What are carbohydrates, what are their benefits and are they really the dietary villain behind the global obesity epidemic? Dr Alan Barclay investigates
Popular diets come and go over the years, much like our changing clothing preferences. Back in the 1970’s, carbohydrates were the dietary villain and very low carbohydrate diets were made popular by Dr Robert Atkins. Low fat diets then became popular thanks to authors like Nathan Pritikin and remained so for much of the 1980’s and 1990’s. In the late 1990’s, Dr Atkins released a new edition of his “diet revolution” book, and low carbohydrate diets came back in to vogue and they have remained fashionable ever since. What are carbohydrates, do they have any benefits and are they really making us fat?
“Many people are eating less than the recommended amount of carbohydrate„
What are carbohydrates?
The three most common kinds of carbohydrate in foods are sugars, starches and dietary fibres. There are many different types of sugars. A sugar can be a single unit of carbohydrate e.g. glucose, fructose and galactose, or could be two of these carbohydrate units joined together e.g. sucrose, which is made up of fructose and glucose. What is surprising is that once consumed, pretty much all sugars and starch are broken down by the body into glucose, which then circulates in the blood stream to be used by the body for energy.
Added sugars are defined by the World Health Organisation as all mono and disaccharides added to foods by food manufacturers, cooks or consumers including refined fructose, glucose and sucrose. The term “free sugars” includes all added sugars, plus the sugars naturally present in honey, syrups such as maple and rice, fruit juices and concentrates.
Starches are made up of long chains of one type of sugar – glucose – and are found naturally in a wide range of foods from grains such as rice and wheat, legumes such as beans, lentils and chickpeas, starchy vegetables such as corn, potatoes and pumpkin, and nuts and seeds.
Dietary fibres come mostly from plants. They are not very well digested and so pass through your digestive system. This helps keep your bowels healthy and helps prevent digestive problems.
We now know that dietary fibres provide far more than relief from constipation and eating sufficient fibre is important for all aspects of health including regulation of cholesterol, boosting blood sugar control and helping to achieve good immunity.
What are the health benefits of eating carbohydrates?
Starches and sugars are used as an energy source by our bodies and are the preferred fuel for our brains and nervous systems and for our exercising muscles, particularly when exercising intensely.
Dietary fibres help increase faecal bulk and transit time so helping normal bowel function and help lower blood cholesterol levels. Higher fibre foods form the basis of many traditional cuisines associated with wellbeing and longevity including the Mediterranean diet, which focuses on breads, pastas, legumes and fruit, and the Okinawan diet (from Japan) which includes sweet potatoes, peas, beans, lentils and rice.
“People are eating less than half the amount of fibre they need in their diets„
How much carbohydrate are we eating?
The most recent National Diet and Nutrition Survey in 2013-14 found that almost half of the calories men and women ate every day were from carbohydrate. Many people are eating less carbohydrate now than they were at the turn of the century and less than the amount recommended for good health.
The UK’s Scientific Advisory Committee on Nutrition (SACN) recently recommended that people eat no more than five per cent of their daily calories from free sugars. However, both men and women are eating and drinking double the amount of free sugars than recommended.
Sadly, most people in the UK are not eating nearly enough fibre in their diets. The recommended amount of fibre is 30 grams a day, but both men and women are on average eating less than half of what they need.
The bottom line is that in general, people aren’t eating too much carbohydrate in total, but they are eating the wrong kind of carbohydrate. However, what is true is most people are eating too much refined starch and sugar in their diets and these foods are low in dietary fibre.
Why do some people think carbohydrates are fattening?
Some carbohydrates have a powerful effect on our blood glucose (sugar) and insulin levels and for this reason, many popular authors have singled them out as the main reason for the global rise in obesity. However, these authors are either unaware, or ignore the fact that proteins and fats in food affect blood glucose and insulin levels too!
Insulin is a hormone that plays a very important role in our bodies. It’s quite well known that foods high in carbohydrate increase insulin but, interestingly, so does protein. Whey protein is the strongest stimulator of insulin production followed by fish, beef, egg and chicken. Fats can also increase the amount of insulin you need but a little later after eating – usually about three to five hours after a meal.
So, when you read the latest diet book singling out carbohydrates as the dietary villain behind the global obesity epidemic, advising you to eliminate them and replace them with protein and fats, stop and think! Remember that fats and protein also influence our blood glucose and insulin levels, so simply avoiding carbohydrate foods in your diet is definitely not the answer.
What carbohydrate foods should you eat and how much is needed for optimal health?
Choose carbohydrates from minimally processed plant foods such as fruit, vegetables, beans, peas, lentils, seeds, nuts and wholegrains. These foods, and the traditional staples we make from them, such as noodles, pasta and good-quality grainy breads, are rich in dietary fibre, vitamins and minerals.
Aim to fill one quarter of your plate with wholegrains, beans, peas or lentils, half with fruit and vegetables and one quarter with lean protein such as red meat, poultry, seafood, eggs, reduced fat dairy, or a vegetarian alternative.
Dr Alan Barclay is an accredited practicing dietitian and a Research Associate at the University of Sydney in Australia. He works in clinical dietetics maintaining a private practice in Sydney. He has co-authored more than 30 peer reviewed articles in the scientific literature and is the author of Reversing Diabetes and a co-author of The Good Carbs Cookbook, Low GI Diet: Managing Type 2 Diabetes, and The Ultimate Guide to Sugars and Sweeteners.