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 underpriveleged 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:

• Breast milk contains 4-6 micrograms per liter (mcg/L)
• Milk-based infant formula contains about 30-50 mcg/L
• Some soy formula contain 200-300 mcg/L

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 akin to 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

Dr. Mercola's Comments: Manganese can be quite a significant neurotoxin in high levels. This is a classic example of where too much of a nutrient can have a devastatingly serious side effect. Mark Purdey, who did some ground breaking work on Mad Cow's Disease, confirmed this when he traveled to Groote Eylandt, an island north-east of Australia where 25% of the world's Manganese is currently produced. He wrote a long detailed account of his journey on his web site. About one in thirty people in the largely aboriginal village, where the fine mine dust regularly settles most heavily, have Groote Syndrome, a progressive neurological disease. This is the end stage of severe manganese toxicity. With respect to soy here are some key issues: Many people associate soy with Asians, good healthy and longevity. However the Chinese did not eat unfermented soybeans as they did other legumes such as lentils because the soybean contains large quantities of natural toxins or "anti-nutrients". First among them are potent enzyme inhibitors that block the action of trypsin and other enzymes needed for protein digestion. These inhibitors are large, tightly folded proteins that are not completely deactivated during ordinary cooking. They can produce serious gastric distress, reduced protein digestion and chronic deficiencies in amino acid uptake. In test animals, diets high in trypsin inhibitors cause enlargement and pathological conditions of the pancreas, including cancer Soy also contains goitrogens - substances that depress thyroid function. Since it is likely that over 50 million women have impaired thyryoid function, this is a significant issue. Additionally 99% -- a very large percentage of soy -- is genetically modified and it also has one of the highest percentages of contamination by pesticides of any of our foods. Soybeans are high in phytic acid, present in the bran or hulls of all seeds. It's a substance that can block the uptake of essential minerals - calcium, magnesium, copper, iron and especially zinc - in the intestinal tract. Although not a household word, phytic acid has been extensively studied; there are literally hundreds of articles on the effects of phytic acid in the current scientific literature. While phytic acid may actually help those who have high iron levels, it can clearly be a problem for many women who are menstruating and losing large amounts of iron and other minerals. Related Articles: How Safe is Soy Infant Formula? Responses to Manganese in Soy