The American Academy of Pediatrics recommends that breastfeeding continue for at least 12 months and then as long after that period as it is mutually desirable. However, that is not always the reality. A study by Yale researchers last year found that most women in underprivileged populations do not continue breastfeeding after four months because they lack the confidence they will be able to do so and think their infants prefer formula. Of the 64 women who participated in the study, 27% had stopped breastfeeding their infants after one week; 37% after two weeks; 70% after two months, and 89% by four months.

These figures have special importance due to the recently released study on manganese in infant formula and possible links to behavioral problems in children. In the study, the researchers found that newborn rats fed a mineral found in higher levels in infant formula -- especially soy formula -- than in breast milk may have attention-related changes in a brain chemical. The preliminary findings need to be confirmed in larger studies before it is known if manganese is definitely linked to behavioral problems.

The reason manganese is such a concern is that it can be toxic in very high levels, even though it is essential for life, as it helps cells gather energy. The levels of manganese differ considerably in different infant foods:

The study included 32 newborn rats that were fed 0 to 500 micrograms of manganese daily. The amounts given to rats were designed to mimic the amounts in breast-fed and formula-fed infants. Those rats who received no or very low doses of manganese didn't show any chemical irregularities, but those on the highest level of manganese dose were associated with lower levels of dopamine, a brain chemical that helps in problem-solving tasks.

The researchers chose manganese because past research on miners who were exposed to very high doses of the mineral developed serious health problems similarto Parkinson's disease. They are worried about soy formula because it contains approximately 80 times the manganese of human breast milk, but they caution that other minerals in the formula could offset the effects of the manganese. Iron and milk calcium are known to protect against manganese toxicity.

Two prominent manufacturers of soy-based formulas are Ross Products, a division of Abbott Laboratories, and Mead Johnson Nutritionals. Ross products makes, Isomil, and Mead Johnson makes ProSobee. ProSobee and Isomil both contain 25 mcg of manganese per 5 fluid ounces of normally diluted formula. This is still 400% higher than breast milk.

One important fact to remember, however, is that the rats were not given infant formula - only a manganese supplement, so the results are definitely not conclusive as of yet. Much more study needs to be done to establish a relationship between the mineral and health problems.

NeuroToxicology 2002; 145: 1-7  Pediatrics 2001 March; 107(3): 543-8