Conclusion – Vits as ergogenic aids• No ergogenic benefit vitamin supplementation

given an adequate diet.– Except perhaps vit. E at altitude, C and multi B in hot

climates?– Evidence exercise may increase req for riboflavin and

vit B6– Those on poor diets/restricted energy/restricted food

groups – consider supplement

• Mega-doses (RDA x 10-1000) of vitamins may be toxic, particularly the fat-sol.– Hypervitaminosis A – case study adolescent footballer

(Fumich and Essig, 1983)

Dietary antioxidants and exercise

• Radicals - molecules that possess an unpaired electron in outer shell/orbital

• Highly reactive and promote damaging oxidation reactions with cellular proteins, lipids or DNA oxidative stress (impaired cellular function)

• Exercise results in increased production of radicals (Davies et al., 1982)

• Primary source is mitochondria – 2-5% of oxygen undergoes 1 electron reduction superoxide radicals

Antioxidants

• Cells protected by – endogenous antioxidants eg. superoxide dismutase,

glutathione peroxidase and catalase;

– Exogenous dietary antioxidants eg. Vits E, C, carotenoids, flavenoids, ubiquinones (eg. Coenzyme Q)…

– Also trace minerals act as co-factors for antioxidant enzymes eg. Cu, Zn, Fe, Se, Mn

– Nb Vits C and β-carotene can function as both anti- and pro-oxidants

Antioxidant deficiencies and performance

• Antioxidant deficiencies not widely reported in athletes (Clarkson, 1995)

• Animal studies - antioxidant deficiency impairs performance;• However Vit E deficiency in humans did not affect

performance (Bunnell et al., 1975)• In contrast to animal studies antioxidant supplementation do

not enhance performance– Except study at altitude where Vit E maintained anaerobic threshold

(Simon-Schnass and Pabst, 1988)

• Little evidence to recommend antioxidant supplementation to enhance performance.

• – reduced IL-6 release from contracting muscle & thus cortisol response

• Fischer et al. (2004) 4 weeks combined supplementation with vit C (500 mg/d) and vit E (400 IU/d) prior to a 3-h knee extension exercise reduced muscle IL-6 release systemic rise in cortisol

• However, randomized double-blind, placebo controlled study, 1500 mg/d vit C for 7 d before ultramarathon race with vit C in a CHO drink during the race (subjects in the placebo group consumed the same CHO drink without added vit C) did not affect oxidative stress, cytokine or immune function measures during and after the race.

Are athletes at increased risk of oxidative stress?

• Training related oxidant stress increases in enzymatic antioxidants • However still see oxidative stress in highly adapted skeletal muscle• If exercise higher requirement of antioxidants – would expect

exercise to link via oxidative stress to morbidity• Equivocal results as to levels of plasma antioxidants post-exercise; and

to effects of supplementation on exercise-induced oxidative stress.– Vitamin E has been shown in some studies to decrease muscle damage.

E.g. supp with 400 iu vit. E and 200 mg vit C daily for 30 d reduced CK concentrations following a marathon (Rokitski, et al. 1994; cited in Sen, et al. 2000)

• High levels of antioxidants may blunt cellular adaptations induced by exercise.

• Overall dietary supplementation with antioxidants cannot be recommended at present time.

Immune Function• Protects against, recognises, attacks and destroys

foreign elements• Innate – natural and non-specific

– 1st line of defense• Physical/structural barriers;• Chemical barriers;• Phagocytic cells and cytotoxic cells

• Acquired – adaptive and specific– Monocytes/macrophages ingest, process and present

foreign material (antigens) to lymphocytes– Proliferation of T- and B-lymphocytes which recognise

antigen if host is re-infected

Immunity and elite athletes• Moderate exercise reduces risk of URTI cf. sedentary

(Matthews et al., 2002)• Heavy training impairs immunity

– ↑susceptibility to infections, esp. URTI (Peters and Bateman, 1983; Nieman et al., 1999)

– Not supported by all studies – no clinical confirmation of infection – reported symptoms eg. Sore throat may be due to inflammation of mucosal surfaces/inhalation dry air/pollutants.

– Post-exercise immune function is most depressed when exercise is continuous, prolonged (>1.5hrs), of mod to high intensity (55 – 75% VO2max) and performed without food intake.

– Periods of overreaching (intense training >1week) also depress immune function (MacKinnon,2000)

– However• Very few studies that show a link between exercise-induced immune

depression and increased incidence of illness in athletes.

Acute effects exercise and immunity

• Single bout prolonged, strenuous exercise temporary reduction in immune function

• Due to immunosuppressive actions of adrenaline, cortisol;– Muscle derived IL-6 appears partly responsible

for cortisol response to exercise– Any factor affecting stress hormones (duration,

intensity, subject fitness) will affect immune response

Nutrition and Immunity

• Prevalence/severity of infections are increased by specific nutritional deficiencies (Calder and Jackson, 2000);– Prot, Fe, Zn, Cu, Se

• However….xs intake of individual micronutrients can impair immune function (ω-3 PUFAs, Fe, Zn, Vits A&E); excess Fe can increase risk of infection.

Macronutrients

• Protein– Inadequate protein intake impairs immunity (esp T

cells)– Unlikely athletes would not reach extreme

protein/protein/energy malnutrition unless dieting severely

– Those at risk: • Those restricting food to lose weight;• Vegetarians• Unbalanced diets (xs CHO)• Sports where leanness/low body mass, aesthetic sports, sports

Macronutrients

• Fat– Little known re. fat and immune function;– N-3 PUFAs may improve conditions associated

with overactive immune system e.g. rheumatoid arthritis;

– High n-6:n-3 ratio may exert undesirable effect on immune function during/post exercise (but evidence lacking);

Macronutrients• CHO

– CHO feeding during exercise attenuates rise in plasma IL-6, catecholamines, GH, ACTH, cortisol;

– However• inhibits lipolysis, and may attenuate the expression of metabolic

genes in the exercised muscle

• But may be argued that CHO intake during training allows athlete to work harder/longer.

• No evidence that physiological adaptations are impaired by CHO intake – is indicated that CHO is needed following periods of intense training that temporarily induce overreaching

Macronutrients• CHO

– Evidence CHO feeding for continuous strenuous exercise (during, not before); but

– Magnitude of stress hormone response is higher in those on very low CHO diets cf. normal/high CHO diets – pre-exercise glycogen levels imp;

– If train 2x/day – highest benefit when fed during exercise (Li and Gleeson, 2005)

– Equivocal results for intermittent exercise (football (Bishop et al.1999, 2002 rowing (Nieman et al.1999)

– Or when continuous prolonged exercise is performed to point of fatigue (Bishop et al., 2001)

– Again evidence that CHO feeding reduced incidence URTI lacking. Trend for beneficial effect on post-race URTI in study on 98 marathon runners (Nieman et al., 2002)

Macronutrients• Fluid

– Dehydration associated with increased stress hormone response;

– Fluid prevents dehydration and maintains saliva flow rate

– Saliva contains proteins with antimicrobial properties, and saliva secretion usually decreases during exercise

– CHO-containing drinks maintain saliva flow rates (Bishop et al., 2002).

Micronutrients• Minerals

– Isolated deficiencies rare (apart from Zn and Fe)– Iron deficiency associated with increased morbidity from

infectious disease;– Requirements may be higher in athletes due to losses in

sweat and urine;– Excess Fe and Zn can impair immune function, & Fe can

increase susceptibility to infection– Some evidence Zn can reduce symptoms/severity of

common cold – must be taken within 24 hrs of onset.– Nb. Problems with Zn supps – nausea, taste, lowers HDL,

depressed immune cell function and reduces absorption Cu.

Micronutrients

• Vitamins– Deficiencies of A, E, folic acid, B6, B12, C

impair immune function– Such deficiencies need to be corrected.– Some evidence A & E above normal levels in

very young/elderly enhance immunity (Calder and Jackson, 2000)

– Megadoses of individual vits may impair immunity, or have other toxic effects.

Micronutrients

• Vitamins contd.– Peters et al. (1993) – 600mg

Vit C for 3 weeks prior to 90km untramarathon reduced incidence of URTI cf. placebo.

– Additionally 2 weeks post-race – lower incidence in those with highest mean daily intake of Vit C

– No effect additional fat sol vits

– Due to reduced IL-6 release?

Other nutritional substances

• Glutamine– Most abundant amino acid in plasma and muscle– Energy source for leukocytes– Prolonged exercise associated with fall in plasma

[glutamine]– Little evidence of benefits of supplementation;– 1 study – Castell et al. (1996) – load post-

marathon reduced incidence of URTI

Others

• No evidence BCAA’s, γ-carotone, probiotics

• Echinacea– Berg et al., (1998) – no athletes fell ill before

triathlon– Turner et al., (2005) 437 volunteers exposed to

rhinovirus – NS effects.– Very few good quality studies

Others

• Colostrum– Shing et al., (2007)

• Colostrum suppressed post-exercise decrease in immune parameters and tendency towards reduced URTI

– Crooks et al., (2006)• Increase in salivary IgA in runners

– More studies warranted.

Summary on immunity

• Dietary deficiencies associated with depressed immune function

• Adequate Fe, Zn, A, E, B6, B12 imp and protein• Avoid exercising in CHO-depleted state, high CHO diet,

consume CHO-drinks during exercise (30-60g/hr)• Routine megadoses ill advised – some can impair immune

function• No evidence for immune boosting supplements –

particularly in athletes• Some evidence high dose Vit C to reduce post-exercise

incidence of URTI

Refs

• Gleeson (2007) Immune function in sport and exercise J Appl Physiol 103: 693 – 699

• Gleeson (2006) Can Nutrition limit exercise-induced immunodepression? Nutrition Reviews 64(3): 119-222

• Nieman and Bishop (2006) Nutritional strategies to counter stress to the immune system in athletes, with special reference to football J Sports Sci 24(7): 763 – 772

• Williams et al.,. (2006) Antioxidant Requirements of Endurance Athletes: Implications for Health Nutrition Reviews 64(3):93-108