Why do athletes eat raw onions? Exploring the nutritional and performance benefits

October 20, 2025 •

4 min read

Ancient Greek Olympians reportedly consumed large quantities of onions and even onion juice for strength and stamina before competitions, a practice echoed by modern dietary science. But beyond historical anecdotes, the primary reason why do athletes eat raw onions? lies in potent anti-inflammatory and antioxidant compounds.

Quick Summary

Athletes consume raw onions for their potent quercetin, a flavonoid that reduces post-workout inflammation and oxidative stress. They also aid circulation, boost immunity, and provide essential nutrients for recovery and endurance.

Key Points

Quercetin for Recovery: Raw onions are rich in the flavonoid quercetin, which helps reduce post-workout inflammation and oxidative stress.
Improved Blood Flow: The flavonoids in onions help dilate blood vessels, enhancing circulation and the delivery of oxygen and nutrients to muscles.
Stamina and Endurance: Better oxygen transport and reduced inflammation can contribute to improved stamina and endurance during exercise.
Boosted Immunity: Prebiotic fibers like inulin in onions feed beneficial gut bacteria, strengthening the immune system, which can be compromised by intense training.
Nutrient Density: Raw onions are packed with vitamins C and B6, and minerals like potassium, which are crucial for overall health and athletic function.
Raw vs. Cooked: Eating onions raw preserves higher levels of certain beneficial organic sulfur compounds and Vitamin C that are sensitive to heat.

The Science Behind Raw Onions and Athletic Performance

Onions, particularly when raw, are packed with health-promoting compounds that offer significant advantages for athletes. This is not just a quirky food choice but a targeted nutritional strategy leveraging the powerful bioactive components within the Allium family of vegetables. The primary driver of these benefits is a potent flavonoid antioxidant called quercetin, which is found in high concentrations, especially in red and yellow onions. Raw preparation is key because cooking can reduce the levels of certain heat-sensitive nutrients and sulfur compounds.

The Anti-Inflammatory Power of Quercetin

Intense physical activity, such as endurance training or weightlifting, causes a natural inflammatory response and cellular damage, known as oxidative stress. While inflammation is a necessary part of the healing process, excessive or prolonged inflammation can hinder recovery and decrease performance.

Fighting Oxidative Stress: Quercetin acts as a powerful antioxidant that helps neutralize free radicals, which are unstable molecules created during strenuous exercise. By mopping up these free radicals, quercetin reduces the overall oxidative damage to muscle fibers and other body tissues.
Reducing Post-Workout Soreness: The anti-inflammatory properties of quercetin help calm the body's inflammatory markers, which can translate to less muscle soreness and a quicker return to training. Some studies suggest that quercetin supplementation may help endurance athletes combat the oxidative damage associated with exhaustive exercise.

Enhanced Circulation and Oxygen Transport

Optimizing blood flow is critical for athletic performance, as it ensures efficient oxygen and nutrient delivery to working muscles.

Widening Blood Vessels: Onions are a rich source of flavonoids that promote cardiovascular health and circulation. These compounds help the arteries and veins widen, improving overall blood flow. This vasodilation allows for more efficient oxygen transport, which is especially important during prolonged exercise.
Boosting Red Blood Cell Function: Some compounds in onions, such as sulfur-containing components, may help enhance red blood cell membrane function, potentially improving oxygen transport capabilities. This can lead to increased stamina and endurance.

Digestive Health and Nutrient Absorption

A healthy gut is foundational for overall health and is directly linked to immune function and nutrient absorption. Onions are an excellent source of prebiotics, which are non-digestible fibers that nourish beneficial gut bacteria.

Fueling Healthy Gut Flora: The prebiotics in onions, including inulin and fructooligosaccharides, feed the good bacteria in the intestines. A thriving gut microbiome is essential for immune health, reduces inflammation, and enhances digestion.
Supporting the Immune System: By boosting gut health, onions indirectly strengthen the athlete's immune system. Strenuous exercise can sometimes suppress the immune system, making athletes more susceptible to illness. The nutrients in onions help mitigate this risk.

Raw vs. Cooked Onions: A Comparative Analysis

While cooked onions still offer health benefits, eating them raw maximizes the intake of certain beneficial compounds.


Feature	Raw Onions	Cooked Onions
Quercetin	High concentration, especially in red varieties.	Content is mostly preserved; moves into the cooking broth.
Organic Sulfur Compounds	Highest levels, offering powerful anti-inflammatory and anti-clotting benefits.	Levels can be reduced or altered by heat.
Vitamin C	Higher levels, as this vitamin is sensitive to heat.	Content is significantly diminished by prolonged cooking.
Prebiotic Fiber	Unaffected by preparation method; supports gut health equally.	Unaffected by preparation method; supports gut health equally.
Antibacterial Properties	Stronger, thanks to heat-sensitive compounds like allicin (formed when crushed).	Reduced due to heat degradation of certain active compounds.

Incorporating Raw Onions into an Athlete's Diet

Athletes can easily add raw onions to their meals to reap the benefits.

Salads and Bowls: Add thinly sliced red or white onions to salads, grain bowls, or protein bowls for a flavorful, nutrient-dense crunch.
Salsas and Guacamole: Include finely diced onion in homemade salsas or guacamole to complement the dish while boosting antioxidant intake.
Sandwiches and Wraps: Layer a few rings of raw onion on sandwiches or wraps to add flavor and a nutritional punch.
Flavorful Toppings: Use raw onion as a topping for grilled meats, burgers, or tacos.
Savory Smoothies: For the adventurous, a small amount of mild onion like shallot can be added to savory, vegetable-based smoothies.

Conclusion: A Powerful and Pragmatic Addition

The consumption of raw onions by athletes is not a peculiar habit but a strategic dietary choice backed by nutritional science and historical precedent. The high concentration of anti-inflammatory quercetin, along with vital vitamins and circulation-boosting sulfur compounds, offers a multi-faceted approach to supporting athletic health. From aiding muscle recovery and improving stamina to boosting the immune system through better gut health, raw onions provide a powerful and practical dietary tool. While anecdotal, the historical use of onions by athletes of antiquity, combined with modern research, underscores their potential value for anyone looking to optimize their nutrition for peak performance. For those seeking to strategically enhance their athletic diet, incorporating raw onions offers a simple, accessible, and scientifically sound option. Further reading on this topic can be found through resources like the study on the health functions of onions from Frontiers in Nutrition.

Frequently Asked Questions

Red and yellow onions generally contain higher levels of the potent antioxidant quercetin compared to white varieties, making them a preferable choice for athletes seeking maximum anti-inflammatory benefits.

While there is no standard recommendation, some studies on quercetin supplementation use dosages far higher than a single onion contains. Incorporating a moderate, consistent serving, such as a few slices in a salad daily, is a practical approach for supplementing a balanced diet.

The benefits of onion compounds are more cumulative and long-term rather than providing an immediate boost. Consuming a raw onion right before a run is unlikely to be beneficial and could cause digestive discomfort.

Supplements provide a concentrated dose of compounds like quercetin that would be difficult to obtain from diet alone. However, whole foods like raw onions offer a synergistic blend of nutrients and fiber that supplements cannot replicate.

Consuming large amounts of raw onions can cause gas, bloating, and heartburn in some individuals due to their complex carbohydrates. The potent flavor can also lead to bad breath.

Cooked onions still contain many beneficial compounds, including quercetin, though some heat-sensitive nutrients like Vitamin C and certain sulfur compounds are diminished. Cooking methods like sautéing may not significantly impact antioxidant activity.

Onions contain potassium, an electrolyte that is essential for proper muscle function and fluid balance. This can help prevent muscle cramps, which are often caused by electrolyte imbalances.