W5 - biochemical basis of dietary supplementation Flashcards
What is Pharmacokinetics?
Describe what can be shown:
How long does a supplement usually take to wash out?
- How a drug is absorbed, metabolised, distributed around the body and how much of the medication is excreted
- Allows us to discover when to take a drug:
- Peak of supplement - indicates when before the event the supplement must be taken(using the supplement in the most effective way)
- Usually 4-8hrs to wash out
- Therapeutic range is beneficial
- Toxic range can cause adverse response
What is Pharmacodynamics?
What a drug does to the body:
-Involving receptors, enzymes, ion channels, physiological systems
What are the 3 types of effects that a drug can cause?
- Additive effect – Where two or more substances produce a response equivalent to the sum of the individual effects (e.g., B + C = A)
- Synergistic effect – Where two or more substances produce a response greater than the sum of the individual effects (e.g., C + D = A)
- Antagonistic effect – Where the action of one substance diminishes the effect of another (e.g., A + D = C)
Why is more intake of supplements not always better?
What side effect can over consumption cause?
- An appreciation of the dose response relationship is needed to understand when side effects might outweigh potential for performance enhancement
- Potential for gastrointestinal sides effects with:
– Sodium bicarbonate
– Concentrated carbohydrate solutions
– High protein
– High fluid volumes
Why is it important that we understand pharmacokinetics and pharmacodynamics?
- More likely to give correct dose of a supplement = more increase in performance
- Administering the dose at the correct time prior to your assessment
- Improve the biological process (e.g., exercise performance) of interest with this supplementation approach - varies depending on the event of the individual (marathon runner)
- There are inter-individual differences in the pharmacokinetic and pharmacodynamic responses to a given intervention (personalised supplementation needed?)
Which energy system is most likely to be affected by increased creatine supplementation?
How much creatine would an average 70kg adult have?
Which sporting event does this involve? Why is this the case?
Creatine: to boost ATP/PCr system
* Creatine (α-methylguanidinoacetic acid) is a non-essential nitrogenous acid compound
* An average 70 kg adult has a total body creatine pool of ~ 120 g
* Most (~ 95%) of the creatine pool is stored in skeletal muscle [65% as phosphocreatine (PCr)]
Mainly impacts sprinters e.g.: 10-20m
- Type II (fast-twitch) muscle fibres contain more PCr - higher ATPase activity and demand in fast twitch fibres
- Creatine is spontaneously and continuously degraded to creatinine at a rate of ~ 1.6% (~ 2 g) per day
- Continued creatine synthesis is required to sustain the skeletal muscle creatine pool
Why do we not want a marathon runner to take creatine supplements?
We do not want this for a marathon runner as creatine causes water retention, which increases the athletes weight causing them to have a lower running economy = longer race time
Where does natural creatine come from?
- Creatine can be provided exogenously through the diet
- A mixed diet provides ~ 1 g creatine/day
- Dietary sources of creatine: meat and fish, dairy products
– Beef (~ 4.5 g creatine/kg) and pork (~ 5 g creatine/kg)
– Cod (3 g creatine/kg), salmon (4.5 g creatine/kg) and tuna (4 g creatine/kg)
– Milk (~ 0.1 g creatine/kg) - Not feasible to eat enough creatine for performance enhancing effects
- Vegans need to be more careful to ensure the get the correct quantities
What is the recommended dose of creatine?
Why is it not beneficial to take as daily dose of creatine in one go?
- 4-6 x 5 g doses daily with ~ 4 hours between each dose for the first few days of supplementation is optimal to enhance muscle creatine (facilitates myocyte creatine uptake)
- Plasma [creatine] increases dose-dependently following oral creatine ingestion - approx. 1hr after
consuming 20g in 1 serving it will not be taken up by skeletal muscle(receptors become saturated) and rest will be excreted(through the kidneys)
How can short term supplementation improve performance?
What was reported by Harris et al., 1992 about creatine supplementation?
- After a few days of creatine supplementation muscle receptors become saturated
- More of the creatine supplemented is excreted in the urine
- Harris et al. (1992) reported that during a 3 day supplementation period ingesting 6 x 5 g creatine doses daily
– 40% was returned in the urine on day 1
– 61% was returned in the urine on day 2
– 68% was returned in the urine on day 3
What type of athlete benefits most from creatine supplementation?
Why is there less increase in response to creatine in power athletes?
- The ability to increase muscle total creatine and PCr is linked to pre-supplementation levels of muscle total creatine and PCr
- Power based athletes will naturally have more creatine in their skeletal muscles - higher baseline
- More muscle mass which is where creatine is stored
- Even a 20% increase is beneficial to power athletes as it will still boost their key energy system
- In the study of Harris et al. (1992) there were 2 non-responders who already had high total muscle [creatine] (> 145 mmol/kg dm)
How can we increase creatine uptake into muscles?
- Muscle creatine uptake is insulin dependent
- Co-ingestion of creatine and simple carbohydrates increases muscle creatine stores
- Initial studies suggested that each 5 g creatine dose should be accompanied by 93 g of carbohydrate
- More recent studies suggest that ingesting 1g carbohydrate/ kg bm twice daily can increase muscle creatine stores
- Insulin brings receptors to membranes which is useful alongside creatine as it increases amount of creatine brought into the muscle
Once stopping creatine supplementation, do the effects continue?
If we want to keep creatine levels up what is the recommended dose?
- There is a ceiling for muscle creatine stores (150-165 mmol/kg dm) and this is achieved within 3-7 days of supplementation with 20 g/day in 5 g servings(loading phase)
- After ceasing creatine supplementation muscle creatine stores return to baseline within 5-7 weeks
- A lower (2 g) maintenance dose of creatine maintains muscle creatine stores - keeping the muscle saturated with creatine
What mechanisms enhance performance from creatine supplementation?
- Increased ATP synthesis through PCr dephosphorylation by CK
- Increased muscle glycogen and ATP supply through anaerobic glycolysis
- Increased H+ buffering
- Decreased ammonia production
Why would injecting glycogen not be beneficial to athletes that use the anaerobic glycolysis system?
Severe exercise halved the muscle glycogen roughly
- Muscle pH decreased greatly when they relied highly on anaerobic glycolysis
- Increased muscle acidosis - major cause of fatigue
During continued (≤ 10 min) high-intensity exercise there is still sufficient glycogen available in the muscle at exhaustion
– Carbohydrate supplementation is not consistently beneficial until exercise > 2 hours
* pH declines precipitously and is more likely to limit exercise performance at this exercise intensity
