Selenium kept human immunodeficiency virus type 1 (HIV-1) from progressing and increased the number of special immune-defense cells (CD4) in HIV-1-positive men and women in early results from an ongoing 18-month study. Researchers recruited 174 participants who took 200 mcg of high selenium yeast per day or a placebo for nine months. In those who took selenium consistently, HIV-1 levels remained stable and CD4 levels increased. In those who did not take selenium consistently, HIV-1 levels rose and CD4 levels decreased at the same rates as in the placebo group. There were no related adverse events. Researchers adjusted for risk factors including age, ethnicity, sex, income, education, drug use, hepatitis C and other variables, and concluded that a daily selenium supplement can keep HIV-1 from progressing, can increase CD4 levels, and is a safe, simple and inexpensive complementary therapy in HIV-1.