Rather than thinking of energy in terms of macronutrient contributions, let’s understand more about how it is made. Ian Craig unearths three important areas of functional energy provision.

Energy is the cornerstone of every good athlete’s armoury: to have vibrant energy means the ability to cope with tough training sessions and to race with passion; to be without high levels of energy is akin to a career of missed opportunities and unfulfilled goals. In the perception of many sports people, energy has become synonymous with carbohydrate and fat consumption plus biochemical transformation, but macronutrients only convey a small part of the energy story. Production of the chemical form of energy, adenosine tri-phospate (ATP), is a very intricate, whole-body process with many parts to it.

Energy production is influenced by our digestion, detoxification, immune system, our hormones and nerves, the active tissues themselves and also, as demonstrated by our sports psychologist colleagues; our mind and spirit. Genetics also play a massive role in all things physical and recent discoveries have revealed why some athletes simply have an energetic advantage before their toe touches the line.

Only focussing on our fuel needs (e.g. carbohydrates) is akin to simply putting petrol in your car. In order for it to run fluidly and efficiently, you need to check that it has enough fresh oil, that the gaskets are sealing properly and that your spark plugs are igniting vibrantly. These maintenance steps are done according to the make and model (our genes) of the car. This makes your dietary needs a bit more complex than simply ensuring adequate fuel, but the effort will be worthwhile when your performances take on a new dimension.

Let’s get into more detail with regards to the body systems that influence our energy supplies:

Circulation the transport of energy

Early exercise physiology research established that with appropriate exercise training, some individuals could greatly enhance the capacity of their heart and cardiovascular system. For example, whereas the size of a normal man’s heart has been observed to be around 700 to 800ml, some endurance athletes have been shown to double this volume (1), corresponding with a huge upward shift in cardiac output of the heart. This, in turn, would mean more oxygen getting to our active tissues and the potential of more aerobically-produced ATP.

We now understand that some athletes can achieve these cardiovascular adaptations more easily than others. Certain genes have been identified that are associated with vascular growth and control, inferring potential endurance advantages. For example; the Angiotensin Converting Enzyme (ACE) gene, known for its involvement in blood pressure control, has been shown to be highly related to success in endurance or power sports depending on the genotype that an individual possesses (2). Additionally, Vascular Endothelial Growth Factor (VEGF), involved in the growth of new blood vessels, has been related to baseline VO2max levels and VO2max response to training depending on the genotype possessed (3,4).

We can’t do too much about our genetic code, except to accept our strengths and weaknesses and to train and live according to them. But, it is very possible to support our unique cardiovascular nutritional needs, to increase or decrease the expression of certain genes and to aid the degree of adaptations that can be made to training. Athletes, especially endurance athletes who complete high weekly volumes of training, put their cardiovascular system under great strain. This is an essential part of boosting heart size and vascular supply to active muscles, but unless the essential building blocks of the new vascular tissue are supplied, the adaptations won’t happen so quickly.

Let’s examine another model of vascular strain for a moment, that of cardiovascular disease. According to an extensive literature review (5) that assessed the optimal diets for the prevention of coronary disease, the following dietary steps should be made: increase the consumption of omega-3 fatty acids from fish, fish oil supplements and seeds; consume a diet high in fruit, vegetables, nuts, wholegrains and low in refined grain products. In particular, EPA and DHA oils in fish have been shown to improve the function of blood vessel walls, along with improving insulin sensitivity, decreasing inflammation and other cardio-supportive functions (6). Although a young athlete may not relate to problems with cardiovascular disease, it should be motivating to think about the vascular adaptations that could occur by consuming these foods, allowing for optimal energy transportation.

Mitochondria the Powerhouse of the Cell

Collectively, all the cells in our body are thought to contain around 100,000 trillion mitochondria, and since they convert fuel into ATP energy, they play an immensely important role in energy provision to every single body system. Mitochondria are the direct descendants of an α-proteobacteria and because of their ancient bacterial origin, they have their own genome and a capacity for auto-replication. Given this bacterial connection, it will be fascinating to see what information will be unearthed by future research with regards to the relationship between the health of the human microbiota and mitochondrial genetics (7).

The mitochondrial density is highest in cells with the most aerobic activity: for example, around 40 per cent of heart cell volume is made up of mitochondria. They are also extremely numerous in active muscle cells and are therefore supremely important for aerobic exercise capacity. A very interesting study showed this clearly (8): a group of rats were divided into those with the strongest endurance and those with the weakest endurance abilities (by seeing how long they could run at a certain speed). The rats were then allowed to breed within their chosen group and the offspring were again tested for endurance abilities and split again by talent. This pattern was repeated for 11 generations until the researchers had a group of super-rats and a group of couch potato rats. At this stage the high-endurance rats could run 3 ½ times longer than the low-endurance group. What was most interesting about this experiment was that even in an untrained state, mitochondrial content was much higher in the high-endurance rat muscles and the proteins that are responsible for stimulating new mitochondria production were also significantly higher in the high-endurance group. Also, the low-endurance rats displayed many risks factors of heart disease and diabetes, including elevated blood pressure, blood fats and dysregulation of blood sugars.

As noted, mitochondria influence the health of every body system. Therefore, insufficiency or dysfunction of mitochondria not only lead to decrements in physical performance, but have been linked to chronic fatigue, fibromyalgia, cardiomyopathy, various neuromuscular symptoms and possibly even ageing (9).

Genetically, a family of nuclear receptors called PPAR (peroxisome proliferator-activated receptor) have been identified that are associated with growth of new mitochondria (biogenesis). Knowledge of this information can infer potential advantages to endurance athletic performance in some individuals. Let’s focus on one of them: PGC-1α is considered by some to be the master regulator of mitochondrial generation (10). Additionally, this gene is involved in fat metabolism, the forming of fat cells, the use of glucose for energy, thermogenesis, new blood vessel growth and muscle fibre type conversion towards slow-twitch fibres. It is expressed in tissues with high energy demands and is therefore abundant in mitochondria.

Research has shown that a certain PGC-1α genotype (GG) has been strongly associated with elite endurance performance (11,12,13) and a superior response to exercise training, resulting in better improvements in insulin sensitivity and lactate threshold (14).

This information would be useless without something you can do to support your genes. Regardless of our genotype, a number of activities and nutrients have been shown to up-regulate the PGC-1α gene. As shown in Figure 1, exercise itself increases the expression of PGC-1α function, which makes sense so that the body can adapt to harder training loads. Nutritionally, the antioxidant resveratrol (the youthful nutrient in red wine linked to the anti-ageing gene SIRT1) plus lipoic acid, an important mitochondrial antioxidant, have been shown to stimulate PGC-1α function. Nitric oxide (NO), an important vascular dilator, also bolsters PGC-1α activity. Supplementing the amino acid l-arginine will rapidly achieve increases in NO and this has been one way to manage vascular occlusion problems like angina. However, what is much more interesting is recent research into whole foods, high in nitrates.

A particular study demonstrated that short-term increases in dietary nitrates (found in green leafy vegetables and beetroot juice) could boost muscle efficiency during exercise because of increased mitochondrial output (15). In the study, there was actually a 19 per cent increase in the amount of ATP produced per unit of oxygen used which corresponded to a lower consumption of oxygen while riding an exercise bike at a certain intensity. Independent research additionally showed that when half a litre of beetroot juice was consumed daily for six days, running economy improved and endurance time to exhaustion was extended by 16 per cent.

Mitochondrial biogenesis is also triggered by environmental stresses such as exercise, cold exposure, caloric restriction and oxidative stress, cell division, renewal and differentiation, and to this end AMPK (5’ adenosine monophosphate-activated protein kinase) is of particular interest. As eloquently presented by Dr Hannah Moir at the 2015 Sports Nutrition Live conference, AMPK is activated by stressors that decrease cellular energy, including exercise, hypoxia and hypoglycaemia. In an effort to restore cellular energy, the action of AMPK is to promote mitochondrial biogenesis, fatty acid oxidation, glycolysis and glucose uptake, resulting in an increased insulin sensitivity. Foods that activate AMPK include resveratrol (16), catechins (17), capsaicin (18) and curcumin (19).   


 Adapted from Evans 2009 (20)

Energy Production Inside the Mitochondria

Again, it is important to look beyond our genetic make-up and understand how to support these energy systems nutritionally. Looking inside the mitochondria, you’ll find an array of biochemical pathways that are rote learned by every student of nutrition and physiology. As shown in Figure 2, these are the breakdown fuels, the infamous Krebs cycle which generates electrons, and the electron transfer chain, which produces ATP molecules in an oxygen-rich environment.

These pathways have been described in great detail in almost every exercise physiology book written. The focus here is not the biochemistry of energy production, but the micronutrients that are required for the process to proceed efficiently and these are not described in more textbooks. Most people have heard that B-vitamins are important for energy, but now why. Looking at Figure 2, you’ll understand that they are needed for the transfer of carbohydrate and protein break-down products into the Krebs cycle and for the actual circulation of the Krebs cycle. Lipoic acid is also required and is a popular supplement for mitochondrial energy. Also, worthy of mention are carnitine, needed for transfer of fatty acids into the Krebs cycle and Coenzyme Q10 for completion of the electron transfer chain.

Another nutrient that’s gaining more attention these days is the sugar D-ribose. It is produced during the breakdown of carbohydrates and directly supports production of the genetic material, DNA and RNA. It also plays a part in the synthesis of fatty acids, production of anabolic hormones such as cortisol and testosterone and the action of our anti-oxidant enzymes. A recent multi-centre trial (21), which examined 257 patients with chronic fatigue and fibromyalgia (conditions often observed in over-achieving athletes) revealed that a daily dose of D-ribose resulted in an average increase in energy of 61 per cent after only 3-weeks. The researchers also found improvements in sleep, cognitive function and overall function plus a decrease in perceived pain.

Figure 2 - The Krebs Cycle

Adapted from Lord & Bralley (22)


As you can see from this short account, even by staying within the physiological realm, energy is an incredibly complex phenomenon. It can be explained in part by what we eat, but only if we look beyond the typical gram value analysis of our food. Assuming adequate macronutrient flux through the Krebs cycle, energy is strongly reliant on biochemical co-factor needs plus phytonutrient contributions to the cell, that work through means of genetic expression via mechanisms that are slowly, but surely being elicited by science. The next decade of science is going to be fascinating to find out what other biochemical processes we thought we understood, but actually don’t.


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