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Information on the latest vitamin D news and research.

Find out more information on deficiency, supplementation, sun exposure, and how vitamin D relates to your health.

Dear Dr Cannell: Vitamin D, fatigue, and quality of life

Dear Dr. Cannell:

Is there any concrete research that suggests that vitamin deficiency is related to fatigue and tiredness?

My vitamin D levels are at 13 ng/ml (33 nmol/L), which is deficient, could you provide me with links that shows that vitamin can help with fatigue and well-being?

I’m from the UK, we hardly get any sunshine.

Thank you


Dear Cecil:

Muscle weakness, particularly of the hip and shoulder, are classic symptoms of osteomalacia, the disease most traditionally associated with vitamin D deficiency. That is why fatigue, tiredness and weakness are often listed as symptoms of vitamin D deficiency.

Vitamin D likely plays a role in these symptoms, outside the condition of clinical osteomalacia. However, subclinical osteomalacia may be widespread. A number of years ago, Professor Reinhold Vieth demonstrated that general well-being improved with vitamin D supplementation. Fatigue, tiredness, muscle weakness, quality of life and well-being are such interrelated complaints that sometimes it is difficult to separate them in studies. However, a recent paper looked at a number of those symptoms in relation to 25(OH)D levels.

Ecemis GC, Atmaca A. Quality of life is impaired not only in vitamin D deficient but also in vitamin D insufficient premenopausal women. J Endocrinol Invest. 2013 Mar 19.

The authors found that various measurements of better quality of life were directly associated with higher vitamin D levels. When the 60 women in the study were grouped according to 25(OH)D levels less than 30 ng/ml or above 30 ng/ml, physical symptoms, mental symptoms, physical functioning, social functioning, and vitality scores were all significantly better in women with levels above 30 ng/ml. Furthermore, they found these symptoms were still better in women with levels above 30 ng/ml compared to women who only had levels between 20 and 30 ng/ml. In other words, levels over 20 ng/ml were still not good enough; they needed to be over 30 ng/ml.

To the best of my recollection, this was the first time a relationship between quality of life and 25(OH)D has been demonstrated in a normal group of younger people, although earlier studies found it in the elderly.

Zamboni M et al. Relation between vitamin D, physical performance, and disability in elderly persons. J Gerontol A Biol Sci Med Sci. 2002 Jan;57(1):M7-11.

It’s important to note the Ecemis and Atmaca study does not prove that low vitamin D causes these symptoms. It could be that people with fatigue and muscle pain just don’t get outside as much, thus having low vitamin D levels. However, with vitamin D’s role in the weakness of osteomalacia, coupled with the few clinical trials that have shown improvement in general well-being with vitamin D supplementation, I find it likely that vitamin D does play an active role in these symptoms.

Higher vitamin D levels have also improved general well-being in a variety of diseases:

Vitamin D improves quality of life in Crohn’s

Study: Vitamin D improves pain, sleep, and quality of life in chronic pain patients

So, yes, Cecil there are studies showing a relationship between vitamin D and lethargy and weakness, and I predict your tiredness will improve when you get your 25(OH)D above 40 ng/ml (100 nmol/L).

  About: John Cannell, MD

Dr. John Cannell is founder of the Vitamin D Council. He has written many peer-reviewed papers on vitamin D and speaks frequently across the United States on the subject. Dr. Cannell holds an M.D. and has served the medical field as a general practitioner, emergency physician, and psychiatrist.

One Response to Dear Dr Cannell: Vitamin D, fatigue, and quality of life

  1. Rebecca Oshiro says:

    My love affair with vitamin D began in 2010 when I started taking 5,000 IU of D per day and my bone pain, low energy, and chronic blah feeling disappeared. That is not to say that all people who have these problems and start taking D will experience the same relief, but I am certain there are many others out there whose fatigue and depressed mood are directly caused by a vitamin D deficiency.