How much protein do you need to keep in tip-top condition and maximise your endurance performance? Andrew Hamilton looks at the recent evidence.
Once upon a time, many athletes believed that the secret to sporting prowess was protein, and lots of it – hence the popularity of the “steak and eggs” pre-training meal.
However, modern sports science has since taught us that it’s carbohydrate rather than protein consumption that plays the major role in determining your performance – especially endurance performance – which explains the plethora of advice on ensuring ample carbohydrate nutrition, before, during and after training or competition.
Despite this however, protein nutrition – i.e. how much you as a triathlete, cyclist and marathon runner and so on, consume and what type you consume – is still critically important.
Protein is the largest component in your body after water, and most of this mass is found in skeletal muscle. Given all movement comes from muscular contraction, you can appreciate the importance of protein to all athletes, including endurance athletes (see Box 1).
In addition to sport performance, proteins also play a crucial role in providing our bodies with structural integrity, maintaining immunity and enabling numerous other essential biochemical reactions to occur in the body.
In plain English, if your protein intake isn’t high enough to properly support your training, the risk of illness, injury and burnout will be significantly increased.
In the late 1970s and early 1980s, the thinking was that athletes needed no more protein than the average couch potato (around 0.8 – 1.0 grams of protein per kilo of bodyweight per day) regardless of their sport.
Over the following years however, research indicated that athletes engaged in intense training actually need to ingest anything from 1.5 times (endurance athletes) to 2 times (strength athletes) this amount to maintain a positive protein balance – i.e. 1.6g to 2.0g per kilo of bodyweight per day(2-5).
Curiously however, while most sports scientists now agree that athletes of all disciplines (including endurance athletes) do need more protein than those who are sedentary, the protein intake recommendations are quite diverse, which be can confusing to say the least.
For example, the UK government’s Food Standards Agency still recommends that 55g of protein per day (i.e. 0.8g per kilo per day for the “typical” 70kg adult) is sufficient, regardless of activity level. Meanwhile, the European Food Safety Authority recommended in a recent (2012) report that 0.83g of protein per kilo per day is ample for all adults, regardless of activity level.
When it comes to endurance athletes, there haven’t been that many scientific studies carried out on optimum protein intakes. The relative lack of research is partly because protein metabolism is difficult to study.
Unlike carbohydrate, there’s no actual “protein store” in the body, other than muscle tissue, and observing changes in muscle fibres in response to protein ingestion is fraught with difficulties.
A good example of this difficulty is that it can take many hours or days for changes in muscle tissue to become apparent, making the link between protein ingestion and muscle growth or recovery much more difficult to establish.
Having said that, we’ve seen some recent research emerge, which makes for interesting reading. For example, a 2011 study by Canadian scientists surveyed much of the previous scientific research on this subject and came to the following conclusions:
- There is good evidence for recommending athletes consume protein intakes higher than that recommended for sedentary adults.
- Protein intakes in the range of 1.3g – 1.8g per kilo per day consumed over 3-4 meals appear to maximise muscle protein synthesis.
- The amino acid leucine (found in high concentrations in whey protein) is particularly important in stimulating muscle protein synthesis.
Ensuring ample protein consumption has traditionally been associated with power and strength athletes such as weightlifters and bodybuilders, who benefit from high levels of muscle mass when generating large forces.
In recent years however, scientists have begun to appreciate that although their protein needs may be somewhat lower, ensuring optimum protein intakes is still vital for endurance athletes such as cyclists, runners, triathletes, swimmers and rowers for example.
That’s because sufficient muscle mass and strength to perform are still critically important to endurance performance – for the following reasons:
- All other things being equal, a muscle with a larger crosssectional area is able to generate more force and power (i.e. is stronger) – force that you need to propel you forward whether swimming, cycling or running and so on.
- The higher the peak force and power your muscles can produce, the easier it is for them to maintain a given workload (e.g. force applied to the cranks during cycling, or powering through the water when swimming) because they can do this by working at a lower percentage of their maximum force output – this is known as performance economy.
- More muscular strength and power allows for better sprint performance (e.g. at the end of a race or to break away from your opponents).
- Stronger muscles are better able to withstand the stress and strains of repeated impact and loading – i.e. reduce your risk of injury.
In recent years, research has shown that high volumes of endurance training damages and breaks down muscle tissue.
It follows therefore that optimum protein nutrition to maintain muscle mass and strength remains vitally important for endurance athletes, even if their absolute needs are somewhat lower than strength athletes.
- More protein should be consumed during periods of high-frequency or high-intensity training.
- Even higher protein intake (1.8g – 2.0g per kilo per day) might be advantageous for those seeking to lose body fat while preventing lean mass losses.
There’s also some evidence that consuming small amounts of protein (10-20g) prior to training can help maintain muscle mass during exercise.
A number of previous studies suggested that around 1.0 – 1.4 grams per kilo of bodyweight per day is plenty, but given the observation that higher volumes of endurance training can lead to a loss of lean muscle tissue, resulting in reduced strength and increased injury risk.
Researchers set about studying nitrogen balance in 10 female cyclists and triathletes who were training for an average of 11 hours per week and who followed two different diets:
- A “normal protein” diet supplying around 1.4 grams per kilo per day.
- A “high-protein” diet containing exactly the same number of calories but supplying 2.7 grams per kilo per day.
During both of these diets, the cyclists’ and triathletes’ nitrogen intake from food/drink and losses via sweat, urine and faeces were carefully measured – rather than simply being estimated, as is normally the case in nitrogen balance studies. It turned out that while eating the high-protein diet, the women were in positive nitrogen balance.
On the normal protein diet however, they were in negative balance, meaning they were losing muscle tissue. The researchers then calculated that to achieve a neutral balance (i.e. to meet their protein needs), the women needed to consume at least 1.6 grams of protein per kilo of bodyweight per day.
Protein and Performance
The balance of more recent evidence again suggests that endurance athletes not only need more protein than sedentary folk, but also that the oftenquoted guidelines for endurance athletes (1.0 – 1.4g of protein per kilo of bodyweight per day) are insufficient to maintain optimum nitrogen balance.
But does a slight shortfall in protein intake really matter when it comes to performance? The evidence says yes – it does!
Researchers investigated whether a high-protein diet (3.0g per kilo of bodyweight) could boost immunity and reduce the incidence of upper respiratory tract infections (URTIs – i.e. coughs, colds, sore throats, flu, sinusitis and so on) in well-trained cyclists undergoing periods of heavy training(11).
When the cyclists consumed a standard protein intake (1.5g per kilo), increasing the training load produced a significant drop in the immune function. When the cyclists were on the high-protein diet and increased their training loads however, their immune function did not suffer, and remained just as potent as when they were training at normal intensity.
More tellingly perhaps, when the cyclists consumed a high-protein diet and trained hard, they reported significantly fewer URTI symptoms compared to training hard on the lower-protein diet.
In another study, New Zealand scientists examined the effect of giving 2.8g of protein per kilo of bodyweight to trained cyclists in the 4-hour recovery period after completing 2.5-hour high-intensity rides on consecutive days.
After 4 days of consecutive rides, the cyclists’ ability to perform sprints was 4.1% greater when they had consumed post-ride protein compared to consuming carbohydrate only.
The researchers concluded that that athletes involved in several consecutive bouts of hard exercise over a period of a few days could benefit from an increased protein intake over and above the 1.0 – 1.4g per kilo amounts often cited in past guidelines.
In another study relevant to those who have to train and/or race on consecutive days, scientists investigating cycling performance showed that consuming a leucine-rich protein drink following intense training on consecutive days significantly enhanced the subsequent high-intensity endurance performance of the cyclists and also reduced exercise-induced muscle damage.
Importantly, the researchers believed it was the leucine (from the whey protein in the drink) that provided these benefits because, when the drink was not given and extra (non leucine-rich) protein was given in the diet to compensate, no benefits were observed.
‘Nitrogen balance’ refers to the balance of protein intake and protein loss in the body. The term nitrogen is used because all proteins contain nitrogen in their structure – unlike carbohydrates and fats, which contain carbon, hydrogen and oxygen.
A “positive nitrogen balance” means that more protein is being absorbed than is being broken down and excreted, and is associated with an increase in muscle tissue – i.e. muscle and strength gains.
A negative balance means that more protein in the body is being broken down and excreted than is being absorbed – associated with a loss of muscle tissue and a decrease in strength.
A neutral balance means that protein uptake exactly matches that being lost. During periods of intense or high-volume training, many athletes move from neutral nitrogen balance into negative balance, which if prolonged, can increase the risk of illness and injury.
Practical tips on protein use
- Aim to consume around 1.4 – 1.6g of protein per kilo of your bodyweight per day. Keep at the high end of this range during high-volume and/or intense training.
- Take a small amount (10-20g) of protein 30 minutes or so before training, which helps reduce muscle damage during exercise.
- Use a recovery drink containing whey protein immediately after training – whey is rapidly absorbed and rich in leucine, which helps stimulate muscle recovery and growth.
- Rather than consuming a large quantity in one go, consume around 20g of protein immediately after training then another 20g an hour and a half to two hours after training – the staggered intake maximises protein uptake by muscles.
- Consuming a milk protein (slow-releasing protein) drink at bedtime can help keep you in positive nitrogen balance while you sleep, and so accelerate recovery.
- If you struggle to maintain lean body mass as training volume increases (i.e. you have a very slim,
wiry build), try using energy drinks with 20% added whey protein during training (protein-energy drinks).
- Don’t forget that ample carbohydrate is as important as ever for all endurance athletes!