Researchers tested whether red onion peel extract could help Nile tilapia fish grow better when many fish are packed into the same tank. They fed some fish a regular diet while others got food mixed with red onion peel powder. The fish that ate the red onion peel grew bigger, converted their food into body weight more efficiently, and had stronger immune systems. This suggests that red onion peels contain natural compounds that protect fish from the stress of living in crowded conditions. The findings could help fish farmers raise healthier fish while saving money.

The Quick Take

  • What they studied: Whether adding red onion peel extract to fish food helps tilapia grow better and stay healthier when many fish live together in one tank
  • Who participated: 630 young Nile tilapia fish (weighing about 6 grams each) divided into four groups and kept in outdoor tanks for 14 weeks
  • Key finding: Fish fed with red onion peel extract grew significantly larger, used their food more efficiently, and had stronger immune systems compared to fish in crowded tanks without the supplement
  • What it means for you: While this research is about fish farming, it suggests that compounds in red onion peels may have protective health benefits. However, more research is needed before drawing conclusions about human health benefits

The Research Details

Scientists divided 630 young tilapia into four groups and kept them in tanks for 14 weeks. One group had fewer fish (30 per tank) and regular food. The other three groups had more fish (60 per tank) to create crowded conditions. Two of the crowded groups received food mixed with different amounts of red onion peel powder, while one crowded group got regular food with no supplement. The researchers measured how much the fish grew, how efficiently they converted food into body weight, and tested their blood to check immune system strength and antioxidant levels (natural protective compounds in the body).

The study was designed to mimic real fish farming conditions where farmers often pack many fish into limited space to save money. By testing red onion peel extract, researchers wanted to see if a natural, inexpensive ingredient could help fish handle the stress of crowding better.

Fish were fed three times daily until they stopped eating (apparent satiation), which is a standard practice in aquaculture research. This approach ensures all fish had equal opportunity to eat.

This research approach is important because it tests a practical, low-cost solution that fish farmers could actually use. Rather than just studying the extract in a lab, the researchers tested it in realistic farming conditions with crowded tanks. This makes the results more relevant to real-world fish farming operations.

The study used a controlled experimental design with multiple tanks per treatment group, which strengthens reliability. The researchers measured multiple health markers (growth, immune function, antioxidant status, blood chemistry) rather than just one outcome. However, the study was conducted only on fish, so results cannot be directly applied to humans without additional research. The publication in a peer-reviewed journal indicates the work was reviewed by other experts in the field.

What the Results Show

Fish living in crowded tanks without the supplement grew slower and gained less weight than fish in less crowded conditions. However, when crowded fish received red onion peel extract in their food, their growth improved significantly and approached levels similar to fish in less crowded tanks.

The fish that ate red onion peel also converted their food into body weight more efficiently, meaning they gained more weight from the same amount of food. This is important for fish farmers because it reduces waste and increases profits.

Blood tests showed that fish receiving red onion peel had higher levels of protective compounds called antioxidants and stronger immune markers. These are signs of better overall health and ability to fight off disease. The fish also had lower levels of harmful compounds in their blood that indicate cellular damage.

Financially, the group receiving the highest dose of red onion peel extract (500 mg per kilogram of food) produced the best profit margins among all the crowded tank groups, suggesting the supplement pays for itself through improved fish growth.

Additional blood tests revealed that fish receiving red onion peel had better liver function (lower enzyme levels indicating less liver stress) and higher levels of protective blood proteins. Immune system markers like lysozyme activity and immunoglobulin M (antibodies) were significantly elevated in supplemented groups. These findings suggest the red onion peel extract helps fish resist the physical stress of living in crowded conditions.

This research builds on previous studies showing that plant-based compounds can reduce stress in farmed fish. Red onion peels contain polyphenols, which are natural compounds known to have antioxidant and anti-inflammatory properties. While similar compounds have been tested in fish before, this is one of the first studies specifically examining red onion peel extract at realistic farming densities, making it a valuable addition to the existing research.

This study only tested tilapia fish, so results may not apply to other fish species. The research was conducted in outdoor tanks in specific environmental conditions, which may differ from other farming locations. The study lasted 14 weeks, so we don’t know if benefits continue longer or if fish develop tolerance to the supplement over time. Additionally, this research doesn’t directly tell us whether red onion peels would have similar benefits for humans, as fish and people have different digestive systems and metabolism.

The Bottom Line

For fish farmers: Red onion peel extract at 500 mg per kilogram of feed appears to be an effective, economical way to improve fish health and growth in crowded farming conditions (moderate to high confidence based on controlled study design). For general consumers: This research suggests red onion peels contain beneficial compounds, but human studies are needed before making dietary recommendations (low confidence for human application).

Fish farmers and aquaculture businesses should pay attention to these findings as a potential cost-saving strategy. Researchers studying natural feed additives and sustainable farming practices should find this relevant. General consumers interested in the health benefits of red onion peels may find this interesting, but should not assume human benefits without additional research. People with fish allergies or those managing specific health conditions should consult healthcare providers before making dietary changes.

In fish, the benefits appeared within the 14-week study period. If similar compounds were tested in humans, benefits would likely take weeks to months to appear, depending on the dose and individual factors. Any dietary changes should be evaluated over at least 4-8 weeks to assess effectiveness.

Want to Apply This Research?

  • Track daily red onion consumption (in grams or servings) and monitor energy levels, digestion, and general wellness on a weekly basis using a simple 1-10 scale
  • Add red onion peels to smoothies, soups, or roasted vegetable dishes 3-4 times per week as a practical way to increase polyphenol intake from whole food sources
  • Create a 12-week tracking log noting red onion peel consumption frequency, any digestive changes, energy levels, and overall health markers. Compare baseline measurements (week 1) with week 12 results to identify personal patterns

This research was conducted on fish, not humans. While red onion peels contain compounds with potential health benefits, this study does not prove that red onion peels will have the same effects in people. Before making significant dietary changes or using red onion peel supplements, consult with a healthcare provider, especially if you have existing health conditions, take medications, or have food allergies. This information is for educational purposes and should not replace professional medical advice.