Studies show that many people regard themselves as healthy once the discernible symptoms of an illness disappear, and do not leave themselves time for convalescence. This increases their risk of relapse and renewed bouts of illness. And in contrast to professional sportspeople, who are integrated into a network of specialists, ambitious amateur sports lovers often ignore the necessity for phases of regeneration, with the result that their body cannot properly recover and does not develop its full performance capacity. But recuperation is more than just resting. Requirements of micronutrients – especially antioxidants such as vitamins E and C, carotenoids and selenium, B vitamins, and also vitamins A and D plus iron and magnesium – are frequently higher after, as well as during, the period of stress. If the diet does not supply these micronutrients in sufficient amounts, a supplementary intake can be beneficial. The effects of a chronic undersupply of micronutrients in patients and sportspeople usually build up gradually. Often an intake that is less than sufficient, although not yet deficient, will already adversely affect muscle and nerve function, the immune system and the supply of oxygen to the cells. Targeted micronutrient consumption is not a substitute for a phase of regeneration or convalescence, but it may shorten such phases and in any case will help optimize recovery.
Physical exercise, as well as illnesses that require us to fight of germs (viruses and bacteria) places extra strain on the immune system, which is responsible for regulating many processes of regeneration as well as fending off attacks. Thus several different messenger substances of the immune system influence inflammatory and regenerative processes in muscle cells, among others (1). During sporting activities, oxygen utilization is distinctly higher, as is the production of free radicals (reactive oxygen species). In high concentrations (oxidative stress) free radicals can damage cell components (membranes, proteins and DNA) (2). They can also put a strain on the immune system. Hence, oxidative stress is a major factor in inflammatory processes in which the T helper cells of the immune system play a key role (3).
In addition to the body’s own antioxidant defense systems, certain micronutrients with antioxidant properties can help protect the immune system against oxidative damage. Vitamin E, in particular, acts as an antioxidant. Its activity is complemented by the regenerating properties of vitamin C and the trace element selenium. Antioxidants can modulate the immune system and have an anti-inflammatory effect (4, 5). The antioxidant carotenoids – in particular beta-carotene, lycopene and lutein and zeaxanthin – have similar effects (6). The fall in serum levels of carotenoids and vitamin A which occurs during inflammatory processes should be compensated by an appropriate intake (7).
Early clinical studies have provided evidence that wound healing can be improved by supplementation with vitamin C and zinc (8), especially since plasma and tissue concentrations of vitamin C fall after injury and need to be raised again (9). Patients with impaired wound healing, too, could benefit from administration of vitamin C, zinc, selenium and vitamin A (10). One randomized controlled study was able to show that taking a combination of antioxidants containing vitamin E, beta-carotene, zinc, selenium and glutamine accelerated wound healing in trauma patients with impaired wound healing and therefore shortened the period of convalescence (11).
The risk to athletes of immune system weakening (immunosuppression) due to the increased production of reactive oxygen species might possibly be reduced by targeted administration of micronutrients (12). The focus here is on vitamins E and C, which are essential for T-cell differentiation and maintenance of T-cell function (13). It was also shown for vitamins E and C that they reduce the increase in lipid peroxidation induced by physical exertion, and hence could prevent damage to muscle tissue (14, 15). Further, it appears possible that an insufficient intake of selenium, even before selenium deficiency becomes evident, might lead to impaired muscle function (16). Evidence from one clinical study showed that targeted administration of selenium in overweight healthy people could combat the occurrence of oxidated lipids during the phase of regeneration after physical exertion (17).
Vitamins A and D and minerals
Vitamin A and vitamin D are among the micronutrients that have become a focus of research in respect of their importance to the immune system (18). Vitamin A derivatives (metabolites) like retinoic acid can influence cell division (proliferation) and communication between immune system cells like T helper cells. Two different mechanisms evidently underpin the influence of vitamin D: vitamin D restricts the proliferation of adaptive (or acquired) immune system factors like T cells or beta cells, whilst the division of cells of the innate immune system – the monocytes, for instance – is stimulated. For example, a clinical case-control study showed that patients who had recovered from tuberculosis had low blood levels of vitamin D (19), i.e. that the severe infection had possibly decreased their body’s reserves of vitamin D. Vitamin D might also contribute to the regeneration of blood vessels after inflammation of the vessel linings (20). Another clinical study was able to demonstrate that older women who supplemented their diet with vitamin D had greater grip strength six months after breaking the radius bone of the forearm than women who did not take supplemental vitamins (21). Vitamin D is especially important for athletes, because it appears to promote the formation and maintenance of muscle tissue and thus improve physical performance capacity (22).
The trace element iron is a component of the red blood pigment hemoglobin, which binds oxygen and transports it to all the cells of the body (23). Iron also fulfills important functions in the immune system, inter alia as a catalyst for various cellular redox processes (24). If too little iron is available, less oxygen can be bound in the muscles. The consequence is more rapid formation of lactic acid (lactate), which leads to premature tiring of the muscles, limited mobility, poorer coordination and muscle pain in endurance athletes like marathon runners. Iron deficiency also leads to longer regeneration times after physical exertion and running injuries. Iron deficiency can also be a cause of chronic exhaustion and sustained reduced performance capacity. One randomized controlled study revealed that an intravenous administration of iron during a six-week training period was able to prevent exhaustion and mood swings (25). Because of menstrual periods, in particular, sportswomen are especially prone to iron insufficiency. Women participating in endurance sports are at high risk of having too little iron. One study showed that – regardless of iron status during training – the body evidently takes more than 10 days to recuperate (26).
One mineral that is lost through sweat during physical exercise is magnesium. Magnesium is essential for muscle and nerve function and for several enzymes, in particular those involved in energy metabolism. It supports nervous system function and contributes to muscle relaxation and protein synthesis (27). Recent research discovered that dietary supplementation with magnesium could increase physical performance by increasing the bioavailability of glucose in the blood, muscles and brain during physical exertion (28).
A randomized controlled study was able to show that undernourished patients recovered better after a stroke when they consumed a dietary supplement with several micronutrients (29). Possibly, patients with chronic fatigue syndrome could benefit from taking a multivitamin/mineral preparation, which might improve their symptoms and their quality of life (30).
Some B vitamins, in particular vitamins B1, B2, B3, B6 and B12, are involved in protein, lipid and carbohydrate metabolism and are therefore important for energy production (31). Deficiencies can impair performance under both aerobic and anaerobic conditions. Moreover, vitamin B12 can support production of the oxygen carrier hemoglobin and thus the provision of cells with oxygen. Furthermore, vitamins B1, B3, B6 and B12 are essential for nerve function and therefore also influence neuronal control of muscle activities (32, 33). Higher requirements for athletes were determined in particular for vitamins B1, B2 and B6 (34).
One clinical study with patients who had undergone an operation on their gums showed that their wounds healed significantly better when they were given a drink enriched with vitamins B1, B3 and vitamin A, among others (35).
Omega-3 fatty acids
During physical exercise – especially endurance sports – more of the aggressive oxygen compounds are produced in the body, and together with stress-induced injuries, including micro-injuries, in the muscles these can cause inflammatory reactions throughout the body. The consequences are prolonged recovery times and often impaired physical wellbeing, due to muscle pain, for example. Omega-3 fatty acids – like docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) – possess antioxidant and anti-inflammatory properties that combat the inflammation and strengthen immune defenses (36).
In addition, EPA and DHA accumulate in the membranes of cells, for example in the red blood cells and vascular cells, and thus improve their flexibility and pliability. There is early evidence to show that physical activity could increase the already health-promoting effects of EPA and DHA on the cardiovascular system (37).