Vitamin D: 10 Things You Should Know from Scientific Studies

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Surprisingly misunderstood and undervalued, vitamin D is a nutrient worth learning more about. Science knows a lot about this mysterious nutrient and how its impact on your health goes way beyond your bones. (Plus, why a little sunlight isn’t enough to keep you healthy.) Come discover what you should know about vitamin D.

10 Things You Should Know about Vitamin D, Backed by Science

  1. Deficiency is Common

Vitamin D deficiencies are widespread globally, with data from the NHANES that 94% of people (over the age of 1) consume less than the estimated average requirement.

  1. Low Levels Linked with Diseases and Aging

Low levels of vitamin D may be linked with age-related diseases (cognitive decline, depression, osteoporosis, cardiovascular disease, hypertension, type 2 diabetes), according to scientific evidence.

  1. Sunlight Exposure Isn’t Enough

The major source of vitamin D is skin exposure to UVB in sunlight. Those in higher latitudes, spending time indoors or behind glass, the use of sunscreen that blocks UVB exposure, or with more melanin content in their skin have lower blood levels of vitamin D.

  1. Not a Vitamin: A Pro-Hormone

Vitamin D (calciferol) is called a fat-soluble vitamin, but it acts more like a hormone, specifically a steroid hormone.

  1. Essential for Bone Health

Together, supplementation with vitamin D and calcium may support small increases in bone mineral density and some research suggests it has the potential to reduce fracture rates.

  1. Regulates Blood Pressure & Involved in Heart Health

Vitamin D helps regulate blood pressure and inflammation. Deficiency in vitamin D is associated with dysfunction of the vascular system, arterial stiffening, and elevated blood lipid levels. A large study, observing over 247,000 adults, found low vitamin D levels are linked to a greater risk of heart disease, myocardial infarct (heart attack), stroke, and death. The evidence is mounting – a review of 34 studies, (180,667 adults) showed vitamin D levels are inversely associated with total cardiovascular events.

  1. Effects Blood Sugar Control

Vitamin D plays a role in glucose metabolism. There’s an inverse relationship between vitamin D status and blood sugar levels. It stimulates insulin secretion from the pancreas and reduces insulin resistance in the liver and muscles. In addition, its ability to reduce inflammation, has researchers looking into its potential role in type 2 diabetes.

  1. Influences Weight Management

Lower vitamin D levels may be linked to greater body weight, say researchers.

  1. Anti-inflammatory & Immunity

Vitamin D plays a role in the regulation of the immune and inflammatory responses in inflammatory diseases. Many immune cells have receptor sites for vitamin D. Human vitamin D supplementation studies show beneficial effects of vitamin D on immune function. Plus, low vitamin D levels were related to a higher risk of respiratory tract infections. Of note, over 25 clinical trials have shown vitamin D supplementation is safe and protects against acute respiratory tract infections.

  1. Impacts Mental Health

Neurons and areas of the brain thought to be involved in depression have vitamin D receptors. A review of 61 articles found an association between low vitamin D levels and depression, shining light on the need for more research into this nutrient’s role in human happiness.

Which Food has the Most Vitamin D?

Few foods naturally contain vitamin D, with some in mushrooms, fatty fish, and some animal meats. Some juices, milk (including plant milk), and breakfast cereals are fortified with vitamin D. Supplemental vitamin D is available in chewable, liquid droppers, and capsules.

Am I Getting Enough Vitamin D?

These factors put you at higher risk of vitamin D deficiency:

  • Older adults (synthesis of vitamin D declines with age)
  • Limited sun exposure
  • Obesity
  • Dark skin tones
  • Cystic fibrosis
  • Celiac disease, Crohn’s disease, Ulcerative colitis
  • Gastric bypass patients
  • Liver or kidney conditions

Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ 2017 Feb;356:i6583.

Vitamin D: Fact Sheet for Health Professionals. National Institute of Health, Aug 2021.

Usual nutrient intake from foods and beverages by gender and age. What We Eat in America, NHANES 2013-2016, 2019.

Vitamin D and immune function. Nutrients 2013 Jul 5;5(7):2502-21.

The role of vitamin D in the aging adult. J Aging Gerontol 2014 Dec; 2(2): 60-71.

The vitamin D deficiency pandemic: approaches for diagnosis, treatment and prevention. Rev Endocr Metab Disord 2017 Jun; 18(2):153-165.

Vitamin D and calcium for prevention of fractures: a systematic review and meta-analysis. JAMA Netw Open 2019; 2(12): e1917789.

Vitamin D and depression: a critical appraisal of the evidence and future directions. Indian J Psychol Med 2020 Jan-Feb; 42(2): 11-21.

Contributed by Allison Tannis