There is a lot of controversy surrounding how much protein we need to eat and what the best sources of protein are. In this blog post, we will cover this and also explore the healthiest way to include protein in your diet.
After water, protein is the most abundant component of your body. Your hair, muscles, nails, tendons and ligaments are all made up of protein. Protein is also a key component of enzymes, hormones, neurotransmitters, antibodies and other immune cells. Protein helps to maintain body fluid balance, regulate the acid-base balance of the blood and can be a source of energy if your carbohydrate and fat intakes are low. Without enough protein in your diet, you run the risk of contracting infections or developing the wasting disease, marasmus.
There is still a lot of controversy surrounding how much protein we need to eat and what the best sources are. One key point to keep in mind is that we are all individual. Despite that, there are general guidelines that you can adopt and then tweak to meet your requirements.
How Much Protein Do You Need?
The exact amount of protein you need depends on several factors including, your body weight, your activity levels, genetics, health status, environment and on whether you’re pregnant or nursing. On average, a healthy, inactive adult needs around 0.8g of protein per kg of healthy body weight to maintain protein balance. A 57kg sedentary woman, for example, needs only 46kg of protein per day. Bear in mind that 0.8g/kg is the minimum amount you need and not necessarily the ideal amount. If you engage in high-intensity exercise or endurance/weight training, you may need up to 1.4g of protein per kg daily.
Current research shows that it is better to distribute your protein equally across each meal rather than consuming most of it in one meal. It is also advisable to aim for 25-30g of protein at each meal to maintain healthy muscles and bones.
What are the best sources of protein?
Protein is present in all food groups, but most people only associate animal sources such as red meat, poultry, fish, and eggs with protein. All plant foods contain proteins, but legumes, nuts, and seeds contain the highest amounts. Grains and vegetables are also good sources. To properly understand why some foods are better sources of protein than others, it is crucial for you to understand what essential and non-essential amino acids are and what a quality protein is.
Essential amino acids vs Non-essential amino acids
As mentioned, amino acids are the building blocks of all proteins. Your body uses 20 different amino acids to function. It can manufacture eleven of them; these amino acids are known as non-essential amino acids. However, there are nine amino acids that your body cannot make which you must get from your food. These nine amino acids are called essential amino acids. A deficiency in any of them negatively affects tissue growth, its repair and maintenance.
Foods that contain all nine essential amino acids are referred to as complete proteins.
During periods of rapid growth in children, illness or stress, some of the non-essential amino acids can become essential. This usually occurs because the enzymes you need to make these non-essential amino acids are in short supply during periods of stress or illness. Consequently, you should increase your protein intake during these periods.
The quality of a protein is determined by (i) the amount of essential amino acid it contains, and (ii) how easily your body can digest and absorb it. Animal proteins such as meat, poultry, fish, dairy and eggs are regarded as quality proteins because they contain sufficient amounts of all of the essential amino acids and because you can digest them better (~95% digestibility rate) than proteins found in most whole plant foods (~80-85% digestibility rate).
The nutritional quality of animal proteins is not all equal even though they are all highly digestible. Whey protein is considered the highest quality protein, while eggs are the next best. In fact, some believe egg to be a nearly perfect food. Milk and fish are also better sources of protein than beef.
Soybeans and quinoa are the only quality plant proteins. In most cases, plant foods need to be combined (not necessarily at the same meal) to enable you to get sufficient quantities of essential amino acids. Legumes (pulses) and vegetables are typically deficient in the essential amino acid methionine, whereas nuts and grains are limited in lysine. Eating any combination of legumes and vegetables with grains and nuts, such as beans and rice, will provide all of the amino acids you need.
Animal Protein vs Plant Protein
The fact that your body can digest and absorb animal protein better than plant protein does not necessarily imply that they are always better. A high intake of animal protein is linked to certain cancers, hypertension and osteoporosis. Animal sources of protein tend to contain higher levels of saturated fat, excessive consumption of which is linked to cardiovascular disease.
However, not all animal proteins are created equal and not all carry this risk. Fish, for example, are generally lower in saturated fat and are good sources of essential omega-3 fats. Also, animal proteins provide heme-iron, cholecalciferol (vitamin D), docosahexaenoic acid (DHA), vitamin B12, creatine, taurine, carnosine and conjugated linoleic acid (CLA); all essential compounds that are absent in plant foods.
While most plant foods are not quality sources of protein, they are generally lower in saturated fat and lack cholesterol. They also contain phytochemicals including phytates, tannins and saponins that can reduce the risk of certain cancers. Plant foods are the only source of fibre. Fibre is necessary for healthy digestion, and it plays a role in regulating blood cholesterol and glucose levels.
On the flip side, the beneficial phytochemicals and fibre in plants can stop your body from absorbing vital minerals like zinc and calcium from your food. And as mentioned, most plant proteins are incomplete or do not contain all the essential amino acids. Legumes are limited in methionine and cysteine; grains in lysine and tryptophan, vegetables, nuts and seeds in methionine, cysteine, lysine and threonine, and seaweed in histidine and lysine. Plant proteins are also not as digestible as animal proteins. Some studies suggest that you can utilise only a fraction of the plant proteins you consume.
How to eat protein in a health-promoting manner
We are all metabolically and biochemically unique. The way your body processes and reacts to food is dependent on your genetics, environment, age, your current state of health and lifestyle factors. You may thrive by eating only plant proteins, eating only animal proteins or eating a combination. For most people (and in the absence of any underlying conditions), a combination of animal and plant proteins, with a higher emphasis on plant proteins may be the best option. By eating a combination, you get the best of both worlds:
- fibre and beneficial phytochemicals from plants
- highly digestible and absorbable proteins from animal foods
- B12, heme iron, and other essential proteins generally lacking in plant foods and,
- an overall diet that is low in cholesterol and saturated fat, due to higher consumption of plant foods
What are your favourite sources of protein?
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