Yes..I give all my dogs Brewers Yeast w/ Garlic. My little ones think it's a treat in the morning or something. LOL They each get one tablet in the mornings and yes, it will help them not get fleas in the summer. I believe it has something to do with the Garlic though...not the yeast. I have heard that the garlic is emitted from the skin and the fleas do not like the smell. Keep in mind however, you will not smell it.
My mom's dogs have also always gotten their Brewers Yeast w/ Garlic and never once had a problem with fleas in the summer months. It's a proven fact that it works here in Kentucky!