Protein is essential for our bodies to function - but how much should we eat? And how worried should we be about eating the wrong amount? The answer gets a little complicated. By Hatty Willmoth.

Protein powders, protein shakes, protein bars, protein balls, protein yoghurt, protein chocolate pudding... Take a look at the foods arriving on supermarket shelves right now, and you may think the world has gone protein mad.

But is there method behind the protein madness? Do our bodies benefit when we guzzle as much protein as possible, or should we put the shake down, take a deep breath and chill out a bit?

The short answer is, it’s somewhere in between; the long answer gets a little complicated.

That’s because studies disagree about the ideal amount of protein each of us should eat. And, the line at which ‘more’ is no longer ‘better’ depends on a multitude of factors such as age, sex, and activity level. But eating either not enough or too much protein can cause problems.

Let’s break it down.

What is protein?

Protein is vital for our bodies to function.

Katie Shore, a registered nutritional therapist and module coordinator at the Institute for Optimum Nutrition (ION), says: “Protein is one of the major macronutrient groups we all need to be eating every single day, and at every single meal.

“Protein provides us with the essential building blocks for all of our cells, tissues, muscles and organs. The phrase ‘you are what you eat’ can literally apply to protein.”

But protein is not just one thing; it’s a large category of substances called amino acids, which contain nitrogen.

Shore says: “Proteins are made up of amino acids – think of proteins like a string of pearls, with each amino acid being an individual pearl. There are 20 amino acids and nine of these are classified as ‘essential’ which means we must get them from [our] diet.”

A food that contains all of these essential amino acids is called a ‘complete’ protein – but ‘incomplete’ proteins are still proteins too.

What happens if you don't get enough protein?

Since protein is so fundamental to the healthy functioning of our bodies, it is perhaps unsurprising that not eating enough can be bad news.

Shore says: “Eating too little protein can have detrimental effects on our health. Slower healing, compromised immunity, lower bone density (which [can be an issue] as we age) and even muscle wastage can be some of the longer-term effects of protein deficiency.

“On a day-to-day level, people may feel hungry all the time and find their hair, skin and nails are looking dull, weak and lacklustre.”

However, Shore also says that this isn’t usually an issue in the West where we have access to plenty of protein, and the British Heart Foundation says that the average person in the UK eats almost double the protein they need to function.

Satiety and protein hunger

Protein is the most satiating macronutrient; that means it’s better than carbohydrates and fats at making us feel full.

It follows that protein can be helpful for those wishing to regulate how much food they’re eating; once full up on roast chicken, we may not feel the need for dessert.

In fact, some scientists think that ‘protein hunger’ could be a major driving force of Western obesity rates.

A study published in the British Journal of Nutrition, back in 2012, suggested that protein could be the answer to the obesity crisis.

Researchers explained that healthy weight management was dependent on people feeling full despite consuming fewer calories, and that high protein diets could help achieve this.

First put forward in 2005, the ‘Protein Leverage Hypothesis’ suggested that bodies have a strong appetite for protein and actively seek it out.

Yet, because the Western diet is increasingly made up of highly processed foods that are low in protein, people are compelled to eat more food before they reach their body’s protein target.

This hypothesis has been corroborated by multiple recent studies. For example, in November 2022, researchers at the University of Sydney found a link between eating more protein and eating less food overall.

Observing 9,000 Australian participants, those that got a higher proportion of their daily calories (food energy) from protein tended to consume fewer calories in a single day.

This effect was particularly pronounced if participants ate protein-rich meals earlier; those who started their days with low-protein foods tended to consume more calories throughout the rest of the day.

And researchers from Rutgers University, USA, found in June 2022 that dieters who ate slightly more protein made better food choices across the board.

Author Professor Sue Shapses said: “It’s somewhat remarkable that a self-selected, slightly higher protein intake during dieting is accompanied by higher intake of green vegetables, and reduced intake of refined grains and added sugar. But that’s precisely what we found.”

So, it’s important that we get enough protein for our bodies to function properly, and it seems to be beneficial to eat higher quantities for optimal health. But how much is ‘enough’?

How much protein should I eat?

Shore says: “Protein requirements vary by age, sex, activity level and life stage, so blanket numbers (I find) are generally unhelpful.

“It has recently been suggested that our current reference nutrient intake (RNI) set by Government should be considered as benchmarks for disease prevention rather than optimal health.

“The current RNI for protein is set at 0.75g of protein per kg bodyweight per day for average-weight adults.”

She explains that this would equate to approximately 56g of protein per day for men and 45g of protein per day for women, depending on bodyweight.

But for optimal health, plenty of evidence indicates that eating more protein than this could be beneficial.

In a 2016 review, for instance, authors recommended protein intakes of at least 1.2-1.6g per kg bodyweight per day (g/kg/d) – that’s more like 80-110g per person per day – and higher numbers for those with greater protein requirements.

And a 2018 review suggested that dietary guidelines should be adjusted for different groups, stating that individuals needed vastly different quantities of protein based on “various factors, such as age, health status and physical activity level” which were “not reflected in current recommendations for the general population”.

For older people, for instance, some reviews recommend a daily protein intake of at least 1g/kg/d, while up to 1.5g/kg/d has been suggested for pregnant or breastfeeding women; double the RNI.

People who lead active lifestyles may benefit from more protein too, especially if their training is intense and focused on building muscle. Weightlifting, for example, generally requires more protein than running.

Separate studies suggest different amounts for active people and athletes, ranging from 1.2g/kg/d to a whopping 3g/kg/d, but much of the research suggests a peak protein intake of about 1.5g/kg/day.

So, it’s complicated, it’s personal, and the experts disagree.

Not all protein is created equal

But it gets even more complicated, because each source of protein has different pros and cons.

Shore says: “[RNIs] can be confusing because when we look at the volume of protein different foods contain it varies by food type.

“For example, one serving of salmon contains on average 22g of protein, with quinoa coming in at 8g (per cup of cooked quinoa) and one large egg averaging 6g of protein.”

In general, animal sources such as meat, fish and cheese tend to contain higher amounts of protein than plant sources such as lentils and nuts.

And it’s not just that protein quantities vary, but that our bodies handle protein differently depending on where it’s come from.

Protein from meat and animal products, for instance, is very ‘bioavailable’ (meaning our bodies find it easy to extract and use) compared to plant proteins.

Therefore, if you eat meat and animal products, you are likely to find it easier to fulfil your protein quota than people who get their protein from plants.

In fact, one French paper about men and women over the age of 65 argued that older people should prioritise animal proteins in order to avoid deficiencies of protein – and also of iron, zinc, and vitamins D and B12.

But we don’t need to get our protein from meat and animal sources. Plenty of people stick to plant-based diets for all manner of reasons and manage to consume a good amount of protein.

And there is a great deal of evidence pointing to the benefits of eating less meat and more plants.

Shore says: “Often we think protein always needs to equal meat. This isn’t the case and there are many different types of plant-based proteins that can be added to our diets and are tastier than we think.

“Lentils, pulses (beans, chickpeas, etc.), dips and even vegetables like peas or edamame beans are brilliant sources.”

For those who struggle to consume as much protein as they need, supplementation can be a practical and effective solution, but Shore says: “I advocate a food-first approach in the first instance.”

She says it’s important to “focus on the quality of the food not just the quantity” and adds: “Research has shown that higher welfare meat has an increase in nutritional benefits compared to those kept in poorer living conditions.”

Change up your protein sources

Another thing to consider is the completeness of the protein, i.e. whether it contains all the essential amino acids.

As a general rule, animal proteins are complete and plant proteins are incomplete, so anyone avoiding meat products needs to combine different foods to get all the essential amino acids.

However, there are exceptions such as quinoa, tofu, and tempeh: all of these are complete proteins and vegan.

Shore says there’s no need to worry too much about amino acids, as long as we eat a good range of foods.

She says: “Ensuring we have lots of variety of protein sources from both plants and animals is one way to ensure you get a wide range of protein.

“Unless you have a specific health concern or you’re in training for an athletic event, then monitoring specific amino acids isn’t necessary – in which case, I’d recommend working with a dedicated NT [nutritional therapy practitioner] who has knowledge of this and can guide you.”

What happens if you eat too much protein?

So, we’ve established that we need to eat enough protein, and that it’s best to eat a good variety – but can we overdo it?

What if, inspired by Gaston from Beauty and the Beast (arguably the most muscular of Disney characters), someone were to eat four dozen eggs for breakfast, a selection of steaks for lunch, and a buffet of beans for dinner, all washed down with a generous bucketful of protein shake?

Well, they may not end up ‘roughly the size of a barge’ (like Gaston) overnight. The amount of muscle they would build would depend on their workout, and any protein their body did not use – in this case, the vast majority – would be excreted in their urine.

If this became a habit, it could have harmful consequences.

Shore says: “On the opposite side of the coin, eating too much protein can also adversely affect your health by causing digestive upset (either constipation or diarrhoea), dehydration and bad breath.

“In more extreme cases, extreme protein intake can also cause kidney damage, which is why I recommend keto and paleo diets are attempted when under professional supervision like working with an NT.”

There is also some evidence that high protein diets – particularly those containing ample red and processed meat – may be linked with elevated risk of heart disease, osteoporosis and kidney disease, although some reviews dispute this on the grounds of insubstantial evidence.

What should we do?

It can be easy to obsess over whether you’re eating the right amount of protein – particularly if you’re someone who needs more protein than others.

But Shore says there’s no need to stress: “Being conscious about protein intake is the best way to ensure you’re eating enough.

“I don’t recommend everyone carry a calculator with them, but instead aim to eat a portion of protein at each meal and with each snack.

“This could look like: ½ cup of full fat Greek yoghurt at breakfast with a small handful of berries and pumpkin seeds, grilled salmon or tofu salad with quinoa for lunch, and a chicken and vegetable curry in the evening with brown rice.”

Shore advises that we try to eat a good amount of protein at every meal and, if snacking, “[focus] on high protein snacks, e.g. boiled eggs, hummus and crudities, or even a small block (matchbox sized) of cheese.”

She recommends using the BANT wellbeing guidelines as “a great visual guide”. This suggests trying to fill roughly a quarter of your plate with protein, but you may need more than this on a plant-based diet.

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