Can Vitamin D decrease fatigue?

By: Glenn Huerta-Cnochian, M.D.

Vitamin D’s vital role in calcium absorption and maintenance of bone density and strength is well-recognized. Among some of the vitamin’s potential other benefits are reducing fatigue and improving a person’s overall well-being.

At this time of year, when we face months of clouds and rain, the subject of mood change comes up, specifically seasonal affective disorder, or SAD. In addition to the typical symptoms of depression this condition presents — such as difficulty concentrating and social withdrawal — fatigue is also part of it.

SAD and fatigue are more common in women. Fatigue is actually a common complaint among women and is cited as a frequent reason for visits to their physician. Most of the studies that have examined the benefits of vitamin D in regards to mental health, including fatigue, have had limitations. None of the studies focused on one gender or used a placebo as control or a validated survey tool.

As a gynecologist, I was particularly interested in seeing if vitamin D supplementation in women who were deficient in it might ease the symptoms of SAD, particularly fatigue. So, some five years ago, I oversaw a local clinical trial studying the effects of vitamin D on women’s well-being.

The primary goal of the study, funded by a John C. Erkilla Foundation grant, was to evaluate whether or not moderately high doses of vitamin D supplementation could improve feelings of well-being and reduce fatigue in healthy adult women with normal thyroid function and low vitamin D levels. Note: The normal range is 30.0 to 74.0 nanograms per milliliter (ng/mL.)

The study, conducted over six-week periods during two consecutive winters, was a randomized placebo-controlled trial of vitamin D3 supplementation in local women ages 18-65. In year one, the 53 women involved either took between 2,000 UIs a day for two weeks and then 4,000 IUs a day for four weeks, or a placebo over the full six weeks. In year two, which involved 68 women, the protocol was changed to a shorter, more intensive course of vitamin D3 of 6,000 IUs a day or a placebo for four weeks.

In each year, vitamin D levels rose significantly in treated women. In year one, survey results suggested a potential benefit, but this could not be confirmed in year two. Thus, the study concluded that intensive vitamin D supplementation in healthy but fatigued adult women with vitamin D deficiency was not shown to provide a provable benefit.

Nevertheless, make sure your level of Vitamin D is adequate. Even though vitamin D is produced when humans are exposed to adequate sunlight, vitamin D deficiency is common, especially for those living in northern climates, such as Oregon. The prevalence of vitamin D deficiency has been estimated to range from 36 percent to nearly 100 percent of northern Europeans.

Very few foods in nature contain vitamin D. The flesh of fatty fish (such as salmon, tuna, and mackerel) and fish liver oils are among the best sources. Small amounts of vitamin D are also found in beef liver, cheese, and egg yolks.

Typically, supplementation may be necessary. I recommend women consider having their vitamin D levels checked by a physician beginning early in life. It’s especially important to have it checked for women over 50 with a family history of osteoporosis, as well as in women with gastrointestinal disorders that may cause malabsorption.

In general, the current recommended levels of the vitamin are probably too low. Those levels, 400 to 600 units a day, were set many years ago to prevent rickets. More appropriate levels to optimize health might be as high as 2,000 to 3,000 units a day.

Studies also suggest that higher levels of vitamin D improve energy, concentration and muscle strength, and may even play a role in diabetes, hypertension, multiple sclerosis and certain cancers. However, definitive studies are still needed to prove or disprove these potential benefits.