Fetal Protection

Abstract

Pregnancy involves puzzling aversions to nutritious foods. Although studies generally support the hypotheses that such aversions are evolved mechanisms to protect the fetus from toxins and/or pathogens, other factors, such as resource scarcity and psychological distress, have not been investigated as often. In addition, many studies have focused on populations with high-quality diets and low infectious disease burden, conditions that diverge from the putative evolutionary environment favoring fetal protection mechanisms. This study tests the fetal protection, resource scarcity, and psychological distress hypotheses of food aversions in a resource-constrained population with high infectious disease burden. The role of culture is also explored. In the first of two studies in Tamil Nadu, India, we investigated cultural explanations of pregnancy diet among non-pregnant women (N = 54). In the second study, we conducted structured interviews with pregnant women (N = 94) to determine their cravings and aversions, resource scarcity, indices of pathogen exposure, immune activation, psychological distress, and emic causes of aversions. Study 1 found that fruits were the most commonly reported food that pregnant women should avoid because of their harmful effects on infants. Study 2 found modest support for the fetal protection hypothesis for food aversions. It also found that pregnant women most commonly avoided fruits as well as "black" and "hot" foods. Aversions were primarily acquired through learning and focused on protecting the infant from harm. Our findings provide modest support for the fetal protection hypothesis and surprisingly strong support for the influence of cultural norms and learning on dietary aversions in pregnancy.

Innate food aversions and culturally transmitted food taboos in pregnant women in rural southwest India: Separate systems to protect the fetus?

“…Placek & Hagen (2015) also found that pathogen avoidance seemed to best explain avoidance of meat. This study did not systematically distinguish foods that were avoided due to aversive reactions versus those that were avoided due to advice from others, however (instead relying on mothers to make that distinction); did not determine from whom avoidances were learned; and its best-fitting exploratory model of meat aversions used number of household members as an index of pathogen exposure (McDade, Rutherford, Adair, & Kuzawa, 2009), which is an indirect measure at best.…”

“…Alternatively, because physiological cues of toxicity, such as bitterness and nausea, do not reliably indicate teratogenicity, women might have evolved to individually and socially learn associations between foods and poor pregnancy outcomes, independent of their own or others’ aversive reactions (Hagen, Roulette, & Sullivan, 2013; Placek & Hagen, 2015), consistent with generic cultural transmission models (e.g., Boyd & Richerson, 1985). Under this hypothesis, individual learners would know why they avoided a food, but might or might not transmit this reason to others (e.g., “do not eat papaya because it causes abortion” vs. “do not eat papaya.”).…”

“…Pregnancy is considered a period of increased heat in the body during which women must avoid “hot” foods (“hot” does not refer to spiciness or temperature) and only consume “cooling” foods in order to bring internal balance and thus ensure a successful pregnancy outcome (Nag, 1994; Placek & Hagen, 2015; Van Hollen, 2003). …”

“…Placek & Hagen (2015) found that humoral theory had a strong influence on pregnancy diet: South Indian women primarily avoided “hot” foods, mostly fruits but also some meats; often acquired food avoidances via learning; and frequently stated that foods were avoided to prevent fetal or infant harm. Placek & Hagen (2015) also found that pathogen avoidance seemed to best explain avoidance of meat.…”

“…Henrich & Henrich, 2010; Placek & Hagen, 2013, 2015). The Semai horticulturalists, for example, avoid unripe fruit in pregnancy because consumption is believed to cause malaria and subsequent fetal death (Dentan, 1966).…”