The May 21 issue of TIME magazine sparked heated debate over the age at which a child should stop nursing.
Its cover – which featured Los Angeles mother Jamie Grumet nursing her son – went “viral” because the boy was much older than most breast-fed children and was standing to suckle.
Titled “The Man Who Remade Motherhood”, the article probed the so-called “attachment” approach to parenting, popularized by pediatrician William Sears, M.D.
But Steven Gaulin, Ph.D., of UC Santa Barbara – the co-author of a striking new breast milk study – noted that controversy over the TIME cover missed a key point.
Breast milk from Bolivia's Tsimane Indians is higher in omega-3 DHA, vs. American mothers' milk.
Tsimane mothers' milk also has a much healthier (higher) ratio of omega-3 to omega-6 fatty acids.
Findings underscore the benefits of traditional and hunter-gatherer diets, versus the standard American diet.
As he said, “The American diet is eroding one of the most important benefits breast milk can provide – fats that are critical to infant brain development.” (UCSB 2012)
For decades, it's been assumed that Americans' diets are more nutritious than those of people in poor countries.
That's probably true if we compare the standard American diet to the calorie- and vitamin-deficient diets of the many poor countries where people subsist on little but starches like white bread, rice, or yucca root (Kuipers RS et al. 1998; Brenna JT et al. 2007).
But it's becoming clear that people who follow hunter-gatherer lifestyles enjoy better nutrition and health … though it often goes overlooked that they're also far more active and fit than the average American.
Now, findings by U.S. researchers appear to affirm one key advantage of the diets of “primitive” Amazonian peoples, and hold implications for infant health and development.
Bolivian Indians show high levels of omega-3s in breast milk
The study was conducted by researchers from the University of Pittsburgh, the Cincinnati Children's Hospital, and anthropologists at UC Santa Barbara (Martin MA et al. 2012).
The study compared breast milk from women in the U.S. to milk from women of Bolivia's Tsimane tribe, who primarily eat locally grown staple crops (rice, corn, and yucca root), wild game, and freshwater fish.
The Tsimane: More evidence favoring traditional diets
Evidence that traditional diets of all kinds yield better health than modern, industrial diets do was first collected by researcher Weston A. Price, DDS.
Dr. Price traveled the word in the 1930s, and found good dental and overall health among people who followed any traditional (pre-industrial) diet.
His work finds some echoes in research on the so-called “paleolithic” (prehistoric) diet, which is very low in carbohydrates and high in fats and protein, compared with the standard American diet.
The Paleolithic diet persists today only among isolated hunter-gatherer societies in remote jungle regions of Amazonia, Africa, and Oceania.
The Tsimane Indians of Bolivia fit this model only partially, but still have healthier breast milk than the average American.
The Tsimane are an Amazonian forager-horticulturalist group inhabiting a vast area of lowland forests and savannas east of the Andes.
They obtain food by slash-and-burn agriculture, hunting, fishing, and gathering wild plant foods.
The Tsimane resist assimilation, due to a desire to maintain a social identity and a deep mistrust of non-indigenous Bolivians.
The American team found high levels of beneficial omega-3 fatty acids in the breast milk of economically impoverished Amerindian woman, compared to women in the United States.
Samples of Tsimane mothers' milk contained significantly higher percentages of the omega-3 fatty acid called DHA, which is crucial for infants' cognitive and visual development … and for adult brain and eye health.
According to graduate student and lead researcher Melanie Martin of UCSB, “The Tsimane mothers' average milk DHA percentage was 400 percent higher than that of the Cincinnati mothers ...” (UCSB 2012)
The percentages of DHA in the Indian women's breast milk did not drop significantly across the first two years postpartum … the period during which infant brains experience maximal uptake of DHA and peak growth.
This was also true for the American mothers, though the levels of DHA in their milk remained lower than the levels in the Tsimane mothers' milk.
And, as Martin said, the Amerindian women's milk had a much healthier (higher) ratio of omega-3 to omega-6 fats:
“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 ratios were four to one, much closer to the ancestral estimates than observed in U.S. women.” (UCSB 2012)
Although Tsimane women frequently consume plant foods such as corn that provide modest amounts of omega-6 linoleic acid (LA), they rarely consume vegetable oils that are extremely high in LA (e.g., corn, soy, safflower, sunflower) or processed foods made with these oils.
Martin noted that the average percentages of [omega-6] linoleic and trans fatty acids in breast milk from Tsimane mothers were 84 percent and 260 percent lower, respectively.
She made a key point:
“Despite living in economically impoverished conditions, Tsimane mothers produce breast milk that has more balanced and potentially beneficial fatty acid composition as compared to milk from U.S. mothers.” (UCSB 2012)
The omega-3/6 ratio problem plaguing Americans
Unfortunately, as the researchers said, the ratio of omega-6 to omega-3 in industrialized diets varies from 10 to one to as high as 20 to one.
They proposed that this imbalance “is most likely due to the absence of fish, and overconsumption of processed foods and vegetable oils rich in omega-6 linoleic acid [LA].” (UCSB 2012)
Further, as they said, “High intakes and blood levels of omega-6 fatty acids have been linked to increased risks of obesity, inflammation, and cardiovascular disease.” (UCSB 2012)
And they stressed the fact that high intakes of omega-6 LA – which are typical of the standard American diet – interfere with the conversion of short-chain omega-3s found in certain plant foods to long-chain omega-3 DHA.
Short-chain, plant-source omega-3s are useful primarily as precursors to omega-3 DHA, though diets high in them do have modestly beneficial impacts on heart and metabolic health.
The study's findings highlight important questions about infant formula, the fatty acid content of which 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,” Martin explained. “And nutritional recommendations for infants should account for the prolonged requirements of fatty acids that breast milk naturally provides.” (UCSB 2012)
Given the fast-growing body evidence in favor of that position, we couldn't agree more!
Brenna JT, Varamini B, Jensen RG, Diersen-Schade DA, Boettcher JA, Arterburn LM. Docosahexaenoic and arachidonic acid concentrations in human breast milk worldwide. Am J Clin Nutr. 2007 Jun;85(6):1457-64.
Kuipers RS, Smit EN, van der Meulen J, Janneke Dijck-Brouwer DA, Rudy Boersma E, Muskiet FA. Milk in the island of Chole [Tanzania] is high in lauric, myristic, arachidonic and docosahexaenoic acids, and low in linoleic acid reconstructed diet of infants born to our ancestors living in tropical coastal regions. Prostaglandins Leukot Essent Fatty Acids. 2007 Apr;76(4):221-33. Epub 2007 Mar 23.
Martin MA, Lassek WD, Gaulin SJ, Evans RW, Woo JG, Geraghty SR, Davidson BS, Morrow AL, Kaplan HS, Gurven MD. Fatty acid composition in the mature milk of Bolivian forager-horticulturalists: controlled comparisons with a US sample. Matern Child Nutr. 2012 Jul;8(3):404-418. doi: 10.1111/j.1740-8709.2012.00412.x. Epub 2012 May 24.
Pickert K. The Man Who Remade Motherhood. TIME magazine. May 21, 2012. Accessed at http://www.time.com/time/magazine/article/0,9171,2114427,00.html
- UC Santa Barbara (UCSB). Study by UCSB Anthropologists Finds High Levels of Omega-3 Fatty Acids in Breast Milk of Amerindian Women as Compared to U.S. Women. June 8, 2012. http://www.ia.ucsb.edu/pa/display.aspx?pkey=2740