Blackcurrant extract increases fat oxidation 30% when exercising in the heat

    on May 13, 2020

    AN exertional heat stress study has found that New Zealand blackcurrant extract has a ‘strong effect’ on fat oxidation during prolonged running in both men and women.

    The findings point to blackcurrant extract’s potential as an ergogenic aid when exercising in the heat, particularly in ultra-endurance events.

    The study also found that New Zealand blackcurrant extract had no detrimental effects on thermoregulation and is safe to use in both temperate and warm conditions.

    The University of Chichester study was performed on 12 men and 6 women in 34°C, 40% humidity, following seven days intake of 600mg (two capsules, 210mg anthocyanin) of New Zealand blackcurrant extract.

    In a double-blind, crossover study, participants ran for 60 minutes at moderate intensity following a 12-hour overnight fast and were tested for metabolic and thermoregulation responses. Results showed:

    • Enhanced fat oxidation by 30% in both men and women
    • Moderate sparing of carbohydrate expenditure by 11%
    • No adverse effects on thermoregulation
    • Heat stress did not reduce the beneficial alterations to substrate metabolism observed following blackcurrant supplementation in ‘normal’ conditions

    Studies have shown that blackcurrant anthocyanins enhance blood flow, performance and fat oxidation during exercise under normal temperatures, but little is known about their physiological effects or potential negative responses when used in a hot environment.

    While performing in a fasted state is unrepresentative of performance nutrition practices, it has been shown to improve adaptive responses to training. This study raises the question of whether blackcurrant could further stimulate adaptive pathways during physical training. 

    In this study there were no changes to skin temperature, rectal temperature or whole body sweat rate and blackcurrant extract was confirmed as safe to use in hot and temperate environments.

    The importance of testing ergogenic aids under such conditions are illustrated by the example of beetroot, which raises core temperature in hot conditions by 11% and is not advisable in the heat.  

    The findings came as a surprise to the researchers.

    Mark Willems, Professor of Exercise Physiology at the University of Chichester, says: “Athletes participating in really long events like IronMan don’t have fat-loading strategies, they have carbohydrate-loading strategies before and during the race.

    “The consequence of using more carbohydrate is that its by-products lead to greater fatigue than if you were burning fat. So, it’s a good thing if you can rely less on carbohydrate.

    “What we are seeing here is blackcurrant causes a really substantial increase to fat oxidation in the heat. It may help restore fat burning closer to rates associated with exercise in normal conditions.

     “We weren’t expecting to find anything, so we have no idea why blackcurrant is providing such a stimulus in these conditions.

    “An increase of 30% is a very high value for a supplement, even in a fasted state. We don’t know the reason but it’s a very exciting finding.”

    Dr Ben Lee, the lead researcher on the study, highlights that participants were tested following 12 hours of fasting, which is not representative of ‘real world’ performance nutrition practices, and more work needs to be done testing blackcurrant supplementation in conjunction with normal food intake.

    Additionally, there is limited evidence to suggest that increased fat oxidation for exercise durations of two-three hours directly improves endurance performance. The findings may be more relevant to those competing in ultra-endurance events greater than four hours.

    Dietary supplementation with New Zealand Blackcurrant Extract Enhances Fat Oxidation during Submaximal Exercise in the Heat was published in the Journal of Science and Medicine in Sport  doi: 10.1016/j.jsams.2020.02.017