Protein for endurance athletes: the part of fuelling runners skip

Endurance nutrition advice is almost entirely about carbohydrate: carb loading, gels per hour, what to eat at 4am before a marathon. Protein gets left to people who lift. But a week of long runs or big rides breaks down and rebuilds a lot of muscle. The research now suggests endurance athletes need more protein than the old guidelines said. Here is how much you need, when to eat it and where it does not belong.

Why endurance training needs protein at all

Two things happen during long sessions. A small share of your energy, usually estimated at a few percent, comes from burning amino acids. That share rises when glycogen runs low late in a session. Then, after the session, your body spends the next day or two repairing muscle fibres and building the extra mitochondria that make you fitter. Both draw on protein.

If protein intake is short, you can still finish the sessions. What suffers is how well you absorb them: slower recovery between hard days, more lingering soreness and less adaptation from the same training load.

How much protein do endurance athletes need?

Start with the floor. The Australian Recommended Dietary Intake is about 0.84g per kilogram of body weight for men and 0.75g/kg for women. That prevents deficiency in people who do not train. It is too low for anyone running or riding most days.

The joint position statement from the American College of Sports Medicine, the Academy of Nutrition and Dietetics and Dietitians of Canada puts athletes at 1.2 to 2.0g/kg per day. For endurance specifically, the long-standing advice sat at the lower end of that range, around 1.2 to 1.6g/kg.

A practical way to use this: 1.4g/kg on easy weeks, up to 1.8g/kg in heavy blocks or when you are trying to lose weight while training.

1. 60kg runner, 40 to 50km a week. 60 x 1.5 = about 90g a day.
2. 70kg marathoner in a build. 70 x 1.8 = about 125g a day.
3. 80kg cyclist riding 10 to 12 hours a week. 80 x 1.6 = about 130g a day.

When to eat it

For endurance athletes timing matters almost as much as the total, because recovery is happening for most of the day after a big session.

• Spread it out. Aim for about 0.3g/kg per meal, which is 20 to 25g for most people, every three to four hours.
• After key sessions. Within about two hours of a long run, a hard interval session or a big ride, have 20 to 30g of protein together with carbohydrate.
• Before bed on big days. Studies using 30 to 40g of slow-digesting protein before sleep found more overnight muscle building. Greek yoghurt or milk both work.

What about protein during a race?

This is where carbohydrate clearly wins. When you are already taking in enough carbohydrate, adding protein during a race or long ride has not been shown to improve performance. It is also harder on the stomach at race effort. Spend your fuelling budget on carbohydrate: around 60g an hour for most events and up to 90g an hour beyond two and a half hours, if you have trained your gut for it.

If you want the detail, read do energy gels actually work? and our hour-by-hour Sydney Marathon fuelling plan.

A note on amino acid products. AminoVITAL 2500 is a carbohydrate gel first, with 24g of carbohydrate and 2500mg of amino acids in a sachet. Use it as race fuel. It does not replace protein after the session.

Three groups who need to pay more attention

• Plant-based athletes. Most plant proteins contain less leucine, the amino acid that switches on muscle building. Use slightly bigger servings of around 30 to 40g. Soy and pea perform best. A yohemite Daily Protein Shake has 22g of pea-based plant protein.
• Masters athletes. From about 50, muscle responds less to the same dose of protein. Research in older adults suggests about 0.4g/kg per meal, which is closer to 30g for most people.
• Anyone under-eating. Protein cannot do its job if total energy is too low. Persistent fatigue, frequent illness, stress fractures or missed periods can all be signs of low energy availability, which the Australian Institute of Sport calls RED-S. That needs a GP or an Accredited Sports Dietitian, not more protein.

A long-run day, laid out

Here is roughly 125g across a Sunday for a 70kg runner doing a 28km long run.

1. 6am, before the run: mostly carbohydrate. Toast with honey and a banana. About 8g of protein.
2. During the run: a gel every 30 to 40 minutes. No protein needed.
3. Straight after, in the car: a shelf-stable chicken pack from the kit bag with a carbohydrate drink or a sandwich. About 30g.
4. Lunch: rice, eggs and vegetables. About 30g.
5. Afternoon: a protein shake or yoghurt. About 20g.
6. Dinner and before bed: fish or meat with potatoes, then a glass of milk. About 40g.

The post-run slot is the one most runners miss, because it happens in a car park with nothing to eat. A Tuk-Dak pack with 24 to 26g of protein lives in a kit bag for months without a fridge, which is exactly why runners use it.

The short version

• Endurance athletes need well above the Australian RDI. Plan on 1.4 to 1.8g/kg a day.
• Spread it across the day in doses of about 0.3g/kg. Do not skip the meal after key sessions.
• During races and long sessions, carbohydrate does the work. Save protein for afterwards.
• Plant-based and masters athletes need bigger servings per meal.
• If you are always tired or often injured, check total energy intake before adding protein.

Sources: Thomas, Erdman and Burke, ACSM, Academy of Nutrition and Dietetics and Dietitians of Canada joint position statement (2016). Jäger et al., International Society of Sports Nutrition position stand on protein and exercise (2017). Kato et al., Nutrients (2016). Australian Institute of Sport, RED-S position statement. NHMRC Nutrient Reference Values for Australia and New Zealand.