Vitamin D

Vitamin D also known as the sunshine vitamin plays a vital and pivotal role in our immune system, bone health and much more. It’s a fat-soluble vitamin available in food sources and through dietary supplementation.  

 What is the role of Vitamin D?

Vitamin D helps promote calcium absorption in the gut and maintains normal bone mineralization. This helps bone growth and bone remodeling as without Vitamin D, bones can become thin or brittle. 

Vitamin D also reduces inflammation and modulates processes such as cell growth, glucose metabolism, cell differentiation and regulation. 

There have been studies looking at low serum levels of Vitamin D and increased risk of cancer. We are now hearing about low levels and increased complications with COVID-19. 

Vitamin D helps regulate the renin-angiotensin-aldosterone system (blood pressure), vascular cell growth and inflammatory and fibrotic pathways. For this reason, Vitamin D has been linked to heart health and risk for cardiovascular disease. 

Vitamin D and Age-Related Macular Degeneration Oct 2017. Nutrients 9(10):1120

How do we get Vitamin D?

Vitamin D is obtained through sun exposure and goes through a chemical reaction called hydroxylation in our liver. This converts the Vitamin D to an active form called 25-hydroxyvitamin D. After this process, it goes through a second hydroxylation in the kidneys which then forms the physiologically active 1,25- dehydroxyvitamin D. 

Use of Vitamin D in clinical practice. April 2009. Alternative Medicine Review: a Journal of Clinical Therapeutic 13(1): 6-20

One of the ways to obtain Vitamin D is through protein sources such as:

• Salmon, sardines, herring, mackerel, or any fatty fish

• Cod liver oil

• Egg yolks

• Beef liver

• Dairy fortified with Vitamin D

 Did you know mushroom is the only vegetable that naturally provides Vitamin D? When mushrooms are exposed to UV light, they can synthesize Vitamin D2. Some mushrooms have purposely been treated with UV light to increase their D2 levels. 

 How do you know if you have enough Vitamin D?

 A blood test that checks for serum concentration of 25(OH) is the main indicator of Vitamin D status. (You don’t want to check 1,25 (OH)2D as it is not a good indicator of Vitamin D and has a very short half-life). Vitamin D insufficiency affects almost 50% of the population worldwide. An estimated 1 billion people worldwide, across all ethnicities and age groups, have a vitamin D deficiency. This pandemic of hypovitaminosis D can mainly be attributed to lifestyle (for example, reduced outdoor activities) and environmental (for example, air pollution) factors that reduce exposure to sunlight, which is required for ultraviolet-B (UVB)-induced vitamin D production in the skin.

What causes Vitamin D deficiency?

•  Older people and people with dark skin are less able to produce Vitamin D from sunlight.

• Given our indoor lifestyles and depending on where you live in the world, most of us have low levels of circulating Vitamin D given our exposure to sunlight is limited compared to our primitive ancestors. 

• Poor absorption of Vitamin D from the digestive track

• Diets low in Vitamin D

• Breastfeeding infants

• Genetic polymorphisms that cannot convert Vitamin D in the liver. 

• People who have medical conditions that prevents fat from being absorbed. 

• Obesity: Obese people need greater intakes of Vitamin D to achieve 25(OH)D levels like those people with normal weight.

• People who are on cholesterol lowering medications like statins. Our body needs cholesterol to make Vitamin D!

• Sunscreen

How much do I take if I am deficient in Vitamin D?

Obtaining sufficient vitamin D from natural food sources alone is difficult. Consumption of vitamin D-fortified foods and exposure to some sunlight are essential for maintaining a healthy vitamin D status. Dietary supplements might be required to meet the daily need for vitamin D in some group of people. The answer depends on how deficient you are. For most cases of Vitamin D deficiency, taking the recommended dietary allowance (RDA) of 600 IU is unlikely to be helpful. It is important to work with a health care provider who can help guide you and recheck levels every 12 weeks. 

What are the health risks for excessive Vitamin D?

Because of the popularity of supplementation, Vitamin D levels may become toxically elevated especially if people are supplementing with high doses (10,000 IU and more/ day) and not checking levels. High vitamin D levels can cause

• Elevated calcium levels

• Nausea, vomiting and muscle weakness

• Loss of appetite

• Dehydration

• Excessive thirst and excessive urination

• Kidney stones

• Severe cases can cause calcification in the coronary vessels and renal failure

 Conclusion

Numbers of people with Vitamin D deficiency are continuously increasing; the importance of this hormone in overall health and the prevention of chronic diseases are at the forefront of research. It is also suggested to measure the serum 25-hydroxyvitamin D level as the initial diagnostic test in patients at risk for deficiency. Working with a functional medicine doctor can help guide you in determining appropriate treatment and guidance. 

Margaret Apostol MD, ABFM, ABOIM, IFMCP

 Sources: 

https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/ 

https://www.hsph.harvard.edu/nutritionsource/vitamin-d/

Vitamin D and Age-Related Macular Degeneration Oct 2017. Nutrients 9(10):1120

Use of Vitamin D in clinical practice. April 2009. Alternative Medicine Review: a Journal of Clinical Therapeutic 13(1): 6-20

Vitamin D and Human Health Int J Mol Sci. 2019 Jan; 20(1): 145

Vitamin D in health and disease: Current perspectives Nutr J. 2010; 9: 65.

Vitamin D: The “sunshine” vitamin J Pharmacol Pharmacother. 2012 Apr-Jun; 3(2): 118-126