0 of 1
Much debate and conflicting evidence has been presented in scientific journals about the role of carbohydrates in a healthy diet. The controversy includes the emergence of the high-fat, low-carbohydrate paradigm.
There is little doubt that there has been a global explosion of obesity, metabolic syndrome and Type 2 diabetes in the past few decades. This change has coincided with the increased availability and marketing of refined carbohydrates and sugar-sweetened beverages produced by the industrial food sector.
The question is: are all carbohydrates bad?
A recent study in the Lancet journal projected that life expectancy would increase significantly in 35 industrialised countries by 2030. The leading four countries in this study were South Korea, France, Spain and Japan. By 2030, women in South Korea would have a 90% probability of living to 86.7 years. The study also indicated men had a 95% probability of living to at least 80 or longer in South Korea, Australia and Switzerland.
Other studies also show increased life span is expected around the world. So does diet play a role in this?
Nothing wrong with croissants, then
A brief review of traditional diets of the four industrialised countries with the greatest projected longevity is interesting.
The typical South Korean diet always includes rice and has a high proportion of vegetables, legumes and fish, and low red meat levels. French cuisine consists of meat, vegetables, cheese, breads and dessert, while the staples of Spain include ham, eggs and rice.
Finally, the typical Japanese diet includes rice as a staple carbohydrate together with a high consumption of fish, salted foods and green tea.
Clearly, carbohydrates are an integral component of the diets of both developed and developing countries. Carbohydrate intake in these countries does not seem to have adversely influenced projected longevity.
In a meta-study, we investigated the relationship between total carbohydrate intake and obesity. The results of this survey revealed no link between total carbohydrate consumption and obesity.
A further frequent observation was that many studies showed obesity being linked to a high-fat, high-sugar diet; the consensus remains that body weight is a function of calorie intake versus energy expenditure.
We also observed that weight loss on restricted-calorie diets was equally effective on both high-and low-carbohydrate diets, though there are differences in serum lipid profiles.
This raises the question: are there good and bad carbohydrates in terms of obesity?
Refined carbohydrates and sugars have long been labelled as the cause of "saccharine disease" that manifests in obesity and many noncommunicable diseases. Conversely, the protective "healthy" role of unrefined carbohydrates in disease prevention is equally well demonstrated.
The case against carbohydrates
Regarding Tim Noakes's anti-carbohydrate views, the case against a "safe" intake of "healthy" carbohydrates is relatively simple.
First, the supporters of Banting-type diets argue, the body has no requirement for carbohydrates, because the liver produces all the glucose needed.
Second, it is argued that whenever and whatever carbohydrate is ingested, insulin must be secreted, and high-carbohydrate intake is linked to insulin resistance. And this triggers many chronic diseases, including obesity, Type 2 diabetes, hypertension, Alzheimer's and cancer.
Third, all carbohydrates, "good" or "bad", are absorbed as glucose and the insulin-secreting mechanisms cannot distinguish between the two.
Fourth, South Africa is critically reliant on a nutrient-poor diet that includes maize as its primary staple. Clear evidence exists that this type of diet drives obesity and disease.
Since all carbohydrates increase insulin secretion, there is no health benefit from replacing maize with other carbohydrates and no scientific evidence to show any benefit from eating so-called "healthy" carbohydrates.
Noakes's plan promotes the eating of meat, fish, dairy and eggs because they contain no carbohydrates and are rich in nutrients.
A bit more balance
However, our view (that of Kurt and Benn Sartorius and Sharon Fonn) is that a more pragmatic approach to unrefined carbohydrates should be adopted in South Africa, because they are affordable and appear not to influence longevity. At the same time, we agree refined carbohydrates and sugars should be restricted.
In effect we agree with Noakes about the biology of carb consumption - but disagree that you cannot practically exclude carbs in a cash-strapped setting
Every country includes carbohydrates in its diet because mass-produced staples such as rice and maize are cheap.
A healthy diet for the average citizen most likely should include good carbohydrates (unrefined grains) and exclude bad carbohydrates (refined grains and sugars).
• Kurt Sartorius is professor at the school of accountancy at the University of the Witwatersrand, Benn Sartorius is associate professor at the school of nursing and public health at the University of KwaZulu-Natal, Fonn is a professor at the Wits school of public health, and Noakes is retired from the University of Cape Town
