Times have changed in the health-food business. Lost to the beef culture are the local health-conscious restaurants of old. Natura's, Eureka's, and Preston's have all succumbed to the Atkins diet and gone belly up. Low-fat now means chicken-fried steak without the gravy. Mega-health food stores with enclosed food courts rule the day. For those who like their carrot juice freshly chilled and their wheat grass freshly mowed, there is still Roy's in Preston Royal Shopping Center. This health-food store is small but hands-on, a holdover from the organic health food movement of the '60s when wheat germ was king. Knowledgeable devotees peddle a vast array of vitamins and supplements to keep you thinking that you are doing something, anything, to stay young. Try the protein plate if all else fails.