What is Muscle Atrophy?

Muscle atrophy can be considered as the degradation or loss of muscle tissue that results in an overall decrease in muscle mass and therefore strength. Muscle atrophy can drastically impact one’s overall quality of life, with physical capabilities and general mobility seriously hindered. There are typically 4 forms of muscle atrophy recognised in science: 4

• Disuse Atrophy – muscle deteriorates due to a lack of mobilisation. This can be low physical activity levels, either self-administered or due to illness or injury. The process unfolds surprisingly quickly.

• Neurogenic Atrophy – a spinal cord injury or conditions such as amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS) are commonly associated with this type of muscle atrophy. The nerves that control our muscles are seriously damaged which causes severe muscle loss.

• Cachexia – owing to a decreased appetite and increased metabolic rate, stemming from chronic illnesses such as cancer, heart failure or AIDS, this rather complex syndrome involves muscle wasting, serious weight loss and fatigue.

• Sarcopenia – associated with the natural ageing process. As humans get older, they will experience a gradual loss of muscle function and mass. This, subsequently, increases the risk of falls and fractures.

The importance of preventing and treating muscle atrophy should not be understated. Sufficient muscle function is essential for quality of life and overall health and wellness. The absence increases the risk of falls and injuries, reduces the ability to recover thereafter, speeds the ageing process, knocks independence and mobility which impacts mental health and can even affect cardiovascular and metabolic health. This also emphasises the need to spot the symptoms early, which include: a tangible reduction in muscle size, weakness in the affected muscle(s), difficulty in performing physical tasks, imbalance and reduced endurance.

Whilst regular exercise, adequate nutrition and medical treatment have all been postulated as potential cures or prevention strategies for muscle atrophy, this particular article focuses on the role of antioxidants in the equation. What is the role of antioxidants in muscle health? Which specific antioxidants are most involved in the maintenance of muscle function? What are the dietary sources of antioxidants? But first…

...What are Antioxidants?

Oxidative stress occurs when unstable molecules, named free radicals, elicit cellular damage. The role of antioxidants is to mitigate this harm, acting as the molecules that protect the cells in our body. This is facilitated by the donation of an electron from an antioxidant to a free radical, neutralising the harmful cells in favour of damage reduction and prevention. Two types of antioxidants can enact these effects. The first being endogenous (produced within the body) and the second being exogenous (consumed from the diet or supplementation). They are detailed below:

Endogenous Antioxidants (produced within the body):

• Superoxide Dismutase (SOD) – involved in the conversion of superoxide radicals into less damaging molecules.

• Glutathione – detoxifying the body, this meta-antioxidant is even involved in the maintenance of other antioxidants.

• Catalase – reduces oxidative stress by breaking down hydrogen peroxide into oxygen and water.

Exogenous Antioxidants 3 (consumed from the diet or supplementation):

• Vitamin C – a water-soluble vitamin typically found in fruits and vegetables (e.g., oranges, kiwis, bell peppers).

• Vitamin E – a fat-soluble vitamin typically found in green leafy vegetables, nuts and seeds.

• Beta-carotene – considered a precursor to vitamin A, this antioxidant can also be found in colourful fruits and vegetables (e.g., carrots, sweet potatoes and spinach).

• Polyphenols – a group of compounds known for their diversity. Found in plant-based food like tea, cacao, red wine and berries. Some examples include flavonoids, resveratrol and quercetin.

• Selenium – a trace mineral abundant in Brazil nuts, meats and seafood.

What is the Role of Antioxidants in the Body?

This section looks at the multifaceted role of antioxidants in the body from a more detailed perspective. It has been established that antioxidants are responsible for reducing oxidative stress and protecting cells, but what does this mean? These processes help to reduce the risk of chronic diseases, support immune function, promote skin health and enhance cognitive function, all through that anti-inflammatory mechanism. It is this same principle that can prove so impactful with respect to muscle health. 6

The Role of Antioxidants in Muscle Health: 5

First, it is important to appreciate the mechanisms through which muscle atrophy can occur before establishing how antioxidants can indeed prevent it from happening. Protein degradation pathways (e.g., ubiquitin-proteasome system [UPS] and autophagy-lysosome pathway) can cause the loss of muscle mass and strength through a complex process that results in the destruction of proteins and organelles. Another mechanism occurs through the mTOR pathway, where deficiency in key nutrients and other stressors reduces the synthesis of protein which causes a depreciation of muscle mass. Similarly, decreased activation of satellite cells (involved in the reparation and growth of muscle) can seriously hinder muscle regeneration and contribute to muscle loss. Yet another mechanism concerns hormonal changes, namely cortisol, insulin and insulin-like growth factor 1 imbalances. Cytokines causing chronic inflammation can also promote muscle protein breakdown and the inhibition of protein synthesis. Other examples include neuromuscular changes, mitochondrial dysfunction (decreased energy production) and oxidative stress through reaction oxygen species (ROS). 7

Muscle atrophy is inherently complex as an inability to detoxify the build-up of harmful compounds can prove incredibly damaging to muscle health. The activation of catabolic pathways, like the aforementioned ubiquitin-proteasome system, and inhibition of anabolic pathways, like the mTOR pathway, amongst the other mechanisms highlighted above are the stimuli for muscle atrophy. Antioxidants, both endogenous and exogenous, act on these mechanisms to mitigate their effect on muscle health. The following will detail how they act on these pathways and the inflammatory effects generated by the muscle-harming systems.

1. Neutralise ROS – as previously alluded to, antioxidants will donate an electron to reactive molecules which prevents them from damaging proteins and DNA integral to muscle health. This protects the muscle cells and ultimately wards off muscle atrophy.

2. Inhibiting protein degradation pathways – stopping the UPS and autophagy-lysosome pathways at source, helps maintain the content of muscle protein and thus prevents degradation.

3. Enhancing protein synthesis – the simultaneous act of supporting the activation of the mTOR pathway proves essential in muscle protein synthesis and will counteract muscle atrophy.

4. Inflammation reduction – antioxidants have been shown to reduce the impact of pro-inflammatory cytokines which promotes a more anabolic internal environment conducive to the growth of muscle as opposed to degradation.

5. The protection of mitochondrial function – enhanced energy production through the protection of mitochondrial DNA and proteins can reduce apoptotic signalling which helps to prevent muscle atrophy.

6. Enhancing muscle regeneration – satellite cell function is elevated by antioxidants which is crucial for muscle regeneration and thus prevents atrophy.

7. Metabolic modulation – antioxidants have been shown to improve insulin sensitivity and enhance the uptake of glucose in muscle cells. This improved metabolic health correlates to improved muscle health.

Now that the exact role of antioxidants in muscle health has been established, it is important to identify which antioxidants are actually involved in the process of preventing and treating muscle atrophy. 10

Key Antioxidants in Muscle Atrophy

The following antioxidants have been highlighted and categorised into exogenous or endogenous types previously in this article. The purpose of this section is to demonstrate the impact that each has on muscle health: 8

1. Vitamin C (Ascorbic Acid) – neutralises free radicals, supports connective tissue through collagen synthesis and enhances immune function by reducing inflammation.

2. Vitamin E (Tocopherol) – maintains the integrity of muscle membranes, and promotes faster recovery after exercise by reducing muscle damage during.

3. Selenium – supports antioxidant defences, reduces oxidative stress and has even shown to be associated with the prevention of muscle atrophy attributed to ageing and disease.

4. Glutathione – this antioxidant enacts its effects intracellularly, neutralising free radicals and supporting detoxification which only enhances muscle regeneration.

5. Alpha-lipoic acid (ALA) – with potent antioxidant effects in both fat- and water-soluble environments, ALAs can even regenerate other antioxidants like the vitamins C and E. Improved insulin sensitivity, reduced oxidative stress and mitochondrial support are just some of its many functions in maintaining muscle size.

6. Coenzyme Q10 (CoQ10) – a key player in energy production within mitochondria which supports their function and reduces oxidative stress which ultimately improve muscle health.

7. Polyphenols – support muscle recovery and function through strong anti-inflammatory properties.

8. Carotenoids – protect muscle cells from oxidative stress by reducing inflammation.

A diverse diet rich in whole foods, containing plenty of fruits (e.g., berries, citrus fruits, cherries, etc.), vegetables (e.g., leafy greens, cruciferous vegetables and root vegetables), nuts and seeds (e.g., almonds, chia seeds, walnuts, etc.), grains and legumes (e.g., oats, quinoa and beans), spices and herbs (e.g., turmeric, cinnamon, garlic, ginger, oregano, thyme, etc.), green and black teas, coffee, red wine, olive oil and dark chocolate, is ideal to maximise antioxidant intake and mitigate the atrophy of muscle. Establishing a good balance can reduce oxidative stress, protect against cellular damage and boost overall health too. 9

The Scientific Evidence

There have been plenty of clinical trials and case studies that support the role of antioxidants in muscle health and justify the proposition in this article. For example, a study by Ristow and colleagues (2009) 1 helped highlight the beneficial effects of vitamin C and E supplementation for people exercising regularly, whilst Aoi and colleagues (2015) 2 were able to identify glutathione supplementation as a suppressant of muscle fatigue. Other studies have been spread throughout the article as further supporting evidence for each point made.

Practical Applications

The Antioxidant Diet:

If you are looking to incorporate an antioxidant-rich diet into daily life, here is an ideal day of eating abundant in antioxidants that can stave off muscle atrophy:

Breakfast: Berry and Spinach Smoothie Bowl

- Ingredients:

 1 cup mixed berries (e.g., blueberries, strawberries, raspberries)

 1 medium banana

 1 cup fresh spinach

 1 tbsp of chia seeds

 1 cup unsweetened almond milk

 1 tbsp of almond butter

 Toppings: sliced almonds, additional berries, coconut flakes

Green Tea

- Preparation:

 Brew a cup of green tea and add a slice of lemon for an extra boost of antioxidants.

Mid-Morning Snack: Apple Slices with Almond Butter

- Ingredients:

 1 sliced medium apple

 2 tbsps of almond butter

Lunch: Quinoa Salad with Kale, Pomegranate, and Walnuts

- Ingredients:

 1 cup cooked quinoa

 1 cup chopped kale

 1/2 cup pomegranate seeds

 1/4 cup walnuts, chopped

 1/4 cup diced cucumber

 1/4 cup diced red bell pepper

    Dressing: 2 tbsps of olive oil, 1 tbsp of lemon juice, 1 tsp of Dijon mustard, salt and pepper.

Water with a Slice of Lime or Lemon

Afternoon Snack: Greek Yogurt with Berries and Honey

- Ingredients:

 1 cup of Greek yogurt

 1/2 cup of mixed berries (blueberries, raspberries)

 1 tsp of honey

 1 tbsp of flaxseeds

Dinner: Grilled Salmon, Sweet Potatoes and Broccoli

- Ingredients:

 1 salmon fillet

 1 sliced medium sweet potato

 1 cup of broccoli

 Olive oil

 Herbs and Spices: garlic powder, paprika, salt, and pepper

- Preparation:

 Salmon: Season the salmon with salt, pepper, and a drizzle of olive oil. Grill or bake at 190°C (375°F) for around 15-20 minutes or until cooked      through.

 Sweet Potatoes and Broccoli: Mix the sweet potato slices and broccoli florets with olive oil, and the herbs and spices (garlic powder, paprika, salt, and pepper). Roast at 190°C (375°F) for 25-30 minutes or until tender.

Side Salad:

- Ingredients:

 Mixed greens (e.g., spinach, arugula, kale)

 Halved Cherry tomatoes

 Sliced Cucumber

 Sliced Avocado

 Olive oil and balsamic vinegar for dressing

Evening Snack: Dark Chocolate and Almonds

- Ingredients:

 1oz of dark chocolate (70% cocoa or higher)

 Handful of almonds

Supplementation:

It is always recommended to aim for dietary sources of antioxidants as a precedence but for an extra boost of supplementation can be a good way to go. Here are some basic recommendations but always be sure to do due diligence before supplementation:

- Vitamin C: 500mg in the morning

- Vitamin E: 200 IU in the morning

- Coenzyme Q10 (CoQ10): 100mg in the morning

- Selenium: 100mcg mid-morning

- Alpha-lipoic acid (ALA): 300mg mid-morning

- Glutathione: 250mg in the afternoon

Other recommendations might include 500mg of curcumin in the afternoon, 1000mg of Omega-3 Fatty Acids in the evening or 200-400mg of magnesium at night.

Conclusion

From the evidence presented in this article, it becomes clear how important a role antioxidants play in muscle health and indeed in reducing muscle atrophy. The maintenance of muscle mass is integral to preserving strength and health as the ageing process unfolds. It ensures that recovery and growth can be optimised by inhibiting oxidative damage to muscle cells through the neutralisation of free radicals.

Prioritising a diet abundant in antioxidant-rich foods will go a long way to aiding the process and subsequently reducing muscle atrophy. Targeted and strategised supplementation can also help with the preservation of muscle mass and function, ensuring a comprehensive approach to keep muscle loss at bay and keep you strong and healthy.

Reference List

1. Ristow M, Zarse K, Oberbach A, Klöting N, Birringer M, Kiehntopf M, et al. Antioxidants prevent health-promoting effects of physical exercise in humans. Proc Natl Acad Sci U S A. 2009 May 26;106(21):8665–70.

2. Aoi W, Ogaya Y, Takami M, Konishi T, Sauchi Y, Park EY, et al. Glutathione supplementation suppresses muscle fatigue induced by prolonged exercise via improved aerobic metabolism. J Int Soc Sports Nutr [Internet]. 2015 Feb 6 [cited 2024 Jun 20];12:7. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4328900/

3. Bouayed J, Bohn T. Exogenous antioxidants—Double-edged swords in cellular redox state. Oxid Med Cell Longev [Internet]. 2010 [cited 2024 Jun 20];3(4):228–37. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2952083/

4. Bonaldo P, Sandri M. Cellular and molecular mechanisms of muscle atrophy. Dis Model Mech [Internet]. 2013 Jan [cited 2024 Jun 20];6(1):25–39. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3529336/

5. Agrawal S, Chakole S, Shetty N, Prasad R, Lohakare T, Wanjari M. Exploring the role of oxidative stress in skeletal muscle atrophy: mechanisms and implications. Cureus [Internet]. [cited 2024 Jun 20];15(7):e42178. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10439769/

6. Powers SK. Can antioxidants protect against disuse muscle atrophy? Sports Med [Internet]. 2014 [cited 2024 Jun 20];44(Suppl 2):155–65. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4213375/

7. Ji Y, Li M, Chang M, Liu R, Qiu J, Wang K, et al. Inflammation: roles in skeletal muscle atrophy. Antioxidants [Internet]. 2022 Sep [cited 2024 Jun 20];11(9):1686. Available from: https://www.mdpi.com/2076-3921/11/9/1686

8. Bonetto A, Penna F, Muscaritoli M, Minero VG, Fanelli FR, Baccino FM, et al. Are antioxidants useful for treating skeletal muscle atrophy? Free Radical Biology and Medicine [Internet]. 2009 Oct 1 [cited 2024 Jun 20];47(7):906–16. Available from: https://www.sciencedirect.com/science/article/pii/S0891584909004055

9. Deledda A, Annunziata G, Tenore GC, Palmas V, Manzin A, Velluzzi F. Diet-derived antioxidants and their role in inflammation, obesity and gut microbiota modulation. Antioxidants [Internet]. 2021 May [cited 2024 Jun 20];10(5):708. Available from: https://www.mdpi.com/2076-3921/10/5/708

10. Lian D, Chen MM, Wu H, Deng S, Hu X. The role of oxidative stress in skeletal muscle myogenesis and muscle disease. Antioxidants (Basel) [Internet]. 2022 Apr 11 [cited 2024 Jun 20];11(4):755. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9026549/