To Carb or not to Carb that is the Question

Owing to the widespread popularity of weight-loss diets centred on the restriction of its' consumption, carbohydrate has become a much maligned foodgroup and something of a victim of popular opinion. healthpro Dietetic Clinic provides a timely reminder of what carbohydrates are, what function they perform, and what the most current evidence tells us about their effects on the body.

What are they? 

Carbohydrates are sugar compounds produced by the process of photosynthesis in plants. They are divided into three categories, simple carbohydrates, complex carbohydrates, and dietary fibre, based on the number of sugar units they contain and how those units are joined together. Simple carbohydrates contain one or two sugar units, with the former referred to as monosaccharides, and the latter as disaccharides. Examples of monosaccharides are fructose (fruit sugar) and glucose (derived from the disgestion of carbohydrates). Examples of disaccharides are sucrose (table sugar) and maltose (malt sugar). Complex carbohydrates have three or more sugar units and are referred to as polysaccharides, an example of which is starch (found in pasta, rice and potatoes and composed of many glucose units joined together). Dietary fibre is also a polysaccharide, examples of which are cellulose (another compound composed of many glucose units) and pectin (a compound found in apples which is composed of galactose, arabinose, galacturonic acid). In general terms, the simpler mono and disaccharides tend to be sweeter in taste than the more complex polysaccharide molecules.

What is their purpose? 

The primary fuel of the body is glucose. Inside every cell in the body, glucose is converted into a substance known as adenosine triphosphate, or ATP, which provides the energy for that cells' function. Simple and complex carbohydrates in the diet provide glucose, or sugar units which are readily converted into glucose, for cellular energy production. Excess glucose is stored by the body in the liver and muscle tissue in a more complex form known as glycogen. When glycogen stores reach capacity, any additional glucose can be converted into fat. To satisfy energy needs, the body preferentially uses glucose in the blood, followed by stored glycogen. When these sources are depleted, as may be the case when following a carbohydrate-restricted diet for example, the body begins to burn protein tissue in order to generate glucose, an obviously unsustainable process!

In addition to energy production, dietary carbohydrates also provide nutrients for bacteria that aid digestion, and contribute to the absorption of certain vitamins and minerals. The sugar units contained in dietary fibre cannot be digested by the body, and so cannot contribute to energy production, but play a vital role in maintaining a healthy digestive tract and may also contribute to the regulation of blood cholesterol.    

What does the evidence say about their effects on health?

In June 2014, The Scientific Advisory Committee on Nutrition (SACN), a group of independent experts that provides advice to  UK government agencies and departments to inform public health policy, published a detailed document entitled 'Draft Carbohydrates and Health report'. In this report (http://www.sacn.gov.uk/reports_position_statements/reports/scientific_consultation_draft_sacn_carbohydrates_and_health_report_-_june_2014.html) SACN members performed an evaluation of the existing scientific evidence on the relationship between dietary carbohydrates and health. Based on combined results from the research studies investigated, the conclusions of the committee can be summarised thus:

• In children and adolescents, consumption of sugar-sweented beverages, as compared with non-calorie sweetened beverages, results in weight gain and an increase in body mass index
• In children and adolescents, higher consumption of sugars, sugar-containing foods, and sugar-containing beverages is associated with a greater risk of dental carries
• Sugar, or sugar-sweetened beverage intake is not associated with the incidence of colo-rectal cancer
• There is no relationship between the incidence of type 2 diabetes mellitus and total or individual sugar intake, but a greater risk is associated with higher intake of sugar-sweetened beverages
• Increasing intake of sugar and sugar-sweetened foods and beverages does not effect inflammatory markers or cardiovascular risk factors
• There is no relationship between total carbohydrate intake and the incidence of cardiovascular disease endpoints, type 2 diabetes mellitus, glycaemia, or colorectal cancer
• In children and adolescents, there is no relationship between total carbohydrate intake and body mass index or body fatness
• An energy-restricted higher carbohydrate, lower fat diet, as compared with a lower carbohydrate average fat diet, may be effective in reducing body mass index 
• A diet rich in dietary fibre is asscociated with a lower incidence of cardiovascular diseases, coronary events, type 2 diabetes mellitus and colo-rectal cancer
• Higher intakes of oat bran and isolated β-glucan (a polysaccharide contained in cellulose) have beneficial effects on fasting blood lipid concentrations and blood pressure

The results of this authorative report show that carbohydrates are not the anathema to good health that many would have us believe. Whilst the evidence clearly indicates that the intake of sugars and sugar-sweetened foods and drinks should be minimised to control weight gain and the risk of dental carries in the young, total carbohydrate intake as a whole is not associated with any adverse health effects investigated in the report. It also indicates that decreases to body mass index can be achieved without cause to dietary carbohydrate reduction per se. Furthermore, the report shows that intake of carbohydrate in the form of dietary fibre is associated with lower rates of cardiovascular disease, type 2 diabetes, and certain cancers.

If you require nutrition and dietetic information, advice or treatment, please contact the healthpro Dietetic Clinic for an appointment on +353864119222 or email info@healthpro.ie 

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