The document discusses the relationship between sleep, vitamins such as vitamin D and B12, and cardiovascular disease. It summarizes the author's findings that 9 out of 10 patients seen for daily headaches had abnormal sleep studies, and that treating underlying vitamin deficiencies through supplementation improved sleep and reduced symptoms for many patients. The author hypothesizes that vitamin D, which is a hormone rather than a vitamin, plays a key role in regulating sleep and other bodily functions through receptors in the brainstem and other areas.