Whether yogurt and other fermented dairy products (such as kefir) provide probiotic health benefits is debatable, but they are excellent foods, high in protein and calcium. The voluntary “Live and Active Culture” seal from the National Yogurt Association is the best assurance that a certain number of bacteria were present at the time of manufacture—though this may not mean much since many may have perished since. And note that the Food and Drug Administration (FDA) has not approved the seal. Also, be aware that yogurts that are heat-treated after fermentation do not contain live organisms.
If you are lactose intolerant, you’ll probably have less of a problem with yogurt than milk, because the live bacteria will have digested some of the lactose (milk sugar).