Researchers looked at 94 different studies to understand how different types of carbohydrates affect asthma risk. They found that eating foods with fiber, whole grains, and natural sugars may lower your chances of developing asthma or wheezing. On the flip side, eating lots of foods with added sugars appeared to increase asthma risk. This large review suggests that choosing better carbohydrates—like whole grains and fruits instead of sugary snacks—could be an important way to help prevent asthma, especially for kids and families looking to stay healthier.

The Quick Take

  • What they studied: Whether eating different types of carbohydrates (sugars, grains, and fiber) affects the chances of getting asthma or experiencing wheezing
  • Who participated: This wasn’t one study with people—instead, researchers combined results from 94 different studies that had already been done. These studies included people of different ages and backgrounds from around the world
  • Key finding: Eating more fiber, whole grains, and natural sugars was linked to about 12-16% lower risk of asthma. But eating lots of added sugars was linked to about 18% higher risk of asthma
  • What it means for you: If you or your family members have asthma or wheeze, choosing whole grain bread, brown rice, fruits, and vegetables instead of sugary drinks and processed snacks might help reduce symptoms. However, diet alone won’t cure asthma—it’s one helpful piece of the puzzle alongside medical treatment

The Research Details

This is called a meta-analysis, which means researchers didn’t do one new study themselves. Instead, they searched through thousands of published studies from 1995 to May 2025 looking for ones that studied how carbohydrates affect asthma. They found 94 studies that met their quality standards—26 that followed people over time, 8 that compared people with asthma to those without, and 60 that took a snapshot of people’s diets and health at one point in time.

The researchers then combined all the results using special math to find patterns across all these studies. They looked at five different types of carbohydrates: free sugars (added sugars), natural sugars, refined grains (white bread, white rice), whole grains (brown bread, oatmeal), and fiber (found in vegetables, fruits, and beans).

To make sure their findings were solid, they tested whether the results stayed the same when they removed individual studies or adjusted their methods. This helps prove the findings weren’t just a fluke from one unusual study.

By combining 94 studies instead of looking at just one, researchers get a much clearer picture of whether carbohydrates really affect asthma. Single studies can sometimes give misleading results by accident, but when many studies point to the same answer, we can be more confident it’s true. This approach is especially important for nutrition research because people eat so many different foods and have different genetics

The studies included were published in respected medical journals and used solid research methods. However, the researchers found significant differences between studies (what they call ‘heterogeneity’), meaning not all studies showed exactly the same results. This is normal in nutrition research because people eat differently in different countries and cultures. The researchers checked their findings multiple ways to make sure the results were stable and reliable, which strengthens confidence in the conclusions

What the Results Show

The study found clear links between carbohydrate quality and asthma risk. People who ate more dietary fiber had about 12% lower risk of asthma and 16% lower risk of wheezing. Those who ate more whole grain foods had about 15% lower asthma risk. People who consumed more natural sugars (like those in fruit) had about 8% lower asthma risk and 19% lower wheezing risk.

The opposite pattern appeared with added sugars: people who ate more foods with added sugars had about 18% higher asthma risk. This was one of the strongest findings in the study.

These percentages might sound small, but when applied to millions of people, they represent significant numbers of asthma cases that could potentially be prevented. For example, if 10% of kids have asthma, a 15% reduction would mean preventing asthma in about 1-2 out of every 100 kids through better eating habits.

The researchers tested their findings multiple times using different methods, and the results stayed consistent, suggesting these aren’t just random findings but real patterns in the data.

The study also found that refined grains (white bread, white rice) didn’t show a clear connection to asthma risk in the same way that whole grains did. This suggests it’s not just about eating grains—it’s about eating the right kind. The difference between whole grains and refined grains is that whole grains keep their fiber and nutrients, while refined grains have these removed during processing. The protective effect seemed strongest for fiber and whole grains, suggesting that the fiber content might be the key ingredient helping prevent asthma

This research builds on earlier studies that suggested inflammation in the body might play a role in asthma. Foods high in fiber and whole grains are known to reduce inflammation, which could explain why they help prevent asthma. Added sugars, on the other hand, can increase inflammation. This study is one of the largest and most comprehensive looks at this connection, bringing together evidence that was previously scattered across many smaller studies. It confirms what nutrition scientists have been suspecting: the quality of carbohydrates matters more than just the total amount

The biggest limitation is that most of these studies asked people to remember what they ate, which isn’t always accurate. People might forget foods or underestimate portion sizes. Also, most studies were done in developed countries, so the findings might not apply equally to everyone worldwide. The studies also couldn’t prove that carbohydrates directly cause asthma—they only show associations, meaning people who eat better carbohydrates happen to have less asthma, but we can’t be 100% sure the carbohydrates are the reason. Other factors like exercise, air pollution, and genetics also affect asthma risk. Finally, the studies varied quite a bit in how they measured diet and asthma, which is why the researchers found significant differences between studies

The Bottom Line

Based on this research, eating more whole grains, fiber-rich foods, and natural sugars while reducing added sugars appears to support asthma prevention. Practical steps include: choosing whole wheat bread instead of white bread, eating oatmeal for breakfast, snacking on fruits and vegetables instead of candy or soda, and reading labels to avoid foods with lots of added sugar. These changes should be made gradually and as part of an overall healthy diet. Confidence level: Moderate to High for the association, though diet is just one factor in asthma prevention

This research is most relevant for families with a history of asthma, children at risk for developing asthma, and anyone currently managing asthma symptoms. It’s also valuable for parents making food choices for their kids. However, this is not a replacement for asthma medication or medical care—it’s a complementary approach. People with severe asthma should continue following their doctor’s treatment plan while also considering dietary improvements

Changes in diet typically take 4-12 weeks to show effects on inflammation and asthma symptoms. Some people might notice improvements in wheezing or breathing within a few weeks, while others might take longer. The benefits are likely to be gradual rather than dramatic, and they work best when combined with other asthma management strategies like medication and avoiding triggers

Want to Apply This Research?

  • Track daily fiber intake (goal: 25-30 grams for adults, age-appropriate amounts for children) and servings of whole grains (goal: at least 3 servings daily). Also monitor added sugar consumption (goal: less than 25 grams daily for women, less than 36 grams for men, less for children). Log any changes in wheezing or breathing difficulty alongside these dietary markers
  • Set a specific goal like ‘Replace one refined grain with a whole grain daily’ or ‘Add one fiber-rich snack daily.’ Users could photograph meals to track progress, receive reminders to choose whole grains at meals, and get notifications when they hit daily fiber targets. Create a simple swap list: white bread→whole wheat, regular pasta→whole wheat pasta, sugary cereal→oatmeal, soda→water with fruit
  • Weekly review of fiber and whole grain intake with monthly check-ins on asthma symptoms or wheezing frequency. Users can create a simple symptom log (1-10 scale for breathing difficulty) and correlate it with their dietary choices over 8-12 weeks to see if their personal pattern matches the research findings. This personalized tracking helps users see whether these dietary changes actually help their individual asthma

This research shows associations between carbohydrate types and asthma risk but does not prove that diet alone causes or prevents asthma. Asthma is a complex condition influenced by genetics, environment, and many other factors. This information is not a substitute for medical advice from your doctor or asthma specialist. If you or a family member has asthma, continue taking prescribed medications and following your healthcare provider’s treatment plan. Before making significant dietary changes, especially for children or if you have other health conditions, consult with your doctor or a registered dietitian. Individual results may vary based on genetics, overall lifestyle, and other health factors.