Diet & Fatigue

By Linda McCourt Scott (MA (Oxon), MSc Nutritional Medicine, author of Natural Home Pharmacy)

Carbohydrates in food (including sugars and starches) are the main sources of fuel for the body. They are broken down into glucose, a simple sugar, by the process of digestion before being absorbed into the bloodstream. Glucose is then taken up by the body’s cells where it is used to provide energy through a series of chemical reactions. While glucose is the fuel or source of energy for the body, the production of energy is totally dependent on the presence of certain vitamins and minerals.

McNab’s Energy Tabs have been formulated to provide therapeutic amounts of the essential ‘energy’ nutrients that are most likely to be limiting in today’s diets, helping to ensure all-day energy and feelings of well being.

The role of vitamins and minerals in energy production

Over 20 vitamins and minerals are required directly and indirectly to provide energy for muscles and brain activity. If the supply of one or more of these nutrients is restricted the production of energy will be impaired. The most important nutrients required directly for energy metabolism include the B complex vitamins, magnesium, phosphorus, sulphur, iron, zinc and copper.

These nutrients are needed to convert food into Adenosine Triphosphate (ATP), the body’s most important immediate source of energy for all cellular metabolic processes. ATP is used for all energy-dependent processes in the body.

Energy production

The first stage of energy production from glucose is called glycolysis. This is an anaerobic process which produces a relatively small amount of ATP and is dependent on vitamin B3 and magnesium. Glucose is converted into pyruvate and then into acetyl CoA, which enters the Krebs or citric acid cycle, the second stage of energy production. If glucose is not available for use as a fuel, fatty acids and/or amino acids will be used instead.

The Krebs cycle is therefore the part of the metabolic pathway that involves the conversion of carbohydrates, fats and proteins into carbon dioxide and water to generate usable energy. The Krebs cycle is followed by oxidative phosphorylation, the third and final stage of energy production. This process extracts the energy from NADH and FADH₂, recreating NAD⁺ and FAD, so that the Krebs cycle can continue. The Krebs cycle itself does not use oxygen, but oxidative phosphorylation does.

The Krebs cycle and oxidative phosphorylation are directly dependent on an adequate supply of vitamins B1, B2, B3 and B5 and calcium, magnesium, iron, phosphorus, sulphur and copper. For instance magnesium acts as a metallo-coenzyme in more than 300 phosphate transfer reactions and therefore has a critical role in the transfer, storage and utilisation of energy within the body. Iron is of central importance since its presence in haemoglobin is essential for the transport of oxygen to cells for energy production. This is why fatigue is the dominant symptom of iron-deficiency anaemia.

Dietary and biochemical surveys have shown that certain sub-clinical vitamin and mineral deficiencies are surprisingly common in Western societies. Supplementation with B complex vitamins have been shown to help improve energy levels, mood and alertness, with the degree of benefit being inversely proportional to the vitamin B status. The brain, with its high metabolic rate and therefore dependence on an adequate supply of energy, is particularly sensitive to even slight nutrient deficiencies. Psychological symptoms, especially negative changes in mood and cognitive function, are probably the first indications of a deficient dietary intake of micronutrients and/or absorption problems. These symptoms are generally reversible and positively respond to an improved dietary intake or appropriate supplements, suggesting a causal relationship between deficient micronutrient status and depressed mood and energy levels.

Experimental deprivation of thiamine (vitamin B1) has been shown to induce feelings of depression and irritability, which disappear with thiamine supplementation, implying a physiological correction rather than a pharmacological action. Several double-blind studies have confirmed that mood is positively correlated to thiamine status, and that thiamine supplementation also improves mood, some aspects of cognitive function and energy levels in subjects who are not thiamine-deficient, according to current definitions. This suggests that current recommended levels for thiamine intake (and possibly other micronutrients) may be inadequate for optimal brain function and well-being.

Up to 50% of people in Western societies, particularly the elderly and adolescents, may have a marginal thiamine intake because of nutrient-poor, highly refined diets. Symptoms associated with a chronic deficiency of thiamine include violent mood swings, erratic temper, depression, anxiety and fatigue. Marginal deficiencies of other B vitamins including B2, B3, B5, B6, B12 and folate are also associated with emotional instability, fatigue, irritability, anxiety and depression, because of their role in energy metabolism and brain neurotransmitter function. Extra B vitamins are required as a result of an increased energy expenditure, a high carbohydrate (especially sugar) intake, a moderate to high alcohol intake, and a reduced absorption capacity (which can be due to certain medical conditions or as a natural consequence of ageing). This means that athletes, people on poor diets, the elderly and people who regularly consume alcohol are all susceptible to micronutrient deficiencies.

Whether we eat a micronutrient dense diet or a nutritionally inadequate diet can therefore have dramatic ramifications on how we feel and our energy levels, and scientific evidence suggests that persistently negative moods and fatigue should alert us to the possibility of sub-clinical micronutrient deficiencies.

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