Glaister & Gissane, 2018.

doi: 10.1123/ijspp.2017-0312.

It is widely acknowledged that caffeine is the most consumed drug or psychoactive substance throughout the globe, mainly via the medium of coffee, the world’s most popular beverage, with north of a billion cups being sold daily, in saying this, in recent years the way in which caffeine is consumed has changed with the development of pre workout formulas & energy drinks. Much research has been done into the topic of just how caffeine impacts sports performance, and what we know for sure is that it has a net positive impact, exactly how this is achieved is still debated.

This blog is mainly going to focus on the paper published in the journal of human kinetics in 2018 which looked at the effects of caffeine on physical parameters of sports performance, with one or two other factoids making an appearance along the way. Before we get into the nitty gritty I just want to point out some general things in relation to the usage of caffeine as an ergogenic aid (a substance that enhances sports performance). It is accepted that typical doses of caffeine to see a benefit in any sport, whether it be long steady state, field sports or repeat sprint efforts, is accepted as 3-6mg/kg, to put this into context, an 80kg man would have to consume the equivalent of a triple espresso to have any tangible benefit on his sporting performance (that’s a lot of coffee), caffeine takes about 45mins to peak in your blood stream if consumed as a drink like coffee, and as little as 15mins if consumed as caffeine gum or powder, which tend to be dosed in around 150-200mg per serving.

Consuming in excess of 500mg daily can lead to negative health consequences (this is about 6 coffees) whereas getting above 600mg daily may trigger a positive doping test. The sweet spot from a health perspective is not necessarily noted for caffeine itself, but for coffee, it is 3 a day for maximal protection against all cause mortality, liver fat buildup and dementia. Back to the task at hand.

You have likely done the maths in your head already and figured out how much caffeine you might need, and when you should be taking it, if you are satisfied and are not interested in the science, go forth and caffeinated yourself. If you are a habitual coffee drinker, and are wondering (as I am always asked this) if that will make caffeine supplementation less effective for you, the answer is no, caffeine supplementation at higher doses equally effects those who do and do not consume caffeine, with no difference in terms of enhancement of performance between those who drink the equivalent of one weak cup and those who drink 2-3 stronger cups daily. Now really, back to the research paper.

This study was a meta analysis, basically this means it pooled together a bunch of studies on the topic of caffeine supplementation, amalgamates all of the results to make broader conclusions, in most cases this is seen as the highest form of evidence, though it is not always ideal for nutrition based studies. 26 double blinded studies were included, with the most common dosage being 5-6mg/kg, which is the first caveat, as this is an uncommonly high ingestion rate, and for many it’s unrealistic from a tolerance point of view (and safety depending on weight), with the most common ingestion time being 60mins pre workout. The majority of the studies were done in cyclists and runners, with the exercise intensity ranging from 60-85% VO2max, or steady state aerobic range.

The findings of the study were as follows:

  1. No difference in effect between males & females
  2. Prior habitual caffeine consumption appeared not to be an issue in it’s effect
  3. Caffeine versus placebo saw significant increases in minute ventilation, blood glucose levels & blood lactate levels
  4. Caffeine versus placebo saw significantly lower ratings on the perceived effort scale
  5. There were no differences in heart rates or fat oxidation rates

The interesting thing that this study posits is that the subjects using caffeine were breathing heavier and at a higher rate per minute (minute ventilation) but were perceiving the exercise to be lower in it’s effort to complete it. There are still some unknowns about the mechanisms by which caffeine exerts it’s effect, what is thought to be a possibility is that adenosine (which is displaced by caffeine as it binds to adenosine receptors instead) can disrupt glucose clearance and glycolysis levels, having a clear impact on blood glucose levels. With blood glucose levels rising this would posit a logical basis to point to the cause of the increased lactate levels in the blood.

The final piece of the puzzle is that caffeine changes how sensitive chemoreceptors are to CO2 buildup in the bloodstream, prompting a higher minute ventilation rate versus placebo to lower this (you do not want high levels of CO2 in your blood), possibly accounting for the mismatch between minute ventilation rate, fat oxidation and blood glucose levels. This data is mechanistic in nature and has a number of hypothetical elements yet to be fully elucidated in the research.

Just for reference, a bottle of coke is about 40mg of caffeine, a cup tea is about 40-60mg, an espresso shot is about 80mg, a double is 160mg & an aeropress can be anywhere from 140-200mg depending on brew time and amount of grind used. Lighter roast coffees tend to give off high caffeine contents.

Brass tax – caffeine works, we just don’t completely know how yet.

Enjoy your cuppa.


This is the final part of the series relating to iron, and will focus predominantly on how this effects athletes, when it’s time to supplement, symptoms to look out for and how you can keep yourself healthy. If you haven’t read parts I & II, covering how iron is absorbed, digested and regulated in the body, you can get part one here, and part two here.

Many people supplement blindly with an iron supplement, assuming that it is a silver bullet and flawless plan for treating and preventing anemia and iron deficiency. There are a number of drawbacks to using iron supplements, including the potential for gastric upset and the ease at which they can lead to toxicity levels. So what, then, can or should an athlete do to keep anemia at bay?

Just to reiterate the fact that there is a difference between iron deficiency and anemia, the former being a depletion in storage iron in the liver, spleen and bone marrow – resulting in depressed stores, decreases in decreased transport and an increase in TIBC, eventually leading to decreasing serum iron (see previous article if that doesn’t make sense). Iron deficiency starts to turn into anemia when ferritin levels drop below 12ug/L and your haemoglobin starts to fall out of range. Taking an iron supplement before this point will have no impact on performance, and one should wait until they are down near this 12ug/L range before supplementing with iron. Until you get to this stage, the best thing to do is to bolster your diet with foods rich in haem-iron and fortified products such as grains and cereals.

How can you tell if you are iron deficient or anemic? The simple and most effective answer is to get a blood test, it is a good idea to this annually anyway, or bi-annually if you are an elite athlete or in the at risk demographic (female endurance athlete). That really is the only definitive way to draw a distinction and place you in a distinct spot on the continuum of iron deficiency, but if your like me, you hate needles, and you won’t get a voluntary blood unless it is absolutely vital, what else can you do to keep tabs of your iron? There are a few physical and clinical signs you can look at, that may point you towards a conclusion.

Having pale skin, thinning hair, kyphosis (spoon shaped fingernails), pale conjunctiva (the red bit behind your eyelids) and noticing a decrease in training performance, by becoming short of breath much quicker and having a decreased exercise tolerance. Whilst this is useful info, it is important to note, that clinical and physical symptoms don’t usually precipitate until you are anemic or borderline. Alongside this, ferritin depression without drops in serum iron or haemoglobin, doesn’t actually impact on your ability to perform on the track, on the road or on the bike, as your oxygen transport capacity isn;t effected until your haemoglobin levels drop.

So, right now, what you can do is book a blood test (maybe wait until COVID has relaxed a tad), and ensure you get adequate iron intake, and pay special attention to the rich food sources and inhibitors, and start emphasizing this on a day to day basis. The biggest thing is to swap to wholegrain products over white options, getting your green veggies, pulses and nuts in on a day to day basis, consuming vitamin C with all these examples and if it’s possible, include lean red meat or offal 1-2 times per week, liver if you can hack it (I cannot).

If you would like some help with nailing your diet, click here to sign up for online coaching, and nail much more than optimizing your iron intake, or, if you just want a 60 minute session with a dietary analysis to get some quick and effective pointers, then click here to book a session in the athlete clinic, at a time that suits you, from the comfort of your own home!

I hope you enjoyed this three part series on iron, it is a vital nutrient for any athlete or sportsperson to optimize in their diet, and can very easily and quickly unravel an athlete’s sporting ambitions. I would love to hear your feedback, if you found it useful or helpful, and if you think others can benefit from it, please share it!

Happy trails,


This article is going to be the first on the topic of iron, how much we need, the roles it plays, how it’s used, digested and how our body’s maintain our iron stores, and how athletes are more prone to having lower iron stores. This will all result in a final breakdown of anemia or iron deficiency development, and it’s effects on athletic performance.

Iron is found in our diets in both plant and animal products, and it is found in it’s elemental (ferric) form. Human’s need to consume iron on a daily basis, as we can store between 1-3g in the body, in various forms, but we lose iron all the time via intestinal cell recycling (enterocytes), sweat, menstrual cycles and loss of skin cells. These losses account for approx. 1-2mg per day. Iron is used to carry oxugen around the blood and in the muscles, it is also used ot make red blood cells in bone marrow and is stored in the liver mainly as ferritin, this is your back up store, inadequate iron will result in poorer oxygen transport, saturation and breathing difficulties, it can also lead to extreme fatigue and cognitive impairment.

Although iron is found in both plant and animal products, animal sources are typically more bioavailable, as they contain heme iron (hemoglobin + myoglobin), which is absorbed better than the non-heme iron found in plant products, due in part to the high level of phytates found in plant foods, which impact on absorption. The absorption rate of heme iron is around 15-35%, whereas non-heme iron absorbs at rates of 2-20%. The varied rates of absorption are down to the bioavailability, transporter acitivity and inhibitors – Calcium, Zinc, Magnesium, Polyphenols and tannins (things that give tea & coffee colour) will all impede on iron absorption. It is recommended to get between 10-20mg per day, people following plant based diets should aim closer to 20mg, whereas standard diets can aim between 10-15mg. Unless an individual has iron deficinecy anemia, classified as low ferritin stores, haemoglobin, increased transferrin and TIBC, supplements are not recommended. Iron shouldn’t be taken in a prophylactic manner, to prevent deficiency, in certain cases, it is warranted, but this is not applicable to 99% of poeple reading this. Interestingly enough, your body actually down-regulates iron absorption rates when your stores are adequate or high, to keep it in or bring back to range.

It should be noted however, that consumption of vitamin C with iron rich foods, over rides any absorption inhibitors, as it is acidic, and helps activate the ascorbate ferrireductase transmembrane protein along cytochrome B, transforming the ferric iron into ferrous iron. Ferrous iron is then shuffled byt DMT1 into the intestinal cells (enterocyte). Heme iron has the distinct advantage of being absorbed directly by heme transporters, whereas the ferric iron must be reduced into ferrous iron first.

The vast majority of iron absorption occurs in the duodenum and the jejunum, these are both sections of the small intestine, and both are in close proximity to the stomach. This is likely due to the fact that iron requires an acidic environment (remember vitamin C a.k.a. ascorbic acid) to be better absorbed. Iron absorption is typically somewhere between 1-2mg per day, we do not absorb all of the iron from our diets, this is a good thing, as our bodies have no real excretion mechanism, it simply leaves our body when cells die, or with blood loss. Iron absorption is closely controlled by ferroportin and tranferrin, ferroportin is essentially the door that allows iron out of the intestinal cells into the blood, and transferrin is what carries it around the body to the liver, muscles or bone marrow. When iron levels get too high (there are reference ranges fro men and women), the body releases hepcidin, which blocks ferroportin, essentially trapping iron in intestinal cells, thus rendering us unable to absorb iron. Haemochromatosis is a genetic condition, where individuals have defective hepcidin, and the iron can build up to limitless levels. High levels of serum iron are neurotoxic, and cause a lot of redox and tissue damage, alongside providing a perfect growth medium for infectious bacteria.

That’s requirements and absorption in a nutshell, our bodies have an easier time absorbing heme iron sources, but it is still possible to get your needs via a plant based diet (harder to do), and there are things that will impact on our iron absorption, which is lower than you may have thought. Your body is very clever and resourceful at managing iron levels, and will exude a series of responses including changing ferroprotin, transferrin and intestinal ferric reductase activity, and hepcidin levels, in order to maintain tight control of our iron levels.*

*In a healthy person

Next up, how anemia and iron deficiency occurs, followed by a final article on anemia & athletes.

Practical application series


            Supplements and ergogenic aids are all the rage at present, and represent a multi-billion-dollar industry that sits on a house of cards and is fuelled by one thing; hope. When we reach for a supplement, what we are looking for is a better outcome, an improvement, a shortcut to a desired endpoint, for some, they believe it is the only answer to a problem. This paradigm partly arises due to the fact that the supplement industry is not heavily regulated, in terms of amounts of active ingredients, and in terms of the strength of the evidence used to support a “scientific claim”, and how misleading that term can actually be. However, there are a list of evidence based and supported supplements, that do have merit in certain circumstances, let’s discuss!


            First, to clear up, there is a difference between a medically contextual application, and a general health/sporting application, sometimes there isn’t a distinction drawn between those two lines, and as someone who works on both sides of this fence, it bothers me. Let’s take for example BCAA’s, branched chain amino acids, and how they are widely promoted for their anabolic potential and supporting muscle growth. BCAA’s are metabolized in muscle, but muscle protein synthesis doesn’t occur unless ALL 20 amino acids, adequate calorie intake and anabolic signalling are in place, BCAA’s only consist of approximately 3 of 20 amino acids. BCAA’s are also found in higher concentrations in actual foods, such as meat/poultry, than in actual serving dosages of BCAA’s themselves! IN the sporting context, it doesn’t make sense to take them in the first place during exercise, as muscle protein is the last thing you will metabolize during a workout, as long as you have adequate calorie intake, overall protein intake and fuel appropriately, they are irrelevant in the equation. Now, in medical contexts, BCAA’s can be used very effectively in patients with liver failure, or cirrhosis, who have compromised ability to metabolize protein, thus supplementing intakes, they can also be used as an adjunct to aid in prevention of sarcopenia in conjunction with proper diet & exercise. Note that these scenarios do NOT apply to most people.

            Also, to note, study methods are vital to know, a study method that focuses on one cellular pathway, or metabolic interaction, may miss the point, as above, the example of BCAA’s increasing anabolic signalling, is misleading, as a rise in mTOR or insulin does not mean muscle protein synthesis, as discussed above. Signalling does not equate to physiological effect. Some studies also don’t report how they control for diet, or calorie intake, which means the results are always open to scrutiny. For example, if you took the time to read about a supplement that purported to increase performance and decrease muscle loss, you may find that the control group, were starved overnight, and the study group are given a supplement, as a lecturer once told me, if you had a control group that were starved or fasted, and a study group that licked a lollipop, there would be a difference! Sometimes, results don’t actually mean anything.


            There are 5 main evidence based supported ergogenic aids, which we will cover, along with some sports foods and nutritional products, and we will look at the context in which they are appropriate. Caffeine, creatine, nitrate/beetroot juice, Beta-alanine and bicarbonate are the supplements we will evaluate, and we will look at whey, carb powders/gels and iron supplements in addition.


            Caffeine works as an ADP receptor agonist, it doesn’t give you energy per se, it simply stops you from feeling more tired. Depending on the dosage, it can also cause central nervous system excitement and raise cortisol levels. Caffeine has mixed effects on people, due in part to built up tolerance and to genetic variants of gene CYP1A2, which dictates how it is metabolized in the liver. Caffeine doses of 3-6mg/kg confer performance benefits when consumed 60 mins prior to exercise, however opting for the lower dose of 3mg per kg wills still offer ergogenic benefit, and will decrease the likelihood of gastric distress the higher dosage can lead to. Increasing the dosage of caffeine past 9mg/kg does not continue to offer increasing benefit, due to the varied responses to caffeine, and tolerance variation, it is worth trialling out for yourself your race tactics, in training, so as to avoid any unexpected stomach issues, anxiousness or sleeping issues. Don’t worry if you’re a habitual coffee addict, your general caffeine intake will not impede the effect of the lower dosage. Evidence states that caffeine can be beneficial with the aforementioned doses if taken in a 2.5hr period prior to exercise or during, towards the latter end of the race. Caffeine doesn’t give you more energy, as some would say, it simply stops you feeling more tired, and makes you more alert, stokes the nervous system making it easier co-ordinate hard efforts, however, the psychological phenomenon is just as valid as a physiological change, in terms of aiding performance. For reference, a standard coffee had approx. 80mg of caffeine, and a gel would have anywhere from 30-80mg.


            Creatine has stood the test of time, and the hype is real. Creatine helps the body resynthesize phosphocreatine at a high rate, and also increases phosphocreatine stores. which is useful for any sport or training sessions involving explosive effort and maximal outputs. For explosive work, or anything max effort up to 6 seconds, you use your ATP-PC system, however this naturally runs out very rapidly, creatine helps replenish this, ultimately allowing one to do higher volumes of maximal and intense work, which is what leads to the strength and performance gains. Creatine has its best effects in efforts lasting under 30 seconds, it doesn’t necessarily make sense for an endurance athlete to load up on creatine, as gaining a lot of lean muscle may affect power to weight ratios, VO2 max ratio, in which case, the weight gain may neutralize any strength gains. However, early season or off season, when in general prep phase, creatine may be good to take with gym sessions, long term creatine use may avoid the weight gain noted with loading protocols, and can alter cell signalling to promote glycogen storage in cells, which may benefit the ultra-endurance athlete. Bog standard creatine monohydrate is king, no need to get fancy with it, increasing price doesn’t increase effectivity. Opt for lower doses of 2-5g per day long term as opposed to the 20g per day loading phase doses recommended for power athletes, increase your water intake, if you want to take creatine. I would recommend optimizing protein intakes, training to your max, optimize fuelling in sessions, and then, if you need extra, as an endurance athlete, to go to creatine.


                Beetroot juice has gotten a lot of press as a superpower in the media, and whilst that claim is likely to be quite an overestimation, there may be some efficacy to it, let’s take a look. Nitrates are the components in beetroot juice that offer up the benefits. Nitrates work by increasing vasodilation and oxygen uptake, which also happens naturally when you exercise. The jury is out due to mixed results and insufficient data. Some evidence dictates that intakes of nitrates offer benefits in the 2-3-hour periods post consumption, with bolus intakes of 310-560mg investigated. Elite athletes or anyone in good nick, who has a VO2 of over 60ml/kg/min, may not experience much benefit, as there is already little room for improvement, and some researchers warn that the side effects such as upset stomach may outweigh the potential gains when risks are weighed up too. This would be one to try in training, and would not be the first line of action for increasing sports performance.


                This supplement may not be too familiar for endurance athlete populations, but will be for gym goers most likely, and is known widely for its ability to give you a tingling sensation in your face, also known as skin paraesthesia. Taking beta-alanine increases muscle cell (myocytes) carnosine content, which has buffering and anti-oxidant properties, and has been shown to increase maximal exercise tolerance. There are positive intake and performance correlations across training level and elite status athletes, though the correlation is markedly weaker in increasingly elite performers. Doses of 3.2-6.4g/day split into equal doses every 3-4 hours for 4-12-week periods show efficacy, however, this is likely not realistic and does not mimic what typical consumers can or would be willing to do, making it a supplement that is likely difficult to adhere to. Some research also showed huge intra-individual differences in cell content of beta-alanine during dosage periods, as beta-alanine stays elevated for long periods of time in the body, meaning supplementing needs to be individualized and that likely more data is needed.


                This has been shown to slightly increase performance in short, high intensity events, translating to 2% improvements for events lasting less than 60 seconds. Sodium bicarb. Has similar properties to beta-alanine, but has an acute spike between 75-180 mins post consumption, meaning it would need to be trialled out repeatedly to figure optimal timing with doses of 0.2-0.4mg/kg. Also, unlike beta-alanine, this product buffers extracellularly, i.e., in the blood stream, as opposed to inside the cells. Sodium bicarb. Is very likely to lead to stomach upset and vomiting, and consuming 3-4 smaller doses per day for 3-4 days prior to the event can have the same effect, without the side effects. If that is not possible, two split doses in a 4-hour period pre-race taken with carbs, will help ease gastric suffering.


            The rest I have yet to mention are in my opinion, cupboard staples. As an endurance athlete, or active person in general, your intake needs for protein are just higher, to the tune of at least 1.2g/kg per day, which is not always easy to eat. Whey protein simply makes it easy to do, and for people getting all up in arms, higher protein intakes do not cause kidney failure, or damage your liver. If you are healthy, and have no pre-existing conditions, high protein intake is fine, and whey powder is simply dried milk. Casein is a good option prior to bed, as it is slow release, and may improve your sleep quality a tad. If you are in a power sport, injured or in a heavy training block, protein needs re higher again. Making it easy means it’s practical, means you’ll do it for longer.  

            Carb powders and gels are almost ergogenic aids, we’ve just known about them for so long. If you plan to perform maximally, or are doing anything involving long distance with some hills and sprints (cycling/triathlon), you will smash your glycogen levels and rely on glycogen stores to get you from A to B. Doing some training fat fuelled is good for metabolic conditioning, but you don’t do it race day, or in key sessions, in a similar vein, it would be like wearing ankle weights in training to get stronger, and lining up with them on race day. Carb units will help maintain exercise tolerance, increase time to fatigue, decrease muscle catabolism and improve recovery, talking to a sports nutritionist about how to toe the line between optimal carb & fat fuelling will get you the best of both worlds, alongside practicing your fuelling protocol for training scenarios.

            Iron levels, haemoglobin and red blood cells are all vital for oxygen transport, get a blood test, see where you’re at, you can likely raise it, if you can, do. Get your red meat, green veg and adequate protein and calories in the hatch, and consider an iron supplement for a course, and take a break. Repeat bloods are a good idea to see how your progressed, as red blood cells have a lifespan of about 12 weeks, so changes don’t really occur for about 3 months.

            Now to the bad and unnecessary, and these are ones I see quite a lot, the first being high dose Vitamin C or antioxidants, the effervescent type, which I see people taking on the way to training. Think about this, antioxidants help to alleviate oxidative damage, so they may limit the metabolic stress and acid build-up that occurs with exercise, theoretically making you perform better and recover better, or so the legend goes. Let me put it this way, if I were to attach a small hidden motor onto your bike, you would perform much better, and recover better, training would be easier, but what would be the point? Unless your goal is to sit on an uncomfortable seat for hours on end and move as fast as possible, in which case you should get a motorbike. If you take something that takes away or drastically reduces the stimulus (localized muscle fibre damage and oxidative stress), you don’t get anything to adapt to or recover from, and you have more or less wasted your time. Taking high dose antioxidants takes away the gains you get from training, not totally, but to a certain extent, also, it isn’t worth the potential diarrhoea, and to note, you don’t need high dose vitamins to boost your immune system, you need adequate vitamins, only a deficiency or overload will cause issues. In terms of totally unwarranted, it is electrolyte tablets, if you eat fruit and veg, you get many of your electrolytes, and you likely sprinkle salt on your food, you don’t need electrolyte tabs. Sodium is the major concern, as it is lost in sweat, but sports drinks/gels and powders contain it, and normal Western civilized folk actually consume in excess of sodium intake recommendations, you simply don’t need the tablets, especially if you are doing something that is less than 90 mins in duration. If you are doing an ironman, or huge stage cycle, you may lose some more potassium that would need replacing, however, many sports fuels contain this in minor amounts, and potassium deficiency is incredibly rare. Bottom line, ditch the electrolyte tablets, stick to sports products with electrolytes and carbs (TORG energy/HIGH5/Tailwind etc.)

            I hope this helps, there are many more supplements, there are tonnes of totally useless ones, and potentially some more that could make this list in years to come, just because a bottle says something, or the claim seems super legit, does not mean it is. Always think, is this relevant for me. For help tailoring a supplement guide to support your goals, get in touch!

Thanks for reading,