Why is the birth rate so low in the United States?

Corporate stooges will misdirect your attention away from the endocrine disrupting chemicals that are ubiquitous in consumer goods and chalk up below replacement fertility rates to higher education attainment, cost of living, widespread contraception and cultural shifts none of which explain why fertility rates are falling across the world and falling below replacement levels even in third world countries with high rates of poverty like Brazil and India and Islamic theocracies like Iran and UAE. These stories also don’t explain why sperm counts have declined 62% across the world, why age adjusted testosterone levels have declined every year for the past few decades even among men with normal BMI, why rates of chronic diseases have exploded with the advancements of the medical field. In short, they do not explain any of the physiological reasons for below replacement fertility rates and ignore the reality that changes in hormones like progesterone and testosterone can change behavior related to mating and reproduction.

A study evaluating the effects of benzyl butyl phthalate, a common plasticizer, and its metabolites in roundworm germlines, reveals that exposure to this phthalate increases DNA damage through double strand breaks in the germline leading to early p53 induced germ cell death and X-chromosome nondisjunction that increases the frequency of gametes with the wrong number of chromosomes during sex cell division. Put more simply that is the way by which this particular phthalate and likely many of its analogues reduce human fertility and make reproduction less likely to occur and like many endocrine disruptors, this phthalate does not produce greater genotoxic effects at incrementally higher doses on a typical dose response curve but impacts sex cell division on a Non-monotonic dose response curve. In this particular experiment 10 micrometers of BBP produced a 1.7x increase in X-chromosome nondisjunction which was greater than the impact found for doses of 100 and 500 micrometers. That dose produced metabolite concentrations similar to those found in human female amniotic fluid, cord blood and urine samples during pregnancy.

UPF Consumption Leads to Higher Exposure to Phthalates and PFAs

As I mentioned in a prior answer about the price of food diets high in ultra processed foods, which sadly constitute approximately 58% of caloric intake for the average American consumer, increases the risk of several different metabolic disorders, depression and all cause mortality. This may not only be caused by higher consumption of added sugars and trans fatty acids via hydrogenated seed oils but also higher absorption of endocrine disrupting phthalates that are prevalent in higher concentrations in such food stuffs.

A cross sectional study that included a urinalysis of samples provided by participants who answered a 24 hour dietary recall survey and physical activity questionnaire in the larger 2013-14 National Health and Nutrition Examination Survey (n = 2,212), found that each 10% increase in total energy intake from ultra-processed food was associated with a 9% increase in urinary concentrations of three different phthalate metabolites among adults, a 5% increase among adolescents and a 17% increase among children. The association was strongest for consumption of typical fast food products and frozen dinners which were also associated with higher urinary concentrations of bisphenol metabolites. The highest quartile of energy intake from UPF (79.2-100% of total energy intake) was associated with a 25-50% higher urinary concentration of phthalate metabolites and bisphenols with soda consumption.

Another cross sectional study that included participants in the 2009-16 National Health and Nutrition Examination Survey that completed two 24 hour dietary recall surveys, socio-demographic questionnaire and health examination in a mobile examination center where blood and urine samples were collected (n = 9,420) found a similar dose response relationship between UPF consumption by total energy intake and urinary concentration of several phthalate metabolites including the one for benzyl butyl phthalate. The highest quintile of UPF consumption by total energy intake had 23.4% to 10.7% higher urinary concentrations of phthalate metabolites, 6.2% higher concentrations of bisphenol A and 25% higher concentrations of bisphenol F.

A cross sectional study conducted in the Republic of China that included a urinalysis of sample provide participants who answered a 24 hour dietary recall survey, demographic questionnaire and International Physical Activity Questionnaire as part of the Taiwanese version of our NHNES (n = 516) found that participants in the second highest and highest quartile of UPF consumption by energy intake had 108% and 128% higher urinary concentration of monoethyl phthalate metabolites compared to participants in the lowest quartile of UPF consumption which became a 65.7% and 75% increase after adjusting for confounding variables.

A prospective pregnancy cohort study of mother-child pairs recruited from the Memphis metro area and enrolled during their second trimester (n = 1,031) found that a 10% greater proportion of UPF consumption by energy intake is associated with a 13% higher urinary concentration of several different DEHP (di-ethylhexyl phthalate) metabolites including an 11% higher concentration of urinary phthalic acids. Fast food items and sodas were once again the culprit for most elevated phthalate concentrations while a 10% greater proportion of minimally processed foods were conversely associated with an 11% lower urinary concentration of DEHP metabolites.

A Brazilian birth cohort study conducted in a public maternity ward in Rio de Janeiro with pregnant women child pairs (n = 131) enrolled during the third trimester of pregnancy who provided umbilical cord blood samples (n = 118) and extensive dietary and lifestyle information found that infants of pregnant women who regularly consumed 3 or more subgroups of UPF had the highest concentrations of PFAs in umbilical cord blood samples (2.47ng/mL) compared to the infants of mothers who consumed no UPFs (1.86ng/mL).