Updated 05 March 2013

High-protein diets: are they safe?

From South Beach to Atkins, Zone to Dukan, and now the 'Tim Noakes' diet - every few years a high-protein diet makes the headlines and reignites the protein vs. carbs debate.

From South Beach to Atkins, and Zone to Dukan - every few years a new high-protein diet makes the headlines and quickly gains a popular following.

The latest diet to enjoy the news spotlight is the so-called "Tim Noakes" diet. This high-fat, high-protein dietary approach by the renowned Cape Town sports scientist has sparked a raging debate about the benefits and potential dangers among followers and critics alike.

It’s not a new diet, though. It is an eating plan based on another popular high-protein diet called the Paleo Diet (also known as the Cave Man Diet), which consists of foods that early humans ate during the Paleolithic Era (the time before the agricultural revolution 10 000 years ago). This diet includes foods that had to be hunted or fished (such as meat and seafood), or gathered (such as eggs, fruit, seeds, mushrooms and vegetables). It excludes all foods that had to be farmed (such as grains, legumes, dairy and sugar, which all happen to be carbohydrates).The result is a diet high in fat andprotein, and low in carbs. 

But why are high-protein diets so popular and why do they attract so much controversy?

High-protein diets remain popular as they promote weight loss by restricting carbs and increasing protein. They also help people to feel full for longer and stabilise blood sugar levels. 

The high-protein diet, and especially the Paleo Diet, is also very popular among athletes as it is believed to increase their strength, speed and endurance levels.  

Prof Noakes, who claims to be "carbohydrate-intolerant" and pre-diabetic, has reported a significant improvement in his health since changing to this new eating plan. "I am at my lightest weight in 20 years and I am running faster than I have in 20 years," he wrote in an article for Discovery Magazine. He also believes this diet could protect him from developing type 2 diabetes.

Risks of high-protein diets

Protein is an essential nutrient that the body needs to build and repair muscles, red blood cells, enzymes and other tissues. "Proteins are the building blocks of the body," explains Berna Harmse, registered dietician and president of the Association for Dietetics in South Africa (Adsa).

“High-protein diets, however, also carry a number of potentially serious health risks,” she warns. “A diet too high in total energy and protein/fat could lead to obesity, cardiovascular disease, diabetes, osteoporosis, kidney failure and damage to various organs.”

According to Harmse the body needs carbohydrates for energy. “Carbs are the essential source of fuel for humans. If you don't eat enough carbs to make energy, your body will turn to its fat and protein stores (including your muscles) to make energy instead.

"Once your body begins to burn large amounts of body fat, compounds called ketones are accumulated in the body. When these ketone levels become too high, you could succumb to a diabetic coma, which could be fatal if not treated immediately," Harmse cautions. 

"Dangerously high ketone levels in your body also cause your body to burn protein in the tissues of your organs (such as your heart, liver and kidneys) for energy. This causes damage to organs, which can lead to organ failure."

Harmse continues to explain that the high amount of saturated fats and kilojoules in animal protein can lead to obesity, whereas the saturated fats increase the risk of cardiovascular disease (heart disease and stroke) by raising cholesterol levels and clogging arteries. 

Prof Noakes, however, argues that the heart disease theory is flawed and that saturated fats and raised cholesterol levels are not the cause of heart disease. "There is no definitive evidence that reducing especially the saturated fat in the diet prevents heart disease,” Noakes commented in his book Challenging Beliefs.

A Mediterranean diet with a moderate amount of fat and high proportion of mono-unsaturated fats (found primarily in plant based fats) has been shown to provide cardiovascular benefits.

What amount of protein and carbs should you eat?

“Protein should make up about 15% of a healthy individual’s daily intake, with the focus on lean sources such as chicken and fish,” Harmse recommends. “Oily fish such as tuna, salmon and sardines are great sources of omega-3 fatty acids and should be included in our diets regularly.” 

She suggests that 45% to 60% of our daily intake should come from carbohydrate-rich sources. “These carbs should be complex (such as whole grains, fruits, vegetables and legumes) and high in fibre. We need at least 25-35g of fibre daily for normal bowel movements,” she explains.

(Keep in mind that simple or refined carbs, such as sugar, sweets, soft drinks, chips, cakes and donuts are high in kilojoules and low in nutritional value and will only pile on the kilos.)

And what about combining protein and carbs in meals? Isn’t it bad for you?

“Some people believe that it is not good to combine protein and carbs in meals as the body’s enzymes will get ‘confused’ and not know which food groups to target, supposedly leading to weight gain and fatigue,” says Harmse."This, however, is not scientific as there are specific enzymes that target specific food groups.”


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