Current leader of the 3360km, 3-week long race around France, British rider Chris Froome of the UK-based Sky cycling team, denied using them or even knowing what they are when asked in a press conference after a stage of the race in the Pyrenees mountain range this week.
”I had to Google it to find out what it is. I can say 100% that the team does not use ketones,” Froome said yesterday.
Sir David Brailsford, Sky’s sporting director, said the team had never used them, contrary to reports in some European press outlets. Some animal and human research indicates ketone supplementation can promote efficient fat burning in stressed situations, while preserving glycogen stores.
Kieran Clarke, professor of physiological biochemistry at Oxford University Department of Physiology, Anatomy & Genetics and CEO of UK ketone-focused start-up, TdeltaS, said “7 to 8 other pro cycling teams” had contacted her firm over the years to procure ketones but she has refused all requests because the corn-sourced nutrients are awaiting EU novel foods approval (necessary for all ingredients not on market before May, 1997).
Mark Tallon, PhD, managing director of UK firm Legal Foods said “ketones delivered from a beverage for performance enhancement would likely only be beneficial where athletes are already pre-adapted to using ketones as a fuel (low carb dieters).”
“Those that are non-adopted would likely be efficient at using glucose, and ketones in those situations would likely not be ergogenic and potentially inhibit peak performance.”
Ketones are compounds normally made by the liver when someone is fasting or on a low-carb diet to be used when dietary glucose is low, mostly by the brain. They can be found in meat, cheese and fruits like raspberries, and can be manufactured from sources like corn.
There is much debate about how bioavailable ketones are from varying sources and only raspberry ketones, which research indicates are not metabolised well by the body, are widely approved in Europe – but as a flavour, not a nutrient.
Despite this, there are many ketone-based products on-market targeting weight loss, with authorities beginning to raise red flags. But these are not thought to be the kind of ketones being utilised by pro athletes.
The dosages within these products ranges from 100 to 1,400 mg per day – between 26 and 368 times higher than the highest estimated exposure from the diet, but much lower than the 150,000 mg that the liver can make each day.
The natural occurrence in raspberries can be up to 4.3 mg per kg.
Ketone forms like acetone, acetoacetate, acetophenone and 3-beta-hydroxybutyrate have appeared on-market for 1000s of euros per litre.
Stephen Moon, the CEO of leading UK-based sport nutrition firm, Science In Sport, said his firm was aware of ketone research and use but had no plans to develop any ketone sports nutrition products.
A health claim application linking Rubus idaeas (raspberry) extract – BERI-08 – and thermogenesis production, satiety and consequent weight loss was rejected by the European Food Safety Authority (EFSA) in 2011 due to a lack of evidence.
TdeltaS' novel foods application to the UK Food Standards Agency (FSA) for its ketone ester specifies high-performance sports. The FSA has requested safety data, which professor Clarke said TdeltaS is in the process of compiling – a process that may take several years.
Professor Clarke has been working in ketone and ketogenic (low-carb) diet research for about 20 years, much of it focused on health issues like diabetes, Alzheimer’s and Parkinson’s.
Expert view: Mark Tallon, PhD, managing director of UK firm, Legal Foods
“It’s a product purported to be used by elite athletes based on science primarily from rodent and unpublished human trials.
“If we look at basic biochemistry and the use of subjects following keto-adapted diets we see an increase in the use of fats as fuel. However, this effect should be placed in context as the effect occurs at intensities of less than 70% of maximum effort. Most endurance performance occurs above this level of intensity during stage endings such as the Tour de France I.e. Final 20-30mins. At this point the body needs carbohydrates.
The area of increasing fat utilisation is nothing new as we have had the high fat diets, low carb diets, use of Medium-chain triglycerides (MCTs) and more recently 3-beta-hydroxybutyrate and acetoacetate. However I am yet to see externally valid (race/event specific) data to convince me of their benefits especially when high intensity is involved.
There may be benefits in glycogen sparing but if current nutritional strategies (carb intake) address this - then we need to see data that ketones outstrip carbohydrates as a recovery aid. Over the distance and intensities of the Tour de France I am not a believer at this time based on the available data that supplemental ketones are more effective than carbs for recovery and or performance.”