Men with low levels of vitamin D are at increased risk for frequent headaches, according to a new Finnish study. The study analyzed information from about 2,600 Finnish men ages 42 to 60 who gave blood samples and answered questions about the frequency of their headaches. Nearly 70 percent of the men in the study had blood vitamin D levels below the threshold for vitamin D deficiency. Low vitamin D levels are a particular concern in Finland and other Nordic countries because these countries are farther north and have less exposure to sunlight.