Astaxanthin: a short, sharp shock for performance

If you don’t love oxygen, you should! Its special reactivity provides us with the energy required to sustain life, including the ability to power movements and muscular contraction. This explains why oxygen metabolism - and the ability to absorb, transport and use it in muscles - is so very important to athletes who are seeking maximum endurance performance. Unfortunately however, there is a downside to oxygen metabolism; the same chemical reactivity that liberates energy during aerobic metabolism can also unleash damage in muscle cells due to the formation of transient but reactive and potentially destructive molecular species called ‘free radicals’, which are produced unavoidably as a consequence of harnessing the chemical energy of oxygen within the body.

Antioxidant defences

In recent years, there has been much research into athletes and muscle damage induced by free radicals. Athletes not only consume more oxygen than others to fuel their training, but also frequently train at or near their maximum oxygen uptakes. Unsurprisingly therefore, they are at increased risk of free radical-induced damage, or ‘oxidative stress’^(1,2). Athletes don’t just process a larger volume of oxygen in muscle tissue than their sedentary counterparts – they also process it at a higher rate; during training or competition, the rate of oxygen processing by the mitochondria (the energy producing furnaces in the cells) can rise by a factor of 20, placing exceptionally high demands on their antioxidant defence systems.

Given the importance of optimum muscular performance for athletes, a lot of the research into antioxidant protection for athletes has focused on the ability of antioxidant nutrients to help protect against muscle damage during hard training/competition. This exercise-induced muscle damage often manifests as delayed-onset muscle soreness (DOMS) as well as delayed or reduced recovery from training and competition⁽³⁾. One class of antioxidant nutrients that has attracted particular interest are the naturally occurring brightly colored plant phytochemicals such as lycopene, flavanols and anthocyanins founds in a wide range of fruits and vegetables (see box 1)⁽⁴⁾. Not only do they appear to support (and maybe even enhance) athletic performance, they also confer long-term health benefits.

Box 1: Fruity protection

In addition to antioxidant nutrients such as vitamins C and E, and the mineral selenium, there’s also been a lot of research into fruit phytochemical antioxidant supplementation to enhance athletic performance and recovery. In cyclists for example, black grape (81 grams per litre [g/L]), raspberry (93g/L) and redcurrant (39g/L) concentrates reduced DNA damage compared to cyclists not taking the fruit concentrates⁽⁵⁾. Meanwhile, chokeberry juice reduced free radical damage in rowers undergoing strenuous exercise bouts⁽⁶⁾ and tart cherry juice was found to reduce muscle damage and DOMS in distance runners performing a 26km (16.2-mile) run⁽⁷⁾. Scientists believe that it’s the high levels of various natural phytochemical compounds (eg anthocyanins) found in berries and cherries that make these fruits particularly effective as antioxidants.

Astaxanthin: the fishy antioxidant

While there’s been much focus on vegetable and fruit antioxidants, a rather unusual antioxidant nutrient called ‘astaxanthin’ - has been attracting increasing attention from sports scientists. Although it resembles the plant phytochemical ‘carotene’, which is found in orange and red vegetables such as carrots and tomatoes, astaxanthin is not a plant phytochemical but a dark-red carotenoid-like compound found in aquatic animals such as salmon and shrimp. Like plant phytochemicals, humans cannot synthesize astaxanthin and can only acquire it and benefit from it via dietary intake.

What makes astaxanthin different from many other antioxidants is its special free radical neutralizing activity; its unique molecular structure (see figure 1) gives it an exceptionally high capacity to capture and render harmless free radicals containing oxygen and nitrogen atoms (reactive oxygen nitrogen species)⁽⁸⁾. In fact, it turns out that astaxanthin’s antioxidant capacity is much higher than many of the more well known antioxidants that are available in food and taken in supplements; in a 2018 study, researchers compared the antioxidant power of various antioxidant nutrients and found that astaxanthin is actually many times more powerful than that of: tea polyphenols, anthocyanins, glutathione, coenzyme Q10, vitamin C, and vitamin E⁽⁹⁾.

Figure 1: Astaxanthin, beta-carotene and lutein*