Once cast in more of a supporting role, protein has recently become a centre-stage nutrient – but not everything we hear about protein is correct.
Protein is a vital nutrient – without it your body would simply waste away. However, while too little protein means you cannot grow or sustain your body properly, too much protein may actually increase your risk of certain health problems.
Learn how to strike a good protein balance here.
What is protein?
Or perhaps you should ask, what isn’t protein? Remove the water from your body, and protein accounts for around 75 percent of what’s left. Your hair, skin, muscle, bone and almost every other body part or tissue is made up of protein; you are protein!
But what does this have to do with protein in your diet? Dietary protein is often described in terms of amino acids, which are the building blocks your body uses to make the proteins that keep you alive. Your body needs 22 different amino acids (called essential amino acids) in order to make all the necessary proteins. Thirteen of these amino acids are made by the body itself, but nine of them must come from food, which is why you need protein in your diet.
The foods we eat for protein can be described in two ways:
Complete protein – These are foods which contain all nine amino acids that you need in your diet. All meat and other animal products are sources of complete proteins. These include meat, poultry, fish, shellfish, eggs, milk, and milk products.
Incomplete protein – These are foods that are low in protein or contain only some of the nine amino acids you need in your diet. Vegetable protein is usually considered incomplete because it is missing one or more essential amino acids. However, as long as you eat a variety of foods throughout the day, it’s easy to still get all nine amino acids without eating animal products.
What is protein for?
Protein is body food. It is used to build new tissue, which is why there is an increased need for protein during periods of growth such as in infancy, childhood, adolescence and pregnancy. Here are some of the things protein does:
- Provides the structure for muscles, hair and blood
- Repairs worn-out body tissue proteins resulting from general “wear and tear” to the body
- Supplies emergency energy when there is not enough carbohydrate or fat in your diet
- Helps transport important nutrients such as iron and cholesterol throughout your body
- Enhances your immune system
- Builds cardiac (heart) muscle
- Contributes to numerous essential body secretions such as hormones and enzymes. The only protein-free body fluids are urine and bile.
Protein and muscle. People are often misled about the role of protein in building muscles. Although muscles are made of protein, carbohydrate is actually the best form of “fuel” for muscles exercised for long periods. In fact, a diet high in protein and fat, but low in carbohydrate, can significantly reduce the performance of endurance-sports athletes. Excess protein in foods will not build bigger muscles. It is simply converted to, and stored as, fat.
How much protein do I need?
On average, Australians eat far too much protein. The current recommendation is that proteins make up around 15-20 percent of your total calories for the day. Protein has four calories per gram, so for a 2000 calorie-a-day diet you could eat 75-100 grams of protein. However, most of us consume more than that. Eating too much protein is damaging to your body.
A more accurate way of calculating protein needs is to allow 0.8g of protein per kg of body weight. For example, a 60kg person would need 48g of protein per day. Growing children need about one gram of protein for every one kilogram of body weight. For example, a 25 kg child needs about 25 grams of protein a day to sustain her growth.
The table below lists the recommended minimum protein intake for different people.
Recommended Daily Protein Intake (grams)
|Minimum Protein Requirements|
Source: Allan Borushek’s Pocket Calorie, Fat and Carbohydrate Counter 2007.
High-protein diets – are they safe?
Weight loss in the first few months of a high-protein diet is sometimes faster than with a calorie-controlled diet, primarily because of increased water loss. However, studies have shown that after a year weight-loss results are the same on a calorie-controlled diet.
But is a high-protein diet safe? Evidence suggests the answer to this question is no – especially if it’s followed for more than a few weeks. Expert studies show that the average Australian already eats double the amount of protein that is recommended. People on high-protein diets put away even more than that, consuming up to 34% of their total calories from protein and up to 53% from fat, much of which is saturated fat (the “bad” fat) from meat and dairy products.
The extra fat, alone, is enough to increase your risk for coronary heart disease, stroke and other illnesses. But excess protein has also been proven to have negative consequences for health and well-being. For example:
- When there is too much protein and not enough carbohydrate in the diet, the body is forced to burn fat because it is deprived of its essential natural carbohydrate energy. This process is called ketosis. The energy from fat is “last resort” energy and does not provide the body and mind with the fuel they need, which is why people on high-protein diets feel easily tired and can suffer exhaustion.
- Ketosis also produces ketone bodies. When too much protein is consumed these ketones build up in the body causing damage to the liver and kidneys.
- When protein is broken down and metabolised it also raises the levels of uric acid in the blood. The more protein you consume, the more of this toxic by-product the body has to deal with. The body pumps a lot of water through the kidneys and urinary tract to try and flush it out. This water loss not only gives a false indication of weight loss, it is also detrimental to the body in many other ways.
- Digesting too much protein releases acids that the body usually neutralises with calcium. As calcium reserves are used for this instead of for building bones, the risk of bone deficiency and osteoporosis increases.
- Other common discomforts of a high protein diet can include bad breath, bad body odor, constipation, dehydration, dizziness, headache, mental fatigue, sleep problems and nausea.
Do vegetarians get enough protein?
It was once widely believed that vegetarians had to carefully combine plant protein sources in each meal in order to obtain all nine essential amino acids. However, studies have now shown that the human body can store essential amino acids and combine them as necessary. So, while combining beans and rice, or peanut butter and bread produces a “complete” protein, in most cases it’s not necessary to consciously do this at every meal. As long as you are eating enough calories to meet your daily energy needs, and have a reasonably varied diet, getting enough protein is generally not a problem. It’s actually difficult to become protein deficient unless you quit eating all together! If you have concerns, talk with your doctor or dietitian.
Vegetarian foods highest in overall protein content include legumes or pulses (dried beans and peas), soy products of various kinds (tofu, tempeh, meatless “meats”), eggs and dairy products for those who consume them, and some nuts.
Choose your proteins wisely!
A recent study suggested that eating too much protein from red meat and dairy products increases the risk of dying from coronary heart disease. Participants in the study who ate the highest amount of vegetable-protein sources such as beans, nuts, tofu, and peanut butter were found to be 30 percent less likely to die from heart disease. Fish and chicken were not linked to heart risks in the study.
Even if animal protein and vegetable protein have the same effects on your health, it’s probably what comes with the protein that makes it a more – or less – healthy choice.
Use the following table to help you make wise protein choices:
|Examples of Common Foods Containing Protein||Protein (g)||Calories||Fat (g)||Carbs (g)|
|Animal protein foods:|
|Beef, rump steak, lean, grilled, 100g||32g||200||7g||0|
|Chicken, breast, baked, no skin, 100g||28g||157||5g||0|
|Milk, full cream, 1 cup, 250 ml||8g||160||9g||12g|
|Milk, skim, 1 cup, 250 ml||9g||83||0.3g||12g|
|Yoghurt, natural, 200g||12g||160||8g||10g|
|Yoghurt, natural, low-fat, 200g||12g||160||3.8g||17g|
|Cheddar cheese, 30g||8g||120||10g||0|
|Cottage cheese, low-fat, 30g||4g||27||0.8g||1g|
|Egg, large, boiled or poached||7g||81||6g||0g|
|Tuna, 95g tin||18g||78||1g||1g|
|McDonald’s Big Mac||25g||481||25g||35g|
|Hungry Jacks Whopper||29g||656||39g||46g|
|Plant protein foods:|
|Red kidney beans, 200g||10g||170||1g||31g|
|Soy beans, 200g||17g||210||11g||6g|
|Lentils, cooked, 200g||18g||232||1g||40g|
|Peanuts, roasted and salted, 30g||7g||176||15g||6g|
|Soy milk, 1 cup, 250 ml||8g||161||8g||12g|
|Potato, boiled, 100g||2g||87||0||20g|
|Rice, white, cooked, 1 cup, 160g||4g||208||0||45g|
|Special K cereal, 1 cup, 40g||8g||150||0||28g|
|Weet-Bix, 2 biscuits, 33g||4g||117||0||22g|
|Broccoli, boiled, 2 florets, 45g||1g||16||0||3g|
|Apple, average all types, small||0.3g||55||0||15g|
Refer to the Calorie King Food Database or Allan Borushek’s Pocket Calorie, Fat, and Carbohydrate Counter for more extensive listings.