For the last 10 years, I have awakened three or four times a week between 2 and 4 a.m. with a migraine.

I read an article about people taking melatonin for jet lag and wondered if my headaches were due to a body clock problem. The article didn’t say anything about migraines, but I tried an experiment. I started taking one 3-milligram melatonin tablet each evening, and I stopped waking up with a headache in the wee hours.

You get credit for creative thinking. Scientists have also looked at the role of melatonin in treating migraine and found these headaches might indeed be related to biorhythm disturbances. One study is titled: “Melatonin, 3 mg, Is Effective for Migraine Prevention” (Neurology, Aug. 24, 2004).

Astragalus has been recommended to me as an immune system support to help prevent flu and colds. Can you tell me about its safety and its use?

Astragalus is a traditional Chinese medicine, and most of the research on it is in Chinese. Compounds in the root seem to boost immune system function. Astragalus root is usually given in a tea or chicken soup.

Astragalus should be avoided before surgery, and it may interact with blood thinners. Side effects are not common, but digestive upset has been reported.