What is the optimal amount of protein we should be having every day?

There are multiple factors that play a role in determining how much protein you need in your diet. These predominantly include weight, age, health status and level of physical activity. As a rough guide, the recommended dietary intake (RDI) for protein is as follows:

  • 75 grams of protein per kilogram of body weight for adult women
  • 84 grams of protein per kilogram of body weight for adult men
  • Approximately 1 gram of protein per kilogram of body weight for pregnant and breastfeeding women, and for men and women over 70 years of age.
  • The needs of children and adolescents also vary according to their age and weight.

The RDI is the amount of a nutrient you need to consume to meet your basic nutritional requirements. In a sense, it’s the minimum amount you need to keep from getting sick — not the specific amount you are supposed to eat every day. Most Australians eat far more protein than they actually need, so deficiencies are rare.

There may be certain population groups or health conditions that require higher amounts of protein. For example, people who are physically active need more protein than people who are sedentary. Other instances where you might require more protein is if you have a physically demanding job, you walk a lot or do any form of exercise.

Athletes, in particular strength and resistance training athletes e.g. body builders, and contact and power sport athletes are among the population who require the most amount of protein (1.4 – 1.7g/kg body mass), followed by endurance athletes (1.6 g/kg body mass). This is to aid in muscle recovery and building, and to meet their higher energy requirements.

Elderly people also need significantly more protein to help prevent age-related health conditions and/or diseases such as osteoporosis and sarcopenia (reduction of muscle mass and strength).

Finally, people who are recovering from injuries or surgery and those with chronic disease may also require more protein to help prevent further tissue damage and assist repair.

What are specific health effects from having too little or too much protein in our diet?

As mentioned above, protein deficiencies in Australia are not common, but may occur in specific population groups and in people with special requirements. In addition to these groups, people following strict vegetarian or vegan diets must make sure that they eat a wide range of plant proteins every day or they might be at risk of protein deficiency and malnutrition.

Symptoms associated with protein deficiency include:

  • Wasting and shrinkage of muscle tissue
  • Oedema (build-up of fluids, particularly in the feet and ankles)
  • Muscle and/or joint pain
  • Muscle weakness
  • Thinning or brittle hair
  • Anaemia (low iron/iron deficiency)
  • Slow growth and development (in children)
  • Low energy, moodiness and stress
  • Slow wound healing
  • Difficulty sleeping

In regards to consuming a diet very high in protein and thus consuming too much protein, the consequences are as follows:

  • In comparison there is usually a very low intake of carbohydrates. If your body does not receive enough dietary carbohydrate, it will break down muscle tissue to make glucose (your body’s preferred fuel source). This causes muscle wastage, reduced metabolism and a build-up of ketones.
  • High protein diets usually lack fibre (predominantly from carbohydrates such as wholegrains and legumes). Avoiding these foods leads to an overall low-fibre intake, which can result in constipation, bowel disorders and increased risk of colon cancer.
  • High protein intake (predominantly from animal products) may also be high in saturated fats and cholesterol, which is associated with a range of chronic inflammatory conditions including heart disease and type 2 diabetes.
  • The liver and kidneys are put under strain because they have to detoxify and eliminate unusually high quantities of protein by-products. This may not necessarily be the case in healthy individuals but kidney problems may be exacerbated in people with diabetes.
  • There is an increased risk of developing gout (inflammation in the joints) and gall bladder problems.
  • Greater losses of body calcium may increase the risk of osteoporosis.
  • Mild dehydration due to increased water loss through urine. Dehydration puts the body under pressure.
  • Higher risk of osteoporosis as consumption of high animal protein products cause people to excrete more calcium than normal through their kidneys.

Which foods have the best source of protein? 

Generally speaking, animal protein provides all the essential amino acids (building blocks for protein) in the right ratio for our bodies to make full use of them. Good quality animal protein sources include:

  • Lean meat, poultry and fish
  • Eggs
  • Dairy products such as milk, cheese, yoghurt

It is possible to build complete protein from plant-based foods by making sure you consume a variety of them over the course of a whole day. However, you will need to consume approximately 20-25 percent more plant-based protein to have the same benefits that animal-based protein sources provide. Some good quality sources of protein from plant-based foods include:

  • Legumes and beans (such as peas, chickpeas, kidney beans and lentils)
  • Nuts, seeds and nut butters and milks
  • Soy products e.g. tofu, tempeh and soy milk
  • Spreads such as hummus and tahini
  • Some grain and cereal based foods such as quinoa, amaranth, brown rice, whole wheat bread and pasta, oats, barley

Are heavy meat based diets e.g. paleo, healthy?

There is a lot of controversy around whether or not high protein diets like the Paleo diet is healthy or not. There are many pros about the diet but there are also some cons, especially when it comes to the topic of longevity. The reason being is that proteins and their amino acids regulate the two major pro-aging pathways. Eating lots of protein seems to “up-regulate” those pathways and leads to the promotion of higher rates of both death and disease.

Having said this, there are many people who may benefit from paleo style of eating such as those with food allergies and/or intolerances, autoimmune disease, type 2 diabetes and insulin resistance. However, by following a particular diet people may lose perspective on the benefits of other foods.

An optimal diet for longevity as well as preventing disease is a whole-foods, plant-based diet that is naturally low in animal protein, harmful fats and refined carbohydrates. This means that the focus of food intake should be on low red meat intake and higher fish consumption; mostly vegetables, fruits, whole grains, legumes and soy products in their natural forms; no or very few simple and refined carbohydrates such as sugar and white flour; and sufficient ‘healthy fats’ such as fish oils, extra virgin olive oils, avocado, and nuts and seeds.

It is important to mention that as well as diet (and the focus should be on quality not quantity), other interventions, including stress management, social support and moderate exercise are important to optimise vitality and longevity.

Are protein shakes/power smoothies healthy? 

There is no nutritional advantage to using protein powders or shakes over high-protein food. However, protein shakes and smoothies can certainly serve a purpose in certain situations. They are convenient portable, easily prepared and easy to consume, which make them a good option for athletes and gym goers as a pre- and post-training snack. They are also a good solution for athletes, elderly and chronically ill people who may struggle to eat enough food to meet their increased energy or protein needs.

Depending on the protein powder used in the shake/smoothie, it might be more easily digested for people with gut issues that have trouble digesting large quantities of meat and fish. These shakes have also been useful in many fat loss programs as it is a method of minimising your calorie intake but keeping your daily protein intake at a safe level so your body does not break down muscle. These type of programs, however, should only be seen as a short-term solution and not a long-term practice to replace wholefoods.

There are different forms and sources of protein powders ranging from whey, casein, pea, hemp, soy and rice. All have different amino acid profiles and thus react differently in the body as well as each serving different purposes. To understand which protein powder is best suited to you and why, you are best to speak with an accredited practicing dietitian or sports dietitian who have extensive knowledge in this area and can prescribe you the best protein powder to help you achieve your goals.