Nutrition and health concerns become a focus in March. Nationally recognized as Nutrition Month, this is the time when health education programs for the layman reach an annual peak. Nutritionists in the Washington area follow suit with a number of seminars and lessons, with a Nutrition Month preview in February on the future of the food supply.

* Nutritionist Mary Goodwin will discuss how politics will affect the diets of our children at 8 p.m. Thursday at the Wheaton Library, 11701 Georgia Avenue. The Kensington Branch of the American Association of University Women, which sponsors the event, invites all college graduates to attend the lecture.

* A review of nutrition's influence on the prevention, treatment and control of heart disease is scheduled for March 11 at the National 4-H Center on 7100 Connecticut Ave. NW. Speakers will include representatives from the National Heart Lung and Blood Institute, and the Mayo Clinic.

Registration fee for the day-long symposium is $35 before Feb. 28 and $40 thereafter, although Heart Association members and students get special discounts. For more information, call the American Heart Association Brightwood Office, (202) 726-8950.

* Concern about weight loss reaches new heights as bathing suit season approaches. The Montgomery County Cooperative Extension Service in Gaithersburg has scheduled a series of classes on nutrition, eating habits and exercise. The classes, from 10 to 11:30 a.m. every Thursday from Feb. 24 through April 7, cost $1 at the door. For more information, call the extension office at 948-6744.

* Time and energy are the two big considerations when you begin cooking. The folks at the Montgomery County Cooperative Extension Service think you can save both by making multipurpose mixes in advance, and they'll teach you how to do it. Both morning and evening classes are scheduled on March 7; each costs $2. For more information, call the extension office at 948-6744.

* Free cooking lessons are available through the Fairfax County Department of Extension and Continuing Education. Another in a series of "masters" programs, this class offers a three-day blitz training session March 7, 8 and 9 from 9:30 a.m. to 2:30 p.m. Those finishing the course are asked to volunteer their expertise and time in other demonstrations and talks. Call 691-3433 for more information.

* The Fairfax County Extension Service ushers in National Nutrition Month with educational programs geared to all age groups and interests on March 10 at the McLean (Virginia) Community Center, 1236 Ingleside Avenue. Lessons in snacks for children, adolescent nutrition, physical fitness, nutrition for senior citizens and more. For information, call 691-3433.