. . . and older than you may care to admit if you remember (and you should--there's no slackening of your mental powers after 65) how often you've read Lelord Kordel's keeping-youthful-and-staying-fit regimens. A veteran nutritionist and honcho of sunflower seed and safflower oil, Kordel opposes almost all unnatural remedies (be they sleeping pills, laxatives, cosmetics, convenience foods) and claims that protein, the B vitamins, calcium, exercise will give you most of what you need. This particular book is designed for the senior citizenry, with some of the more usual problems--the heart, the back, arthritis, senility and its avoidance, sex and its non-avoidance, the choice of a doctor, and other options. A few virtuously dismal recipes are interspersed--which should do as much as anything to avoid avoirdupois.