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Older estimates of 0.8g per kg of body weight are probably too low for optimal health, repair, and performance – so, asks Krista Scott-Dixon, what does modern science say?

Protein is having a moment lately.

On the one hand, high protein may be seen as ‘healthy’ and desirable. For instance, breakfast cereals advertise their protein content. Food bloggers tell us how to bake with protein powder. Advocates of paleo and low carb-type diets argue that a high-protein diet is one of the most basic human eating patterns.

On the other hand, high protein may be seen as ‘unhealthy’ and risky. Many advocates of plant-based eating tell us that we eat ‘too much’ protein, and advise us to dump animal products for health reasons.

Much like hemlines in fashion, nutrition recommendations for specific macronutrients go up and down. However, unlike fashion, nutrition isn’t simply about seasonal whims — it’s a set of scientifically grounded principles that reflects the best evidence we have to date.

As trainers and fitness professionals, we aren’t researchers or medical dietitians. We can’t prescribe or treat; we can’t run lab tests on our clients. In fact, our scope of practice limits us to making basic, general recommendations about ‘healthy diets’.

So what do we do? How do we talk about what might be a ‘healthy diet’ when it comes to protein?

First, let’s understand just what protein is

You may have heard that proteins are the building blocks for the body. Indeed, most of our physical structures are made of proteins. Proteins can create incredibly complex configurations of three-dimensional shapes that make up things like:

  • muscle tissue
  • connective tissues: ligaments, tendons, cartilage, etc.
  • skin, hair, fingernails
  • hormones and cell signals (cytokines)
  • most cell structures and organelles
  • our DNA.

Amino acids 


These complex 3-D shapes are made up of basic protein molecules known as amino acids. Amino acids are so named because they have an amine group that contains nitrogen, plus a carboxyl (-COOH) acid group and a side chain. The side chain is what gives amino acids their chemical ‘personalities’ and unique behaviours.

Humans use about 21 amino acids to make more complex proteins. We call some of those amino acids ‘essential’, meaning that we have to get them from food. Others, we call ‘conditionally essential’, which means that sometimes our bodies can make them, but at certain times (for instance, if we are sick or injured), we may need to get these from our food as well.


The 30-second article

  • Proteins make up most of our physical structures, including muscle tissue; connective tissues like ligaments, tendons and cartilage; skin, hair and fingernails; hormones; most cell structures; and our DNA.
  • These structures are made up of basic protein molecules known as amino acids, many of which we get from food
  • Animal products contain the highest amounts of protein, while beans, legumes and whole grains are the richest sources of plant-based protein
  • Older estimates of recommended protein consumption were too low, and now most experts agree that protein should make up about 25-35% of total daily energy intake – which equates to around 1 to 2g of protein per kg of body weight per day, or more.


Where protein is found

Because proteins make up many physiological structures, most foods contain at least some protein. Of course, because animals’ muscle and connective tissues are mostly protein, foods that come from those sources will contain the most protein. This includes:

  • red meat (beef, pork, lamb, wild game, kangaroo)
  • poultry (chicken, turkey, duck)
  • fish and seafood
  • other animal products such as eggs and dairy, which are also higher in protein.

While these are the most commonly eaten foods in Australia, Western Europe, and North America, other parts of the world also include other animals such as guinea pigs and other rodents, whale, seal, moose and reindeer, insects, snails, frogs, snakes, alligator and turtle as part of the animal protein roster.

When it comes to plants, the best sources of protein are where plants store nutrients – in seeds such as beans and legumes, e.g. lentils or peanuts. Soybeans are particularly high in protein, and soy products include foods such as tofu or tempeh. Many nuts and seeds and whole grains also contain protein. So how do they compare?

Protein science in the 21st century

Protein may indeed be an ancestral food, but only 21st century science is able to explore exactly how it is digested, absorbed, and used. We’re also now able to literally see specific proteins – we can look at their structure, and understand how that three-dimensional shape makes them work.

New lab measurement techniques, developed in the past decade or so, tell us that our original estimates of what constitutes protein intake may be too low.

For example:

  • Older people probably need much more protein than we originally thought, because of something called ‘anabolic resistance’, whereby their bodies are less effective at using the protein they eat to replenish and rebuild new tissues.
  • People who are seriously sick or injured (for instance, in hospital ICUs) recover more quickly if given extra protein.

Older estimates of 0.8g per kg of body weight per day (so, for a 70kg person, that would be 56g of protein per day) are likely too low for optimal health, repair, and performance.

How much should we eat?

In general, most experts suggest that for most people, protein should make up about 25-35% of total daily energy intake (calories or kilojoules). Below 10-15% and we start to see signs of malnutrition.

In terms of grams, this is closer to 1 to 2g of protein per kg of body weight per day, or even higher. For a 70kg person, this means somewhere between 70g and 140g of protein per day – or more. Importantly, a higher-protein diet is not necessarily a ‘low-carb’ or ‘high-fat’ diet. The other 75-65% that isn’t protein can be anything else: plants, higher carbs or higher fat.

Though some have suggested that high protein is unsafe, the research doesn’t support this. Some studies have given people up to 4.4 grams per kg per day for months with no ill effects. For a 70kg person, this would be 308g daily, equivalent to about 10-12 large chicken breasts a day.

In fact, studies of high-protein diets have found:

  • More protein often means more lean mass, including better bone density. This is especially important for athletes as well as older people.
  • More protein often means less body fat. People who eat more protein may stay the same weight, or even gain weight, but lose fat.
  • More protein often means better appetite control. Because protein helps release satiety hormones, people feel fuller and more satisfied when protein is higher, even if they actually eat less food.

How to help your clients do this

As fitness professionals, we need to remember the difference between researchers/experts and trainers/coaches. Researchers and experts are concerned with precision, details, and the exact amounts of things. Trainers and coaches are concerned with helping clients do simple actions consistently.

Fundamentals first


A basic, realistic, one-size-fits-most recommendation for protein intake is:

  • People should try to get 1 to 2 palm-sized portions of higher-protein foods at most meals.
  • Athletes and those looking to gain muscle mass should probably have 2 palms per meal, and focus on doing this more consistently.
  • Consistency and frequency are more important than getting the ‘perfect’ amount.

You can make it more complicated than this if you are working with advanced clients (and are certified to do so), but there’s no need.

One of the best things you can do is to consistently educate clients about what foods are better sources of protein. Many vegetarian clients, for instance, end up eating a lot more peanut butter than they need: it may have similar protein content to steak, but it also has almost three times the energy!

Variety if possible 


Encourage clients to eat a wide variety of higher protein foods. With plant-based eaters in particular, encourage them to keep their protein roster as diverse as possible, whether that’s trying different beans, legumes and high-protein grains, or including some occasional animal products such as eggs.

Be realistic and supplement as needed


People who struggle to get enough protein from ‘real food’, or people looking for a convenient, portable, shelf-stable protein source may also benefit from supplementing with protein powder.

Dr Krista Scott-Dixon is the Director of Curriculum for Precision Nutrition. Previously, she was a professor at York University in Toronto, Canada, as well as a researcher for a public health institute. She is the co-author of The Essentials of Sport and Exercise Nutrition.


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