The Association Between Allostatic Load and Breastfeeding
by Anne Eglash MD, IBCLC, FABM
Allostatic load is an overall score of biomarkers that is associated with chronic stress, and can predict health risks in a more precise way than evaluating single biomarkers. For example, high cholesterol is associated with heart disease, but combining biomarkers of high cholesterol, BMI, gender and race may be more predictive of heart disease than just cholesterol by itself.
According to the authors of this week’s study, a higher allostatic load is associated with several adverse health outcomes such as metabolic syndrome, cardiovascular disease, arthritis, cancer and depression. Higher allostatic load among women is associated with preterm birth and low infant birth weight. Black women have the greatest risk of high allostatic load, followed by Black men. Although one would expect poverty to play a role in allostatic load, non-poor Black individuals have a higher allostatic load than poor White individuals.
The authors sought to evaluate breastfeeding’s influence on allostatic load, to determine if breastfeeding would reduce the racial and ethnic differences in allostatic load, or health inequity. If breastfeeding lowers the allostatic load, is it simply because breastfeeding women tend to be white, older, and in a higher income category?
They evaluated data from 1999-2018 NHANES surveys selecting 1302 nonpregnant women who were within 2 years postpartum and who completed the breastfeeding status question on the reproductive health questionnaire. The authors chose the following 10 biomarkers to calculate allostatic load: BMI, waist circumference, total and HDL cholesterol, serum albumin, serum creatinine, hemoglobin A1c, and RBC distribution (as a marker of inflammation).
Approximately 28% of the participants were breastfeeding at the time of the survey and they were more likely to be older, more highly educated and in a higher income level compared to the non-breastfeeding participants.
When adjusting for maternal age, race, ethnicity, education, and poverty status, breastfeeding remained significantly associated with a lower allostatic load.
What else? Check out the question!
- The breastfeeding participants had a higher total cholesterol.
- There was no difference in waist circumference in breastfeeding vs non-breastfeeding participants.
- There was no difference in average blood sugars between the breastfeeding and non-breastfeeding participants.
See the Answer
The postpartum period is a critical transition period when exposures to protective factors such as breastfeeding can have long-lasting health impact. Studies have suggested downregulating effects of breastfeeding on stress biomarkers such as cortisol but have not explored the way breastfeeding interacts with allostatic load, a multisystem indicator of chronic stress.
We aimed to examine the association between breastfeeding and maternal allostatic load among women within 2 y postpartum using nationally representative data.
A cross-sectional analysis of 10 waves of data from the NHANES (1999–2018) was conducted in a sample of 1302 women aged ≥18 y who provided information on breastfeeding through the reproductive health questionnaire. Clinical and empirical allostatic load scores (range: 0–10; higher numbers associated with increased risk) were derived for each participant based on 10 biomarkers reflecting metabolic, cardiovascular, and immune health. Multiple linear regression tested associations between breastfeeding and allostatic load, adjusting for maternal age, race and ethnicity, education, poverty level, and survey wave.
Breastfeeding had a significant inverse association with allostatic load in unadjusted and adjusted models. Controlling for age, race and ethnicity, education, poverty level, and survey wave, breastfeeding women had a 0.36- point lower clinical allostatic load score than non-breastfeeding women (β = −0.36, SE = 0.11; 95% CI: −0.59, −0.14; P = 0.002) and a 0.44-point lower empirical allostatic load score (β = −0.44, SE = 0.15; 95% CI: −0.74, −0.14; P = 0.005).
Our study suggests that breastfeeding is protective of maternal stress and provides a more comprehensive picture of breastfeeding’s influence on multiple body systems, exemplifying physiological benefits beyond effects on single biomarkers. However, limitations of cross-sectional data and non-classification of breastfeeding duration, mode, and intensity should be considered when interpreting these findings, and further research to address the role of breastfeeding and allostatic load is needed.
In this study, the breastfeeding women had a smaller waist circumference than the non-breastfeeding women, and a higher cholesterol, but the HDL, or good cholesterol, was also higher. There was no difference in average blood sugars. This study was small, and only included women who were breastfeeding at the time of the questionnaire. It did not consider duration of breastfeeding or whether they had breastfed at all in the last 2 years. This was a limitation of using this particular dataset.
Allostatic load represents the risk of chronic disease and is like the boulder that we have to move to widen the path to improved health long term. Although chronic disease is often largely attributed to race, ethnicity, education and poverty, this study demonstrates that breastfeeding itself can shove that boulder to widen the path to health despite these socioeconomic stressors. And, this is not simply because people at lower risk for chronic disease (older, White, higher income) breastfeed more.
The authors propose a few theories on breastfeeding’s physiologic impact. These include downregulation of stress related to oxytocin, and the higher caloric demands that mobilize fat stores.