Benefits of micronutrient supplementation on nutritional status, energy metabolism, and subjective wellbeing.

INTRODUCTION: The human body, particularly the brain, requires energy, stored in the form of adenosine triphosphate. Energy metabolism during cellular respiration is dependent on the presence of multiple micronutrients, which act as essential components, coenzymes, or precursors at every stage. An adequate supply of multiple micronutrients is vital for efficient energy production. However, micronutrient intakes below the recommended dietary allowance are common, even in industrialized countries. Intakes of vitamins A, D, E, folate, iron, zinc, and selenium are suboptimal across all age groups. Suboptimal micronutrient levels have been shown to contribute to low energy levels, physical and mental fatigue, and impaired cognitive performance and wellbeing - symptoms frequently present in the general population. When supplemented in combination in well-conducted trials, multiple micronutrients ± coenzyme Q10 reduced oxidative stress in chronic fatigue syndrome; in healthy people they increased cerebral blood-flow hemodynamic response, energy expenditure, and fat oxidation; reduced mental and physical fatigue; improved the speed and accuracy of cognitive function during demanding tasks; and reduced stress. The results from these clinical trials suggest that even in industrialized countries, where adults might be assumed to have a healthy, balanced diet, there is a rationale to supplement with multiple micronutrients, including coenzyme Q10, to improve nutritional status, support energy metabolism, and improve subjective wellbeing.

INTRODUCCIÓN: El cuerpo humano, particularmente el cerebro, requiere energía, almacenada en forma de adenosina trifosfato. El metabolismo de la energía durante la respiración celular depende de la presencia de múltiples micronutrientes, que actúan como componentes esenciales, coenzimas o precursores en cada etapa. Un aporte adecuado de múltiples micronutrientes es vital para una producción eficiente de energía. Sin embargo, la ingesta de micronutrientes inferior a la recomendada es frecuente, incluso en los países industrializados. Las ingestas de vitaminas A, D, E, folato, hierro, zinc y selenio son subóptimas en todos los grupos de edad. Se ha demostrado que las situaciones subóptimas en relación con diversos micronutrientes contribuyen a tener niveles bajos de energía, fatiga física y mental, y deterioro del rendimiento cognitivo y el bienestar, síntomas presentes a menudo en la población general. Sin embargo, cuando se suplementa en ensayos bien controlados, con una combinación de diversos micronutrientes ± coenzima Q10, se constata una reducción del estrés oxidativo en el síndrome de fatiga crónica y, en las personas sanas, se observa un aumento de la respuesta hemodinámica del flujo sanguíneo cerebral, el gasto energético y la oxidación de la grasa; una reducción de la fatiga mental y física; una mejora de la velocidad y la precisión de la función cognitiva durante la realización de tareas exigentes, y una reducción del estrés. Los resultados de estos ensayos clínicos sugieren que, incluso en los países industrializados, donde se podría suponer que los adultos tienen una dieta saludable y equilibrada, hay motivos para complementarla con múltiples micronutrientes, incluida la coenzima Q10, con el fin de mejorar el estado nutricional, respaldar el metabolismo energético y mejorar el bienestar subjetivo.

Benefits of micronutrient supplementation on nutritional status, energy metabolism, and subjective wellbeing / Beneficios de la suplementación con micronutrientes sobre el estado nutricional, el metabolismo energético y el bienestar subjetivo

The human body, particularly the brain, requires energy, stored in the form of adenosine triphosphate. Energy metabolism during cellular respiration is dependent on the presence of multiple micronutrients, which act as essential components, coenzymes, or precursors at every stage. An adequate supply of multiple micronutrients is vital for efficient energy production. However, micronutrient intakes below the recommended dietary allowance are common, even in industrialized countries. Intakes of vitamins A, D, E, folate, iron, zinc, and selenium are suboptimal across all age groups. Suboptimal micronutrient levels have been shown to contribute to low energy levels, physical and mental fatigue, and impaired cognitive performance and wellbeing – symptoms frequently present in the general population. When supplemented in combination in well-conducted trials, multiple micronutrients ± coenzyme Q10 reduced oxidative stress in chronic fatigue syndrome; in healthy people they increased cerebral blood-flow hemodynamic response, energy expenditure, and fat oxidation; reduced mental and physical fatigue; improved the speed and accuracy of cognitive function during demanding tasks; and reduced stress. The results from these clinical trials suggest that even in industrialized countries, where adults might be assumed to have a healthy, balanced diet, there is a rationale to supplement with multiple micronutrients, including coenzyme Q10, to improve nutritional status, support energy metabolism, and improve subjective wellbeing. (AU)

El cuerpo humano, particularmente el cerebro, requiere energía, almacenada en forma de adenosina trifosfato. El metabolismo de la energía durante la respiración celular depende de la presencia de múltiples micronutrientes, que actúan como componentes esenciales, coenzimas o precursores en cada etapa. Un aporte adecuado de múltiples micronutrientes es vital para una producción eficiente de energía. Sin embargo, la ingesta de micronutrientes inferior a la recomendada es frecuente, incluso en los países industrializados. Las ingestas de vitaminas A, D, E, folato, hierro, zinc y selenio son subóptimas en todos los grupos de edad. Se ha demostrado que las situaciones subóptimas en relación con diversos micronutrientes contribuyen a tener niveles bajos de energía, fatiga física y mental, y deterioro del rendimiento cognitivo y el bienestar, síntomas presentes a menudo en la población general. Sin embargo, cuando se suplementa en ensayos bien controlados, con una combinación de diversos micronutrientes ± coenzima Q10, se constata una reducción del estrés oxidativo en el síndrome de fatiga crónica y, en las personas sanas, se observa un aumento de la respuesta hemodinámica del flujo sanguíneo cerebral, el gasto energético y la oxidación de la grasa; una reducción de la fatiga mental y física; una mejora de la velocidad y la precisión de la función cognitiva durante la realización de tareas exigentes, y una reducción del estrés. Los resultados de estos ensayos clínicos sugieren que, incluso en los países industrializados, donde se podría suponer que los adultos tienen una dieta saludable y equilibrada, hay motivos para complementarla con múltiples micronutrientes, incluida la coenzima Q10, con el fin de mejorar el estado nutricional, respaldar el metabolismo energético y mejorar el bienestar subjetivo. (AU)

Multiple Micronutrients, Lutein, and Docosahexaenoic Acid Supplementation during Lactation: A Randomized Controlled Trial.

Breastfed infants require an adequate supply of critical nutrients for growth, tissue functions, and health. Recommended intakes for several nutrients are considerably higher in lactating than non-lactating women but are not always met with habitual diets. We report a randomized, double-blind clinical trial in 70 healthy lactating women in Germany evaluating the effects of supplementation with multiple micronutrients, lutein, and docosahexaenoic acid (DHA) compared to placebo on maternal nutrient status and milk composition. The primary endpoint was the effect on the change of human milk DHA content (as a proportion of total milk fatty acids) during 12 weeks of supplementation. Maternal blood and milk biomarkers were measured as secondary endpoints. Supplementation increased maternal milk DHA by 30% compared to a decline in the placebo group. Supplementation also increased maternal blood DHA (17%), eicosapentaenoic acid (4%), 25-OH-vitamin D (24%), vitamin B12 (12%), lutein (4%), and beta carotene (49%), while homocysteine decreased. No significant difference in the number of adverse events was observed between supplementation and placebo groups. In conclusion, multi-micronutrient supplementation was safe and increased maternal blood and milk concentrations of selected nutrients in healthy women.

Multiple Micronutrients and Docosahexaenoic Acid Supplementation during Pregnancy: A Randomized Controlled Study.

Maternal dietary intake during pregnancy needs to meet increased nutritional demands to maintain metabolism and to support fetal development. Docosahexaenoic acid (DHA) is essential for fetal neuro-/visual development and in immunomodulation, accumulating rapidly within the developing brain and central nervous system. Levels available to the fetus are governed by the maternal diet. In this multicenter, parallel, randomized controlled trial, we evaluated once-daily supplementation with multiple micronutrients and DHA (i.e., multiple micronutrient supplementation, MMS) on maternal biomarkers and infant anthropometric parameters during the second and third trimesters of pregnancy compared with no supplementation. Primary efficacy endpoint: change in maternal red blood cell (RBC) DHA (wt% total fatty acids) during the study. Secondary variables: other biomarkers of fatty acid and oxidative status, vitamin D, and infant anthropometric parameters at delivery. Supplementation significantly increased RBC DHA levels, the omega-3 index, and vitamin D levels. Subscapular skinfold thickness was significantly greater with MMS in infants. Safety outcomes were comparable between groups. This first randomized controlled trial of supplementation with multiple micronutrients and DHA in pregnant women indicated that MMS significantly improved maternal DHA and vitamin D status in an industrialized setting-an important finding considering the essential roles of DHA and vitamin D.

A Review of Micronutrients and the Immune System-Working in Harmony to Reduce the Risk of Infection.

Immune support by micronutrients is historically based on vitamin C deficiency and supplementation in scurvy in early times. It has since been established that the complex, integrated immune system needs multiple specific micronutrients, including vitamins A, D, C, E, B6, and B12, folate, zinc, iron, copper, and selenium, which play vital, often synergistic roles at every stage of the immune response. Adequate amounts are essential to ensure the proper function of physical barriers and immune cells; however, daily micronutrient intakes necessary to support immune function may be higher than current recommended dietary allowances. Certain populations have inadequate dietary micronutrient intakes, and situations with increased requirements (e.g., infection, stress, and pollution) further decrease stores within the body. Several micronutrients may be deficient, and even marginal deficiency may impair immunity. Although contradictory data exist, available evidence indicates that supplementation with multiple micronutrients with immune-supporting roles may modulate immune function and reduce the risk of infection. Micronutrients with the strongest evidence for immune support are vitamins C and D and zinc. Better design of human clinical studies addressing dosage and combinations of micronutrients in different populations are required to substantiate the benefits of micronutrient supplementation against infection.

Immune Function and Micronutrient Requirements Change over the Life Course.

As humans age, the risk and severity of infections vary in line with immune competence according to how the immune system develops, matures, and declines. Several factors influence the immune system and its competence, including nutrition. A bidirectional relationship among nutrition, infection and immunity exists: changes in one component affect the others. For example, distinct immune features present during each life stage may affect the type, prevalence, and severity of infections, while poor nutrition can compromise immune function and increase infection risk. Various micronutrients are essential for immunocompetence, particularly vitamins A, C, D, E, B2, B6, and B12, folic acid, iron, selenium, and zinc. Micronutrient deficiencies are a recognized global public health issue, and poor nutritional status predisposes to certain infections. Immune function may be improved by restoring deficient micronutrients to recommended levels, thereby increasing resistance to infection and supporting faster recovery when infected. Diet alone may be insufficient and tailored micronutrient supplementation based on specific age-related needs necessary. This review looks at immune considerations specific to each life stage, the consequent risk of infection, micronutrient requirements and deficiencies exhibited over the life course, and the available evidence regarding the effects of micronutrient supplementation on immune function and infection.

Vitamin C and Immune Function.

Vitamin C is an essential micronutrient for humans, with pleiotropic functions related to its ability to donate electrons. It is a potent antioxidant and a cofactor for a family of biosynthetic and gene regulatory enzymes. Vitamin C contributes to immune defense by supporting various cellular functions of both the innate and adaptive immune system. Vitamin C supports epithelial barrier function against pathogens and promotes the oxidant scavenging activity of the skin, thereby potentially protecting against environmental oxidative stress. Vitamin C accumulates in phagocytic cells, such as neutrophils, and can enhance chemotaxis, phagocytosis, generation of reactive oxygen species, and ultimately microbial killing. It is also needed for apoptosis and clearance of the spent neutrophils from sites of infection by macrophages, thereby decreasing necrosis/NETosis and potential tissue damage. The role of vitamin C in lymphocytes is less clear, but it has been shown to enhance differentiation and proliferation of B- and T-cells, likely due to its gene regulating effects. Vitamin C deficiency results in impaired immunity and higher susceptibility to infections. In turn, infections significantly impact on vitamin C levels due to enhanced inflammation and metabolic requirements. Furthermore, supplementation with vitamin C appears to be able to both prevent and treat respiratory and systemic infections. Prophylactic prevention of infection requires dietary vitamin C intakes that provide at least adequate, if not saturating plasma levels (i.e., 100-200 mg/day), which optimize cell and tissue levels. In contrast, treatment of established infections requires significantly higher (gram) doses of the vitamin to compensate for the increased inflammatory response and metabolic demand.

The effect of a single dose of multivitamin and mineral combinations with and without guaraná on functional brain activity during a continuous performance task.

OBJECTIVES: Relatively few studies have explored the possibility of acute cognitive effects of multivitamin ingestion. This report explores the acute brain electrophysiological changes associated with multivitamin and mineral supplementation, with and without guaraná, using the steady-state visually evoked potential (SSVEP). METHODS: Based on the known SSVEP correlates of A-X continuous performance task (CPT) performance, and sensitivity to acute psychopharmacological manipulations, the A-X CPT was adopted as a task paradigm to explore treatment-related neurophysiological changes in attentional processing. Twenty healthy non-smoking adults aged 21-39 years (mean age = 28.35 years, SD = 5.52) took part in this double-blind, placebo-controlled, randomized, balanced crossover design study. RESULTS: The study demonstrated both transient and tonic changes in the SSVEP response during completion of the A-X CPT following multivitamin and mineral treatment both with and without guaraná. Transient changes in SSVEP response in prefrontal regions were observed after a single dose of a multivitamin and mineral preparation indicative of enhanced activity within brain regions engaged by the attentional demands of the task. This pattern of change in frontal regions was correlated with improved behavioural performance after treatment with the multivitamin and mineral combination. Where tonic shifts in SSVEP response were investigated, multivitamin and mineral treatment was associated with a pattern of increased inhibition across posterior regions, with enhanced excitatory processing in prefrontal regions. In contrast, multivitamin and mineral treatment with additional guaraná showed a tonic shift towards greater excitatory processes after a single treatment, consistent with the caffeine content of this treatment. DISCUSSION: While preliminary in nature, these findings suggest a single multivitamin/mineral dose is sufficient to impact on functional brain activity in task-related brain regions.

The Effects of Supplementation with a Vitamin and Mineral Complex with Guaraná Prior to Fasted Exercise on Affect, Exertion, Cognitive Performance, and Substrate Metabolism: A Randomized Controlled Trial.

Exercise undertaken in a fasted state can lead to higher post-exercise mental fatigue. The administration of a vitamin and mineral complex with guaraná (MVM + G) has been shown to attenuate mental fatigue and improve performance during cognitively demanding tasks. This placebo-controlled, double-blind, randomized, balanced cross-over study examined the effect of MVM + G consumed prior to morning exercise on cognitive performance, affect, exertion, and substrate metabolism. Forty active males (age 21.4 ± 3.0 year; body mass index (BMI) 24.0 ± 2.4 kg/m2; maximal oxygen consumption (V̇O2max) 57.6 ± 7.3 mL/min/kg) completed two main trials, consuming either MVM + G or placebo prior to a 30-min run at 60% V̇O2max. Supplementation prior to exercise led to a small but significant reduction in Rating of Perceived Exertion (RPE) during exercise compared to the placebo. The MVM + G combination also led to significantly increased accuracy of numeric working memory and increased speed of picture recognition, compared to the placebo. There were no significant effects of supplementation on any other cognitive or mood measures or on substrate metabolism during exercise. These findings demonstrate that consuming a vitamin and mineral complex containing guaraná, prior to exercise, can positively impact subsequent memory performance and reduce perceived exertion during a moderate-intensity run in active males.

B-vitamins and cognitive function - what is the evidence? / Vitaminas del grupo B y la función cognitiva - ¿cuál es la evidencia?

Nutrition and micronutrients such as B-vitamins influence both mental and physical performance. It is well established that even mild micronutrient deficiencies can lead to reduced cognitive and physical capabilities. This is corroborated by strong epidemiological evidence indicating that micronutrient status can affect cognitive function at all ages. However, intervention studies with single or restricted vitamin ranges have yielded mixed results. On the other hand trials with multivitamins suggest efficacy in terms of cognitive and psychological functioning. A high-dose vitamin B supplement (Berocca) is one of the rare vitamin and mineral supplements being supported by multiple double-blind, randomized and placebo-controlled clinical trials as outlined in this review. This neurotropic unique vitamin combination containing water-soluble vitamins of the B complex, vitamin C and the minerals calcium, magnesium and zinc is backed up by extensive scientific evidence showing positive effects of supplementation in terms of brain function and mental performance and improvement of some aspects of physical fitness or performance. Given that a large section of the population is unable or unwilling to eat an adequately balanced diet that would satisfy micronutrient requirements it seems that supplementation with multi-vitamins/minerals may be a useful and possibly necessary option to improve their mental and physical performance (AU)

La nutrición y los micronutrientes, como las vitaminas del grupo B, influyen tanto en el rendimiento físico como en el mental. Está bien establecido que incluso deficiencias marginales de micronutrientes pueden afectar el rendimiento físico y cognitivo. Claras evidencias epidemiológicas lo corroboran, indicando que las concentraciones de micronutrientes pueden afectar la función cognitiva a cualquier edad. Sin embargo, los estudios de intervención con una única vitamina o con un número limitado de ellas han mostrado resultados contradictorios. Por otra parte estudios realizados con multivitamínicos sugieren eficacia en términos de función fisiológica y cognitiva. El complemento alimenticio con dosis altas de vitaminas del grupo B (Berocca) es uno de los pocos complementos vitamínicos y minerales soportados con múltiples estudios clínicos, doble ciego, randomizados y controlados con placebo, como se destaca en esta revisión. Esta combinación única de vitaminas neurotrópicas que incorpora todas las vitaminas hidrosolubles, el complejo B y la vitamina C y los minerales calcio, magnesio y zinc, tiene detrás una extensa evidencia científica que muestra los efectos positivos de la complementación, en términos de mejora del rendimiento mental y físico. Dado que para un amplio sector de la población puede ser difícil seguir una dieta equilibrada y completa que satisfaga todos los requerimientos de micronutrientes, parece que la complementación con multivitamínicos puede ser una opción para mejorar el rendimiento físico y mental (AU)

Acute effects of different multivitamin mineral preparations with and without Guaraná on mood, cognitive performance and functional brain activation.

Previous work has identified the positive effects of the acute administration of a multivitamin-guaraná preparation during an effortful executive/working memory task. Here, we aimed to differentiate the effects of multivitamins with and without guaraná and to examine the neural substrates of such effects using functional magnetic resonance imaging (fMRI). Following a double-blind, placebo-controlled, randomised, balanced crossover design, 20 participants (mean age 29 ± 5.54 years) consumed multivitamin preparations with or without guaraná (Berocca® Performance and Boost, respectively) and a placebo. Thirty minutes post-treatment, they underwent neurocognitive assessment, consisting of a 10 min Cognitive Demand Battery, with mood ratings taken immediately before and after the battery. Five additional participants underwent post-treatment fMRI scanning during Rapid Visual Information Processing and Inspection Time activation tasks. The multivitamin with guaraná treatment was associated with significantly enhanced Serial Threes performance and self-rated contentment. fMRI revealed that both multivitamin treatments increased activation in areas associated with working memory and attentional processing, with the effect being greater in the multivitamin with guaraná condition. These data confirm the acute benefits of multivitamins with guaraná on mood and cognitive performance. Furthermore, they demonstrate for the first time increased brain activation from multivitamin preparations both with and without guaraná, as measured using fMRI.

Effects of a multi-vitamin/mineral supplement on cognitive function and fatigue during extended multi-tasking.

OBJECTIVES: A significant minority of the population consume multi-vitamins/minerals for their putative health benefits, including potentially beneficial effects on cognitive performance, fatigue and mood. The current study investigated the effect of supplementation with a multi-vitamin/mineral on fatigue and cognitive function in healthy females. METHODS: In this placebo-controlled, double blind, randomized, parallel groups trial the effect of a multi-vitamin/mineral (Supradyn) was assessed in 216 females aged 25-50 years. Participants attended the laboratory before and 9 weeks after commencing treatment. During both visits cognitive function and the modulation of task related mood/fatigue were assessed in two discrete 20-min assessment periods during which participants completed a four-module version of the Multi-Tasking Framework. RESULTS: Those in the vitamin/mineral group exhibited an attenuation of the negative effects of extended task completion on mood/fatigue. Multi-tasking performance for this group was also improved in terms of accuracy across all tasks, and on two of the individual tasks (Mathematical Processing and Stroop) in terms of both faster and more accurate responses. Analysis of a subsection (N = 102) demonstrated significant reductions in homocysteine levels following the vitamins/mineral supplement. CONCLUSIONS: These findings suggest that healthy members of the general population may benefit from augmented levels of vitamins/minerals via direct dietary supplementation.

Effects of high-dose B vitamin complex with vitamin C and minerals on subjective mood and performance in healthy males.

RATIONALE: A significant proportion of the general population report supplementing their diet with one or more vitamins or minerals, with common reasons for doing so being to combat stress and fatigue and to improve mental functioning. Few studies have assessed the relationship between supplementation with vitamins/minerals and psychological functioning in healthy cohorts of non-elderly adults. OBJECTIVES: The present randomised, placebo-controlled, double-blind, parallel groups trial assessed the cognitive and mood effects of a high-dose B-complex vitamin and mineral supplement (Berocca(R)) in 215 males aged 30 to 55 years, who were in full-time employment. METHODS: Participants attended the laboratory prior to and on the last day of a 33-day treatment period where they completed the Profile of Mood States (POMS), Perceived Stress Scale (PSS) and General Health Questionnaire (GHQ-12). Cognitive performance and task-related modulation of mood/fatigue were assessed with the 60 min cognitive demand battery. On the final day, participants also completed the Stroop task for 40 min whilst engaged in inclined treadmill walking and subsequent executive function was assessed. RESULTS: Vitamin/mineral supplementation led to significant improvements in ratings on the PSS, GHQ-12 and the 'vigour' subscale of the POMS. The vitamin/mineral group also performed better on the Serial 3s subtractions task and rated themselves as less 'mentally tired' both pre- and post-completion of the cognitive demand battery. CONCLUSIONS: Healthy members of the general population may benefit from augmented levels of vitamins/minerals via direct dietary supplementation. Specifically, supplementation led to improved ratings of stress, mental health and vigour and improved cognitive performance during intense mental processing.

Selected vitamins and trace elements support immune function by strengthening epithelial barriers and cellular and humoral immune responses.

Adequate intakes of micronutrients are required for the immune system to function efficiently. Micronutrient deficiency suppresses immunity by affecting innate, T cell mediated and adaptive antibody responses, leading to dysregulation of the balanced host response. This situation increases susceptibility to infections, with increased morbidity and mortality. In turn, infections aggravate micronutrient deficiencies by reducing nutrient intake, increasing losses, and interfering with utilization by altering metabolic pathways. Insufficient intake of micronutrients occurs in people with eating disorders, in smokers (active and passive), in individuals with chronic alcohol abuse, in certain diseases, during pregnancy and lactation, and in the elderly. This paper summarises the roles of selected vitamins and trace elements in immune function. Micronutrients contribute to the body's natural defences on three levels by supporting physical barriers (skin/mucosa), cellular immunity and antibody production. Vitamins A, C, E and the trace element zinc assist in enhancing the skin barrier function. The vitamins A, B6, B12, C, D, E and folic acid and the trace elements iron, zinc, copper and selenium work in synergy to support the protective activities of the immune cells. Finally, all these micronutrients, with the exception of vitamin C and iron, are essential for antibody production. Overall, inadequate intake and status of these vitamins and trace elements may lead to suppressed immunity, which predisposes to infections and aggravates malnutrition. Therefore, supplementation with these selected micronutrients can support the body's natural defence system by enhancing all three levels of immunity.

Contribution of selected vitamins and trace elements to immune function.

Adequate intakes of vitamins and trace elements are required for the immune system to function efficiently. Micronutrient deficiency suppresses immune functions by affecting the innate T-cell-mediated immune response and adaptive antibody response, and leads to dysregulation of the balanced host response. This increases the susceptibility to infections, with increased morbidity and mortality. In turn, infections aggravate micronutrient deficiencies by reducing nutrient intake, increasing losses, and interfering with utilization by altering metabolic pathways. Insufficient intake of micronutrients occurs in people with eating disorders, in smokers (both active and passive), in individuals with chronic alcohol abuse, in patients with certain diseases, during pregnancy and lactation, and in the elderly. With aging a variety of changes are observed in the immune system, which translate into less effective innate and adaptive immune responses and increased susceptibility to infections. Antioxidant vitamins and trace elements (vitamins C, E, selenium, copper, and zinc) counteract potential damage caused by reactive oxygen species to cellular tissues and modulate immune cell function through regulation of redox-sensitive transcription factors and affect production of cytokines and prostaglandins. Adequate intake of vitamins B(6), folate, B(12), C, E, and of selenium, zinc, copper, and iron supports a Th1 cytokine-mediated immune response with sufficient production of proinflammatory cytokines, which maintains an effective immune response and avoids a shift to an anti-inflammatory Th2 cell-mediated immune response and an increased risk of extracellular infections. Supplementation with these micronutrients reverses the Th2 cell-mediated immune response to a proinflammatory Th1 cytokine-regulated response with enhanced innate immunity. Vitamins A and D play important roles in both cell-mediated and humoral antibody response and support a Th2-mediated anti-inflammatory cytokine profile. Vitamin A deficiency impairs both innate immunity (mucosal epithelial regeneration) and adaptive immune response to infection resulting in an impaired ability to counteract extracellular pathogens. Vitamin D deficiency is correlated with a higher susceptibility to infections due to impaired localized innate immunity and defects in antigen-specific cellular immune response. Overall, inadequate intake and status of these vitamins and minerals may lead to suppressed immunity, which predisposes to infections and aggravates malnutrition.

Immune-enhancing role of vitamin C and zinc and effect on clinical conditions.

Vitamin C concentrations in the plasma and leukocytes rapidly decline during infections and stress. Supplementation of vitamin C was found to improve components of the human immune system such as antimicrobial and natural killer cell activities, lymphocyte proliferation, chemotaxis, and delayed-type hypersensitivity. Vitamin C contributes to maintaining the redox integrity of cells and thereby protects them against reactive oxygen species generated during the respiratory burst and in the inflammatory response. Likewise, zinc undernutrition or deficiency was shown to impair cellular mediators of innate immunity such as phagocytosis, natural killer cell activity, and the generation of oxidative burst. Therefore, both nutrients play important roles in immune function and the modulation of host resistance to infectious agents, reducing the risk, severity, and duration of infectious diseases. This is of special importance in populations in which insufficient intake of these nutrients is prevalent. In the developing world, this is the case in low- and middle-income countries, but also in subpopulations in industrialized countries, e.g. in the elderly. A large number of randomized controlled intervention trials with intakes of up to 1 g of vitamin C and up to 30 mg of zinc are available. These trials document that adequate intakes of vitamin C and zinc ameliorate symptoms and shorten the duration of respiratory tract infections including the common cold. Furthermore, vitamin C and zinc reduce the incidence and improve the outcome of pneumonia, malaria, and diarrhea infections, especially in children in developing countries.