Here's some information on Vitamin D from a recent peer reviewed article.
Normal lab values for vitamin D range from 30 -100, but optimal values are over 50.
Auto Immune Disease and Vit.D
The autoimmune diseases rheumatoid arthritis (RA) and systemic lupus erythrematosus (SLE) both are associated with vitamin D deficiency and increased risk of fracture. The glucocorticoid drugs that are frequently used to treat these diseases add further to the risk of fracture, especially when their use is continued beyond 3 months. Such patients should be closely monitored and their vitamin D status adjusted as required.
Higher vitamin D intake is associated with a decreased incidence of RA. Among SLE patients the prevalence of vitamin D deficiency is as high as 67 percent. In these patients, renal disease, photosensitivity, and African American race are strong predictors of low 25D levels (<10 ng/mL). Physicians should consider checking 25D status frequently in these patients, especially in those with osteoporosis or other risk factors for falls.
Cardiovascular Disease and Vit. D
Epidemiological studies suggest vitamin D insufficiency is associated with higher risk for hypertension, and that patients with hypertension and low 25D levels have higher risk for adverse cardiovascular events.
In adults, low circulating 25D levels correlate with congestive heart failure. Vitamin D insufficiency has been correlated with greater mortality from cardiovascular disease, and from stroke.
Long-term therapy with antiepileptic drugs such as phenobarbital, phenytoin and carbamazepine, or the antimicrobial agent rifampicin, can cause the metabolic bone disease osteomalacia due to decreased Vit. D status.
Few foods contribute substantial vitamin D to the diet. Oily fish lead the list, including (roughly in the order of highest to lowest D3 content) catfish, salmon, mackerel, sardines, tuna, and eel, followed by eggs, beef liver (cooked), and fish liver oils such as cod liver oil, butter, red meat, and liver. A 100-gram snack of cooked salmon could provide 360 IU, but should preferably be from wild caught fish since farmed salmon can contain as little as one-quarter the vitamin D of the wild fish. Mushrooms are the only substantial vegan source of vitamin D, as D2/ergocalciferol.