A high-fructose diet during pregnancy may cause harm to mother and baby, say researchers.
Fructose is a form of sugar naturally found in fruits, honey, and some vegetables.
It is commonly used by food manufacturers, who combine fructose with glucose to create high-fructose corn syrup (HFCS), which is often added to foods and beverages to sweeten them.
Senior study author Dr. Kelle H. Moley, of the Washington University School of Medicine in St. Louis, MO, and colleagues point out that there has been a significant increase in consumption of sugar and HFCS in recent years.
According to the Centers for Disease Control and Prevention (CDC), adults in the United States currently get around 13 percent of their daily calorie intake from added sugars - including HFCS - which is significantly more than the recommended 5-10 percent.
"Since the early 1970s, we've been eating more fructose than we should," says Dr. Moley. "It is becoming increasingly critical to understand how fructose consumption is impacting human health."
Previous studies have suggested that a diet a high in fructose may raise the risk of diabetes and obesity, but Dr. Moley and colleagues note that there is limited information on how a high-fructose diet during pregnancy impacts the health of both the mother and offspring.
Pregnant mice fed high-fructose diet had smaller fetuses, larger placentas
To gain a better understanding, the team first fed pregnant mice either a high-fructose diet or standard chow and assessed the impact each diet had on maternal and fetal health.
Compared with other forms of sugar, fructose is processed differently in the body. The researchers explain that fructose is broken down by liver cells, which convert the sugar into triglycerides - a form of fat.
At the same time, levels of uric acid - a waste product found in urine and feces - increase. The team notes that excess uric acid levels can lead to a number of health problems, including obesity and type 2 diabetes.
In their study, the researchers found that mice fed a high-fructose diet during pregnancy had higher levels of triglycerides and uric acid than those fed standard chow.
Additionally, they discovered that the mice fed a high-fructose diet had smaller fetuses and larger placentas than those fed standard chow.
Dr. Moley notes that after birth, a baby that was smaller in the womb is likely to experience increased growth, compared with a baby that was a normal-sized fetus.
"The body tries to compensate for the small growth in utero," she explains. "These babies can become kids and then adults struggling with obesity and other health problems."
Furthermore, increased uric acid and triglyceride levels may raise a mother's risk of pregnancy complications, such as preeclampsia and gestational diabetes, according to the team.
Allopurinol reversed maternal, fetal effects of high-fructose diet
Next, the researchers set out to determine whether their findings were relevant to humans.
They analyzed the fructose intake of 18 pregnant women who had scheduled cesarean sections, finding that those who consumed high fructose during pregnancy experienced similar effects to pregnant mice fed a high-fructose diet, including increased uric acid levels.
"The negative effect of excess fructose in humans is likely to lead to an exacerbation of the problems seen in the mice," says Dr. Moley.
The authors comment:
"[...] our work indicates a novel mechanism by which increased fructose consumption can negatively affect maternal-fetal outcomes.
The work presented herein gives premise to the necessity of understanding the potentially negative effects of high fructose diets in humans, in particular during pregnancy."
While the findings indicate that women should reduce their fructose intake during pregnancy to avoid such negative effects, the authors say there may also be another preventive strategy.
The researchers found that when the pregnant mice fed a high-fructose diet were given the drug allopurinol - used to treat kidney stones and gout - the maternal and fetal effects of excess fructose intake were reversed. This is because the drug lowered levels of uric acid in the placenta.
Dr. Moley notes that allopurinol is considered generally safe for use in the second or third trimester of pregnancy.
Still, she stresses that eating natural foods during pregnancy - rather than processed foods that are likely to contain fructose - remains the best way to reduce the risk of poor maternal and fetal outcomes.