Mitochondria are tiny organelles known as the ”powerhouses” of the cell. Their primary role is to convert the nutrients we eat into energy (specifically into adenosine triphosphate, ATP), which is then used by our cells for everything from breathing to exercising. Increasing the size and number of mitochondria (mitochondrial biogenesis) means a higher capacity to produce energy.
When new mitochondria are created in skeletal muscle (through a healthy diet, exercise, and supplements), the density of mitochondria per cross-sectional area of muscle cells increases, this means more efficient energy production, total energy output to power activity and a resultant increase in exercise performance.
How To Increase Mitochondria Density?
One of the most powerful ways to increase mitochondrial density is exercise training. An exercise is a form of hormesis, which is a term that comes from the Greek word meaning “to excite.” A hormetic stressor is a mild and/or acute stressor that ‘excites’ the body and causes adaptations that increase its health, resilience, and vitality.
The benefits vary by type of exercise, the intensity of exercise when it is performed, and your current level of fitness. Even strength training with the goal of increasing muscle mass has its benefits in reducing mitochondrial dysfunction, which leads to reduced oxidative phosphorylation and increased permeability. Without going into the details of cell biology, it is important to note that the transcriptional coactivator PGC-1α (peroxisome proliferator-activated receptor-gamma coactivator 1 alpha) is the “master regulator” of mitochondrial biogenesis [efn_note]D. A. Hood, L. D. Tryon, H. N. Carter, Y. Kim, and C. C. W. Chen, “Unravelling the mechanisms regulating muscle mitochondrial biogenesis,” Biochemical Journal, vol. 473, no. 15, pp. 2295–2314, 2016.[/efn_note] and is highly responsive to a variety of environmental cues, including temperature, nutritional status, and physical activity.
In untrained subjects, any form of exercise can increase mitochondrial biogenesis. [efn_note]Hood, D.A. “Mechanisms of exercise-induced mitochondrial biogenesis in skeletal muscle.” Appl Physiol Nutr Metab. 2009 Jun;34(3):465-72. doi: 10.1139/H09-045.[/efn_note] Studies have shown that both continuous and interval training exercise have similar effects on mitochondrial biogenesis on untrained subjects when the duration and work have done are the same. Burgomaster et al. in 2008 carried out a study over six weeks, where participants either took part in a HIIT program for three days a week or a steady-state cycling program for five days a week.
In the HIIT program, participants completed six 30 second sprints interspersed with 4/5-minute recoveries, while the steady-state cyclists rode for 40 to 60 minutes at 65 percent of their VO2 max. At the end of the six weeks, similar increases in levels of oxidative enzymes and PGC 1α activation were found in both groups of participants. [efn_note]Burgomaster, Kirsten A et al. “Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans.” The Journal of physiology vol. 586,1 (2008): 151-60. doi:10.1113/jphysiol.2007.142109[/efn_note]
Aerobic Mitochondrial Adaptations
Although many studies show greater improvements in energy, anxiety, depression, and mood from low-intensity aerobic exercise in untrained athletes, [efn_note]Guszkowska, M. “Effects of exercise on anxiety, depression and mood.” Psychiatr Pol. 2004 Jul-Aug;38(4):611-20. PMID: 15518309[/efn_note] a combination of resistance training and endurance exercise dramatically enhances the signaling pathway of biogenesis and has been shown to be superior to endurance exercise alone in increasing mitochondrial density. [efn_note]Groennebaek, Thomas, and Kristian Vissing. “Impact of Resistance Training on Skeletal Muscle Mitochondrial Biogenesis, Content, and Function.” Frontiers in physiology vol. 8 713. 15 Sep. 2017, doi:10.3389/fphys.2017.00713[/efn_note][efn_note]Wang, L., et al. “Resistance exercise enhances the molecular signaling of mitochondrial biogenesis induced by endurance exercise in human skeletal muscle.” J Appl Physiol (1985). 2011 Nov;111(5):1335-44. doi: 10.1152/japplphysiol.00086.2011. Epub 2011 Aug 11.[/efn_note]
In trained athletes, the effects are quite different. Eight weeks of concurrent strength and endurance training does not enhance mitochondrial content or performance. This is probably because if you are a moderately fit or above-average athlete with a high VO2 max, you have most likely reached a point where training volume alone will have no effect on your mitochondria.
However, for trained athletes, sprint interval training (SIT) or high-intensity interval training (HIIT) is a powerful inducer of PGC 1αdd and other genes regulating mitochondrial biogenesis.
In a study conducted by Gibala and McGee, participants were able to double the amount of time they could exercise after just six HIIT sessions over two weeks, for a total of only approximately 15 min of very intense exercise. Subjects were able to bicycle at 80% of their VO2 max (as calculated prior to beginning the study) for 51 minutes on average, up from 26 minutes. [efn_note]Gibala, M.J, McGee S.L. “Metabolic adaptations to short-term high-intensity interval training: a little pain for a lot of gain?” Exerc Sport Sci Rev. 2008 Apr;36(2):58-63. doi: 10.1097/JES.0b013e318168ec1f.[/efn_note] When this exercise is performed with low muscle glycogen or in a fasted state, the effect is synergistic and greatly enhances the magnitude of exercise-induced biogenesis.
Interestingly, sprint exercise performed under fasting conditions is a leptin signaling mimetic in human skeletal muscle, which has powerful implications for increased metabolism and energy levels, fat loss, and mitochondrial biogenesis. [efn_note]Guerra, B., et al. “Is sprint exercise a leptin signaling mimetic in human skeletal muscle?” J Appl Physiol (1985). 2011 Sep;111(3):715-25. doi: 10.1152/japplphysiol.00805.2010. Epub 2011 Jun 9.[/efn_note] Consuming food prior to sprint exercise will block most/all of these mitochondrial benefits. [efn_note]Bartlett, J.D.; Louhelainen, J.; Iqbal, Z.; Cochran, A.J.; Gibala, M.J.; Gregson, W.; Close, G.L.; Drust, B.; Morton, J.P. Reduced carbohydrate availability enhances exercise-induced p53 signaling in human skeletal muscle: Implications for mitochondrial biogenesis. Am. J. Physiol.-Regul. Integr. Comp. Physiol. 2013, 304, R450–R458.[/efn_note] [efn_note]Wojtaszewski, J.F.; MacDonald, C.; Nielsen, J.N.; Hellsten, Y.; Hardie, D.G.; Kemp, B.E.; Kiens, B.; Richter, E.A. Regulation of 5′ amp-activated protein kinase activity and substrate utilization in exercising human skeletal muscle. Am. J. Physiol.-Endocrinol. Metab. 2003, 284, E813–E822.[/efn_note] [efn_note]Van Proeyen, Karen et al. “Beneficial metabolic adaptations due to endurance exercise training in the fasted state.” Journal of applied physiology (Bethesda, Md. : 1985) vol. 110,1 (2011): 236-45. doi:10.1152/japplphysiol.00907.2010[/efn_note]
Supplements for Mitochondria Density
In addition, it has been found that pre-loading with baking soda (NAHCO3) prior to HIIT or SIT physical exercise will augment signaling cascades and gene expression linked to mitochondrial biogenesis in human skeletal muscle. [efn_note]Percival, Michael E et al. “Sodium bicarbonate ingestion augments the increase in PGC-1α mRNA expression during recovery from intense interval exercise in human skeletal muscle.” Journal of applied physiology (Bethesda, Md. : 1985) vol. 119,11 (2015): 1303-12. doi:10.1152/japplphysiol.00048.2015[/efn_note] A meta-analysis concluded that anaerobic performance capacity during a single 60-second sprint is enhanced ∼2% with a further ∼1% modifying effect when sprints are repeated following the consumption of ∼0.3 g/kg of baking soda. [efn_note]Carr AJ, Hopkins WG, Gore CJ. “Effects of acute alkalosis and acidosis on performance.” Sports Med 41: 801–814, 2011, doi: 10.2165/11591440-000000000-00000.[/efn_note]
Further, supplementing with curcumin, resveratrol, DHA, PQQ, cacao, cloves, and cinnamon also increases mitochondrial biogenesis and enhances the effects of energy metabolism for exercise.
Curcumin, a well-known polyphenolic compound, is an abundant component of turmeric. It has been shown to have antioxidant and anti-inflammatory properties, which translates to faster recovery and improved functional capacity during subsequent exercise sessions. [efn_note]McFarlin, Brian K et al. “Reduced inflammatory and muscle damage biomarkers following oral supplementation with bioavailable curcumin.” BBA clinical vol. 5 72-8. 18 Feb. 2016, doi:10.1016/j.bbacli.2016.02.003[/efn_note]Supplementation with turmeric or curcumin extract prior to and just after SIT activates mitochondrial biogenesis and thereby increases mitochondrial density. [efn_note]Ray, Hamidie R.D., et al. “Curcumin treatment enhances the effect of exercise on mitochondrial biogenesis in skeletal muscle by increasing cAMP levels.” Metabolism. 2015 Oct;64(10):1334-47. doi: 10.1016/j.metabol.2015.07.010. Epub 2015 Jul 21.[/efn_note]
Resveratrol is another polyphenol found in high concentrations in the skin of red grapes. Similar to curcumin, supplementation boosts the effects of SIT and HIIT on mitochondrial biogenesis. [efn_note]Muhammad, M.H. & Allam, M.M. J Physiol Sci (2018) 68: 681. https://doi.org/10.1007/s12576-017-0582-4[/efn_note] One study conducted in 2013 by Menzies et al. showed perceptibly that when resveratrol and exercise are combined, a synergistic effect is evident, leading to enhanced activation of PGC-1α and stimulation of mitochondrial biogenesis. [efn_note]Menzies, Keir J., et al. “Sirtuin 1-mediated Effects of Exercise and Resveratrol on Mitochondrial Biogenesis.” The Journal of Biological Chemistry, March 8, 2013, doi: 10.1074/jbc.M112.431155[/efn_note]
PQQ or Pyrroloquinoline quinone is a vitamin-like compound found in plant foods, with a wide range of health benefits. The richest natural source of PQQ is pure, raw cacao powder. It activates the PGC-1α pathway, which, in turn, regulates genes involved with the metabolism and mitochondrial biogenesis. It also protects cells against free radical damage through the activation of the body’s internal antioxidant defense system. Healthy individuals who took 20 mg of PQQ had a significant decrease in levels of C-Reactive Protein (CRP) and IL-6 (which are markers of inflammation). Lower inflammation results in higher levels of the hormone orexin and, therefore, more energy. [efn_note]Chowanadisai, Winyoo et al. “Pyrroloquinoline quinone stimulates mitochondrial biogenesis through cAMP response element-binding protein phosphorylation and increased PGC-1alpha expression.” The Journal of biological chemistry vol. 285,1 (2010): 142-52. doi:10.1074/jbc.M109.030130[/efn_note]
Several studies also show that the spices, cloves and cinnamon, have a profound effect on mitochondrial biogenesis. Through slightly different mechanisms, both clove extract and cinnamon increase activation of PGC 1α and stimulate biogenesis. [efn_note]Gannon, N.P., et al. “trans-Cinnamaldehyde stimulates mitochondrial biogenesis through PGC-1α and PPARβ/δ leading to enhanced GLUT4 expression.” Biochimie. 2015 Dec;119:45-51. doi: 10.1016/j.biochi.2015.10.001. Epub 2015 Oct 9[/efn_note] [efn_note]Tu, Z., et al. “Syzygium aromaticum L. (Clove) extract regulates energy metabolism in myocytes.” J Med Food. 2014 Sep;17(9):1003-10. doi: 10.1089/jmf.2013.0175. Epub 2014 Jul 7.[/efn_note]
Intermittent Fasting for Mitochondria Density
Combining intermittent fasting and/or ketogenic diets with SIT also maximizes the benefits of exercise and enhances biogenesis. It has been found that ketone bodies are likely a metabolic signal that acts as a calorie restriction mimetic and increases mitochondrial density through activation of PGC 1α. [efn_note]Hasan-Olive, M.M., Lauritzen, K.H., Ali, M. et al. “A Ketogenic Diet Improves Mitochondrial Biogenesis and Bioenergetics via the PGC1α-SIRT3-UCP2 Axis.” Neurochem Res (2019) 44: 22. https://doi.org/10.1007/s11064-018-2588-6[/efn_note]
As ketogenic diets are very low in carbohydrates, the levels of glucose available as fuel during exercise is low. When glucose levels are borderline hypoglycemic, the body is forced to use fatty acids for fuel. Unfortunately, the amount of fatty acids that can be oxidized for fuel is limited by your mitochondrial capacity, so when you are glycogen depleted (through fasting or ketogenic diets), and you perform intense exercises, such as SIT or HIIT, you send a powerful signal to increase mitochondrial biogenesis and thus improve oxidative capacity. [efn_note]Bartlett J.D., Louhelainen J., Iqbal Z., Cochran A.J., Gibala M.J., Gregson W., Close G.L., Drust B., Morton J.P. “Reduced carbohydrate availability enhances exercise-induced p53 signalling in human skeletal muscle: Implications for mitochondrial biogenesis.” Am. J. Physiol. Regul. Integr. Comp. Physiol. 2013;304:450–458. doi: 10.1152/ajpregu.00498.2012.[/efn_note]
A recent study by Niklaus et al. found that exercise performed under low glycogen levels augments the expression of the major genetic marker for biogenesis in highly trained cyclists. [efn_note]Psilander, N., Frank, P., Flockhart, M.,Sahlin, K. “Exercise with low glycogen increases PGC-1α gene expression in human skeletal muscle.” European Journal of Applied Physiology, 2013;113(4), 951–963. https://doi.org/10.1007/s00421-012-2504-8[/efn_note]Combining glycogen depletion with high-intensity exercise is an advanced technique that should only be used occasionally by trained individuals. Doing glycogen depleted HIIT or SIT without glycogen repletion is a bad idea and can result in muscle tissue damage, chronic inflammation, and the inability to recover from exercise.
Could Mitochondrial Adaptations Help You Live Longer?
Mitochondria are essential for various biological processes, including cellular energy production. Having more mitochondria means a greater capacity to produce energy, which is necessary for living longer. During energy production, mitochondria produce reactive oxygen species (ROS). It was previously thought that ROS damage cells and lead to an age-dependent decline in biological function, but recent research has found that it can actually delay aging and increase lifespan. [efn_note]Hwang, Ara B et al. “Mitochondria and organismal longevity.” Current genomics vol. 13,7 (2012): 519-32. doi:10.2174/138920212803251427[/efn_note]
One study demonstrated that increased ROS is required for lifespan extension, and antioxidant treatment suppresses this effect. The authors proposed that increased ROS from efficiently working mitochondria elicit protective responses that lead to longevity in C. elegans. [efn_note]Schulz TJ, Zarse K, Voigt A, Urban N, Birringer M, Ristow M. Glucose restriction extends Caenorhabditis elegans life span by inducing mitochondrial respiration and increasing oxidative stress. Cell Metab. 2007;6(4):280–93.[/efn_note] ROS are strong activators of NRf2, which are signaling molecules that regulate expression of the body’s internal (or endogenous) antioxidant defense system or ARE (antioxidant response element). The ARE plays a crucial role in modulating oxidative stress, protecting the mitochondria from oxidative damage, and improving the overall health of the organism. [efn_note]Reddy, Sekhar P. “The antioxidant response element and oxidative stress modifiers in airway diseases.” Current molecular medicine vol. 8,5 (2008): 376-83. doi:10.2174/156652408785160925[/efn_note] This effect of ROS stress is called mitochondrial hormesis or mitohormesis and is hypothesized to be the mechanism for the lifespan-extending and health-promoting capabilities of exercise and glucose restriction.
Conversely, it is a lack of mitochondrial stimulation by mitohormetins that results in lower functionality of the ARE and the subsequent shift in the thiol redox state of the cell. [efn_note]P.H. Willems, R. Rossignol, C.E. Dieteren, M.P. Murphy, W.J. Koopman “Redox homeostasis and mitochondrial dynamics” Cell Metab., 22 (2015), pp. 207-218, https://doi.org/10.1016/j.cmet.2015.06.006[/efn_note] The redox environment of a cell compartment is the overall balance of its oxidation/reduction systems. Its balance is critical for cell viability and function, and its disruption contributes to a range of pathologies, including aging and senescence, as proposed by the “redox stress hypothesis of aging.” [efn_note]Sohal, Rajindar S, and William C Orr. “The redox stress hypothesis of aging.” Free radical biology & medicine vol. 52,3 (2012): 539-555. doi:10.1016/j.freeradbiomed.2011.10.445[/efn_note]
Under normal physiologic conditions, the balance between generation and elimination of ROS maintains the proper function of redox-sensitive signaling proteins, and redox homeostasis ensures that the cells respond properly to endogenous and exogenous stimuli. However, when the redox homeostasis is disturbed, oxidative stress may lead to abnormal cell death and contribute to disease development. [efn_note]Trachootham, Dunyaporn et al. “Redox regulation of cell survival.” Antioxidants & redox signaling vol. 10,8 (2008): 1343-74. doi:10.1089/ars.2007.1957[/efn_note] A lack of mitohormetins results in a lower number of mitochondria and poorer mitochondrial health, which results in less resilience to stress and eventually increased disease and decreased lifespan.
An exercise is a form of hormesis known to activate a number of intracellular signaling pathways that cause mitochondrial adaptations in skeletal muscle that can transform your health and performance. The effects of exercise can be enhanced by hydration, intermittent fasting, ketosis, glycogen depletion and also through supplementation with certain compounds, including PQQ, resveratrol, cacao, cinnamon, and turmeric.
Mitochondrial biogenesis causes an increase in mitochondrial density and thereby results in more efficient cellular energy production. Increased energy production causes a concomitant increase in the formation of ROS, which is a powerful signaler of the body’s ARE. This protects the body from oxidative stress and is important in health promotion and life extension.
These observations highlight the importance of maintaining mitochondrial function and healthy mitochondrial DNA in general and especially for better health and longevity!