Collaborative Group on Hormonal Factors in Breast Cancer,
The Lancet 360:187-195, 2002
This important independent review article concluded that “The longer women breastfeed, the more they are protected against breast cancer. The lack of or short lifetime duration of breastfeeding typical of women in developed countries makes a major contribution to the high incidence of breast cancer in these countries.”
Additionally the study concluded that “the incidence of breast cancer in developed countries could be reduced by more than 50% (from 6.3 to 2.7 per 100 women) if women had the average number of births and lifetime duration of breastfeeding that had been prevalent in developing countries until recently. Breastfeeding could account for more than two thirds of this estimated reduction in breast cancer incidence.”
The collaborative group, consisting of researchers from a number of countries, collected the worldwide data from epidemiological studies of women with breast cancer to determine the relationship between breast cancer and a number of hormonal, reproductive and other factors. The study included 47 studies from 30 countries. This included more than 80% of the global epidemiological data on breast cancer and breastfeeding. All the data were analysed centrally to get consistent scrutiny.
The phytoestrogen genistein induces thymic and immune changes:
A human health concern?
Yellayi, S. et al. Proc Natl Acad Sci 99:7616-21, 2002
Yet another study adds to the continued concerns about the use of soy as a basis for infant formulas. This time the study warns that infant may be at risk for lowered immune capacity. In the U.S. soy formulas account for about 25% of all formulas uses. The use is particularly high in the African-American population. (Editor’s note: in Canada approximately 6% of those formula feeding their infants use soy-based formulas. Also in Canada, infant formula companies distribute free samples of soy-based formulas to pregnant women and new mothers, with messages that these products are as good as breastmilk.)
The research looked at the hormone-like component – genistein – found naturally in soy. When genistein was fed to mice in levels similar to levels consumed by infants fed soy-based infant formula, the mice showed a substantial decrease in the number of immune cells and changes in the thymus, where immune cells mature.
MeadJohnson, a manufacturer of soy formulas, has stated that, “the safety of soy is well documented. Food and regulatory agencies …have approved the use of soy protein in infant formulas based on decades of clinical studies.”
Nutritional effect of including egg yolk in the weaning diet of
breast-fed and formula-fed infants: a randomized controlled trial
Makrides, M. et al. Am J Clin Nutr 75: 1084-92, 2002
Egg yolks are significant nutritional sources of long-chain essential fatty acids, such as DHA, as well as important sources of iron for the infants’ complementary food diet. This Australian study looked at the outcomes of consuming four egg yolks per week in both breastfed (82 infants) and formula-fed (79) infants from six to 12 months of age.
The researchers investigated the effect of egg yolk consumption on the following: DHA status, haemoglobin, ferritin and plasma cholesterol levels as well as plasma iron, transferrin and transferrin saturation.
The results suggest that egg yolk can be a beneficial addition to the complementary diet of infants during the second half of the first year. The outcome indicated that: cholesterol levels did not increase; none of the infants had overt signs of allergy or intolerance to egg yolk; and there was a positive effect on transferrin saturation and plasma iron.
Generally complementary food diets are low in long-chain essential fatty acids. For breastfed infants, this is not a problem as breastfed infants receive an abundant supply. The addition of egg yolks to the diet of formula-fed infants did offset some of this deficit.
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