Researchers studied whether L-theanine, a natural compound found in green tea, could help prevent pregnancy problems in obese mice. They found that L-theanine reduced weight gain, lowered blood sugar and cholesterol levels, and improved gut health in pregnant obese mice. The treatment also helped prevent complications like excessive bleeding after birth and improved the health of newborn pups. While these results are promising, this research was done in mice, so more studies in humans are needed before doctors can recommend L-theanine supplements for pregnant women with obesity.

The Quick Take

  • What they studied: Whether a natural green tea compound called L-theanine could help prevent health problems in pregnant mice that were overweight due to eating a high-fat diet
  • Who participated: Pregnant mice that were made overweight by feeding them a high-fat diet, plus gut bacteria samples from 12 pregnant women (6 obese and 6 normal weight)
  • Key finding: L-theanine treatment reduced weight gain, lowered blood sugar and cholesterol levels, improved gut health, and helped prevent pregnancy complications in obese mice
  • What it means for you: This suggests L-theanine might someday help pregnant women with obesity avoid complications, but this is early-stage research in mice. Pregnant women should not take supplements without talking to their doctor first

The Research Details

Scientists created a mouse model of pregnancy obesity by feeding pregnant mice a high-fat diet and giving them gut bacteria from obese pregnant women. This made the mice gain excessive weight during pregnancy, similar to gestational obesity in humans. They then gave some of these obese pregnant mice L-theanine (a compound from green tea) and compared them to mice that didn’t receive the treatment.

The researchers measured many things in both groups: how much weight the mice gained, their blood sugar and cholesterol levels, how healthy their gut bacteria were, and how well their babies developed. They also looked at specific proteins and pathways in the body that control metabolism and inflammation.

They also analyzed gut bacteria samples from 12 pregnant women—6 who were obese and 6 who were normal weight—to understand how obesity changes the types of bacteria in the gut during pregnancy.

This research approach is important because it helps scientists understand how obesity during pregnancy affects both the mother and the developing baby. By using mice with gut bacteria from obese pregnant women, the researchers created a model that more closely resembles what happens in real human pregnancies. This allows them to test whether L-theanine could be helpful before trying it in humans.

This is laboratory research in mice, which is an important first step but has limitations. The sample size of pregnant women whose bacteria were studied was small (12 total). The study shows what L-theanine can do in mice, but results in animals don’t always translate to humans. This research provides promising preliminary evidence that warrants further investigation in human studies.

What the Results Show

L-theanine treatment significantly reduced weight gain in pregnant obese mice compared to untreated obese mice. The treated mice had lower fasting blood sugar levels, lower insulin levels, and lower cholesterol and triglyceride levels—all markers of better metabolic health.

The treatment also improved gut health by reducing harmful inflammation markers (TNF-α, IL-6, IL-8) and strengthening the gut barrier, which normally prevents harmful substances from entering the bloodstream. This is important because a leaky gut is associated with pregnancy complications.

Newborn pups from mothers treated with L-theanine were healthier, with better birth weights and improved placental function (the placenta is the organ that nourishes the baby during pregnancy). The treatment also reduced the risk of postpartum hemorrhage (excessive bleeding after birth), a serious pregnancy complication.

The researchers found that L-theanine worked by activating specific cellular pathways (FXR/FGF15) that regulate metabolism and reduce inflammation throughout the body.

The study identified specific types of gut bacteria that were abnormal in obese pregnant women. Certain bacteria were associated with better pregnancy outcomes (like Weissella and Subdoligranulum), while others were linked to complications (like Bacteroides vulgatus and Megamonas). L-theanine treatment helped restore a healthier balance of these bacteria. The treatment also reduced liver fat accumulation and improved how the body processes fats and glucose.

Previous research has shown that obesity during pregnancy increases risks for gestational diabetes, high blood pressure, and complications during delivery. This study builds on earlier work showing that gut bacteria play an important role in these pregnancy complications. L-theanine has been studied before for its calming effects and potential metabolic benefits, but this is one of the first studies examining its effects specifically on pregnancy complications related to obesity.

This research was conducted entirely in mice, not humans, so results may not directly apply to pregnant women. The sample of pregnant women whose bacteria were studied was small (only 12 people). The study doesn’t tell us the ideal dose of L-theanine for humans or whether it would be safe during pregnancy. Long-term effects in humans are unknown. The study also doesn’t explain exactly how L-theanine works at the molecular level.

The Bottom Line

Based on this mouse research, L-theanine shows promise as a potential treatment for pregnancy complications related to obesity. However, this is preliminary evidence. Pregnant women should NOT start taking L-theanine supplements based on this study alone. More research in humans is needed first. If you’re pregnant and overweight, talk to your doctor about safe ways to manage your weight and reduce pregnancy risks.

This research is most relevant to pregnant women with obesity who are at higher risk for gestational diabetes and other complications. Healthcare providers studying pregnancy complications and obesity should pay attention to these findings. This is NOT yet a recommendation for the general public. Women who are not pregnant should not assume L-theanine will have the same effects.

In the mouse study, benefits appeared within the treatment period during pregnancy. If L-theanine were eventually tested in humans, it would likely need to be taken throughout pregnancy to be effective. Any human studies would take several years to complete and show safety and effectiveness.

Want to Apply This Research?

  • If a user is pregnant and working with their doctor on weight management, they could track: weekly weight gain (target: 25-35 lbs for normal weight women, 15-25 lbs for obese women), fasting blood sugar levels if monitored by their doctor, and energy/inflammation markers like fatigue and joint pain
  • Users could log dietary choices that support gut health (fiber intake, fermented foods), physical activity appropriate for pregnancy, and any supplements discussed with their doctor. They could also track symptoms of pregnancy complications like excessive swelling or unusual bleeding
  • Create a pregnancy health dashboard tracking weight gain trajectory, blood sugar trends if available, and symptom patterns. Set reminders for prenatal appointments where metabolic markers are checked. Compare trends over weeks to identify patterns and share data with healthcare providers

This research was conducted in mice and has not been tested in pregnant women. L-theanine supplements should NOT be taken during pregnancy without explicit approval from your obstetrician or healthcare provider. Pregnancy is a critical time, and any supplements or treatments require medical supervision. If you are pregnant and overweight, work with your healthcare team on safe, evidence-based approaches to managing your weight and reducing pregnancy risks. This article is for educational purposes only and does not constitute medical advice.