After deliberating for 6 years we finally have the draft report on carbohydrates (1). In view of the current concern about the effects of sugar on health, there is likely to be considerable interest in the findings. The report consists of a comprehensive evaluation of the available scientific evidence which provides information on the role of the various types of carbohydrate in diet and health. However the big problem is that there are limitations with much of the research. Although randomised controlled trials can provide strong evidence for a causal relationship between diet and disease risk, they generally investigate markers and risk factors, rather than actual disease outcomes. Trials are only typically carried out for short periods whilst chronic diet over many years is more relevant to health. With observational studies there is potential for biases so that any associations must be interpreted with caution. Definitions such as ‘whole grains’ may vary markedly between studies.
Nevertheless a number of important recommendations have been proposed.
In particular it was concluded that:
“Since the dietary reference values were last considered, the quality of the evidence indicating that a high intake of free sugars is detrimental to several health outcomes has strengthened. Higher consumption of sugars, and sugars- containing foods and beverages is associated with greater risk of dental caries. Randomised controlled trials conducted in adults indicate that increasing sugars intake as part of an ad libitum diet, either through the substitution of other macronutrient components or by replacement of non-caloric sweeteners by sugars, leads to an increase in energy intake. Consumption of sugars sweetened beverages is associated with an increase in Type 2 diabetes mellitus. Randomised controlled trials conducted in children and adolescents indicate that consumption of sugars-sweetened beverages, as compared with non-calorically sweetened beverages, resulted in weight gain and an increase in body mass index.”
This in turn led to the following recommendations:
- 1. The definition for ‘free sugars’ be adopted in the UK and that this comprises all
monosaccharides and disaccharides added to foods by the manufacturer, cook or
consumer, plus sugars naturally present in honey, syrups and unsweetened fruit
juices, excluding lactose when naturally present in milk and milk products.
- 2. The dietary reference value for free sugars should be set at a population average of
around 5% of dietary energy for age-groups from 2.0 years upwards. This is based
on the need to limit free sugars to no more than 10% of total energy intake at an
individual level, which is likely to lead to a population average free sugars intake
of around 5% of total energy.
- 3. The consumption of sugars-sweetened beverages should be minimised, in both
children and adults. “
The current position was determined by SACN’s predecessor COMA (Committee on Medical Aspects of Food Policy) in 1991 which recommended that the population average for the consumption of ‘non-milk extrinsic sugars’ should be 10% of energy intake(2). SACN is recommending the use of ‘free sugars’ as more appropriate measure of sugar intake. In addition it is recommending that the population average be reduced to 5% of energy. This represents a very significant shift and if implemented would mean that a majority of consumers would have to make quite radical changes in their habitual diet.
Although SACN has been somewhat cautious in its reasoning, it has fallen into line with many other individuals and the recent WHO recommendation. In particular sugar has been identified as an ingredient which has a specific role in the development of various aspects of disease and ill-health. In other words there is a lot more to sugar than just calories. In the past the apologists for sugar have relied on the arguments that sugar as such is not a problem as long as total calorie intake does not exceed calorie output. This was always a rather dubious because of the fact that sugar is ‘empty calories’ so that the higher the sugar content in the diet the greater the dependence on the other constituents in the diet to provide all the other essential nutrients.
SACN was unable to find any convincing evidence that sugar was associated with Type 2 diabetes. However it did identify an association between greater consumption of sugar sweetened beverages and the incidence of diabetes.
The other important aspect of the report is the position on dietary fibre where it was concluded that:
“Overall the evidence from prospective cohort studies indicates diets rich in dietary fibre
are associated with a lower incidence of cardiovascular diseases, coronary events, stroke
and type 2 diabetes mellitus, colo-rectal cancer, colon and rectal cancer; no association
with change in body weight in adults or body fatness in children and adolescents is
indicated. Although the definitions used to define whole grains vary between studies,
higher whole grains consumption is associated with a lower incidence of cardiovascular
disease, stroke, hypertension, type 2 diabetes mellitus and colon cancer, although the
evidence is based on a smaller number of studies than for dietary fibre. Higher cereal
fibre consumption is associated with a lower incidence of coronary events, type 2 diabetes
mellitus, colo-rectal cancer, although the evidence is more limited for constituents of
dietary fibres due to the smaller number of studies.”
As a result SACN recommends that dietary reference value for dietary fibre for an adult population average should be 30g/day. This represents an increase of about 25% on the current advice. This should be largely achieved from a variety of foods, such as whole grains, pulses (e.g. kidney beans, haricot beans, lentils ), potatoes, vegetables and fruits.
This report certainly represents an important step forward in that the dangers of excessive sugar consumption have been recognised. However it has failed to address the issue of refined carbohydrates, presumably because there is no convincing evidence to show that the rapid digestion of starch results in a build up of glucose in the blood. This factor must contribute to the development of diabetes (See for example 4)
The other major limitation is that it has not considered the position on saturated fat (SFAs). It is now evident that the original case for limiting the intake of SFAs was fundamentally flawed and in fact it is now becoming recognised that many of the individual SFAs are actually important nutrients (5). Despite this the government persists with its ludicrous Responsibility Deal in which the food industry is being pressurised to reduce the SFA in the food chain. Unfortunately if sugar intake is to be reduced it will have to be replaced and the obvious choice is foods which are rich in SFAs!
- COMA (1991) Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. London: HMSO.