Lately, I’ve seen a fair few articles raising concerns over the amount of protein in our diets. In fact, I googled “Are we eating too much…” and the most popular predicted next words were “protein” and “meat”. Are we really eating too much protein? How much do we really need? Do some people need more? Does it really damage our kidneys and bones and give us cancer? Here’s the lowdown on all things protein-based.
Quality AND quantity
Protein is one of the three macronutrients (the other two being carbohydrate and fat). It’s made up of smaller units called amino acids, of which there are around 20, with 9 being essential in the diet as our body cannot make them itself. Protein has various functions, making up a large part of the body’s lean muscle tissue, playing a vital role in bone structure and also folding into tiny structures known as enzymes, without which our body’s metabolic processes would not be possible. Protein is an essential macronutrient.
The current reference nutrient intake (RNI) is 0.75g per kg body weight a day, though in 2012, the European Food Safety Authority set this population requirement at 0.8g/kg bw/d. In real terms, if you weigh 60kg, that means you need around 45g protein a day. This is easily achieved through most diets and in the UK, we generally eat more than this. Bear in mind, however, that this figure is actually a minimum requirement and the method for determining this level has been questioned. It is argued that this figure may actually be too low to promote population health.
It’s important to also consider protein quality as well as quantity. Animal protein from meat, fish, eggs and dairy provides all the essential amino acids so is said to be of higher quality than most plant proteins (e.g. from nuts, seeds, pulses or grains), with the notable exception of soya, which is also what’s known as a complete protein. That’s not to say you can’t get all the essential amino acids through a vegetarian or vegan diet. You just need to combine your protein sources, so try to eat a balance of pulses, nuts, seeds, soya (milk, beans or tofu) and grains.
One of the most important essential amino acids is leucine. It is a potent stimulator of muscle protein synthesis which is of importance in situations where muscle loss may be a risk e.g. in ageing and critical illness. Leucine is present in all sources of protein, both plant- and animal-based with larger amounts being present in meat, fish, eggs and milk products.
Is the RNI enough?
If you’re under 50, exercising moderately 2-3 times a week and not trying to lose weight, the RNI should cover your protein needs adequately. But some population groups may have higher requirements.
If you exercise a lot, your protein requirements may exceed the RNI. The International Society of Sports Nutrition (ISSN) recently published their position stand on protein and exercise. They recommend active individuals consume 1.4-2.0g protein per kg body weight per day, with endurance athletes at the lower end and strength athletes towards the higher figure. For example, endurance athletes who consumed protein (0.25g per kg body weight per meal) with carbohydrate during exercise show fewer signs of muscle damage after training. Therefore protein, as well as carbohydrate, plays a vital role in recovery from endurance exercise which is especially important if you train daily with only a short time to recover.
For strength athletes and people who regularly perform resistance training (i.e. lifting weights to failure more than 3 times a week or for those with heavy manual jobs, NOT someone who does the odd body pump class), protein requirements are likely to be at the upper end of the ISSN recommendation. Ideally, protein should be consumed at regular intervals throughout the day, providing 0.25-0.4g per kg body weight, per meal, as well as 20-40g protein post-workout, with the upper end being relevant if a full body workout has been performed.
In weight management, it may also be advantageous to consume a higher protein diet. While all diets work by restricting calorie consumption, those that are the most successful and sustainable are the ones that permit slow and steady weight loss with the best preservation of muscle mass, which is more metabolically active (effectively helping to keep the metabolic rate up during times of calorie restriction). Higher protein diets, particularly when combined with resistance training, have been shown in several meta-analyses to be successful in reducing body weight, body fat and waist circumference, while preserving lean body mass when in calorie deficit. To best preserve lean mass, it’s recommended that 1.8-2.7g protein are consumed per kg body weight per day, with a calorie deficit of around 500kcal below requirements for weight maintenance, and participation in resistance exercise. The caveat is that the diet can only be successful if it is sustainable for the individual. Clearly, what works for one person may be a living hell for another, so it’s important to be flexible with recommendations when it comes to weight management.
As we age, we experience a loss of muscle mass and muscle strength from around the age of 40. We can lose around 0.8% of muscle mass a year but around 2-3% of muscle strength and this has been linked to an increased risk of type 2 diabetes, cancer, metabolic syndrome and reduced mobility. This loss of muscle mass and strength is thought to be due to reduced muscle protein synthesis in response to consuming protein or doing resistance exercise, combined with potentially more muscle protein breakdown. There is currently no recommendation for protein intake in older people, beyond that set for adults but evidence suggests a figure of 1.2g/kg bw/d may be beneficial in reducing muscle loss over time, particularly if combined with resistance exercise. In practical terms, this is equivalent to around 25-30g good quality protein per meal, including a good source of leucine. This is a population group for whom reduced appetite can be an issue, meaning that it can be hard to achieve sufficient nutrients for health promotion. Some older people may therefore benefit from a protein supplement, as long as this is combined with other nutritious foods, for example, at breakfast, which is often lacking in protein. Recent experimental evidence suggests benefits to muscle mass and strength from daily use of a fortified protein supplement but clearly, it’s important to also eat a balanced diet.
What does this mean in practical terms?
Anita Bean’s fantastic article on protein supplements shows how much protein can be found in typical portion sizes of various foods
20g protein can be found in:
For 10g protein, try:
A 60kg active individual combining intensive resistance training and cardio, might require up to 120g protein a day, while an older individual may need around 72g, more if they are active. It possible to achieve these levels through a varied diet but very active people and those with small appetites (such as older people or those who are unwell) may consider a protein supplement to boost their intake. There’s nothing wrong with this but as protein supplements are low on nutrients other than protein, it’s a good idea to combine them with other foods to improve the nutrient density.
Breakfast is typically a low protein meal with toast or cereal offering scant levels of protein. It’s therefore an ideal time to consider introducing protein in the form of eggs, Greek yoghurt or nuts. If you are thinking of using a protein supplement, you could add it to smoothies, overnight oats or porridge so you still deliver a nutrient dense meal at breakfast time.
Can too much protein be harmful?
To support healthy weight loss, consuming amounts of protein up to 2.7g/kg bw/d may be recommended, while in calorie deficit, for preserving lean mass. However, consuming protein in excess of this recommendation is unlikely to yield further benefit.
Concerns that high protein diets or diets containing dairy products, cause a loss of calcium from bones are unfounded and such diets may in fact be beneficial for bone health, particularly if a diet rich in calcium is also consumed. Moreover, there is no evidence to suggest that high protein diets can induce kidney damage in those without existing renal insufficiency. This conclusion is actually supported by the World Health Organisation and Institute of Medicine.
While some observational studies appear to find an association between a higher protein intake and risk of both cancer and type 2 diabetes, it’s important to stress that these studies do not identify a cause and effect relationship. There are many confounding factors that have not been addressed, such as quantity of physical activity and crucially the protein quality, with processed and unprocessed meat being grouped together. There’s clearly a large difference between eating fried sausages and grilled chicken breast! While we should be consuming largely plant-based diets for health and environmental reasons, responsibly sourced and reared, lean animal products can still form part of a healthy balanced diet.
There is a lot of misinformation surrounding the consumption of meat and dairy products. “What the Health” is a film that examines the negative health effects of animal products. Its bad science and sensationalist approach has been critically reviewed, many times, even by a vegan dietitian. In reality, there are both healthy and unhealthy versions of vegan, vegetarian and omnivorous diets. Of course, if you do choose to consume animal products, it is important to ensure that you source them from suppliers with strong animal welfare credentials and broadly stick to lean sources of animal protein.
There are some rare genetic disorders that require a low protein diet such as phenylketonuria or urea cycle disorder, the latter of which, when undiagnosed, led to the death of a bodybuilder in Australia. Clearly, in these incredibly rare cases, a high protein diet would not be advised.
Without a doubt, we have a duty to our environment to eat in a sustainable way. The meat and dairy industry are responsible for considerable greenhouse gas emissions and our demand for animal products shows little sign of abating and so, in spite of the evidence in support of the higher protein quality of such foods, we should find ways to reduce our intake, potentially adopting a more flexitarian approach to eating. How can you cut down on meat and dairy foods while still maintaining your intake of high quality protein?
Eating a wide range of protein sources, including both plant and animal-based proteins (if you’re not vegetarian or vegan) can have many benefits to health but clearly must also balance the need to eat and live in an environmentally sustainable way.
Moderate to high protein diets can support muscle strength and maintenance when combined with resistance training, which is of particular importance for over forties, and can also support healthy and sustainable weight reduction.
The oft quoted concerns about bone and kidney health or cancer risk in relation to high protein diets are unfounded, though as with all diet-associated health risks, more long term studies are needed. It would make sense to try to reduce our intake of processed meats and animal products that are high in saturated fat for all-round health reasons, favouring leaner cuts of meat and fish, including oily fish.
Finally, it’s very important to focus on eating a balanced diet and in your quest for protein, don’t ignore sources of unrefined, high quality carbohydrates and poly- and mono-unsaturated fats. Don’t let protein foods push out vegetables, fruits and high fibre foods. It is all about balance.