The Effect of Beetroot Powder on Exercise Performance in Competitive Swimmers

The Effect of Beetroot Powder on Exercise Performance in Competitive Swimmers

Swimming requires high energy in a short time and involves overcoming water resistance. Besides regular training, swimmers use supplements to enhance performance, correct nutrient deficiencies, and speed recovery. The Australian Institute of Sport (AIS) classifies supplements by evidence level, with nitrate in Group A. Nitrate aids vasodilation and muscle performance via conversion to nitric oxide (NO).

About 25% of dietary nitrate converts to nitrite by oral bacteria, then to NO in the stomach-a valuable oxygen-independent pathway. NO improves exercise by enhancing oxygen efficiency, muscle contraction, and affecting type II fibers. Timing, dose, nitrate source, and individual traits influence its effect. Beetroot, rich in nitrate, is practical as juice for storage and consumption.

Beetroot gels and juices raise plasma nitrate 1-3 hours post-consumption, effective during 10-17 minute exercises. Some studies found no improvement in short-distance swimming, but others reported dose-dependent benefits. Meta-analyses recommend 5-14.9 mmol nitrate ≥150 minutes before acute exercise, and 5-9.9 mmol for chronic intake. Highly trained athletes may need ≥6-8 mmol NO₃-.

JECFA and the European Commission set acceptable daily intake (ADI) at 0-3.7 mg/kg body weight nitrate ion, safe for all ages.

No long-term, controlled studies exist on beetroot powder's effect in swimmers. To address this, a randomized, placebo-controlled, triple-blind crossover study was designed to evaluate beetroot powder supplementation's impact on competitive swimmers' performance, potentially contributing valuable knowledge.

1. Study Design and Participants: This study employed a randomized, double-blind, placebo-controlled crossover design to investigate the effects of beetroot supplementation. Based on a power analysis conducted with a 5% error level and a statistical power of 0.95, a sample size of 36 participants was determined to be sufficient. The study was conducted over a one-year period at the Galatasaray Swimming Club following approval from the institutional ethics committee, and all participants provided written informed consent. Inclusion criteria required voluntary participation with parental consent, an age range of 18-24 years, participation in a structured training program for at least 18 hours per week, no history of chronic disease, no current use of sports or food supplements/medications, and no adherence to a special diet. Conversely, exclusion criteria included irregular training attendance, the presence of chronic diseases, and a failure to cease the use of food supplements one week prior to the study.
2. Product Development and Standardization: Three types of beetroot powder were selected from the Turkish market and analyzed by a laboratory accredited under the TURKAK TS EN ISO/IEC 17025:2017 standard, utilizing the HPLC-DAD method in accordance with NMKL No. 165. Based on these analyses, 1.5 g of beetroot powder, corresponding to a 10 mmol nitrate intervention, was used for product development at the Haliç University Nutrition Principles Laboratory. A base mixture of water, gelatin, pectin, starch, and stevia was heated to 85-90°C for homogenization and cooled to 55-60°C. The intervention product contained 1.5 g of beetroot powder, while the placebo product included food coloring to match the visual characteristics of the intervention. Products were prepared 24 hours before each session, stored in opaque, food-safe packaging at 0-4°C, and coded by an independent researcher using a random number generator to ensure triple-blind conditions.
3. Experimental Procedure and Controls: Participants were instructed to maintain their habitual dietary intake throughout the study and were provided with a list of nitrate-rich foods to avoid. To prevent interference with oral nitrate-to-nitrite reduction, participants were strictly instructed to abstain from mouthwash, chewing gum, sweets, stimulants, and alcohol on all intervention days. The study consisted of five visits. Visit 1 involved providing study information and obtaining informed consent, while Visit 2 included baseline anthropometric assessments and randomization. Visit 3 involved data collection, including food record retrieval, a standardized warm-up, a 200-m freestyle performance test, and post-test measurements of blood lactate, heart rate, and fatigue. A two-week washout period was implemented between intervention phases to eliminate potential carry-over effects, followed by Visits 4 and 5, where the crossover intervention was conducted by repeating the established testing protocols with the alternative condition.
4. Data Collection: Sociodemographic and lifestyle data, including age, sex, education, nutritional habits, and training characteristics, were recorded. Anthropometric measurements included body composition via bioelectrical impedance analysis, height, BMI, and hand grip strength measured by a digital dynamometer. Performance was assessed through a 200-m maximum-effort freestyle swimming test. Physiological assessments included fingertip blood lactate concentration and heart rate (resting, maximum, and average). Finally, subjective fatigue was evaluated using the Perceived Physical and Cognitive Fatigue Scale and the Visual Analog Scale (VAS).

Inclusion Criteria:

• Voluntary participation with parental consent
• Age range: 18-24 years
• Participation in a training program for at least 18 hours per week
• No history of chronic disease
• Not currently using any sports supplements, food supplements, or medications
• Not following a special diet

Exclusion Criteria:

• Irregular training participation
• Presence of chronic diseases
• Failure to cease the use of food supplements one week prior to the study