Researchers studied over 1,000 older adults in Italy to understand how bile acids—substances your body makes to digest fat—affect how well your body handles blood sugar. They found that higher levels of certain bile acids were linked to insulin resistance, a condition where your body struggles to control blood sugar. Interestingly, a hormone called FGF-19 that bile acids trigger showed the opposite effect—higher levels were actually protective. These findings suggest that measuring bile acids and this hormone might help doctors identify who’s at risk for type 2 diabetes earlier, opening new doors for understanding how digestion and blood sugar control are connected.

The Quick Take

  • What they studied: Whether bile acids (digestive substances made by your liver) and a hormone they trigger are connected to insulin resistance, which is when your body has trouble controlling blood sugar.
  • Who participated: 1,049 people aged 60-75 years old living in Northern Italy, with roughly equal numbers of men and women. About 1 in 10 had type 2 diabetes.
  • Key finding: Bile acids were linked to worse insulin resistance, but a hormone called FGF-19 that bile acids activate showed the opposite pattern—it was linked to better insulin control. When researchers looked at all bile acids together, the connection to insulin resistance was very strong.
  • What it means for you: These findings suggest doctors might someday use bile acid and FGF-19 measurements to spot people at risk for diabetes earlier. However, this is one study in older Italian adults, so we need more research before making major changes to how doctors screen for diabetes risk.

The Research Details

This was a cross-sectional study, which means researchers took a snapshot in time of 1,049 older adults and measured their bile acids, FGF-19 hormone levels, and insulin resistance all at once. They took blood samples after people had fasted (not eaten) overnight, which gives the most accurate measurements. The researchers used advanced laboratory techniques to measure 23 different bile acids in each person’s blood. They then looked for patterns between these measurements and insulin resistance, while accounting for other factors that might affect the results, like age, weight, diet, and whether people had high blood pressure or high cholesterol.

This research approach is important because it helps scientists understand whether bile acids and FGF-19 are connected to insulin resistance in real people living their normal lives. By measuring many different types of bile acids rather than just one or two, the researchers got a more complete picture of how these digestive substances affect blood sugar control. The fact that they adjusted for other health factors means the connections they found are more likely to be real rather than just coincidences.

The study has several strengths: it included over 1,000 people, used precise laboratory methods to measure bile acids, and carefully controlled for other factors that could affect the results. However, because it’s a cross-sectional study, it shows relationships but can’t prove that bile acids actually cause insulin resistance—it’s like taking a photo rather than a video. The study focused on older adults in one region of Italy, so the findings might not apply equally to younger people or different populations. The researchers excluded people taking certain medications (fibrates) that affect bile acids, which makes the results cleaner but means those findings don’t apply to people on those medications.

What the Results Show

The main finding was that higher levels of primary bile acids (the main type your body makes) and secondary bile acids (made by gut bacteria from primary bile acids) were both linked to higher insulin resistance. This connection stayed strong even when researchers looked at primary and secondary bile acids together, suggesting both types matter. In contrast, FGF-19—the hormone that bile acids trigger—showed the opposite pattern: higher levels were linked to lower insulin resistance, meaning better blood sugar control. When researchers looked at total bile acids all together, the connection to insulin resistance was particularly strong, suggesting that the overall amount of bile acids circulating in the blood is important for blood sugar control.

The study also found that bile acids and FGF-19 together improved doctors’ ability to identify who had type 2 diabetes. When these measurements were added to standard risk factors, they correctly identified about 3% more people with diabetes compared to using standard factors alone. This might seem small, but in a large population it could help catch thousands of additional cases early.

This research builds on earlier studies showing that bile acids affect blood sugar control through complex signaling pathways in the body. Previous research had suggested FGF-19 might protect against insulin resistance, and this study confirms that finding in a real-world population. However, most previous studies looked at bile acids in people with obesity or diabetes, so this study is valuable because it examines these relationships in a general older population, showing these connections matter for everyone, not just people with weight problems.

This study has several important limitations. First, it’s a snapshot in time, so we can’t tell if bile acids cause insulin resistance or if insulin resistance causes changes in bile acids—the direction of the relationship is unclear. Second, the study only included older adults (60-75 years old) from one region of Italy, so the findings might not apply to younger people or those from different ethnic backgrounds or geographic areas. Third, the study measured bile acids only once, but these levels can change throughout the day and with meals, so a single measurement might not fully represent a person’s typical bile acid levels. Finally, while the study adjusted for many factors, there could be other unmeasured factors affecting the results.

The Bottom Line

Based on this research, there are no immediate changes people should make to their daily lives. The findings are interesting for scientists and doctors but not yet ready for practical use in healthcare. However, if you’re concerned about diabetes risk, the standard recommendations still apply: maintain a healthy weight, eat a balanced diet rich in fiber, exercise regularly, and get screened for diabetes if you’re over 45 or have risk factors. Future research may lead to bile acid testing as part of diabetes screening, but we need more studies first.

This research is most relevant to people aged 60 and older, particularly those concerned about diabetes risk. It’s also important for doctors and researchers studying diabetes prevention and the connections between digestion and blood sugar control. People taking fibrate medications (used for high cholesterol) should know this research doesn’t apply to them since they were excluded from the study. Younger adults should be cautious about applying these findings until similar studies are done in their age group.

This research doesn’t suggest any quick fixes or timeline for seeing benefits. It’s foundational science that helps explain how the body works. If bile acid testing eventually becomes part of diabetes screening, it would likely take 5-10 years of additional research and development before it’s available in typical doctor’s offices.

Want to Apply This Research?

  • Track your fasting blood glucose levels monthly and your weight weekly. If your healthcare provider orders bile acid testing in the future, record those results and compare them over time to see if lifestyle changes affect these markers.
  • Focus on increasing soluble fiber intake (oats, beans, apples) which may influence bile acid metabolism and gut bacteria. Log your fiber intake daily in the app and aim for 25-30 grams per day, as fiber affects how bile acids are processed in your digestive system.
  • Set up quarterly check-ins to review your fasting glucose trends, weight changes, and dietary patterns. If your doctor orders advanced metabolic testing, create a folder in the app to track bile acid levels and FGF-19 measurements alongside your standard glucose and insulin resistance markers to identify personal patterns.

This research describes associations found in one study of older Italian adults and does not establish cause-and-effect relationships. The findings are not yet ready for clinical use in diagnosing or treating diabetes. If you have concerns about diabetes risk or insulin resistance, consult with your healthcare provider about appropriate screening and management strategies. Do not make changes to any medications or medical treatments based on this research without discussing with your doctor. This article is for educational purposes only and should not be considered medical advice.