If you're considering cutting back on carbs make sure you know all the facts first. Nutritionist Jo Lewin discusses the health benefits of 'good' carbohydrates and looks at the pros and cons associated with following a restrictive diet...
An introduction to carbohydrates
Dietary carbohydrates play a central role in nutrition because they are the body’s primary source of energy and are important for the proper function of everything from muscle contractions to brain activity. Carbohydrates are classified into two basic groups: simple and complex:
As their name suggests simple carbs are just that - typically one-sugar molecules (mono-saccharides) or two-sugar molecules (di-saccharides). This category includes refined carbohydrates, which are rapidly digested and release sugar quickly into the bloodstream. They are good when a quick, readily availble source of energy is required, for instance before or during exercise. However, if eaten too regularly and in large amounts they can leave you feeling unsatisfied and prone to energy highs and lows. Examples include white bread, honey, pastries and biscuits.
These starchy carbs are made up of many simple sugars joined together by bonds - the more bonds, the more complex and the longer the carbs take to break down. Eating complex carbohydrates can reduce the chances of feeling fatigued or hungry between meals. The best examples are those that have undergone the least processing – such wholegrains include jumbo oats, brown rice, spelt, rye and barley.
Ideally complex carbohydrates should make up the bulk of your carbohydrate consumption, as they are the best source of nutrients and fibre.
Some research suggests that excessive consumption of carbohydrates – specifically, simple carbohydrates - can be harmful to blood sugar control, especially if you are insulin resistant, experience reactive hypoglycaemia or are diabetic. Carbohydrate excess, especially consuming too many refined carbohydrates, is sometimes associated with weight gain and increased risk of heart disease and some forms of cancer.
Fruit & vegetables
The natural sugar found in fruit and vegetables is called fructose. While fructose is considered to be a simple sugar, the high fibre content means the body digests whole fruit and veg more slowly than say a biscuit that contains no fibre but high amounts of white sugar. As a result, eating high fibre foods containing simple sugars is thought to have less of a dramatic effect on blood sugar levels.
The Reference Intake (RI) for a balanced diet is currently 260g of carbohydrates a day. People following a low-carbohydrate diet often try to stick to less than 50g a day.
Ketosis is often a by-product of a low-carbohydrate diet. Ketones are produced when the body’s glycogen stores have been used up and protein and fat become the primary source of fuel.
Because food choices are limited, low-carbohydrate diets tend to be low in calories yet high in protein and fat. Fruit, bread, grains and starchy vegetables are often limited. The proportion of protein and fat is increased to contribute towards the calories that formerly came from carbohydrate sources.
The Atkins diet and The Dukan diet are well-known ‘classic’ low-carbohydrate programmes, while other plans focus sometimes on the glycaemic index of foods. The glycaemic index (GI) is a rating system for foods based on the extent to which they raise blood sugar levels in the hours after they are eaten. The reference point is pure glucose which is scored at 100. The higher a food scores on the GI scale, the more rapidly the carbohydrate (sugar) is released into the bloodstream.
Low-carbohydrate diets, if followed over a consistent period of time, present a number of health concerns. Such a diet is likely to be low in fibre which may lead to digestive issues including constipation. The lack of carbohydrate in the diet means the body doesn’t have a ready supply of glucose, the brain’s primary source of fuel – this may lead to dizziness and headaches as well poor concentration. Other side effects include halitosis, insomnia and nausea. In addition to this the likely increase in the proportion of protein in the diet places an additional load on the kidneys and may lead to problems with bone-health.
While the exclusion of all carbohydrates often means less refined sugar in the diet which can only be a positive benefit to health, such strict dietary approaches are not conducive to long-term health and should be discussed with a GP or qualified health professional before you start.
If you’ve read all the factsand want to include some low-carb options into your balanced diet, our recipe collection has some delicious suggestions, all containing under 10g of carbohydrates per serving:
Jo Lewin holds a degree in nutritional therapy and works as a community health nutritionist and private consultant. She is an accredited member of BANT, covered by the association's code of ethics and practice.
This article was last reviewed on 27 May 2016 by nutritional therapist Kerry Torrens.
A registered Nutritional Therapist, Kerry Torrens is a contributing author to a number of nutritional and cookery publications including BBC Good Food magazine. Kerry is a member of the The Royal Society of Medicine, Complementary and Natural Healthcare Council (CNHC), British Association for Applied Nutrition and Nutritional Therapy (BANT).
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