Researchers studied how different high-sugar diets affected pregnant rats’ bodies and health. They compared three groups: rats eating normal food with water, rats eating normal food with sugary soft drinks, and rats eating high-sugar solid food with water. The study found that pregnant rats drinking sugary soft drinks consumed much more liquid and produced more urine. All the pregnant rats on high-sugar diets ate more carbohydrates and less protein and fat compared to rats on regular diets. The researchers also discovered that high-sugar diets changed the helpful bacteria living in the rats’ stomachs. These findings suggest that what pregnant animals eat—especially sugary foods and drinks—can significantly impact their bodies and health during pregnancy.

The Quick Take

  • What they studied: Whether eating or drinking high amounts of sugar (fructose) during pregnancy affects a mother’s body, eating habits, blood health, and the good bacteria in her stomach.
  • Who participated: Fifteen pregnant rats divided into three equal groups of five rats each. One group ate normal food and drank water, another ate normal food but drank sugary soft drink, and the third ate high-sugar solid food with water.
  • Key finding: Pregnant rats that consumed high-sugar diets—whether as solid food or sugary drinks—changed what they ate, eating more carbohydrates while eating less protein and healthy fats. Rats drinking sugary soft drinks drank almost twice as much liquid and produced much more urine. The bacteria in their stomachs also changed in unusual ways.
  • What it means for you: This animal study suggests that high-sugar diets during pregnancy may cause significant changes to a mother’s body and eating patterns. While this research is in rats and not humans, it raises important questions about whether pregnant people should limit sugary foods and drinks. Talk to your doctor about healthy eating during pregnancy—this study doesn’t provide direct guidance for humans yet.

The Research Details

Researchers divided 15 pregnant rats into three groups with different diets. The first group (control group) ate standard rat food and drank regular water. The second group ate the same standard food but drank decarbonated sugary soft drink (similar to Sprite with about 6% sugar). The third group ate special food that was 60% sugar and drank regular water. The researchers measured the rats’ weight, blood pressure, how much they ate and drank, blood sugar levels, insulin levels, and cholesterol levels every week during pregnancy. They also collected samples of the rats’ poop before and during pregnancy to study the bacteria living in their stomachs. When the study ended, they examined the rats’ livers and kidneys for any damage.

This type of study is called a controlled experiment because the researchers carefully controlled what each group ate and drank, then measured the results. By comparing the three groups, they could see how different types of sugar (solid versus liquid) affected the pregnant rats’ bodies differently.

The researchers chose pregnant rats because pregnancy puts stress on the body, making it easier to see how diet affects health. This animal model helps scientists understand potential effects before studying humans.

Using pregnant animals to study diet is important because pregnancy naturally stresses the body, making it a good time to see how diet affects health. Researchers can’t do these kinds of controlled diet studies in pregnant people for safety reasons, so animal studies help us understand what might happen. This research helps scientists learn whether high-sugar diets during pregnancy might cause problems that could affect both the mother and baby’s long-term health.

This study was small (only 15 rats total, with just 5 in each group), which means the results are preliminary and need confirmation with larger studies. The researchers carefully controlled the diet and measured many health markers, which is good. However, because it’s an animal study, we can’t be certain the same effects would happen in pregnant people. The study was published in a peer-reviewed journal, meaning other scientists reviewed it before publication. The researchers were honest about their limitations and called for more research to confirm their findings.

What the Results Show

The most striking finding was that pregnant rats drinking sugary soft drinks consumed nearly twice as much liquid and produced much more urine compared to the other groups. This happened in the middle of pregnancy and suggests that sugary drinks may make pregnant bodies work differently.

Both groups eating high-sugar diets (whether as solid food or soft drinks) changed their eating patterns in similar ways. They ate more carbohydrates (sugars and starches) but ate less protein and healthy fats. This shift in eating patterns happened even though the researchers didn’t force the rats to eat differently—the rats naturally chose to eat this way when given high-sugar options.

All three groups of pregnant rats showed changes in their blood cholesterol and fat levels, which is normal during pregnancy. However, the rats eating the high-sugar solid food showed even bigger changes in their blood fats, suggesting that solid high-sugar food may have a stronger effect than sugary drinks on blood chemistry.

The bacteria living in the rats’ stomachs changed noticeably in the groups eating high-sugar diets. These bacteria are important for digestion and overall health, so changes in which bacteria live in the stomach could have long-term health effects.

The study also measured blood sugar levels and insulin (the hormone that controls blood sugar), though specific numbers weren’t highlighted as major findings. The researchers examined the rats’ livers and kidneys for damage but didn’t report major problems in these organs. The fact that all pregnant rats showed some changes in blood fats suggests that pregnancy itself affects how the body handles fats, but high-sugar diets made these changes more extreme.

Previous research has shown that high-sugar diets in non-pregnant animals and people can cause high blood pressure, weight gain, and unhealthy changes in blood fats. This study extends that knowledge by showing that high-sugar diets during pregnancy may have even stronger effects on the body because pregnancy already stresses the system. The finding that high-sugar diets change gut bacteria matches what other researchers have found in non-pregnant animals. This study is one of the first to look at how different types of sugar (solid food versus drinks) affect pregnant animals differently.

The biggest limitation is the small sample size—only 5 rats per group. Larger studies with more animals would give more reliable results. This is an animal study, so we can’t be certain the same effects happen in pregnant people. The study only lasted during pregnancy, so we don’t know if these changes continue after pregnancy or affect the babies’ long-term health. The researchers used decarbonated (flat) soft drink instead of regular carbonated soft drink, which might behave slightly differently in the body. Finally, the study measured many different things, so some findings might have happened by chance rather than because of the diet.

The Bottom Line

Based on this animal research, there’s suggestive evidence that pregnant people should limit high-sugar foods and drinks. However, this is preliminary animal research and doesn’t yet provide definitive guidance for humans. If you’re pregnant or planning pregnancy, talk with your doctor or a nutritionist about healthy eating. General healthy pregnancy nutrition typically includes adequate protein, healthy fats, and limited added sugars—advice that aligns with this study’s findings. Confidence level: Low to Moderate (this is animal research that needs human confirmation).

This research is most relevant to pregnant people and those planning pregnancy, as well as healthcare providers who advise pregnant patients about nutrition. It’s also important for nutrition researchers studying how diet affects pregnancy outcomes. People with diabetes or prediabetes should pay attention since high-sugar diets may be especially problematic during pregnancy. This research is less directly relevant to non-pregnant people, though it adds to the general evidence that high-sugar diets aren’t ideal for anyone’s health.

This study doesn’t tell us how quickly changes happen or how long they last. In the rats, changes in drinking and urine production appeared by the middle of pregnancy (about 10 days into a 21-day pregnancy). Changes in gut bacteria likely develop over weeks. If similar effects happen in pregnant people, changes might appear over weeks to months, but we don’t have specific information about timing.

Want to Apply This Research?

  • Track daily sugar intake (grams of added sugar) and fluid intake (cups of water and other beverages) separately. Note any changes in urination frequency or thirst. For pregnant users, this data could help identify patterns and support conversations with healthcare providers about diet quality.
  • Replace sugary drinks with water, unsweetened tea, or milk. If you enjoy flavored drinks, try adding fresh fruit to water instead of buying sugary beverages. Increase protein intake at each meal (eggs, beans, nuts, fish, chicken) to maintain balanced nutrition when reducing sugary carbohydrates.
  • Weekly check-ins on sugar intake trends and how you feel (energy levels, thirst, digestion). For pregnant users, track these metrics alongside prenatal appointments to discuss with healthcare providers. Monitor whether reducing sugary foods and drinks improves energy, reduces cravings, or improves digestion over 4-8 weeks.

This research was conducted in pregnant rats and does not directly apply to human pregnancy. Animal studies help scientists understand potential effects but don’t prove the same effects occur in people. If you are pregnant, planning pregnancy, or have concerns about your diet, consult with your obstetrician, midwife, or registered dietitian for personalized medical advice. Do not make significant dietary changes during pregnancy without professional guidance. This summary is for educational purposes and is not medical advice.