Vitamin D’s primary function is to maintain healthy bones. It regulates the absorption of bone-healthy minerals, calcium and phosphorus. However, emerging studies and research suggest that Vitamin D could have a bigger, integral role in our health. It helps our brain, heart, lungs, hormones and immune system to function well. Simply put, Vitamin D is excellent for our overall health, and not just bone health.
Low Vitamin D levels have been linked with various health conditions – including diabetes, cardiovascular disease, type 1 diabetes, type 2 diabetes, impaired immunity, depression, cognitive decline, auto-immune disorders, asthma and even cancer. In fact, more and more studies are indicating that Vitamin D supplementation during pregnancy can help reduce childhood allergies, asthma and wheezing disorder.
The Sunshine Vitamin
Our body is designed to synthesize its own supply of Vitamin D. We can make significant amounts of it when we expose our skin to sunlight.
- Sunlight converts cholesterol on the skin into calciol (Vitamin D3).
Vitamin D3 is converted into calcidiol (25-hydroxy Vitamin D3) in the liver.
- The kidneys convert calcidiol into the highly active and usable form of Vitamin D, called calcitriol (1,25-hydroxyVitamin D3).
First, some quick Vitamin D facts:
- Vitamin D is not essentially a Vitamin as our body can produce it on its own. By definition, Vitamins are essential nutrients that we can’t produce in our body and must get from diet and supplements. Vitamin D is actually a pro-hormone.
- Sun exposure and supplements are the best sources of Vitamin D. You can’t get a healthy dosage from food alone.
- Vitamin D regulates more than 200 genes in the body, highlighting its broader role in our health
- You need magnesium to convert Vitamin D to its actual bio-available form.
- UVB rays from the sunlight, responsible for producing Vitamin D in your skin, cannot penetrate glass.
- The further you live from the equator, the longer sun exposure you need to synthesise healthy amounts of Vitamin D.
- Our body is capable of producing thousands of units of Vitamin D, in the range of 15,000-20,000 IU, in just about half the time it would take to cause sunburn or make you turn pink.
- Sunscreen with an SPF of 30 can effectively blocks UVB rays, reducing the production of sunshine Vitamin by 95%.
- UVB rays are at their peak between roughly 10am to 2pm, the best time to get sun exposure for Vitamin D production.
The most well-known function of Vitamin D is to regulate the absorption of calcium and phosphorous. Vitamin D helps to increase the intestinal absorption of calcium required for proper mineralization of bones. Insufficient levels put one at the risk of developing skeletal deformities such as rickets in children and osteomalacia (soft bones) in adults. Vitamin D also helps to prevent weak, fragile bones in adults (osteoporosis).
Several studies suggest that low Vitamin D levels increases the risk of fractures in older adults, and Vitamin D supplementation can be very effective in preventing such fractures.
Studies show that Vitamin D has beneficial effects on immune functions and improves resistance against many infectious diseases. Vitamin D receptors and the enzyme necessary for the conversion of circulating Vitamin D into its active form are present in many cells, including various kinds of immune cells such as monocytes, macrophages, dendritic cells, T cells and B cells . Vitamin D activates our immune defences and enhances both innate and adaptive immunity. For example, it promotes the antibacterial capabilities of macrophages and monocytes. Vitamin D stimulates macrophages’ production of cathelicidin, a protein that is useful in fighting upper respiratory infections and tuberculosis.
The effects of the sunshine Vitamin have been found particularly notable in autoimmune and inflammatory diseases, such as inflammatory bowel disease, rheumatoid arthritis, lupus, multiple sclerosis and type 1 diabetes mellitus.
Low serum levels have been associated with:
- High risk of developing influenza
- Upper respiratory tract infections 
- Increased risk of allergy, wheezing and asthma
Reduced risk of cardiovascular disease
There is robust scientific evidence suggesting an association between Vitamin D and cardiovascular disease. Vitamin D deficiency is considered as a risk factor for heart attacks, congestive heart failure, peripheral arterial disease and fatal strokes.
The active form of Vitamin D acts as a steroid hormone by binding to the Vitamin D receptor (VDR). VDR is found in many cells including cardiomyocytes, vascular smooth muscle and endothelium. Current evidence shows that people who are deficient in Vitamin D are at increased risk of developing cardiovascular disease .
Vitamin D supplements can lower the contributing risk factors for cardiovascular events.
- Improves heart functions
- Reduces blood pressure 
- Prevents inflammation and reduces arterial stiffness, vascular calcifications, thus reducing arthrosclerosis risk .
- Effective in lowering the risk of developing heart disease in kidney patients.
Better mood and mental health
We invariably feel better and happy when we go out in sunlight. Research shows that Vitamin D might play a critical role in regulating mood and keeping depression at bay. Studies show that Vitamin D deficiency is linked to depression. A 2013 study concluded that there is “an inverse association between serum 25(OH)D levels and the risk of depression.” . And more studies have indicated that Vitamin D supplementation may be effective for reducing depressive symptoms in patients with clinically significant depression .
Many parts of the brain have Vitamin D receptors, highlighting its broader role in reducing the risk as well as treatment of a range of mental disorders including anxiety, depression, dementia and cognitive decline in the elderly and Alzheimer’s disease.
Healthy pregnancy and healthy baby
Vitamin D helps to maintain healthy pregnancy. Many studies have demonstrated that Vitamin D deficiency during pregnancy can result in potentially adverse outcomes for both the mother and the baby. Studies show that intake of Vitamin D during pregnancy reduces asthma symptoms in early childhood. Maternal Vitamin D deficiency can result in :
- Increased possibility of caesarean section
- High risk of bacterial vaginosis during pregnancy
- Multiple health issues for the developing foetus, including problems in bone development
- Increased risk of preeclampsia
- Increased risk of gestational diabetes mellitus
- Increased risk of asthma, respiratory tract infections and wheezing disorders in young children
Weight loss and reduced blood sugar levels
Vitamin D deficiency has been linked to obesity and increased risk of developing type 2 diabetes. In a recent 2016 study, it was found that Vitamin D can act in the brain to lower weight and improve glucose tolerance and insulin sensitivity . The study’s main lead Stephanie Sisley explains that hypothalamus, a region of our brain, plays a central role in controlling weight and glucose levels and we have receptors for Vitamin D there.
Many previous studies have pointed out that low serum Vitamin D levels are associated with type 2 diabetes  . It is believed that “Vitamin D may play a functional role in glucose tolerance through its effects on insulin secretion and insulin sensitivity.”
A 2016 study published in Nutrition Research showed that low serum 25-hydroxyVitamin D (25[OH]D) levels are independently associated with microvascular complications in type 2 diabetes mellitus (T2DM) patients . Microvascular complications, for example peripheral neuropathy, nephropathy, retinopathy are common but dangerous issues in diabetic patients.
Vitamin D Deficiency: Contributing Factors
While you can get sufficient amounts of Vitamin D through safe, non-burning sun exposure, many lifestyle, health and environmental factors can interfere with this ability. You may be deficient in the sunshine Vitamin because of the following reasons:
- Sunscreen use
- Spending more time indoors
- Dark skin
- Magnesium deficiency
- Occupation or clothes that prevent sun exposure
- Medical problems such as Crohn's disease and celiac disease
- Milk allergy
- Strict vegetarian diet
- Old age
Getting past the deficiency
Very few foods naturally contain Vitamin D and even those foods really aren’t a substantial source. Fish such as salmon and mackerel have Vitamin D in good amounts. Other possible food sources to get some Vitamin D, though in very small amounts, are tuna, sardine, egg yolk, beef liver, shrimp, mushroom and fortified foods such as milk, orange juice, cereals and infant formula. Milk, unless it is fortified, doesn’t have any Vitamin D power to it on its own.
Sensible sun exposure
When did you last go out in the sun without sunscreen? Sunscreen blocks UVB, something our skin needs to produce Vitamin D. Experts in the field believe that careful sun exposure for about 10-15 minutes, anywhere between 10 am to 2 pm, can help your body produce sufficient amount of Vitamin D.
This exposure, without any sunscreen and with arms, legs and back exposed for two to three times a week, is the best strategy to make your own Vitamin D. When you produce Vitamin D in this natural way, the supply lasts two to three times longer in the body. There is also no danger of toxicity as the body uses the amount it needs while removing extra from the body. Consult your dermatologist, if you or someone in the family have any history or risk of developing skin cancer.
With changing lifestyles, it can be challenging to get sufficient Vitamin D each day through sun exposure alone. If you don’t go out in the sun too often, taking a high quality Vitamin D supplement is a good idea. Ideally, the combination of Vitamin D and calcium is considered the best solution for maintaining strong, healthy bones. We recommend you don’t forget about taking magnesium, as this mineral plays an important role in regulating both calcium and Vitamin D.
- Barbara Prietl, Gerlies Treiber, Thomas R. Pieber, and Karin Amrein. Vitamin D and Immune Function. Nutrients. 2013 Jul; 5(7): 2502–2521..
- Ginde AA, Mansbach JM, Camargo CA, Jr. Association between serum 25-hydroxyVitamin D level and upper respiratory tract infection in the Third National Health and Nutrition Examination Survey. Arch Intern Med. 2009; 169:384-90.
- Urashima M, Segawa T, Okazaki M, Kurihara M, Wada Y, Ida H. Randomized trial of Vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr. 2010
- Martineau et al. Vitamin D for the management of asthma. Cochrane Database Syst Rev. 2016
- Suzanne Judd, Vin Tangpricha. Vitamin D Deficiency and Risk for Cardiovascular Disease. Circulation. 2009.
- Vitamin D supplements can reduce blood pressure in patients with hypertension. European Society of Hypertension. 2012.
- Ioana Mozos, Otilia Marginean. Links between Vitamin D Deficiency and Cardiovascular Diseases. BioMed Research International. 2015
- Vitamin D improves heart function, study finds. University of Leeds. 2016.
- Ju SY, Lee YJ, Jeong SN. Serum 25-hydroxyVitamin D levels and the risk of depression: a systematic review and meta-analysis. J Nutr Health Aging. 2013
- Shaffer et al. Vitamin D supplementation for depressive symptoms: a systematic review and meta-analysis of randomized controlled trials. Psychosom Med. 2014
- Adekunle Dawodu, Henry Akinbi. Vitamin D nutrition in pregnancy: current opinion. International Journal of Women’s Health. 2013
- Sisley et al. Hypothalamic Vitamin D Improves Glucose Homeostasis and Reduces Weight. Diabetes. 2016
- Alvarez JA, Ashraf A. Role of Vitamin D in insulin secretion and insulin sensitivity for glucose homeostasis. Int J Endocrinol 2010. Int J Endocrinol. 2010
- Afsaneh Talaei, Mahnaz Mohamadi, Zahra Adgi. The effect of Vitamin D on insulin resistance in patients with type 2 diabetes. Diabetology & Metabolic Syndrome 2013.