Have you ever noticed an imbalance of the sexes in different countries including the US? Does it seem that we are having more baby boys than girls in the US? Have you noticed that some parents can’t conceive girls no matter what they try? There are a lot of beliefs, strategies and biological techniques on how to select the baby’s sex, but it still doesn’t work for some parents. Nutrition scientists dug into this question for several years as well, trying to find the answers.
Many years ago, scientists proposed a hypothesis to potentially explain the phenomenon: females in better body condition (more energy reserves in adipose tissue) would produce a greater proportion of male offspring. This phenomenon was experimentally tested several times in animals and humans. Animal analysis of experimental trials found that 312 of 422 studies supported the hypothesis, that maternal high fats and glucose levels in the body favor outcome of having the male offspring.
The modern “Western diet” has rapidly spread out all over the world, increasing fat and glucose concentrations in the blood of women. Only a few studies tested the new hypothesis of western diet favoring male offspring. Hence, the Biology of Reproduction published a new study to answer this question. This study focused on if salt and sugar consumption, the amounts similar to “western diet”, would change the sex-ratio in the rat-participants.
Rats were randomly assigned to one of 4 treatment groups: 1) Control diet, just a purified standard rat chow, and tap water; 2) Salt diet, rat chow with 4% NaCl added, and tap water; 3)Fructose diet , standard chow and tap water with 10% fructose added; 4) Fructose/Salt diet, NaCl diet and tap water with 10% Fructose. Each group was made of 20 female rat-dams. Rats were artificially inseminated using a controlled single selected bull’s motile sperm. A purified diet was designed for the rats in which macronutrients (carbohydrates, proteins and fats) and energy density were identical to the Western Diet.
The research team observed interesting findings. The Fructose Fed dams were not found to have significant weight gain, but they were found to consume less food compare to the other 3 groups. Food intake in the Salt Fed group was unaffected by the salt diet. Fluid consumption was increased in both Salt group and Fructose group rats; and exacerbated in the group that consumed both Salt diet with Fructose-water. The energy consumed by the 3 groups was similar, and slightly increased in the Fructose Fed group. Consuming the fructose-sweetened beverage raised maternal plasma cholesterol, glucose and triglycerides, but maternal insulin was unaffected. Maternal salt intake significantly increased urine production rate and urinary albumin:creatine ratio, indicating microalbuminuria and decreased renal barrier function. The research team also observed differences in weight and size of newly born mice. Males tended to have lighter weight than females in all 4 groups, but the Fructose Fed group also was observed to have much smaller litters than the control siblings. The fructose/Salt diet group had the most significant difference in the weights of new born (extremely low) and found a significant shift toward more males in the litter; also they were the only group that had stillborn mice.
In other words, pregnancy consumption of a higher fructose diet did not increase significantly weight in mothers, but showed reduced weight in babies. Westernized diet indicated effects on number of offspring at term as well as the sex ratio in favor of males, and increased risk of stillborn. This study supported the hypothesis that females in better body condition with greater food resources (marked by higher plasma fatty acids and glucose concentration) produce more male than female offspring. Additionally, the study showed that dams (female rats) that consumed both fructose and glucose had difficulties becoming pregnant relative to all other groups.
To conclude, while the mechanism is still not totally understood, the study’s findings suggest mothers that may have problems becoming pregnant should consider seeking dietitian consultation about their diets. Additionally, those moms that searching for a way to conceive with a baby-girl, and are holding some extra body weight, have high triglycerides and glucose level, should consider losing some weight and controlling their triglycerides and glucose level during their conceiving period.