The goodness of protein: adapted from Good Magazine issue 30

Protein is the new nutrition superstar – ever more benefits are being discovered as science delves deeper into how proteins function.
Research Scientist

Page Contents:

As we go about our daily business, our bodies are in a constant state of repair. Most of the body’s tissue replenishes itself (at varying speeds) throughout our lives, and without protein in our diet, we simply couldn’t survive. Nor could we grow, or repair and tone our muscles after exercise.
… without protein in our diet, we simply couldn’t survive. Nor could we grow, or repair and tone our muscles after exercise.
Protein is the stuff we’re made of, the bricks of our biological construction. The word protein comes from the Greek word proteios, which means ‘primary’ or ‘holding the first place’ and it was first used in 1883. Our body uses protein to make blood, skin and hair. It creates all the micromachinery inside our cells, makes antibodies to build immunity and fight off infection, and is the essence of our very brain matter. In fact, 16 per cent of a 76kg man is pure protein.
But contrary to popular opinion, women need almost as much protein as men do. It can even be used for energy if our diets are scarce in sugar and fats. In addition to the job of moving our bodies - 45-70 per cent of our energy is spent each day powering essential internal tasks such as processing food, moving substances around inside our bodies, making and breaking hormones and enzymes, maintaining our bodies at the right temperature and keeping organs such as the heart and the brain sparking. 

A common misconception is that protein-rich foods are the realm of the bodybuilder but this type of physique takes years of extreme training and a super-specialised diet to achieve. “Women aren’t going to bulk up, it’s quite difficult and not something that we naturally do,” says Results Nutrition Centre nutritionist Olivia Green. In fact, some claim that eating protein may help prevent us from over-eating.

In a 2011 study  [1] at the University of Sydney, people on a 15 per cent protein diet were found to snack less between meals than people on a diet with ten per cent protein. The researchers said one possible explanation is the theory that all animals have a fixed amount of protein that they will keep munching towards before they feel full – regardless of how much carbohydrate and fat they eat along the way. It’s a theory known as the ‘protein-leverage hypothesis’. “Counting calories is not enough to manage appetite and body weight in the Western world, where food is abundant,” says University of Sydney nutrition specialist Professor Steve Simpson, in response to the study. “If you reduce your calorie intake but fail to reach your protein target, you will find it hard to resist hunger pangs.”

And so, to bust another myth. Protein plays a critically important role in the diet of all of us: it’s vital for everyone from children and busy women to adolescents and the elderly. “Muscle mass, which then influences body tone, starts to go down from age 35,” says David Cameron-Smith, Professor at the Liggins Institute in Auckland. “Most people don’t start becoming aware of that subtle change until their mid-40s, but certainly by the time they get into mid- 50s it is very visible both to the person and to everyone else how their body has changed. They don’t look like the spunk they thought they did when they were in their 20s and 30s. It’s sad but true.” 

Looks aside, protein has far more fundamental effects on mobility and life satisfaction. In a recent pilot study carried out by Fonterra, adults aged 50-75 who supplemented their diet with 20g of protein at breakfast and lunch for three weeks claimed to feel a measurable increase in strength, sustained energy and increased movement. 

When should we be upping our protein level? 

A higher-than-normal protein intake may also be advantageous in some cases. We need to be more aware of eating sufficient quantities and quality of protein if we’re on a low food-intake diet, if we’re pregnant or lactating, if we’re training hard (especially after exercise, when our aching muscles are crying out for protein and are particularly able to absorb it), if we are at risk of developing obesity or diabetes, if we have an illness (such as cancer) or an injury, or if we’re elderly or adolescent. Or maybe we’re so run off our feet that sometimes it’s just easier to eat a bread roll rather than spend time cooking an egg or preparing meat. 

Are we getting the right type of protein? 

Over the last decade we have discovered that as well as quantity, it’s the quality that matters. “Just as we discovered in the 1960s that oils aren’t simply oils (there are many types, good and bad), we are increasingly discovering that proteins ain’t just proteins,” says Cameron-Smith. Meat, poultry, seafood, dairy, soy and other plant sources are all absorbed, and used, differently by your body. And they either meet your unique needs (in terms of required amino acids) or they don’t. 

Amino acids join together to make protein, and there are 20 amino acids in existence. Nine are essential for us to consume because they cannot be synthesised by our bodies. A complete protein contains all essential amino acids, and New Zealand scientists at the Riddet Institute in Palmerston North, have helped develop a brand new way of rating protein, and an important outcome is that animal sources of protein come up trumps. 

The new method pinpoints the efficacy of protein sources more accurately than before, and it has shown that the protein in soy (although it is a complete protein) and other plant sources is less digestible, and has less essential amino acids, than the protein in dairy. Milk protein concentrate, for example, is rated about 30 per cent higher in quality than soy. However, a balanced diet is always necessary to get a full range of vitamins, minerals and fats, so we should think about combining various sources of protein within a meal. 

“When you eat, say, milk and bread, you come up with a very balanced diet. This is because the wheat proteins are deficient in certain amino acids, and the milk has got surplus amounts of those amino acids – so together they are a very nice balanced food,” says Professor Paul Moughan of the Riddet Institute. “If you have a meal that’s just a mixture of beans and bread without high-quality proteins, you end up with a meal that’s more poorly balanced and won’t be as well used.” Added to a diet, high-quality protein is “beneficial in bringing about a balanced intake of amino acids. Egg, dairy and meat all came out really well on the new scoring system,” says Moughan. “Soya is not bad for you, but not as powerful as some others in forming a balanced protein diet.” 

Vegetarians and vegans need not despair – but they must carefully plan their diets. Quinoa has taken the healthy living market by storm because it is a complete (and non-meat) protein. Otherwise, combining complementary protein sources is the best way to get complete protein. Take, for example, corn and beans: corn is missing the amino acid lysine but is high in methionine, while beans lack methionine but are high in lysine. 

To cook or not to cook? 

The way a protein has been processed or cooked can make it easier or more difficult to digest. An egg is a great example – through cooking, it is changed from poor- to good-quality protein, even though it’s still made of the same components! A Journal of Nutrition study [2], found 91 per cent of protein from cooked eggs is absorbed, while only 50 per cent of raw egg protein is absorbed. But in other protein sources, says Moughan, the opposite effect occurs. For example, raw meat is quite digestible, but the more it is cooked, the less digestible it becomes. The amino acids in raw soya beans are poorly digestible. If it’s treated at the right temperature, digestibility levels are good; but if it’s overheated, digestibility and quality will plummet. As pieces of the protein puzzle become clear, one fact remains: all bodies are different, so eat what works for you. 

Are we getting enough? 

Severe protein deficiency is rarely seen in the developed world. In the worst cases of malnutrition (such as those occurring in some parts of Asia, Africa and Latin America), a lack of protein causes severe muscle wasting, a swelling of the extremities and belly, liver enlargement, and depigmentation of skin and hair. Protein is essential, but you needn’t go overboard on it (apart from in some specific cases – see next page for details). For most adults, a typical Western adult diet that includes 11-15 per cent protein is generally sufficient to avoid deficiency, but it’s not necessarily the optimum levels. Taking the New Zealand diet as an example, the New Zealand Ministry of Health guidelines [3] say the main sources of protein in the average diet is meat, poultry and fish (about 33 per cent), cereals and cereal-based foods (about 25 per cent) and dairy foods (about 16 per cent). Vegetables provide about eight per cent protein. 
It’s difficult to overdose on protein – it would take very heavy supplementation and a low carbohydrate intake to cause ill effects. But too much of any good thing is not healthy, and excessive protein intake can exacerbate liver or kidney problems in those who are already prone. The key questions for most of us are: what’s the right amount for our body’s needs, and which are the best sources? 

The goodness of dairy 

A closer look at dairy protein is throwing up all sorts of surprises – which is slightly less surprising when you consider it’s engineered for one of the most important stages of growth and development: it was developed by nature to nurture calves. 

The new DIAAS measurement has shown that dairy has more digestible essential amino acids than soy, and that this excess of amino acids has an impact in the body. It has long been known dairy protein is especially rich in a group of amino acids called branched-chain amino acids (BCAA’s). These BCAA’s have a whole range of interesting biological functions that scientists are only just now discovering – “this includes healing, building muscle, and helping with fatigue and diabetic symptoms,” says the Liggins Institute’s David Cameron-Smith. Whey protein is especially rich, with around 25 per cent made up of branched-chain amino acids. 

The fact that dairy often comes in liquid form is also a plus, says Cameron- Smith. Liquids take less time than solids to be broken down, so the protein hits your bloodstream in a large surge, in the same way that your glucose levels spike when you have a sugary drink. But a surge in dairy protein, particularly branched-chain amino acids, has health benefits – like increased ability to make muscle, reduced blood glucose levels, and improved blood pressure regulation. Team that with the easily absorbed vitamins and minerals found in dairy (calcium, phosphorous, potassium, magnesium, zinc, B vitamins and vitamin A), and it’s not hard to see why dairy products shouldn’t be dismissed as an essential part of a healthy diet. Unless, of course, you are lactose intolerant. 

Lactase deficiency, as it is sometimes called, is the inability to digest a sugar called lactose that is found in milk and dairy products, due to a lack of the lactase enzyme needed for digestion. It is estimated to affect around 8 per cent of the New Zealand population but in some African and Asian countries, almost the entire population suffers from it, and can cause stomach pain, bloating or diarrhoea. One solution for those who are lactose intolerant is to choose dairy products with lower lactose levels, such as yoghurt, hard cheese or even lactose-free milk, which is pre-treated with lactase. Low or lactose free dairy solutions are a great way to ensure those with lactase deficiency still get their hit of high quality protein.

“Protein, and dairy protein in particular, will be the nutrition superstar of the future,” predicts Cameron- Smith. “So many discoveries are being made about how proteins work, and the complexity of milk continues to astonish scientists. There is something about milk or dairy that seems to really help the body recover or repair.”


[1] Gosby AK, Conigrave AD, Lau NS, Iglesias MA, Hall RM, et al. (2011) Testing Protein Leverage in Lean Humans: A Randomised Controlled Experimental Study. PLoS ONE 6(10): e25929. doi:10.1371/journal.pone.0025929
[2] Pieter Evenepoel, Benny Geypens, Anja Luypaerts, Martin Hiele, Yvo Ghoos4, and Paul Rutgeerts (1998) Digestibility of Cooked and Raw Egg Protein in Humans as Assessed by Stable Isotope Techniques, J. Nutr. October 1, 1998 vol. 128 no. 10 1716-1722
[3] New Zealand Ministry of Health. 2012. Food and Nutrition Guidelines for Healthy Children and Young People (Aged 2–18 years): A background paper (1st Ed). Wellington: Ministry of Health (http://www.health.govt.nz/publication/food-and-nutrition-guidelines-healthy-children-and-young-people-aged-2-18-years-background-paper)
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