Research on whether saw palmetto works to treat hair loss is limited but promising. An extract of saw palmetto berries may block 5-alpha-reductase, an enzyme that converts testosterone to dht. Dht is the molecule responsible for hair loss and also is involved in the enlargement of the prostate. Saw palmetto generally is considered to be safe, but it's not recommended for children, or pregnant and breastfeeding women. Rare side effects include mild headaches and stomach pains.