Mitochondrial damage can result in excess fatigue and could contribute to a variety of chronic diseases associated with ageing, such as neurodegenerative and cardiovascular diseases. Fortunately, there are ways to protect our mitochondria: by exercising regularly (the most efficient form of exercise being interval training), by following the Mediterranean diet, with chronic cold exposure and by prioritizing sleep. You can jump to the end of the article for more detailed, actionable tips.

Let’s start by going back to what we learned in our high school biology classes.

What are mitochondria?

Mitochondria, which are often labeled as the powerhouse of the cell, are little organelles whose primary role are to generate ATP, our body’s source of energy.

Which processes contribute to our mitochondrial health?

Mitochondria are continuously undergoing cycles of fusion, fission, and mitophagy. This contributes to the quality control of mitochondria, and ensures that they can create ATP efficiently to power us through the day. In short, the more mitochondria we have and the more efficient they are, the more energy we’ll be able to produce. Here is a quick overview of the different processes:

Mitochondrial fusion

Mitochondrial fusion is the physical merging of two distinct mitochondria. It allows the exchange of contents: DNA and metabolites, including those of damaged or senescent mitochondria, thus promoting their survival and offering protection from the effects of mitochondrial DNA mutations.

Mitochondrial fission

Mitochondrial fission is part of the process of mitochondrial biogenesis or the generation of new mitochondria. Novel proteins of pre-existing mitochondria are recruited, followed by the division of the mitochondria into two separate mitochondrial organelles. In short, this translates to more mitochondria, and thus a bigger capacity to create ATP. In addition, mitochondrial fission contributes to apoptosis, a type of programmed cell death, enabling the removal of damaged mitochondria.

Mitophagy

Mitophagy is a process that specifically targets dysfunctional mitochondria, enabling their removal.

The processes of mitochondrial fusion, fission and mitophagy are triggered by various stressors, such as exercise and cold exposure, which we’ll explore in this article.

Ways to optimize your mitochondrial health

Exercise

Exercise, depending on the type, has been shown to 1) increase total mitochondrial protein content, thus improving the capacity for providing energy to the muscles during exertion; 2) increase the number of mitochondria; and 3) promote mitophagy. This translates to better performance, endurance, recovery from various stressors, and overall health.

A word on fiber types (refer to article Exercise physiology and diet recommendations to optimize exercise recovery)

• • There are 3 types of muscle fibers: type 1, type 2, and type 2a.

• • Type 1: red, slow-twitch fibers
    
    • • Slow-twitch fibers generate less strength but can be used to sustain an activity for longer. They are used during low-intensity activities (at exercise intensities as low as 40%), such as walking, tai-chi, or pedaling on a bike.
    • • They have a high content in mitochondria.

     

• • Type 2b: white, fast-twitch fibers
    
    • • Fast-twitch fibers generate more power and strength, but get fatigued faster than slow-twitch fibers and require a longer recovery time. They are used during high-intensity physical activities (intensities of 75% or more), such as powerlifting, sprinting, or HIIT.
    • • They have a low content in mitochondria.

     

• • Type 2a: Mix of slow-twitch and fast-twitch fibers. Most muscle fibers are type 2a fibers.

• • In order to adapt, specific fibers need to be recruited. In other words, to improve mitochondrial health in type 1 muscle fibers, type 1 fibers need to be used. This is why Olympic sprinters may have more efficient type 1 muscle fibers than a marathoner.

• • Compared to long-distance endurance exercise with recruits mostly type 1 fiber, interval training such as sprint-interval training (SIT) and high-intensity interval training (HIIT) recruit all motor units, which can lead to diverse mitochondrial adaptations in all muscle fibers of the muscles.

Types of exercises: endurance exercise, and interval training (HIIT, SIT)

• Endurance exercise
  
  • Definition: Endurance exercise training is a type of long-duration aerobic exercise (for example, long-distance running or cycling).
• Interval training: HIIT and SIT
  • SIT
    • Definition: Sprint interval training is composed of sessions of an ‘all-out’ maximal effort that lasts less than 1 minute for each sprint, performed at intensity ≥ 90% of the maximal power output.
    • SIT has been shown to increase mitochondrial content to at least a similar extent to endurance training.
  • HIIT
    • Definition: High-intensity interval training is a type of exercise characterized by moderately high volume with sessions of 3-5 minutes of intensity levels ≥ 75% of the maximal power.

    • Some studies suggest that HIIT leads to a greater increase in mitochondrial content compared to endurance exercise, despite a lower exercise duration.

• Which is most beneficial: endurance training, HIIT, or SIT?

  • • Interval training methods, such as HIIT and SIT, have recently been shown to induce adaptations at least similar to endurance exercise while requiring less time.
  • • We also saw that interval training recruits all types of muscle fibers, while endurance training elicits adaptation in mostly type 1 fibers.
  • • In a study, the increase in mitochondrial respiratory capacity was greater after SIT compared to HIIT (and moderate intensity exercise), even though it required less time. Thus, exercise intensity is an important factor in the mitochondrial response, more so than exercise duration.
  • • Especially if you have limited time available and desire to maximize your performance, you might obtain a greater mitochondrial adaptation using a SIT protocol.

• • There is also evidence that working out twice every day or twice every second day may be superior to working out daily to increase mitochondrial content.

• • To keep on improving your mitochondrial health, you would have to implement progressive overload, through the increase of the intensity (preferably) and/or duration of your workouts.

Cold exposure

• In response to cold exposure, thermogenesis occurs.
  • Thermogenesis can be defined as the production of ATP by mitochondria in the cells of brown adipose tissue.
• Chronic cold exposure has been shown to increase the number and activity of mitochondria in brown adipose tissue, and to increase whole-body lipolysis and fatty acid oxidation to support the increase in energy demand.To get started, end your hot showers with 30 seconds of cold water. You can gradually increase the duration as your tolerance improves.

• Diet

• • Mitochondria require a variety of nutrients to ensure their optimal function.

• • A review article evaluated the impact of various diets on multiple mitochondrial physiology aspects, such as function, biogenesis, mitophagy, and mitochondrial fission/fusion.

• • Diets evaluated in the article
    
    • • Mediterranean diet
        
        • • A Mediterranean diet includes olive oil as the main fat. It is based on the consumption of plant-derived foods such as fruits, vegetables, legumes, nuts and seeds, and whole-grain cereals. It is also characterized by a moderate intake of red wine, seafood and dairy products, poultry and eggs, and the low consumption of sweet desserts, red and processed meats.
    • • High-fat diet
        
        • • A high-fat diet is a diet where at least 30-35% of the total calories are derived from fats.
    • • Ketogenic diet
        
        • • The ketogenic diet differs from the high-fat diet by being more restrictive: while the total calories in fat remain high, the amount of carbohydrates is low, and the intake of protein is moderate.
      • Fasting
        
        • • Fasting is the abstinence from food and drink for specified, recurring periods of time, ranging from 12 h to 3 weeks.
    • • Caloric restriction
        
        • • Calorie restriction can be defined as a chronic reduction in calorie consumption (20-30%) without leading to malnutrition. Adequate levels of vitamins and minerals should be maintained.

• • Here is a summary of their findings:
    
    • • A high-fat diet decreases mitochondrial function and fusion, while it can induce mitochondrial fission.
    • • The calorie restriction diets appear to reduce mitochondrial biogenesis and function but stimulate mitophagy.
    • • • The ketogenic appears to induce mitochondrial function and biogenesis, while contradictory results exist for mitochondrial dynamics and mitophagy.
        • Finally, fasting and the Mediterranean appear to induce mitochondrial biogenesis and fine-tune mitochondrial function. On the contrary, fasting appears to induce mitochondrial recycling and the clearance of problematic mitochondrial units, while the Mediterranean has the opposite effect on mitochondrial dynamics and the autophagic process.
      • A high-fat diet appears to be most detrimental to mitochondria and can lead to the development of metabolic diseases. A Mediterranean diet would probably be the easiest (and safest) to implement for most people.

• Sleep

• • Several studies have demonstrated that sleep deprivation triggers increased oxidative stress, which can lead to mitochondrial dysfunction. Indeed, reduced enzyme activity and protein levels have been observed in the mitochondria of individuals who have undergone sleep deprivation or suffer from insomnia.

• • To optimize your sleep (and your mitochondrial health), The Canadian 24-Hour Movement Guidelines for Adults recommends that you get 7-9h of good quality sleep, on a regular basis, with consistent sleep and wake times for health benefits.

Summary – actionable tips

• Exercise
  
  • Exercise regularly, preferably by including sprint interval training.
  • Avoid extended periods of rest. After only 1 week of complete detraining, studies indicate that mitochondrial respiration is reduced by as much as 50%.
  • Implement progressive overload, through the increase of the intensity and/or duration of your workouts.
  • Don’t neglect the importance of rest between your workouts to reap the benefits.
• End your showers with 30 seconds of cold water. You can gradually increase the duration as your tolerance improves.
• Follow the Mediterranean diet.
• Sleep: Ensure you get at least 7-9 hours of good-quality sleep a day on a regular basis, with consistent sleep and wake times.

References

• Youle RJ, van der Bliek AM. Mitochondrial fission, fusion, and stress. Science. 2012;337(6098):1062-1065. doi:10.1126/science.1219855

• Amorim, J.A., Coppotelli, G., Rolo, A.P. et al. Mitochondrial and metabolic dysfunction in ageing and age-related diseases. Nat Rev Endocrinol 18, 243–258 (2022). https://doi.org/10.1038/s41574-021-00626-7
  

• MacInnis MJ, Gibala MJ. Physiological adaptations to interval training and the role of exercise intensity. J Physiol. 2017;595(9):2915-2930. doi:10.1113/JP273196

• Sorriento D, Di Vaia E, Iaccarino G. Physical Exercise: A Novel Tool to Protect Mitochondrial Health. Front Physiol. 2021;12:660068. Published 2021 Apr 27. doi:10.3389/fphys.2021.660068

• Granata C, Oliveira RS, Little JP, Renner K, Bishop DJ. Training intensity modulates changes in PGC-1α and p53 protein content and mitochondrial respiration, but not markers of mitochondrial content in human skeletal muscle. FASEB J. 2016;30(2):959-970. doi:10.1096/fj.15-276907

• Saltykova, M.M. Cold Adaptation as a Means of Increasing Antioxidant Protection. Neurosci Behav Physi 49, 323–330 (2019). https://doi.org/10.1007/s11055-019-00735-x

• Ivanova YM, Blondin DP. Examining the benefits of cold exposure as a therapeutic strategy for obesity and type 2 diabetes. J Appl Physiol (1985). 2021;130(5):1448-1459. doi:10.1152/japplphysiol.00934.2020

• Melhuish Beaupre, L.M., Brown, G.M., Gonçalves, V.F. et al. Melatonin’s neuroprotective role in mitochondria and its potential as a biomarker in aging, cognition and psychiatric disorders. Transl Psychiatry 11, 339 (2021). https://doi.org/10.1038/s41398-021-01464-x

• https://www150.statcan.gc.ca/n1/pub/82-003-x/2022003/article/00001-eng.htm

• Kyriazis ID, Vassi E, Alvanou M, Angelakis C, Skaperda Z, Tekos F, Garikipati VN, Spandidos DA and Kouretas D: The impact of diet upon mitochondrial physiology (Review). Int J Mol Med 50: 135, 2022