Researchers wanted to know if whey protein powder could help improve the bacteria living in older adults’ stomachs and intestines. Sixteen older adults drank a whey protein shake every day for three weeks. The study found that whey protein increased the variety of good bacteria in people who started with fewer types of bacteria. The good bacteria increased while harmful bacteria decreased. However, people didn’t notice big changes in how their stomachs felt or their bathroom habits. This suggests whey protein might be a simple way to help keep gut bacteria healthier as we age.

The Quick Take

  • What they studied: Whether drinking whey protein every day could improve the types and variety of bacteria living in older people’s guts
  • Who participated: Sixteen older adults who drank a whey protein shake containing 35 grams of protein each day for three weeks
  • Key finding: Whey protein increased the diversity of gut bacteria, especially in people who started with fewer types of bacteria. Good bacteria like Lactobacillus and Faecalibacterium increased, while potentially harmful bacteria decreased. These changes started appearing within 3 days and lasted after the study ended.
  • What it means for you: If you’re an older adult with limited gut bacteria diversity, whey protein might help create a healthier gut environment. However, this was a small study, so more research is needed before making it a standard recommendation. Talk to your doctor before starting any new supplement.

The Research Details

This was a small research study where scientists gave 16 older adults whey protein isolate (a purified form of whey protein) every day for three weeks. Whey protein isolate is different from regular whey protein because it has most of the lactose and fat removed, leaving mainly the protein and beneficial compounds. The researchers collected stool samples from participants to analyze what bacteria were living in their guts before, during, and after the study. They used advanced laboratory techniques to identify which bacteria were present and measure how many of each type existed.

The study measured something called ‘Simpson diversity,’ which is basically a way to count how many different types of bacteria someone has and whether the bacteria are evenly distributed or if just a few types dominate. The researchers also looked at specific bacteria groups to see which ones increased and which ones decreased. They asked participants about stomach symptoms and checked their stool consistency to see if the protein caused any digestive side effects.

Understanding how foods affect our gut bacteria is important because scientists have discovered that the bacteria in our intestines play a huge role in overall health, especially as we get older. When we age, our gut bacteria naturally become less diverse and change in ways that might not be healthy. This study matters because it tests whether a simple, affordable food supplement could help fix this problem. Whey protein is already popular with older adults for building muscle, so if it also helps gut bacteria, it could be a two-for-one benefit.

This study has some strengths and some limitations to keep in mind. The strength is that researchers used modern DNA technology to accurately identify bacteria, and they tracked changes over time. However, the study was quite small with only 16 people, which means the results might not apply to everyone. There was no control group (a group that didn’t take whey protein) to compare against, which makes it harder to know if the changes were really from the whey protein or from something else. The study was also short—only three weeks—so we don’t know if the benefits last longer or if they’re consistent over months or years.

What the Results Show

The main finding was that whey protein isolate increased the variety of gut bacteria in older adults, but especially in people who started with low bacterial diversity. Think of it like this: if someone’s gut was like a forest with only a few types of trees, the whey protein helped more types of trees grow. The researchers saw these changes appear very quickly—within just 3 days of starting the supplement—and the changes stayed even after people stopped taking it.

The study identified specific bacteria that increased, including Lactobacillus, Lactococcus, and Christensenella. These are considered ‘good’ bacteria that are associated with better health. At the same time, bacteria groups that might cause problems, like Proteobacteria and Streptococcaceae, decreased in the people who had low diversity to begin with. This shift toward more beneficial bacteria is what researchers hope to see when trying to improve gut health.

Interestingly, even though the bacteria changed significantly, people didn’t report feeling different in their stomachs. No one complained of more bloating, gas, constipation, or diarrhea. Their stool consistency also didn’t change noticeably. This is actually good news because it means the whey protein appeared to work without causing uncomfortable side effects.

The study found that the benefits were most pronounced in people who started with low bacterial diversity. This is important because it suggests whey protein might be most helpful for older adults whose gut bacteria have become less diverse with age. People who already had good bacterial diversity didn’t see as much improvement, which makes sense—if your gut bacteria are already healthy and diverse, there’s less room for improvement. The researchers also confirmed their findings using different analysis methods, which strengthens confidence in the results.

Previous research has shown that whey protein is excellent for helping older adults maintain muscle mass and strength, which is why it’s already widely recommended. This new study adds to that knowledge by showing whey protein might also benefit gut health. Other studies have shown that different foods and supplements can change gut bacteria, but this is one of the first to specifically test whey protein isolate in older adults. The findings align with what scientists know about how certain proteins and amino acids can feed beneficial bacteria.

Several important limitations should be considered. First, the study included only 16 people, which is a small number. Results from small studies might not apply to larger, more diverse groups. Second, there was no control group—no one taking a placebo or dummy supplement to compare against. This makes it harder to be certain the whey protein caused the changes rather than something else in the participants’ lives. Third, the study lasted only three weeks, so we don’t know if the benefits continue over months or years, or if people’s bodies eventually adjust. Fourth, the study didn’t measure whether these bacterial changes actually led to health improvements like better immune function or fewer infections. Finally, the study didn’t look at whether different amounts of whey protein or different types of whey products would work better or worse.

The Bottom Line

Based on this research, whey protein isolate may be worth considering if you’re an older adult concerned about gut health, especially if you have low bacterial diversity (something only a doctor can determine through testing). A reasonable approach would be to consume 30-40 grams of whey protein daily as part of your regular diet. However, confidence in this recommendation is moderate because the study was small and short-term. Always consult with your doctor or registered dietitian before starting any new supplement, especially if you have lactose intolerance, dairy allergies, or take medications that might interact with supplements.

This research is most relevant to older adults (typically 65+) who are concerned about maintaining muscle mass and gut health. It may be particularly interesting for people who have been told they have poor gut bacteria diversity or who experience digestive issues. People with dairy allergies or severe lactose intolerance should avoid whey protein isolate. Younger adults might benefit from whey protein for muscle building, but this study doesn’t tell us if the gut benefits apply to them. People taking certain medications should check with their doctor before adding whey protein supplements.

Based on this study, changes in gut bacteria appeared within 3 days of starting whey protein, which is quite fast. However, you might not feel any physical changes in your digestion or energy levels for several weeks. The study only tracked people for three weeks, so we don’t know the optimal timeline for seeing health benefits. Most experts recommend giving any dietary change at least 4-6 weeks before deciding if it’s working for you.

Want to Apply This Research?

  • Track daily whey protein intake (grams consumed) and rate digestive comfort on a 1-10 scale each day. Also note energy levels, bathroom regularity, and any bloating or gas. After 4-6 weeks, review the data to see if there are patterns.
  • Add one whey protein shake or powder serving (30-40g protein) to your daily routine at a consistent time, such as after breakfast or as a post-workout snack. Start with this amount and stay consistent for at least 4 weeks before evaluating results.
  • Use the app to log weekly photos or notes about how you feel overall, including energy, digestion, and general wellness. Set a monthly reminder to assess whether you’ve noticed any changes in your digestive health or how you feel. If possible, work with your doctor to get stool testing done before starting and after 6-8 weeks to objectively measure bacterial changes.

This research is preliminary and based on a small study of 16 participants lasting only three weeks. The findings suggest potential benefits but are not definitive proof that whey protein will improve everyone’s gut health. This information is for educational purposes only and should not replace professional medical advice. Before starting whey protein supplements, especially if you have dairy allergies, lactose intolerance, kidney disease, or take medications, consult with your doctor or registered dietitian. Individual results may vary significantly. If you experience unusual digestive symptoms after starting whey protein, discontinue use and contact your healthcare provider.