamin D orally in addition to doing your best to get adequate sun exposure.
What prevents vitamin D absorption
Vitamin D can be prevented by many factors, including some we’ve already mentioned like daily sunscreen use. High-coverage clothing, living in certain climates with less and lower quality sun exposure, and skin tone can also hinder vitamin D synthesis and absorption through the skin.
Vitamin D is naturally found in seafood sources like salmon, oysters, tuna, shrimp, and sardines, so if you are allergic to seafood and/or shellfish or don’t regularly consume seafood, your vitamin D levels may be lower. You can also find vitamin D in food sources such as egg yolks, mushrooms, and organ meats. 
While increasing vitamin D levels can help improve gut health, an already inflamed and imbalanced gut is predisposed to absorb less vitamin D. When the gut lining is leaky or injured, it is much harder to absorb many nutrients, including vitamin D. Pathogen overgrowth, such as candida and parasites, can also steal nutrients from our cells, impairing vitamin D absorption.
Besides the gut itself, impaired digestion can also block the absorption of vitamin D. Without appropriate levels of stomach acid, bile, and digestive enzymes, the body will have trouble absorbing this fat-soluble vitamin. Bile as a fat emulsifier is especially critical to break it down. 
Supplements that help improve vitamin D absorption and use
Although our main pathway for vitamin D synthesis is via sunlight on the skin, no nutrient in the body works alone. Vitamin D can be optimized by other nutrients and is often required to combine with other vitamins and minerals to properly support our cells. Here are some of the key partners that improve vitamin D absorption and use in the body.
Magnesium and vitamin D are closely related. Both are used by every organ in the body, and their deficiency can lead to serious health concerns.*
Unfortunately, they are so closely interdependent on each other that taking high doses of vitamin D can actually lower magnesium. So, for the optimal use of both nutrients, taking them together is beneficial.  The RDA values for vitamin D and magnesium are 600 IUs of vitamin D daily and between 310mg and 420mg per day of magnesium depending on your age and gender. 
However, the RDA values indicate the level of a nutrient needed to simply maintain life, not thrive, especially in our world of high stress and toxins. Your needs are likely to be much higher, particularly if you have a chronic health condition or are pregnant. Consult with a trusted practitioner to determine a therapeutic dosage for you.
You might have seen by now that many vitamin D supplements are often paired with vitamin K, particularly K2. These two powerhouse vitamins are paired together in supplementation because they are both fat soluble vitamins and are integral to proper calcium absorption.*
Studies have linked vitamin D and K supplementation with increased bone mass density in postmenopausal women. A connection has also been made between D and K supplementation and improved glucose metabolism. 
Appropriate zinc levels are critical for stomach acid and GI homeostasis.* Improving zinc levels may therefore improve digestion, which is critical for absorption of any nutrient, including dietary vitamin D absorption.* It’s especially relevant for vitamin D and the fat-soluble vitamins, since unlike water-soluble vitamins, they are not as easily absorbed. 
Vitamin D and butyrate have a somewhat cyclical relationship. Let’s start with butyrate. Butyrate is a powerful postbiotic metabolite that promotes the health of the colon cells (colonocytes) as well as microbiome and immune health. It has also been shown to have healing capabilities for IBD patients, lowering inflammation in the GI system.
A study of 567 men showed that those with higher levels of the active form of vitamin D also had higher levels of butyrate in their colons. In turn, higher levels of butyrate mean a healthier gut, healthier colonocytes, and a more robust microbiome, which encourages better dietary vitamin D absorption.* 
You can increase your butyrate levels by eating certain foods, mostly fruits, vegetables, grains, and starches, as well as through supplementation.
Maximize your vitamin D absorption with BodyBio
Taking any supplement or increasing your food intake of a nutrient is only as helpful as much as your body can absorb and use that nutrient. Fortunately, there are many ways to support vitamin D absorption, which can have anti-inflammatory, neuromodulatory, and immune-boosting effects.If you’re taking a vitamin D supplement but seeing little improvement in your levels or symptoms, you may want to consider adding a synergistic component like BodyBio Zinc, Magnesium, or Butyrate to help with absorption.*