A new meta-analysis (study of studies) from the U.S. Department of Health and Human Services helps answer that question.
This study looked over 9,000 studies on breastfeeding from developed countries, weeded out the ones with poor methodology, and came up with an overall percentage for each one. This is harder than it sounds because "breastfeeding" is defined differently in each study. Nevertheless, here is what they found.
Breastfeeding reduces babies' risk of these diseases by:
- Sudden Infant Death Syndrome (SIDS): 36%
- Type 1 Diabetes: 19-27%
- Type 2 Diabetes: 39%
- Leukemia (acute lymphocytic) : 19%
- Leukemia (acute myelogenous): 15%
- Asthma: 27%
- Gastrointestinal infections: 64%
- Lower respiratory tract diseases: 72%
- Atopic dermatitis: 42%
- Acute otitis media: 50%
And breastfeeding reduces mothers' risk of these diseases by:
- Type 2 Diabetes: 4-12%
- Ovarian cancer: 21%
- Breast cancer: 28%
This study looked at the relationship between breastfeeding and a small list of health conditions. Breastfeeding protects against many more diseases, and the evidence is growing all the time. Here's a list of studies just from 2006, and you'll find more from 2007 here.
So, you see why I get so upset about contests that formula companies run to try to get mothers to use formula instead of breastfeeding? On the one hand, a significant reduction in risk of having lifetime - and even life-threatening - diseases, and on the other hand...a free sandwich. Shouldn't our doctors and nurses know better?