Vitamin D Benefits, Deficiency, and Recommended Daily Intake

Vitamin D the sunshine vitamin
Vitamin D the sunshine vitamin

Vitamin D has been in the news lately as studies are showing that most people are not getting enough of what is commonly called the “sunshine” vitamin. Vitamin D helps the body absorb calcium, which is important for strong bones and teeth. However, vitamin D also acts to remove calcium from bones if you are not taking in sufficient amounts of calcium. It is important to understand how vitamin D impacts health and what are the recommended amounts to take.

Vitamin D and Calcium Absorption

According to Boston School of Medicine professor and vitamin D expert Dr. Michael F. Holick, in an article by Cynthia K. Buccini called “Sunny Dispositions,” the ultimate role of vitamin D is to normalize blood levels of calcium for other bodily functions, and using calcium for the bones is lowest on the body’s list of priorities.

When levels of calcium and phosphorous are insufficient, the bones lose out in favour of the heart and other functions. When there are sufficient calcium and phosphorous levels, the body then needs enough vitamin D to absorb it. Holick is quoted as saying that with insufficient amounts of vitamin D present, only 10 to 15% of the calcium will be absorbed. With sufficient amounts of vitamin D, the absorption rate is about 30 to 40% (Buccini).

Benefits of Vitamin D

Vitamin D is actually a hormone. The body requires it for healthy bones and teeth, muscle strength, and heartbeat regulation. It aids in the prevention of breast cancer, colon cancer, osteoarthritis, osteoporosis, and hypocalcemia. It boosts the immune system and helps the thyroid to function correctly. It also helps blood to clot normally. (Balch, 24)

In a forward to the book The Vitamin D Solution, by Dr. Michael F. Holick, Dr. Andrew Weil presents many more benefits of vitamin D, such as the treatment of obesity, arthritis, high blood pressure, back pain, muscle cramps, fibromyalgia, and a variety of cancers in addition to the aforementioned breast and colon cancers (Holick, xiii).

Possible Results of Vitamin D Deficiency

Low levels of vitamin D are associated with the following conditions/symptoms:

  • rickets in children
  • osteomalacia in adults
  • loss of appetite
  • burning in the mouth and throat
  • diarrhea
  • insomnia
  • weight loss
  • viral infections
  • increased risk of developing both types of diabetes

Recommended Amounts of Vitamin D

Based on the variety of issues that vitamin D appears to relieve, getting a sufficient amount of it should be a priority for everyone. Too little is obviously undesirable, but since vitamin D is fat soluble, it is possible to get too much of a good thing. So, how much, then, is enough and how much is too much?

Osteoporosis Canada’s posted guidelines recommend between 400 to 1,000 IU daily for people under the age of 50 who neither have osteoporosis nor a condition that interferes with vitamin D absorption. For those over 50 years of age, they recommend 300 to 2,000 IU per day. As the maximum, Osteoporosis Canada recommends no more than 2000 IU without medical supervision (Osteoporosis Canada).

However, according to Dr. Michael F. Holick, it is possible to take up to 10,000 IU without suffering adverse effects (Buccini). But, keep in mind that vitamin D and calcium work together and that a surplus of vitamin D without sufficient calcium intake can create an imbalance that may decrease bone mass.

Sources of Vitamin D

Vitamin D3, or cholecalciferol, is the natural form of the vitamin and is created in the skin when the skin is exposed to sunshine. In supplements, D3 is derived from lanolin, an animal source, so vegans take note. Vitamin D2, or ergocalciferol, can be obtained from food. Vitamin D5 is a synthetic form of the vitamin.

Getting vitamin D from the sun has become controversial, as the sun is associated with premature ageing and skin cancer. However, now there are proponents in the scientific community for getting vitamin D from sun exposure, but they still recommend exercising caution. Food sources of vitamin D include fish liver oils, dairy products, dandelion greens, eggs, shiitake and chanterelle mushrooms, sardines, sweet potatoes and some herbs such as alfalfa and parsley.


15 Health Benefits of Vitamin D, According to Science (+ 15 Best Vitamin D Foods),” Jenn Reviews (Accessed January 21, 2018).

Balch, Phyllis A., CNC. Prescription for Nutritional Healing: A Practical A-to-Z Reference to Drug-free Remedies Using Vitamins, Minerals, Herbs & Food Supplements, Fourth Edition, New York: Avery, 2006.

Buccini, Cynthia K., “Sunny Dispositions“, Boston University (Accessed July 28, 2010).

Gignac, Tamara, “Daily dose of vitamin D should be doubled, says study,” Calgary Herald (Accessed July 28, 2010).

Holick, Michael F., Ph.D., M.D., The Vitamin D Solution: A 3-Step Strategy to Cure Our Most Common Health Problem, London: Penguin Books, 2010.

Vitamin D: A Key Factor in Good Calcium Absorption,” Osteoporosis Canada (Accessed July 28, 2010).

Image: Courtesy of Bob Tobin

Disclaimer: The information on this website is not intended to substitute advice from your physician or health-care professional. Before beginning any health or diet program, consult your physician.