When speaking to people about diets, the health effects of fat and carbohydrates can often be controversial. However, most people agree that protein is an essential component of a healthy diet.
But what exactly is protein? And why is it so important for optimal health and well-being?
What is protein?
Protein is one of the three major macronutrients that make up your diet, the other two being fat and carbohydrates.
Protein is considered the building block of life and your body needs it to stay healthy and work the way it should. There are more than 10,000 types of protein in the body, found in everything from your organs to your bones, muscles and other soft tissue, skin and hair.
Proteins are made up of long chains of amino acids. 20 different amino acids exist linking together to form different proteins. The sequence in which the different amino acids are arranged helps determine the role of that particular protein.
Amongst other things, proteins play important roles in the body such as:
- Transporting molecules throughout the body, including oxygen in the blood.
- Repairing damaged cells and synthesising new ones, including wound healing and tissue regeneration.
- Making antibodies to protect the body from viruses and bacteria and fight off infections and illness.
- Promoting proper growth and development in children, teenagers, and pregnant women.
- Protein can also be used as fuel by the body, especially in the absence of carbohydrates.
Complete VS Incomplete Proteins
The quality of a protein, or its nutritional value, depends on its amino acid content, specifically its essential amino acid content, and the digestibility and bioavailability of amino acids.
As mentioned above there are 20 amino acids that make up all proteins. Of those 20, there are 9 essential amino acids. Your body can’t make the essential amino acids on its own and needs to get them from the food you eat.
The protein you consume in your diet is broken down by the body into amino acids which are then used to make new proteins for their respective uses within the body.
The amino acid profiles of protein sources differ. Animal-derived protein sources contain all the essential amino acids and are considered complete proteins. Plant-sourced proteins, except for soybeans and quinoa, only supply some amino acids and are considered incomplete proteins.
To ensure your body gets all the essential amino acids it needs, it’s important to fill your diet with a variety of protein-rich foods. People following vegetarian or vegan diets should aim to combine protein sources from plant-based foods to ensure they receive an adequate mix of essential amino acids in their diet.
Sources of Protein
Protein is found naturally in many nutritious whole foods and can increasingly be found in many processed foods. Animal-derived protein sources generally contain higher concentrations of protein than plant-derived sources.
Some whole-food sources of dietary protein include:
- lean meats – beef, lamb, pork, veal, kangaroo
- poultry – chicken, turkey, duck
- fish and seafood – fish, prawns, crab, lobster, mussels, oysters, scallops, clams
- eggs
- dairy products – milk, yoghurt, some cheese (especially cottage cheese)
- nuts and seeds – almonds, walnuts, macadamias, hazelnuts, cashews, pine nuts, pumpkin seeds, sesame seeds, sunflower seeds
- legumes and beans – all beans, lentils, chickpeas, split peas, tofu
- Some grains are also sources of protein but generally have a lower protein content.
Protein is also found in processed meats such as bacon, ham and salami, however, it is best to limit the amount of protein you obtain from these products. Some types of cheese, while still containing protein, are more highly processed and have higher fat content. Limiting the protein you get from these products is also a good idea.
Sources of Protein Beyond Whole Foods
Despite many natural whole foods being great sources of protein it is still easy to find hundreds of manufactured high-protein goods on your supermarket shelves. These days you can source your protein from powders, snack bars, desserts and other protein-enhanced products like bread, pancake mixes, and chips.
When consuming processed foods or supplements for their protein content it’s important to look at the nutrition label. Just because a product has a high protein content it isn’t necessarily healthy overall. Some of these products may contain high amounts of fat and/or sugar and often contain other food additives.
Supplements can be a good way to increase your protein intake if your diet is lacking in protein, however, it is better to obtain your protein from whole food sources if possible. Whole foods are generally healthier and provide other nutritional benefits such as essential vitamins and minerals that many processed options don’t.
Some groups that can benefit more from supplementing protein in their diets are athletes, people that regularly strength train, and older people who may struggle to get enough from their diet.
How Much Protein do You Need?
While it is important to get adequate protein in your diet every day, the amount you need will vary depending on your weight, gender, age and health.
Current recommendations for daily protein intake in Australia for healthy adults are 64 g per day or 0.84 g per kilogram of body weight for men, and 46 g per day or 0.75 g per kilogram for women. These recommendations, developed in 2006, are based on healthy normal-weight individuals between the ages of 19-70 years. These recommendations, while sufficient for preventing protein deficiency, are often seen as outdated. Indeed, the CSIRO, Australia’s government-funded science organisation, recently highlighted several limitations to these recommendations when it comes to developing optimal diets for individuals.
When these recommendations were formulated they used reference body weights of 76kg for men and 57kg for women, average weights for the Australian population at the time. These reference weights are not reflective of the average population in Australia today, in which more than 60% of adults are overweight or obese.
The recommendations also assume a protein and energy balance. When someone is losing weight they will likely have a negative protein balance, meaning that protein breakdown exceeds protein synthesis, and tissues lose protein faster than it is replaced. Negative protein balance can also occur in individuals who train or exercise a lot, especially when not consuming adequate amounts of protein
Furthermore, the recommendations assume that individuals have an adequate muscle mass. In a population that is becoming increasingly sedentary, individuals are less likely to have optimal muscle mass for their age and weight.
The recommendations were made to meet the requirements for most healthy individuals but do not consider optimal muscle mass, training loads or individual goals. Recent studies suggest an upwards adjustment of absolute protein figures and that individual protein needs should take into account a person’s age, gender, body mass, and goals such as weight loss or muscle gain.
While most people consume enough protein to prevent deficiency, some individuals would do better with a much higher protein intake. Although figures vary, most recent research on adequate protein intake suggests that previous figures were too low and that protein consumption should be upwards of 1g per kg of body weight per day. Numerous studies suggest that higher-protein diets have major benefits for weight loss and metabolic health.
So, How Much Protein do I Really Need?
Recent research suggests that older people should consume an average daily intake of 1.0 to 1.2 g protein per kg of body weight per day, aiming to consume 25 to 30 g protein per meal. Further research indicates that diets containing between 1.2 and 1.6 g protein per kg of body weight per day have been successful in making improvements in appetite, body weight management, and cardio-metabolic risk factors as well as addressing the protein needs of older individuals.
When it comes to building muscle, numerous studies have attempted to determine the optimal amount of protein, with varying conclusions and conflicting results. Some studies suggest consuming more than 1.8g per kg of body weight has no benefit, while other studies have found 2.2g per kg of body weight to be ideal. This can be confusing for those trying to work out the optimal amount of protein they should be consuming to build muscle. However, many experts agree that consuming between 1.6g-2.2g per kg of body weight will be sufficient for muscle gain.
If you are carrying extra body fat, it is a good idea to use your lean body mass or your target weight as a reference for your protein intake rather than your total weight.
What Are Some of the Benefits of Protein in Your Diet?
Reduces Appetite and Hunger Levels
Studies consistently show that of the three macronutrients, protein is the most satiating. It helps you feel more full with less food.
Protein intake reduces the levels of ghrelin, the hunger hormone, in your body. Protein can also boost levels of peptide YY and cholecystokinin, hormones that have been linked to reduced appetite.
Because of these effects, people eating sufficient amounts of protein may take in fewer calories over the day helping to create a calorie deficit. On top of this, Protein also takes longer to digest than carbohydrates and the more protein you have the longer the effect lasts.
Boosts Metabolism
For a short time after eating, your metabolism is increased because calories are used to digest the food and extract the nutrients within it. This is known as the thermic effect of food. The thermic effect of protein is higher than that of fat or carbohydrates and a higher intake of protein can significantly boost metabolism and help you burn more calories.
Helps to Improve Body Composition
Numerous studies show the benefits of a higher protein intake on improved body composition. Because of its metabolism-boosting effects and ability to reduce cravings and hunger levels, high-protein diets often lead to reductions in calorie intake and increased weight loss.
Muscle is made primarily of protein and Eating adequate amounts of protein along with a sufficient resistance training routine helps to promote muscle growth. Higher protein intake is also associated with greater fat loss and less loss of lean body mass when people undertake a weight loss regime.
Helps Maintain Weight Loss
Protein’s beneficial effects in weight management are well established within the scientific literature and recent studies continue to highlight the important role of protein when it comes to weight loss. Some of those studies found that even when matching energy intake, higher protein diets led to greater average weight loss and greater preservation of lean mass when compared with lower protein, higher carbohydrate diets. Studies have also found that higher protein diets led to improved measures of waist circumference, blood pressure, fasting insulin and triglycerides. Another finding is that a higher protein diet led to less weight regain than a lower protein high carbohydrate diet.
Good for Your Bones
Despite some people believing the myth that protein, particularly animal protein, is bad for your bones most long-term studies highlight the benefits of protein on bone health. Consuming more protein helps you maintain bone density as you age and helps to reduce the risk of osteoporosis and fractures.
Helps You Stay Fit as You Age
One unfortunate consequence of aging is that you will gradually lose skeletal muscle, this is referred to as age-related sarcopenia. This condition begins at around 50 years of age and is one of the main causes of frailty, bone fractures, and reduced quality of life among older adults. Consuming more protein and staying physically active is one of the best ways to maintain muscle mass as we age and reduce the effects of sarcopenia. This is not only important for overall health and wellbeing but also to maintain an adequate level of physical ability and prevent injury from falls and other accidents.
When Should You Consume Protein?
For the average Australian, daily protein intake is skewed towards their evening meal. Breakfast and lunch typically include limited amounts of Protein. Recent studies have shown that there are beneficial impacts on body composition and lean body mass for evenly distributing protein intake throughout the day. Consuming 25-30g of protein per meal is more effective at stimulating muscle protein synthesis and increasing satiety than consuming the majority of your protein intake in one meal.
There is also increasing evidence supporting higher morning protein intakes for appetite control. Recent studies have found that consuming a high protein breakfast leads to more feelings of fullness and less late-night snacking. These findings may be related to improvements in the function of dopamine, a hormone involved in cravings and addiction. Studies have found that neural activation in brain regions associated with reward and cravings are reduced after high protein intakes at breakfast.
There is also increasing evidence that the form of protein consumed in a meal may also affect appetite control. Liquid protein sources appear to provide earlier satiating effects, while solid proteins provide later satiety effects. Liquid proteins may help you feel full straight away, however, solid protein sources will keep you feeling fuller longer.
Can You Have Too Much Protein?
There is a common perception that consuming too much protein in your diet damages the kidneys. While it is true that people with pre-existing kidney damage need to restrict their protein intake, there is no evidence that a high protein intake harms healthy kidneys. The kidneys filter approximately 200 litres of blood per day and remove approximately 2 litres of waste, toxins and water. Increasing the intake of protein in your diet may increase the work your kidneys have to do a little bit but it is fairly insignificant to the work they already do daily.
There is no evidence that a high protein intake causes any harm to healthy individuals. On the contrary, there is quite a significant amount of evidence highlighting the benefits of a higher protein intake.
Unlike fats or carbohydrates, your body can’t store protein. Any protein that is not used by the body will be excreted as waste. However, it is important to remember that any excess calories from the protein you eat may still lead to unwanted weight gain if you are in a caloric surplus
Protein Deficiency
Because protein is found in a wide variety of food it is very uncommon to not get enough protein if you’re consuming a typical western diet. When you are not consuming sufficient amounts of protein in your diet, protein deficiency can occur. Although rare in western countries like Australia, protein deficiency may occur in some populations such as older people and those following strict vegetarian or vegan diets. It can also be caused by eating disorders like anorexia or bulimia.
Protein deficiency can cause weakness, fatigue, headaches, and issues with the nails, skin, and hair. Prolonged protein deficiency can cause serious health issues such as wastage and shrinkage of muscle tissue, stunted growth and development, weakened functioning of organs including the heart and lungs, and fatty liver.
