Researchers in Singapore tested whether eating more protein helps protect the hearts of older adults. They studied 55 people over 16 weeks, comparing those who followed a healthy diet alone versus those who added extra protein powder—either from milk (casein) or soybeans. The results suggest that adding protein, especially from soy, helped keep cholesterol and heart disease risk factors stable, while people eating the regular healthy diet saw their triglycerides (a type of fat in blood) increase. This research suggests protein might be a helpful addition to a healthy diet for older adults concerned about heart health.

The Quick Take

  • What they studied: Whether adding extra protein to a healthy diet helps protect the hearts of older adults, and whether the type of protein (from milk or soybeans) makes a difference.
  • Who participated: 55 older adults living in Singapore, divided into three groups of roughly equal size. All participants were healthy enough to participate in the study.
  • Key finding: People who added protein powder to their healthy diet maintained stable cholesterol and heart disease risk markers, while those eating only the healthy diet without extra protein saw their triglycerides (blood fats) increase by about 0.33 units. The soy protein group showed the most benefit, with cholesterol actually decreasing.
  • What it means for you: If you’re an older adult worried about heart health, adding protein to your already-healthy diet may help keep your cholesterol stable. Soy protein might work slightly better than milk protein, but both appear helpful. However, this is one small study, so talk to your doctor before making major diet changes.

The Research Details

This was a randomized controlled trial, which is considered one of the strongest types of research. Researchers randomly divided 55 older adults into three groups. One group followed a healthy diet pattern (lots of vegetables, whole grains, healthy fats). The second group followed the same healthy diet but added 20 grams of milk-based protein powder daily. The third group followed the healthy diet and added 20 grams of soy-based protein powder daily. The study lasted 16 weeks, and researchers measured heart disease risk factors like cholesterol, blood pressure, and triglycerides at the beginning and end.

The researchers also looked at special blood cells that help repair blood vessels (called endothelial progenitor cells) and tested how well blood vessels could expand and contract. These measurements help scientists understand if the diet changes were actually helping the heart and blood vessels work better, not just improving numbers on a blood test.

Randomized controlled trials are valuable because randomly assigning people to groups helps ensure the groups are similar at the start, making it easier to tell if the diet changes caused the results.

This research design matters because it goes beyond just measuring cholesterol numbers—it also looks at whether the diet actually helps blood vessels stay healthy. For older adults, maintaining muscle mass is important, but doctors worry that high-protein diets might harm the heart. This study helps answer whether protein can do both: support muscles AND protect the heart. By comparing two different protein sources, the researchers could see if where the protein comes from matters.

This study has several strengths: it’s a randomized controlled trial (the gold standard), it measured multiple heart health markers (not just one), and it looked at blood vessel function directly. However, there are limitations to consider: the sample size is relatively small (55 people), all participants were from Singapore so results might differ in other populations, and the study only lasted 16 weeks. Longer studies would help confirm if these benefits continue over months or years.

What the Results Show

The control group (healthy diet only) experienced increases in triglycerides and composite heart disease risk scores during the study. Their triglycerides went up by 0.33 units, their atherogenic index (a measure of harmful cholesterol) increased by 0.31 units, and their predicted long-term heart disease risk increased by 0.8%. This suggests that without the extra protein, heart disease risk markers got worse over the 16 weeks.

In contrast, both protein groups maintained stable cholesterol and heart disease risk markers—meaning they didn’t get worse. The soy protein group showed even better results, with total cholesterol actually decreasing by 0.28 units. This suggests that adding protein, especially from soy, helped protect against the worsening of heart disease risk factors that occurred in the control group.

All three groups showed increases in CD34+ cells, which are special blood cells involved in healing blood vessels. The soy protein group showed the most promise for improving how these cells function to create new blood vessels (a process called angiogenesis). However, other measures of blood vessel function didn’t change significantly in any group.

While blood pressure and other vascular function measures didn’t show significant changes across groups, the increase in CD34+ cells in all groups suggests that the healthy diet itself may support blood vessel health. The fact that the soy protein group showed the most improvement in blood vessel cell function suggests that soy protein might have special properties that support vascular health beyond just providing protein. This aligns with previous research suggesting soy has compounds that may benefit heart health.

Previous research has shown that high-protein diets can help older adults maintain muscle mass, which is important for staying active and independent. However, some doctors worried that extra protein might increase heart disease risk. This study suggests those concerns may be unfounded—at least when the protein is part of an overall healthy diet. The finding that soy protein performed better than milk protein aligns with some earlier research suggesting soy has additional heart-protective properties beyond its protein content. However, this is one of the first studies directly comparing protein sources in older adults within a healthy dietary pattern.

The study is relatively small with only 55 participants, which means the results might not apply to all older adults. All participants were from Singapore, so the findings might differ for people from other ethnic backgrounds or geographic regions. The study only lasted 16 weeks, so we don’t know if the benefits continue long-term or if people can stick with the diet changes. The study didn’t measure actual muscle mass changes, so while protein is meant to support muscles, we don’t have direct evidence it did so in this group. Finally, the study didn’t track whether participants actually stuck to the diet perfectly, which could affect the results.

The Bottom Line

For older adults already following a healthy diet, adding 20 grams of protein daily (about the amount in a protein shake) appears safe and may help maintain heart health markers. Soy protein may offer slightly more benefit than milk protein, though both appear helpful. This recommendation has moderate confidence based on this single 16-week study; longer-term research would strengthen the evidence. Always consult with your doctor or a registered dietitian before significantly changing your protein intake, especially if you have kidney disease or other health conditions.

This research is most relevant for older adults (the study focused on this age group) who are concerned about heart health and want to maintain muscle mass. It may be particularly useful for those already following a healthy diet who want to optimize their protein intake. People with kidney disease should be cautious and consult their doctor, as high protein intake can be problematic for some kidney conditions. Younger adults and people without heart disease risk factors may not need to make changes based on this research.

The study showed changes in cholesterol and triglycerides within 16 weeks, so you might expect to see improvements in blood work within 3-4 months if you make these dietary changes. However, benefits to blood vessel function may take longer to develop. Realistic expectations are that you’ll see stable or improving cholesterol numbers within a few months, but you should plan to maintain these changes long-term for sustained heart health benefits.

Want to Apply This Research?

  • Track daily protein intake in grams (aim for 20g additional protein from powder or whole food sources) and log weekly cholesterol or triglyceride readings if available from your doctor. Also track energy levels and muscle strength using simple measures like how many stairs you can climb without stopping.
  • Set a daily reminder to consume a protein shake or add protein-rich foods to one meal daily. Start with 20 grams of protein and gradually increase if tolerated. If using powder, mix with water, milk, or add to smoothies. Track which type (soy vs. milk) you’re using and how you feel on each.
  • Check in monthly with blood pressure and weight measurements. Request cholesterol and triglyceride tests from your doctor every 3 months to track changes. Monitor energy levels, muscle strength, and how your clothes fit as indirect measures of muscle maintenance. Keep notes on any digestive changes or side effects from the added protein.

This research summary is for educational purposes only and should not replace professional medical advice. The study involved a small group of older adults in Singapore over 16 weeks, so results may not apply to all populations or long-term outcomes. Before making significant changes to your protein intake or diet, especially if you have kidney disease, heart disease, diabetes, or take medications, consult with your doctor or a registered dietitian. This single study provides promising but not definitive evidence; more research is needed to confirm these findings. Always discuss dietary supplements and major diet changes with your healthcare provider.