Breast-feeding moms can keep on running.

Research has shown that pregnancy is compatible with running, benefiting both mother and infant, but what about running and lactation? Will you be able to meet your growing infant's needs? Multiple studies have shown that maternal exercise benefits the mom and does not slow infant growth. Research has also dispelled longstanding breast-feeding lore that exercise made breast milk unpalatable for your infant. Studies have shown that only very intense, anaerobic threshold exercise, like running intense intervals, has an adverse effect on breast milk due to the build up of lactic acid. Moderate aerobic training such as base runs or long runs have no adverse effect. Doctors used to have concerns about dieting, exercise, and breast-feeding, worrying that the energy drain of limiting calories on top of the energy demands of lactation and exercise would have an adverse effect on breast milk quality. Again, research has alleviated those concerns.

Now there is evidence to show that breast-feeding may prevent obesity in your baby's future while it helps you get fit again after pregnancy. Two new studies evaluating the effects of breast milk versus formula on body weight later in life found that breast-feeding decreases the risk of being overweight down the road. In a large study of over 15,000 adolescents, kids fed primarily breast milk for the first six months were 22% less likely to be overweight by age 14. The longer the babies were breast-fed the lower the risk of being overweight as teens. The connection between breast-feeding and obesity held constant even when caloric intake, exercise, and maternal weight were controlled. In the second study the same connection (although slightly weaker) was seen among children aged three to five.

So run to your heart's content even if you're breast-feeding, with advantages for both you and your baby. You can schedule your runs just after you nurse--it can be more comfortable to "run on empty" and even if you have a tough workout there is smaller chance that lactic acid will affect your milk. For more information on pregnancy, childbirth, breast-feeding and exercise see Exercise Through Your Pregnancy, by James F. Clapp, III, M.D., 1998, Human Kinetics, Champaign, IL, 245 pp., $16.95.

(J of the Amer Medical Assn, 2001, Vol. 285, No. 19, pp. 2453-2460; 2461-2467; Canadian J of Applied Physiology, 2001, Vol. 26, No. 1, pp. 55-75; J of Nutrition, 1998, Vol. 128, No. 2, pp. 386S-389S)