The humble potato – villain or victim?

Abstract: Does the potato hold a clue to obesity in South Africa?…

Outside of a daily dose of aspirin, few things we pop into our mouths have vacillated so much in their fortunes as the humble potato. One minute it’s a staple food source packed with goodness, the other it’s nothing more than a lump of carbohydrates heralding all sorts of maladies.

In South Africa, a recent event in the media reinvigorated the debate. Tim Noakes, the Professor of Sports Science at UCT, appeared on Carte Blanche passionately presenting the benefits of a high-protein low-carbohydrate diet. More importantly, he suggested that guidelines recommending carbohydrates should form the basis of a healthy diet could in fact be behind the high levels of obesity and other lifestyle health problems that are evident in South Africa.

He has since emphasised a point made in the interview that his diet was designed around his specific needs and biological condition, “My biology is such that I am unable effectively to clear from my bloodstream, the breakdown product of ingested carbohydrate, glucose.”

However, the effect of a man of Prof Noakes’ reputation and prominence in the nation’s collective conscience being so vocal in his convictions was to encourage a hasty re-evaluation of what we put on our plates, especially our fondness for starch such as maize and potatoes.

According to Prof Noakes, because the potato is readily turned into glucose in the intestine and absorbed as such, only those who have a superb capacity to metabolize carbohydrates should enjoy potatoes: “I do not have that ability and so I must avoid them. Many South Africans are like me although they may not know it.”

If this is the case it begs the question as to whether the humble potato holds a key to obesity in South Africa? In a country where 68 percent of the population is overweight and 33.5 percent are considered obese, is the potato a villain or a victim of some misunderstanding?

From a purely physiological standpoint, obesity develops when a person consumes more calories than they burn through daily function and physical activity. The surplus calories are then turned into fat. However, obesity is not simply a case of balancing consumption with exercise. It can be influenced by a number of conditions, including genetics, shifts in metabolism, psychological circumstances, environmental and socio-economic factors, and, of course, lifestyle.

But in South Africa, there could be another, altogether worrying, driver. Shifting cultural norms and beliefs are behind what appears to be a resurgence of obesity as a desirable condition. A recent report in the SA Journal of Clinical Nutrition has shown how the perception of body size among black urban women is linked to attitudes towards HIV/Aids, with 69.3% of women interviewed associated being underweight with being infected with HIV; and, consequently, a significant percentage associating being overweight with being healthy.

This is a concern for Prof Noakes, who believes the obesity epidemic in South Africa is, to a large degree, caused by highly palatable addictive foods specifically engineered to be irresistible because they have a specific content of fat, carbohydrate and salt, “We then overeat these foods because they trick our appetite into wanting more whereas we do not have any need for the added calories.” Carbohydrates, claims Prof Noakes, contribute to the problem in that they have been made cheap and readily available as an addictive food source in snacks and fast foods. He presents French fries and potato crisps as guilty parties.

But ‘carbohydrates’ is such a broad-term, and therefore an easy, unfortunate and, arguably, inaccurate target. In chemistry, ‘carbohydrates’ is the collective name for various organic compounds of carbon, hydrogen and oxygen in the body that are involved in various roles such as storing energy, preventing tissue breakdown and developing the immune system. But ‘carbohydrates’ is also a term used in food science to refer to those foods that contain either simple carbohydrates – such as sugar – or the more complex carbohydrate known as starch – which is found in pasta, bread, and cereals. Importantly for South Africa and other developing countries, starch is also found in many staple foods such as maize, sorghum, millet, yams, and of course, potatoes.

This is one of the reasons why organisations such as the Medical Research Council (MRC) have supported the recommendations by the South African Guidelines for Healthy Eating that carbohydrates should be at the very foundation of a healthy diet.

One of the driving forces behind this is Professor HH Vorster, the highly respected Director of the Centre of Excellence for Nutrition at North-West University, Potchefstroom, “In planning meals, the starchy food should be the central or main food, and the rest of the meal planned around this food.” Her research is based on convincing evidence that high-carbohydrate diets lower risk of several chronic diseases such as obesity, non-insulin-dependent diabetes mellitus, cardiovascular disease, cancer and other gastro-intestinal diseases.

Jenny Meyer, a registered clinical dietitian who sits on the executive committee of the Association for Dietetics in South Africa (ADSA), agrees on the need for carbohydrates: “It is true that a high intake of carbohydrates, specifically refined carbohydrates and sugars, have contributed towards an increased incidence of obesity and diabetes, but it is important to remember that carbohydrates do still play an important role in the diet, and they are the main source of fuel for the body and the brain.”

So how does the potato fit into the picture? Can it provide the necessary nutrition of carbohydrates, and remain a staple food for a developing nation like South Africa, but without the dangers suggested by Prof Noakes?

Jenny Meyer agrees it can, but insists it must be prepared healthily: “A potato, cooked in its natural, unprocessed form, and in controlled portions, will provide beneficial nutrients; and the skin is a good source of fibre. This can definitely form part of a healthy balanced diet.”

Maureen Storey, the CEO of the US-based Alliance for Potato Research and Education, is, understandably, a vocal proponent of the benefits of potatoes as part of a healthy diet and proposes an added benefit of the potato outside of its role as a complex carbohydrate: “There is some research that suggests potatoes have a positive effect on satiety, that is, people feel satisfied when they’ve eaten a meal with potatoes and, therefore, consume fewer calories.”

The problem with the potato starts when it is processed and starts to lose some of its nutrients (e.g. peeling the skin off the potato significantly reduces its fibre and nutrient content), and when extra fats (such as oils, butter, margarine) are added during the cooking process.

There’s a further problem – and this is where the typical South African braai-diet is particularly guilty – when potatoes are then served with added fats such as butter, margarine, and sour cream dropped onto potatoes; and when mayonnaise is mixed into a potato salad. These add extra calories increase the energy density of the meal, which can result in weight gain as the meal becomes a much more concentrated source of calories.

The potato does, it seem, hold a key to obesity in South Africa, but it’s not so much in this staple food’s chemical constitution as in how we like to eat it; and it’s in fast foods, snacks-on-the-run, and the heaped portions we serve ourselves at a braai where the danger seems to lie. A healthy portion of potato should be served boiled or as a baked jacket potato or sweet potato, in portion control, without the addition of extra fats.

So, what would be a healthy lunchtime meal for someone living an active, business lifestyle? For Jenny Meyer, there’s definitely room for a potato: “Ideally, a chicken, tuna or salmon salad with a small amount of corn or boiled potatoes added for starch.”

Originally published in the Business Day, 18 July 2012