Vitamin D myths and facts (SQ-142)
One of the most well-known roles of vitamin D is to help the body absorb calcium and phosphorus. This makes vitamin D a very crucial nutrient when it comes to your bone and muscle health.
While this function alone is enough to make the sunshine vitamin indispensable, experts believe that vitamin D may have some especially important extra skeletal benefits, thus contributing much more towards your overall health.
However, a lot of myths surround this incredible nutrient, which your body can make when you expose your skin to sunlight. In this article we are going to bust some myths around vitamin D as well as highlight important facts and health benefits associated with this fat-soluble vitamin, that is technically not a vitamin but a hormone.
Myth: Sun exposure is the best way of getting vitamin D
It is true that your body makes vitamin D when you expose your skin to the sunlight. More specifically, the UVB rays of the sunlight reacts with (a form of) cholesterol present within skin layers and convert it into pre-vitamin D3. This form enters the bloodstream and travels to the liver and other tissues, and finally to the kidneys, where it is converted into calcitriol - an active form of vitamin D3 that your body can now use to carry out various functions, including calcium absorption.
Ideally, you can make almost all the vitamin D you need by getting out in the sun for about 15-20 minutes a few times a week. But this process depends on many factors, such as where you live, the colour of your skin, season, air quality, cloud cover and also the time of the day you go out and seek sun exposure.
Important things to remember:
- It is the UVB rays that trigger vitamin D synthesis in the skin.
- People living close to the equator can make vitamin D from the sun's rays throughout the year. But things change as you move away from the equator.
- The ozone layer absorbs a major part of UVB rays at higher latitudes. So, if you happen to live at latitudes above 37 degrees north or below 37 degrees south of the equator, your skin will only make insignificant amounts of vitamin D3 from the sunlight during winter. This is because less UVB reaches the earth. And if you live farther North and South (for example, Boston in the US,Edmonton in Canada, and Bergen in Norway), you can’t make any vitamin D3 through sunlight for about 6 months of the year.
- Time of the day impacts your ability of make your own vitamin D. UVB rays are not strong in the early morning and late afternoon. These rays are strongest around the middle of the day. You know you are making sufficient vitamin D when your shadow is shorter than your actual height.
- Skin colour also plays an important role. People with dark skin need to spend more time out in the sun, than people with lighter skin tone, to make same amount of vitamin D. Melanin, a pigment that gives our skin its colour, works as a natural sunscreen and blocks some UVB rays.
- The amount of skin you expose also matters. So, people who have to wear full clothing out of their cultural or religious beliefs, and those who work, or train indoors will likely not be able to make any vitamin D through sunlight.
Whether you are taking only supplements or using a combination of diet, supplements and sensible sun exposure to get your vitamin D, your body processes it all the same. But sun exposure comes with its own risks as the same UVB rays that trigger vitamin D synthesis also cause skin cancer.
Other factors that put you at a risk of vitamin D deficiency include age, obesity, liver or kidney disorders, weight loss surgery, celiac disease, Crohn's disease, and prolonged use of certain medications such as anti-convulsant and cholesterol lowering drugs (statins).
“Your body can make sufficient amounts of vitamin D, if you expose your skin to sunlight for about 15-20 minutes, three to four times a week and under the right conditions. Factors such as latitude, skin color, season and time of the day can significantly impact the amount of vitamin D you can make through sunlight exposure. On the flipside, prolonged exposure to sunlight can increase your risk of skin cancer.”
Myth: You can get sufficient amounts of vitamin D from food
Oily fish (tuna, mackerel and sardines), egg yolks, beef liver and mushrooms are a good source of dietary vitamin D. Good old cod liver oil and fortified foods such as milk, cereals and orange juice also contain some amounts of vitamin D. But it's not possible to meet your daily vitamin D needs through food alone.
“Vitamin D is found in very few foods such as fatty fish, egg yolks and beef liver. But one has to consume a lot of these foods every day to get the amount of vitamin D you need.”
Myth: You can get vitamin D sitting by a glass window
If you believe that by enjoying warm rays of sunshine streaming through a glass window at home or in your car you will improve your vitamin D status, think again.
Your body produces vitamin D when UVB rays penetrate your skin layers and react with chemicals within your skin. Glass and plexiglass block all UVB radiations that you need to trigger vitamin D synthesis in the skin.
On the other hand, sitting indoors by a glass window can have an opposite effect. Glass can’t filler out UVA radiations, which can give you a tan and a sunburn. Long exposures to UVA rays can also cause skin cancer.
“You can’t improve your vitamin D levels from sunlight through a glass window as it blocks UVB rays which you specifically need to trigger vitamin D production in the skin.”
Fact: You need magnesium to fully utilize vitamin D
You need vitamin D to absorb calcium, but did you know you also need healthy magnesium levels to use and absorb vitamin D that you are getting from sun, food or supplements?
Your body needs magnesium to convert vitamin D into its active form calcitriol. Magnesium also works as an essential co-factor and activates enzymes required for vitamin D metabolism in the liver and kidneys. 
Magnesium also plays a direct role in maintaining bone health and integrity. A 2017 study found that low levels of magnesium increased fracture risk in elderly men. 
If you have magnesium deficiency, taking high doses of vitamin D will do no good. In fact, taking huge quantities of vitamin D will impact magnesium stores as your body will rob the mineral from tissues such as muscles and bones. This can make your magnesium deficiency worse, resulting in symptoms such as muscle cramps, migraines, irregular heart-beat and bone pain.
“You can’t make use of vitamin D if your magnesium levels are too low. Magnesium helps the body to absorb and utilize vitamin D. Taking high doses of vitamin D may go against your health if you have a magnesium deficiency.”
Fact: Vitamin D maintains healthy bones and muscles
Vitamin D helps the body absorb calcium and phosphorus from the intestinal tract, which keeps bones and muscles healthy and strong. Low levels of vitamin D causes low calcium and impaired bone mineralization. This can lead to osteoporosis (weak and brittle bones), and increased risk of fractures.
Severe and prolonged vitamin D deficiency can cause rickets (softening of bones, formation of bowlegs and bone pain) in children and osteomalacia (soft and weak bones that can break easily) in adults.
Let's see how it works. Most of your body tissues contain vitamin D receptors. For example your intestines, brain, blood vessels, muscles prostate, brain, and endocrine glands like thyroid, all have vitamin D receptors.
Now, vitamin D attaches to and stimulates these receptors to turn on (and turn off) genes that make different proteins and enzymes. Your body uses these proteins to carry out critical functions including calcium absorption and fighting germs.
In the intestine these receptors bind to Vitamin D and turn on genes that make proteins needed to absorb calcium. Vitamin D also blocks the secretion of parathyroid hormone, that borrows calcium from the bones and puts it in the blood.
“Vitamin D helps the body to absorb calcium from the food and supplements, thus playing an important role in bone and muscle health.”
Fact: Vitamin D supports healthy immune function
Data from emerging studies indicate that you need healthy levels of vitamin D to maintain your immune function as well as to prevent autoimmunity. Your immune cells, like most other cells in the body, contain Vitamin D receptors. Immune cells also have enzymes required for the production of Vitamin D3.
Vitamin D stimulates the production of antimicrobial proteins in the body. These proteins fight bacteria, virus, and fungi and boost the innate or natural immunity of the body. Vitamin D also influences immune cells in a way that prevents autoimmune disturbances. It reduces inflammation by regulating the production of pro-inflammatory cytokines. In autoimmune disorder, misfiring of immune cell releases inflammatory chemicals called cytokines. These signalling molecules call upon and activate other immune cells, thus leading to more and more inflammation and damage.
It has been found that people with autoimmune disorders such as multiple sclerosis, Hashimoto’s thyroiditis, rheumatoid arthritis, psoriasis, inflammatory bowel disease, celiac disease and Crohn’s disease, have low levels of vitamin D3. While more research is required here, a number of studies hint that vitamin D deficiency may increase the risk of auto-immune disorders  
“Vitamin D not only helps the body to fight infections but also reduces the risk of allergies and autoimmune conditions.”
Fact: Vitamin D is important for your thyroid health
It seems that vitamin D may have a role in keeping your thyroid gland healthy. Many studies indicate that people with hypothyroidism have low levels of Vitamin D.
In hypothyroidism, the body can’t make enough thyroid hormones that your body needs to control various important functions such as growth, reproduction, body temperature, heart rate and metabolism.
One of the most common causes of hypothyroidism is Hashimoto’s thyroiditis, an autoimmune condition where your immune cells attack and destroy the thyroid tissue. Vitamin D proves to be useful in this condition as it can prevent abnormal immune responses by regulating certain immune cells relevant to autoimmunity.
Vitamin D is also required for the conversion of inactive T4 hormone into a more active T3 hormone that your cells use. You also need zinc, selenium, B vitamins, magnesium, iron and healthy fats for proper T4 to T3 conversion. This conversion can easily go haywire due to factors such as poor gut health, chronic stress, elevated cortisol and nutritional deficiencies.
“Vitamin D3 helps the thyroid gland to function properly and may also help in Hashimoto’s thyroiditis, which is an autoimmune disorder.”
Fact: Vitamin D supports eye health
Vitamin D is important for your eye health and its anti-inflammatory properties may help in conditions such as age-related macular degeneration, dry eyes, myopia and diabetic retinopathy. [5-11]
This study showed that vitamin D supplements reduces inflammation and improves the symptoms associated with dry eye syndrome. It also stimulates tear secretion, which keeps eyes moist and reduces the risk of infections. 
“Vitamin D3 is a crucial nutrient for eye health as it reduces inflammation, improves tear function and may reduce the risk of macular degeneration, dry eyes and diabetic retinopathy.”
Fact: Vitamin D supports healthy pregnancy
Healthy vitamin D levels in pregnant women means reduced risk of pre-eclampsia, gestational diabetes, and premature delivery. Inadequate vitamin D levels may cause imbalances in blood sugar levels during pregnancy. High blood pressure and high sugar levels also increase the chance of delivery by C-section. Taking vitamin D supplements may help in improving insulin and blood sugar levels in pregnant women. [13-15]
Low levels can also affect the health of your baby and increase the un-born child’s risk of low birth weight, poor bone health, obesity, allergies, asthma, poor respiratory health, and wheezing disorder.
“Vitamin D3 supports healthy pregnancy and enables healthy outcomes in both the mother and the unborn child. Vitamin D deficiency may increase the risk of various pregnancy related complications such as preeclampsia, gestational diabetes and premature birth. It also impacts the health of a new-born.”
Vitamin D3 may offer more health benefits
Going by emerging studies, one can say that vitamin D deficiency is an important risk factor for developing heart problems. For example, low levels are associated with an increased risk of heart attack, stroke, congestive heart failure and peripheral artery disease. In addition, it can also increase the risk of high blood pressure and diabetes and these conditions are especially detrimental for your heart health. Studies show vitamin D3 reduces inflammation in the arteries, improves blood vessel health, and regulates blood sugar levels. [16-18]
In addition, there is some impressive evidence that vitamin D may also improve beta cells functions and insulin sensitivity in people who are at high risk of developing diabetes and also in people who are recently diagnosed with type 2 diabetes. 
The health benefits of vitamin D3 extend beyond bone and muscle health. It is important to understand how you can improve your vitamin D levels safely and effectively, and what factors can increase your risk of vitamin D deficiency, giving rise to several health problems. The good news is that you can easily reverse this deficiency and maintain healthy levels by combining the use of high-quality vitamin D3 supplements, judicious sun exposure and to some extent diet.
- Uwitonze et al. Role of Magnesium in Vitamin D Activation and Function. The Journal of the American Osteopathic Association. 2018
- Kunutsor et al. Low serum magnesium levels are associated with increased risk of fractures: a long-term prospective cohort study. European Journal of Epidemiology. 2017
- Yang et al. The Implication of Vitamin D and Autoimmunity: a Comprehensive Review. Clin Rev Allergy Immunol. 2013.
- Ifigenia Kostoglou-Athanassiou, Lambros Athanassiou and Panagiotis Athanassiou. Vitamin D and Autoimmune Diseases. Intechopen. 2019.
- Zhang et al. Relationship between vitamin D deficiency and diabetic retinopathy: a meta-analysis. Can J Ophthalmol. 2017
- Luo et al. The Association between Vitamin D Deficiency and Diabetic Retinopathy in Type 2 Diabetes: A Meta-Analysis of Observational Studies. Nutrients. 2017
- Millen et al. Association between vitamin D status and age-related macular degeneration by genetic risk. JAMA Ophthalmol. 2015
- K.M Williams et al. Association Between Myopia, Ultraviolet B Radiation Exposure, Serum Vitamin D Concentrations, and Genetic Polymorphisms in Vitamin D Metabolic Pathways in a Multicountry European Study. JAMA Ophthalmol. 2017
- Tideman et al. Low serum vitamin D is associated with axial length and risk of myopia in young children. Eur J Epidemiol. 2016
- JIn et al. Correlation of vitamin D levels with tear film stability and secretion in patients with dry eye syndrome. Acta Ophthalmol. 2017
- Yildirim et al. Dry eye in vitamin D deficiency: more than an incidental association. International Journal of Rheumatic Diseases. 2015.
- Bae et al. Vitamin D Supplementation for Patients with Dry Eye Syndrome Refractory to Conventional Treatment. Sci Rep. 2016
- Hollis et al. New insights into the vitamin D requirements during pregnancy. Bone Res. 2017
- Sasan et al. The Effects of Vitamin D Supplement on Prevention of Recurrence of Preeclampsia in Pregnant Women with a History of Preeclampsia. Obstet Gynecol Int. 2017
- Bakacak et al. Comparison of Vitamin D levels in cases with preeclampsia, eclampsia and healthy pregnant women. Int J Clin Exp Med. 2015
- Ioana Mozos, Otilia Marginean. Links between Vitamin D Deficiency and Cardiovascular Diseases. BioMed Research International. 2015
- Vitamin D improves heart function, study finds. Science Daily. University of Leeds, 2016
- Khan et al. Nanomedical studies of the restoration of nitric oxide/peroxynitrite balance in dysfunctional endothelium by 1,25-dihydroxy vitamin D3 – clinical implications for cardiovascular diseases. International Journal of Nanomedicine. 2018.
- Lemieux et al. Effects of 6-month vitamin D supplementation on insulin sensitivity and secretion: a randomised, placebo-controlled trial. European Journal of Endocrinology. 2019.