A group of researchers from the Institute of Neuroscience in Sweden have recently found that vitamin D may help with muscle fatigue in patients with myasthenia gravis.
Askmark H, Haggård L, Nygren I, Punga AR. Vitamin D deficiency in patients with myasthenia gravis and improvement of fatigue after supplementation of vitamin D3: a pilot study. Eur J Neurol. 2012.