Micronutrients and performance Flashcards
macrominerals requirement
> 100 mg/day
Trace elements requirement
< 20 mg/day
Explain B vitamins for performance (water soluble)
- All 8 B vitamins are involved in energy metabolism.
- Primary role as co-enzymes in energy-producing pathways.
- Thiamine, riboflavin, B6, niacin, folic acid, and B12 are involved in nervous function and muscle contraction.
- B12 and folic acid are involved in nucleic acid synthesis
Rationale for increased B vitamin needs in active individuals
- exercises stress metabolic pathways that utilise B vitamins
- loss of nutrients in urine or sweat, increased turnover
- increased need due to training-induced biochemical adaptations
- increased demand for co-factors for mitochondrial enzymes
Does B vitamin status affect performance?
- sub-clinical single B deficiencies unlikely to affect performance
- combined depletion of thiamine, riboflavin and B6 resulted in 12% decrease in VO2max, 9% decrease in peak power
Does B vitamins supplementation improve performance capacity?
- not if the athlete has good vitamin status
- possibly if the athlete has poor vitamin status
Why is iron important for athletes?
- functional component of Hb and myoglobin
- key component of erythropoiesis
- energy production, cytochromes in electron transport chain
What is the prevalence of iron deficiency amongst athletes?
- 52% of female and adolescent athletes
- higher prevalence in endurance and sports with a high incidence of eating disorders
- male gymnasts, 45% prevalence
Name some risks factors for iron deficiency in athletes
- strenuous training
- sweat loss
- blood loss
- inadequate dietary iron intake and/or low nutrient bioavailability
How does low iron status affect performance?
Iron deficiency anaemia:
- reduced VO2max
-reduced task duration before the onset of fatigue
- poor concentration
- negative effects higher in less trained/during adaptation to training
Explain dilutional pseudo-anaemia (sports anaemia)
Reduction in iron content in an individual’s blood as a result of strenuous exercise
True or false
Mineral deficiency may impair performance if operating in sub-optimal state
True
When is necessary to supplement with iron?
- on low diets or periods of inappropriate food intake, e.g. female athletes with iron-deficiency anaemia
- during ultra-endurance events, addition of minerals to meal replacements may be recommended to compensate for sweat or urine loss
What are antioxidants?
Molecules that can be present in small concentrations that prevent or reduce the extent of oxidative damage due to other biologically relevant molecules.
Neutralise reactive oxygen species (ROS) to relatively less harmful by-products
What leads to a chain reaction creating more free radicals?
Donation of single electrons
Name some sources of ROS (reactive oxygen species)
- mitochondrial leakage
- skeletal muscle contraction
- muscle damage: neutrophils, monocytes
- enzyme systems
ROS are products of normal metabolism
Explain oxidative stress
disturbance of the oxidation-reduction balance in favour of oxidants, leading to a disturbance in redox signalling and control and/or molecular damage
Name some physiological stimuli (oxidants) for oxidative stress?
- radiation
- alcohol use
- smoking
- exercise
What is redox balance?
Balance between oxidants and antioxidants
Name some dietary (non-enzymatic) antioxidants
- vitamin A
- vitamin C
- vitamin E
- caratonoids (beta-carotene)
- polyphenols (red wine, tea, chocolate, scavenge free radicals)
- anthocyanins
Name some co-factors antioxidants
- Iron (catalase)
- Zinc, cooper (SOD)
- Selenium (glutathione)
Explain Vitamin C
- stabilises hydroxyl radical
- scavenges singlet oxygen
- reduces the oxidised form of Vit E
Which vitamin will impair exercise performance if taken in high doses?
Vitamin C
Safe advice for athletes for vitamins and minerals?
Aim for 5 per day to consume adequate Vitamin C, folate, magnesium, etc
Explain Vitamin E
- a group of 8 compounds classed as tocopherols and tocotrienols
- alpha-tocopherols:
- arrests lipid peroxidation
- scavengers singlet oxygen
- stabilises superoxide and hydroxyl radicals
- stabilises membrane structure
Is there any performance effect from vitamin E supplementation?
Improved anaerobic threshold and reduced pentane exhalation. Mechanism: protects against lipid peroxidation
Chronic intake is not recommended for athletes
Explain some general recommendations for Antioxidant supplementation for athletes
- whole, unprocessed foods appear to provide AO in sufficient quantities and combinations to elicit health benefits
- consume a diet high enough in AO-rich foods to exceed RDI’s rather than supplement
When to supplement with AO?
- beneficial for athletes not consuming a balanced diet
- after exhaustive exercise
- might be effective in particular periods of training (before/after a race, during overtraining syndrome)
Which are forms of oxidative damage caused by reactive oxygen species (ROS)?
- lipid peroxidation
- nucleic acid damage
Which groups are at increased risk of low iron status?
- endurance runners
- female runners
-athletes regularly taking aspirin
-female athletes with restricted eating
What is lipid peroxidation, and which cellular structures does it target?
Is an oxidative damage caused by ROS and damage membrane proteins
Describe one training-induced adaptation which may increase an athlete’s requirements for the B vitamins
- increased blood volume due to greater water reabsorption by kidneys - exercise boosts production of aldosterone and ADH
- increased demand for co-factors for mitochondrial enzymes
Give an example of a vitamin that can impair performance if taken in high doses. Give an example of one of the ways it can impair performance
Vitamin C
long term >1g/day impairs mitochondrial biogenesis
1g Vit C + 600 IU Vit E reduced exercise-induced blood flow
-pro-oxidant effects in high doses
Write a paragraph on the case against antioxidant supplementation in athletes
- ROS essential for normal physiological processes
- AO supplementation may blunt positive training-induced adaptations
- Exercise training up-regulates endogenous AO production
