The study, conducted by anthropologists at UC Santa Barbara in collaboration with researchers at the University of Pittsburgh and the Cincinnati Children's Hospital, examined breast milk fatty acid composition in Tsimane women (who live in Amazonian Bolivia) and U.S. women. The study is published in the journal Maternal and Child Nutrition.
The Tsimane generally consume freshwater fish, wild game and locally grown stable crops. The researchers collected samples of Tsimane mother's milk and found that they contained considerably higher levels of DHA.
Furthermore, the team found that these levels did not significantly decrease in the first two years after giving birth. Infant brains experience peak growth and maximal uptake of DHA during these two years, say the researchers. The team also found this to be true for the U.S. women.
According to the researchers, results from the study indicate that women who breastfeed for an extended period may provide their infants with a constant source of DHA during the vital period of brain development.
Lead author of the study, Melanie Martin, a doctoral student in UCSB's Department of Anthropology, said:
"The fatty acid composition of breast milk varies with the fatty acid composition of a mother's diet and fat stores. Ancestral humans likely consumed omega-6 and omega-3 fatty acids in equal proportions. Tsimane mothers' omega-6 to omega-3 rations where four to one, much closer to the ancestral estimates than observed in U.S. women."
However, in the developed world the ratio of omega-6 to omega-3 in diets varies from 10 to 1 to 20 to 1. According to the researchers this is most likely due to regular consumption of processed foods, vegetable oils rich in linoleic acid (an omega-6), trans fats, and the absence of fresh fish.
Individuals who consume high levels of omega-6 are more likely to develop heart disease, inflammation, and obesity. Furthermore, omega-6 interferes with the synthesis of DHA as well as other omega-3 fatty acids.
"The Tsimane mothers' average milk DHA percentage was 400 percent higher than that of the Cincinnati mothers, while their average percentages of Linoleic and trans fatty acids were 84 percent and 260 percent lower, respectively. Despite living in economically impoverished conditions, Tsimane mothers produced breast milk that has more balanced and potentially beneficial fatty acid composition as compared to milk from U.S. mothers."
The study follows a report in Time magazine, which sparked controversy over how long it is appropriate for a women to breastfeed.
Steven Gaulin, professor of anthropology at UCSV, said:
"Buzz about the recent Time magazine cover missed the point. The American diet is eroding one of the most important benefits breast milk can provide - fats that are critical to infant brain development. It's not surprising that, among developed nations, American children are last on international tests of math and science."
In addition, findings from the study underline vital questions regarding infant formula, of which the fatty acid content is based on the breast milk of U.S. mothers.
"The study suggests that standards of fatty acid composition for infant formulas should be derived from populations such as the Tsimane. And nutritional recommendations for infants should account for the prolonged requirements of fatty acids that breast milk naturally provides."
Written By Grace Rattue