In the past few weeks, I’ve covered lots of information about vitamin D, including appropriate levels, dosage, forms, and supplements. This week I’d like to talk about the benefits of vitamin D and the importance of keeping levels in a healthy range.

In the Northwest, it’s tough to get enough vitamin D because there are only a couple summer months where the sun is at a high enough latitude to stimulate our bodies to produce D. The rest of the year, we’re out of luck unless we travel south. Vitamin D is crucial to our overall wellbeing, and as time goes on more of its significance is being discovered. I’m going mention a few of the important roles vitamin D has in our bodies.


#1 Bone Health

This is probably the most widely known function of vitamin D. In a nutshell, vitamin D helps to absorb calcium when our body needs it. It increases absorption in the intestines from food and decreases excretion in the kidneys. It activates a hormone called parathyroid hormone (from our parathyroid glands), which also helps to absorb calcium. Calcium is one of many components necessary for strong bones. Bone health is an important topic, and one I’ll cover more in depth in the future.


#2 Cancer Prevention

Low levels of vitamin D can increase risk for cancer, including prostate, breast, colon, and many others(1). No exact mechanism has been discovered to date, but it is clear that populations with adequate levels of vitamin D have lower cancer rates(2). Vitamin D has also been shown to be helpful as an adjunctive cancer treatment(3).


#3 Mood

Seasonal affective disorder (SAD) is common in those with low levels of vitamin D(4). Supplementation with D during the winter months can improve mood significantly(5). Other studies suggest that low levels of D can predispose those who are susceptible to other mental disorders like depression, schizophrenia, and bipolar disorder, and that “epidemiological evidence suggests that mental illness has increased as humans have migrated out of the sun and into buildings, cars, and sunblock”(6).


#4 Diabetes Prevention

Low vitamin D levels have been linked to insulin resistance, a key factor in type II diabetes (7). Insulin resistance is also present in other metabolic diseases, such as PCOS and metabolic syndrome (also known as syndrome X). Supplementation with vitamin D has been shown to be beneficial for all of these conditions by improving insulin resistance (8, 9).


#5 Multiple Sclerosis

Multiple sclerosis, or MS, occurs most frequently in northern latitude areas, with Washington state having one of the highest rates in the country. The causative factors of MS are still widely unknown, but it is possible that vitamin D plays a role. MS patients have been shown to have lower levels of vitamin D in their blood than non MS patients, suggesting a protective effect of the nutrient (10).


#6 Muscle Pain

Widespread muscle pain has been associated with vitamin D deficiency, including conditions like fibromyalgia (11). A vitamin D deficiency may mimic symptoms common in chronic fatigue syndrome or fibromyalgia, and a blood test to rule out deficiency should be performed.

Vitamin D plays several important roles in our bodies, many of which we are just beginning to discover. Keeping levels in an optimal range is an easy step we can take to improve our health.


(1) Marshall Protocol Knowledge Base. (2010). Latitude Studies on Vitamin D and Disease.

(2) PMID: 18843026; Calcium, dairy foods, vitamin d, and colorectal cancer risk: the fukuoka colorectal cancer study. Cancer Epidemiol Biomarkers Prev. 2008 Oct;17(10):2800-7.

(3) PMID: 10604343; J Urol. 2000 Jan;163(1):187-90

(4) Gloth, F.M. III, Alam, W., Hollis, B.. (1999). Vitamin D versus broad spectrum phototherapy in the treatment of seasonal affective disorder. Journal of Nutritional Health and Aging. 3(1),5-7.

(5) PMID: 9539254; Vitamin D3 enhances mood in healthy subjects during winter.Psychopharmacology (Berl). 1998 Feb;135(4):319-23.

(6) Cannell, J.J. (2008). Vitamin D and Mental Illness.

(7) Hoffman, R. (2010, March). What lies behind the vitamin D revolution? The Clinical Advisor: For Nurse Practitioners, 13(3), 31-37. ProQuest Nursing & Allied Health Source. (Document ID: 2009224851).

(8) MID: 10433180; Vitamin D and calcium dysregulation in the polycystic ovarian syndrome. Steroids. 1999 Jun;64(6):430-5.

(9) PMID: 17277040; The effects of calcium and vitamin D supplementation on blood glucose and markers of inflammation in nondiabetic adults. Diabetes Care. 2007 Apr;30(4):980-6. Epub 2007 Feb 2.

(10) PMID: 18701572; Higher levels of 25-hydroxyvitamin D are associated with a lower incidence of multiple sclerosis only in women. Mult Scler. 2008 Aug 13

(11) PMID: 6308041; Vitamin D Deficiency, hypocalcemia, and increased skeletal muscle degradation in rats. J Clin Invest. 1983 Jul;72(1):102-12.