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The Importance of Vitamin D

Written by Dr. Meri Rosco

What is vitamin D and why is it important?

Vitamin D helps to build and maintain healthy bones. This is primarily due to calcium requiring the presence of vitamin D to be adequately absorbed. Vitamin D has also been shown to reduce the risk of cancer, diabetes, osteoporosis and cardiovascular disease.1 Sunlight will convert a chemical in your skin into an active form of vitamin D3 (cholecalciferol) but you still might be at risk for vitamin D deficiency. It is estimated that over 1 billion people have a vitamin D deficiency2  and in a study of nearly 4500 people, 41.6% were found to be deficient in vitamin D.1 Risk factors of vitamin D deficiency include obesity, malnutrition, sedentary lifestyle, limited sun exposure, age >65, gastrointestinal, pancreatic, liver or kidney conditions, and taking medications that alter vitamin D metabolism. Those medications include anticonvulsants and glucocorticoids.3 According to Healthline, symptoms of vitamin D deficiency include:

  • Getting sick often
  • Feeling tired or fatigued
  • Bone pain
  • Back pain
  • Depression
  • Slow wound healing
  • Bone loss
  • Hair loss
  • Muscle pain
  • Impaired fertility6

Should one take vitamin D with a meal or with any other vitamins?

Since vitamin D is a fat-soluble vitamin (meaning that it needs fat to be absorbed) you should take it with a food that contains fat such as dairy, nuts, avocado or eggs. It’s also a good time to take your other fat-soluble vitamins, A, E and K. It’s especially important to take vitamin K with vitamin D since they synergistically aid in the absorption of each other and calcium, providing you with vast cardiovascular and bone health benefits.

How much vitamin D should one take and in what form?

There aren’t many foods that contain vitamin D with the exception of fish, egg yolks and fortified grains and dairy. Therefore, if you require additional vitamin D then you will need to supplement.

Vitamins D2 and D3 are two forms of vitamin D. It has been shown that vitamin D3 is more potent, longer acting and has proven to improve all-cause mortality rates among elderly women (not yet proven in younger populations) compared to vitamin D2.4 It is highly recommended, therefore, to take vitamin D3 over D2.

The dosing of vitamin D depends on a few factors including who you ask and what you are trying to achieve thru supplementation. If you want to have just enough to put you out of the deficiency zone and into the low healthy range, then you can follow the RDA‘s recommendation of 600 IU per day. If you want additional benefits such as decreasing your risk of cancer and cardiovascular disease, combating depression and boosting your immune system, then you might want to follow the Endocrine Society‘s recommendation of taking 1,500 to 2,000 IU daily. If your goal is to improve fertility, then most doctors will recommend a daily dose of 4000 IU.5 It all depends on your health needs. As always, however, you should discuss all supplementation and dosing with your physician prior to taking. You should also ensure that your physician understands your medical conditions and concerns as well as is knowledgeable about nutrition and supplementation.

What form of vitamin K should I take and why are fat-soluble vitamins (A, D, E, K) important to someone without a gallbladder?

Read more about vitamin K by clicking here.


  1. Parva NR, Tadepalli S, Singh P, et. al. (June 05, 2018) Prevalence of Vitamin D Deficiency and Associated Risk Factors in the US Population (2011-2012). Cureus 10 (6): e2741. DOI 10.7759/cureus.2741
  2. Penckofer S, Kouba J, Byrn M, et al. Vitamin D and Depression: Where is all the Sunshine? Issues Ment Health Nurs. 2010 June; 31(6): 385-393. DOI 10.3109/01612840903437657.
  3. Vitamin D Deficiency. American Association of Clinical Endocrinologists.
  4. It’s Time to Say ‘Goodbye’ to Vitamin D2 (ergocalciferol).
  5. Vitamin D. PrideAngel.
  6. Grzechocinska B, Dabrowski FA, Cyganek A, et al. The Role of Vitamin D in impaired Fertility Treatment. Neuro Endocrinol Lett. 2013; 34(8):756-62.

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