If you are a nursing mother well-meaning people may warn you to stay away from certain foods -- such as spices and acidic ingredients like tomato sauce or citrus -- over fears that those foods will increase the acid content in your breast milk. However, these warnings stem from old wives' tales; in reality, there is no direct link between what you eat and the acidity of your milk supply.
Breat Milk and Diet
Breast milk is composed of basic nutrient groups, such as fats, proteins and carbohydrates as well as hormones, enzymes and immune system boosters, such as white blood cells. Even though you consume all some of these ingredients through the foods you eat, your diet does not directly affect the composition of your breast milk. In fact, the composition of your milk is affected by what's in your circulatory system. Milk is created from blood in the lobules of your breasts. This blood absorbs processed nutrients from the digestive tract so, as certified lactation consultant Anne Smith points out on her website "Breastfeeding Basics," your baby might be sensitive to allergens or the byproducts of digested food in your bloodstream.
Blood's pH Level
The pH scale measures the relative acidity of an object. This scale ranges from 0 to 14. In the middle, 7 is considered neutral; this is the pH level of pure water. Something with a pH of 0 is highly acidic, while a pH of 14 is highly alkaline. Because water is the most prevalent component in human blood, it also has a mostly neutral pH level between 7.35 and 7.45. Once your blood begins to turn acidic -- a pH of under 7 -- hemoglobin function is impaired, and it becomes harder for the circulatory system to transport fresh oxygen to your body's tissues. Because the composition of your milk is determined by the composition of your blood, in order for your milk to become more acidic, your blood must be more acidic as well.
How Blood Becomes Acidic
As Dr. Ben Kim discusses on his website, it is not possible to change your blood from its natural pH level of 7.35 to 7.45 to a more acidic or more alkaline composition with your diet. In fact, your body has three layers of buffering systems to help blood maintain its pH level. Over time, however, eating or drinking acidic foods and beverages -- such as soda; alcohol; caffeine; grains, including millet, rice, oatmeal, rye pastas and flour; as well as nuts -- can compromise these buffering systems. This can lead to increased acidity levels in the blood that, in turn, can lead to more acidic breast milk.
Effect of Lactic Acid
If you are young and healthy with a well-rounded diet, it is unlikely that your body's pH balancing system is out of whack or affecting the composition of your breast milk. However, there are other ways than diet that can make breast milk become acidic. The most common is a result of intense physical activity. When you work your muscles to the max, they break down; a byproduct of this breakdown of muscle tissue is lactic acid. Lactic acid is absorbed into the bloodstream and ultimately removed from your body. A 1992 study, reported in the journal "Pediatrics," found women who worked out at their maximum heart rates for an extended period before feeding their babies breast milk were more likely to have their babies refuse the milk.