Vitamins are micronutrients that the body cannot produce therefore they must be derived from our diet or supplements. There are many different types of vitamins all with their specific roles in the body, but this article will focus on the role of vitamin D!
Fat-Soluble Vitamin
Vitamin D is a fat-soluble vitamin, meaning it is best absorbed with dietary fat, and then stored in the body's fatty tissues and the liver. As fat-soluble vitamins can be stored unlike water-soluble vitamins, they last longer in the body.
Key roles of Vitamin D in the body
Vitamin D has many roles in the body, it is essential for bone health, it helps with calcium and phosphorus homeostasis, and contributes to immune function.
Bone Health
Vitamin D plays a key role in bone health through its effect on calcium absorption. Vitamin D enhances calcium absorption in the small intestine which increases the calcium available to be stored within the bones. Low vitamin D can lead to decreased calcium absorption, causing the bones to release calcium into the bloodstream. This process of calcium release from the bone can cause weakened bones, and increased fracture risk leading to the development of osteomalacia and osteoporosis.
Osteomalacia: Osteomalacia is a disease of “bone softening” most commonly due to a deficiency in Vitamin D, which can cause loss of calcium in the bones
Osteoporosis: Osteoporosis is a bone disease that develops when bone mineral density and bone mass decrease. This can affect bone strength leading to more fractures.
Immune Function
Vitamin D is a unique nutrient as it is also considered a hormone. It circulates in the blood and binds to receptors to activate a certain action in the body. Many studies over the years have shown that vitamin D has a key role in immune function.
Vitamin D receptors are found in nearly all cells and tissues of the body. Vitamin D promotes immune health by binding to the receptors of immunity cells. Once the vitamin D binds to these cells they are stimulated to produce products that can defend the body against foreign pathogens such as bacteria and viruses!
Studies have also shown that vitamin D helps with inflammation. When the body has a foreign pathogen such as a bacteria, the immune system releases proteins to help fight it, and this can cause over-inflammation, vitamin D has been shown to suppress inflammation.
Research has looked at the role vitamin D plays in respiratory tract infections. Results have shown that supplementing with vitamin D can help reduce the risk of acute respiratory tract infections.
Not Enough Vitamin D
As vitamin D is not naturally present in many foods, we must rely on fortified foods, sun exposure, and consider taking supplements to ensure adequate amounts.
Common symptoms of low vitamin D:
Bone pain and weakness
Fatigue
Hair loss
Feeling of sadness
More susceptible to illness
Pale skin
Trouble sleeping
There are a few reasons why someone could have low levels of vitamin D, including:
Not enough intake through the diet, or not enough sun exposure
The body is not absorbing the vitamin properly (medical conditions)
Medical conditions affecting vitamin D levels
Kidney and liver disease: The kidneys and the liver contain enzymes that convert the vitamin D in our blood to the active form ( the vitamin D our body can use). If these organs are not functioning correctly and there is an inadequate amount of these enzymes this can cause low levels of active Vitamin D in the body.
Crohn's disease: is an inflammatory bowel disease that affects the gastrointestinal tract (GI). Vitamin D levels can be low in patients due to inadequate sun exposure, low absorption, and impaired conversion of the active form of vitamin D
Cystic fibrosis: patients with cystic fibrosis do not properly absorb fat-soluble vitamins, therefore even with vitamin D intake the body may have a hard time absorbing and utilizing it
Celiac disease: when someone with celiac consumes gluten it damages their intestinal cells, untreated it can cause malabsorption of nutrients such as vitamin D
Vitamin D can be obtained from diet, sun exposure, and supplements.
Diet
There are few foods that naturally contain vitamin D, but the best sources include fatty fish such as salmon, mackerel, and tuna. Foods such as egg yolk, beef liver, mushrooms, and cheese also contain some vitamin D. Another way to get vitamin through the diet is with fortified foods examples include:
Cereals
Milk and fortified plant-based milk beverages
Fortified orange juice
Fortified yogurt and margarine
As not a lot of foods contain vitamin D, it is difficult to meet the requirements of this vitamin solely from food. It is important also to get sunlight exposure to ensure adequate amounts.
Sun exposure
When your skin is exposed to sunlight it is able to produce vitamin D. The cholesterol in your skin absorbs the ultraviolet B (UVB) rays from the sun and converts it to pre-vitamin D, which is then converted to the active form of vitamin D. Different factors can influence the amount of vitamin D our skin can produce from the sun, these include the season, the time of day, location to the equator, and even skin colour. Staying indoors, wearing clothing, and wearing SPF can all block UVB rays and therefore reduce or eliminate vitamin D synthesis from the sun.
Time of Day
Studies have shown that the best time to get sun exposure for vitamin D is midday during the summer seasons. At noon the UVB rays are intense meaning you need less time in the sun to get adequate amounts of vitamin D.
Season
People living further away from the equator have a harder time producing vitamin D from the sun, the UVB rays are absorbed by the ozone layer, so more time in the sun is needed for the skin to absorb enough rays to make vitamin D. During winter months, individuals living in these areas are not able to produce much vitamin D from the sun, as the UVB rays are not strong enough.
Skin Colour
A person’s skin colour is determined by a pigment called melanin. Someone with a darker skin colour typically has more melanin than someone with a lighter skin colour. Melanin in the skin absorbs UVB rays to help protect against sunburns and skin cancers. Someone with darker skin may need to spend more time exposed to sunlight to absorb more UVB rays for vitamin D synthesis.
It's important to practice sun safety to reduce your risk of skin damage, and even skin cancer. You should not rely on sun exposure to get enough vitamin D!
Sun Safety
Both UVA and UVB rays from the sun can cause long-term skin damage, cataracts, and even skin cancer! The best way to reduce your risk of these adverse health effects is to practice sun safety and protect yourself from the sun.
Wear sunscreen (broad spectrum, at least SPF 30 or higher) everyday even when it is cloudy
Wear clothing that blocks the sun, including a wide brimmed hat that covers your neck, ears, eyes, and scalp.
Supplements
Studies have shown that vitamin D is a common micronutrient that people around the world are not getting enough of. The reasons include limited foods containing vitamin D, not enough sunlight exposure throughout the year, as well as other factors such as age and health status. Supplementation with vitamin D can be an easy way to increase your vitamin D intake and decrease the risk of deficiency.
Make an appointment with one of our dietitians today to discuss your vitamin D intake, if a supplement is right for you and how much you should be taking!
References
Cesari, M., Incalzi, R. A., Zamboni, V., & Pahor, M. (2011). Vitamin D hormone: a multitude of actions potentially influencing the physical function decline in older persons. Geriatrics & gerontology international, 11(2), 133-142. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4384440/
Ellison, D. L., & Moran, H. R. (2021). Vitamin D: vitamin or hormone?. Nursing Clinics, 56(1), 47-57. Available from: https://pubmed.ncbi.nlm.nih.gov/33549285/
Hall, W. B., Sparks, A. A., & Aris, R. M. (2010). Vitamin D deficiency in cystic fibrosis. International journal of endocrinology, 2010. Available from:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2817861/#:~:text=Exocrine%20pancreatic%20insufficiency%20causes%20intestinal,vitamin%20D3
Raftery, T., & O'Sullivan, M. (2015). Optimal vitamin D levels in Crohn's disease: a review. Proceedings of the Nutrition Society, 74(1), 56-66. Available from: https://pubmed.ncbi.nlm.nih.gov/25497215/#:~:text=Several%20factors%20contribute%20to%20vitamin,vitamin%20D%20hydroxylation%20and%20transport
Wacker, M., & Holick, M. F. (2013). Sunlight and Vitamin D: A global perspective for health. Dermato-endocrinology, 5(1), 51-108. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3897598/#:~:text=During%20exposure%20to%20sunlight%207,which%20have%20unique%20biologic%20properties