It seems that no matter where I look these days, I see the word ‘protein’ being used as a marketing buzz word on food packaging. From cereals, yoghurt, milk and muesli bars to chips, coffee and bottled water, not to mention all the protein powders lining the shelves! Food manufacturers are cashing in on the craze, sales of whey protein apparently skyrocketing.
Boosting protein intake is now being heavily promoted as the key to optimal health and longevity. Consuming more protein is claimed to control appetite and cravings, promote weight loss, boost metabolism, increase muscle mass, and improve bone health.
Whilst some health claims have evidence to support them, one would assume that given the hype, our diets are lacking in protein, and we need to eat more of it. But do we really need more protein, is it possible to overdo it and which sources are best for our health?
The role of dietary protein in health
In addition to carbohydrate and fat, protein is one of the three essential macronutrients we require from our diet to thrive.
Protein is made up of building blocks called amino acids of which there are 20 in total, 9 being essential (can’t be made by the human body and must be obtained from diet) and 11 which are non-essential (can be made by the human body and not required from diet).
With the addition of weight bearing exercise, protein is well-known for its role in building and maintaining muscle mass, hence the popularity of protein powders with body builders and gym goers.
Protein is also critical for growth and maintenance of other tissues, providing structure to skin, hair and nails, assisting with nutrient transport, maintaining pH balance, aiding chemical reactions, supporting immune function, hormone and neurotransmitter production.
Dietary protein sources
Although the word ‘protein’ is often synonymous with meat, it may surprise you to learn that protein is also found in appreciable amounts in most foods including all minimally processed plant foods e.g., vegetables, legumes, wholegrains, nuts, seeds and to a lesser extent fruits. See Table 1 below for examples of high-protein animal and plant foods.
Table 1: Examples of high-protein animal and plant foods
| High protein animal foods | Approximate protein/100g/ml |
| Beef (cooked) | 26g |
| Chicken (cooked) | 27g |
| Salmon (cooked) | 20g |
| Eggs (cooked) | 12.2g |
| Dairy milk | 3.5g (depending on brand) |
| Cheddar cheese | 25g (depending on brand) |
| High protein plant foods | Approximate protein/100g/ml |
| Tempeh (cooked) | 12.6 – 15g (depending on brand) |
| Tofu (cooked) | 9 – 14.5g (depending on brand) |
| Lentils, beans, chickpeas (cooked) | 6-9g |
| Soy milk (fortified) | 3 – 4.2g (depending on brand) |
| Rolled oats (cooked) | 2.5-3g |
| Quinoa (cooked) | 4g |
| Hemp seeds (raw) | 32g |
| Cashews (raw) | 17g |
Protein digestion and absorption
Our body continuously breaks down and loses protein as it cannot store amino acids. To replace protein, we must eat and absorb it from our food.
When we consume protein, it is broken down by digestive enzymes in our digestive tract into individual amino acids. Amino acids are then absorbed by intestinal cells in the small intestine where they are used for energy production or to synthesise required compounds.
Amino acids that are not immediately required are transported across the cell membrane and into the bloodstream for use in cells in other regions of the body.
Recommended protein intake
According to nutrition experts, protein should represent between 10-25% of total daily energy intake. In a 2000 calorie/day diet, protein requirements would represent between 200 to 500 calories, or 50 to 125g protein/day. Note: protein provides 4 calories/gram.
Individual protein needs are based on body weight. For healthy Australian adults, minimum daily protein requirements are as follows:
RDI men (aged 19-70 years): 0.84g per kg per day, equivalent to approximately 64g protein per day for a healthy weight male.1
RDI women (aged 19-70 years): 0.75g per kg per day, equivalent to approximately 46g protein/day for a healthy weight female.1
Older adults, athletes and pregnant and lactating women may benefit from additional protein to help maintain muscle mass, growth and recovery.
The following is a guide for these groups:
Older adults – to help prevent age-related muscle loss aim for 1.0–1.2 g/kg/day, up to 1.5 g/kg/day for those who are frail or recovering from illness.1
Athletes – protein needs vary by training type, but range between 1.2–1.7 g/kg/day.2
Pregnancy – protein needs increase gradually, aim for 1.0g/kg/day in the 2nd and 3rd trimester.1
Breastfeeding – depending on the stage of lactation, aim for 1.1g/kg/day.1
How do I calculate my protein intake?
If you are curious about your protein intake, I suggest using a free app like Cronometer to record your food intake over several days. The app will provide you with a summary of your total daily protein intake, plus carbohydrate, fat, total energy intake, and various micronutrients.
How much protein are we consuming?
Most people in high-income countries meet or exceed their daily protein requirements by consuming the typical Western diet. It is estimated that the average protein intake in Western countries is at least 150% of recommended values.3
In countries like Australia, the UK and US, adults typically get between 1.1 and 1.3 g/kg/day.4 This is mainly due to higher intakes of animal-based foods, 65% of protein coming from animal-based sources e.g., meat, poultry, fish, eggs and dairy and just 35% from plant-based sources.4
Research suggests that this animal-to-plant protein ratio (A:P) is not ideal for human or planetary health with a “healthy protein transition” towards 50:50 or 40:60 recommended.4
What happens if I under or overeat protein?
Inadequate protein intake or an energy deficit may force the body to use amino acids as fuel, leading to malnutrition, poor growth in children and weight loss and muscle wasting in adults.
Although protein deficiencies exist in certain countries including Africa, Central and South America and parts of Asia due to limited access to nutrition, protein deficiency is incredibly rare in Western countries. Here people at risk of protein deficiency may include the chronically ill, the elderly living alone, people living in poverty, and adults living with drug and alcohol addictions. Dietary intake of protein should be monitored in these circumstances.
Protein consumed in excess of needs is excreted from the body as waste or stored as body fat. Excess protein consumption offers no advantage, and evidence suggests that overconsumption of animal protein may pose health risks.
High animal protein diets are implicated in multiple chronic diseases including heart disease, cancer, Crohn’s disease, ulcerative colitis, osteoporosis and kidney stones.
A diet excessively high in protein can displace foods that would otherwise be present in a healthy balanced diet including complex carbohydrates from whole grains, vegetables and fruits. In our pursuit of increasing protein intake we may also inadvertently increase energy intake, leading to weight gain.
Can plant protein sources meet nutritional needs?
Despite what you may have been told, a well-planned plant-predominant or exclusive diet can fully meet our nutritional needs, at all life stages, from birth to old age and including athletes, growing children and teenagers, pregnancy and lactation.
Assuming you are consuming sufficient energy and a broad range of different plant foods every day you can easily meet your daily protein needs with plant foods, without the addition of traditional protein sources like meat, poultry, fish, dairy or eggs.
Are plant proteins ‘high quality’ proteins?
You may have heard that plant proteins are ‘incomplete’ or ‘low quality’ compared to animal proteins which are often described as ‘complete’ or ‘high quality’. This is because animal protein contains all 9 essential amino acids in a similar composition to human flesh.
However, did you know that plant proteins also contain all 9 essential amino acids? The only difference is that the amino acids found in plants are found in different proportions to animal protein, hence why we need to eat a variety of plant proteins to meet our amino acid requirements. This is not difficult in a well-planned plant-based diet.
For example, some plant proteins like soy, hemp, quinoa and buckwheat have amino acid profiles similar to animal protein whereas grains tend to be lower in lysine and legumes tend to be lower in methionine. However, if we eat a mixture of beans and grains, they combine perfectly to meet our protein needs.
You may also have heard that plant proteins are less bioavailable compared to animal protein, meaning the body absorbs and uses them less efficiently than animal protein. These concerns are based on out-dated animal studies and don’t reflect how we consume protein, as part of cooked, mixed meals.
When you consume an adequate variety of whole grains, legumes, vegetables, nuts and seeds your body gets all the essential amino acids it needs and uses them efficiently. More recent research shows that, within a well-planned plant-based diet, protein bioavailability is not a meaningful limitation.
Is plant protein better for our health?
In addition to helping us meet our protein requirements, minimally processed plant foods have the added benefit of helping us reduce our risk of chronic disease.
Research shows that eating a diet rich in plant foods is linked to a lower risk of developing some of the top killers in the Western world – heart disease, high blood pressure, type 2 diabetes, obesity, and certain cancers.5
These benefits come from including more of the health-promoting compounds found in plant foods including fibre, antioxidants and beneficial phytochemicals, and less of the health limiting components from animal foods including saturated fat, haem iron, TMAO (trimethylamine-N-oxide), and certain cooking by-products such as heterocyclic amines (HCAs), polycyclic aromatic hydrocarbons (PAHs), and advanced glycation end products (AGEs).
In summary
Protein is a vital macronutrient for human health, with most Australians easily meeting or exceeding their daily protein requirements with a typical Australian diet.
For athletes and pregnant and lactating women, protein requirements are increased, but this is usually taken care of by increased appetite from physical activity, growing a baby and milk production.
As we age, ensuring protein intake is slightly above the RDI, in addition to regular weight bearing exercise may help mitigate age-related muscle, strength and bone loss. Simply adding more protein to your diet won’t grow muscle or bone unless you are also adding resistance training. Now is the time to join the gym or create a home routine with dumbbells and resistance bands.
Our current obsession with protein could be driving us further towards chronic disease and environmental degradation if it results in an increased intake of animal protein and highly processed ‘high protein’ powders and food products. Don’t fall for the marketing hype!
To continue to meet protein requirements, lower chronic disease risk and support planetary health, choose healthy plant-based protein sources over animal protein sources where possible. Your body, the planet and the animals will thank you.
See below for my top tips on how to increase your intake of plant protein.
Tips for increasing plant protein intake
- Swap all or some beef mince for beans or lentils in your Bolognese or taco mix.
- Swap all or some chicken for chickpeas in your curry.
- Swap all or some pork for tofu in your stir-fry.
- Try tofu scramble instead of scrambled eggs.
- Add beans, lentils or grated tofu to soups, stews, or pasta sauces.
- Add ½ cup of canned beans to your daily salad.
- Sprinkle hemp, chia or flax seeds on your cereal or add to smoothies.
- Swap dairy milk for calcium fortified soy milk in your cereal, smoothies, tea/coffee.
- Try hummus or peanut butter on your toast vs avocado, jam or vegemite.
- Try pulse pasta instead of wheat or GF pasta.
- Make a tahini-based dressing for your salad vs oil-based dressing.
- Snack on edamame, hummus or unsalted nuts.
- When dining out explore ethnic vegetarian cuisine – think Indian dals, Asian dishes with tofu, Middle Eastern falafel and hummus etc.
References
- Protein | Eat For Health
- The effect of protein intake on athletic performance: a systematic review and meta-analysis – PMC
- Protein production: planet, profit, plus people? – PubMed
- The protein transition: what determines the animal-to-plant (A:P) protein ratios in global diets – PubMed
- Associations between plant-based dietary patterns and risks of type 2 diabetes, cardiovascular disease, cancer, and mortality – a systematic review and meta-analysis – PubMed
