NEW SCIENTIFIC KNOWLEDGE

THE MYTH REMAINS

CONCLUSION

Prepared by the Nutrition Programmes Service, Food and Nutrition Division of the FAO.

INTRODUCTION

The presentation of a nutrition paper in a conference of economists, commodity specialists and traders aiming to discuss sugar production and trade issues is a rare, but laudable event. It is, of course, fully in line with FAO’s broad mandate to assure food availability and nutritional well being for all people and to introduce nutritional considerations in all aspects of economic development.

Sugar in the diet is popular primarily because of its sweetening properties. It also has many other unique properties that make it valuable in a variety of applications in food preservation, processing and preparation. However, its primary nutritional characteristic is that it simply provides a ready source of dietary energy.

Not surprisingly, sugar is highly appreciated and sought after by most people as it has a unique capacity to make foods appealing and desirable. As more and more people over the years have acquired easy access to a variety of sweetened foods, the question of overconsumption has arisen among some in the medical and health communities and, accordingly, in the public at large. Enormous amounts of effort and resources – often applied with a Crusader’s zeal - have gone into denouncing sugar and in trying to identify and quantify the detrimental effects of sugar consumption.

It was around 1850 when an exponential rise in sugar consumption was first observed in the United Kingdom, where at the time, consumption per person per year was similar to that of developing countries today. This major increase in consumption of a substance that appeared to appeal to people’s hedonistic tendencies by virtue of its sweet taste, made it a natural target for society’s ills. The continuing rise in consumption after World War II led researchers to query whether, in fact, high levels of sugar intake could be responsible for a range of health problems. Unfortunately, many were all too quick to supply answers before the results were in. Statements like "white, pure and deadly" and "empty calories" were subsequently picked up by some nutritionists, health professionals and the press, and the still widely believed myths about sugar were created. Sugar was regularly being condemned well before its "scientific" trial was over.

Years of research have now gone into trying to determine if sugar undermines health, and I am pleased to report that the evidence consistently tends to point in the opposite direction. The conclusion today: sugar as generally consumed is a safe and valuable food source. The problem remaining: many people still do not believe it.

Like all commodities, sugar, which is generally refined before being consumed, has a price. It is, therefore, not unexpected that generally more is consumed in industrialised countries than in developing ones. Total consumption figures, including its use outside the household, is around 41 kg per person per year in high sugar-consuming countries while only around 15 kg in low-income countries. Globally, sugars and other sweeteners contribute approximately 9% of the total energy supply of the world’s population with very high variation in national and individual consumption patterns.

Considering the overall world food and nutrition situation, the 1996 Rome World Food Summit showed that, in spite of a decline in chronic undernutrition, there are still over 800 million undernourished people living in developing countries. It is noteworthy that these are generally countries in which large amounts of sugar are not regularly consumed. It is also important to note that much of the world’s sugar is produced in developing countries, and that the issue of whether sugar is good or bad has important implications for its supply and demand. Unwarranted attacks on sugar that affect its production and trade in both domestic and international markets can have far-reaching social and economic consequences. The purpose of this paper is to look at current scientific knowledge about the role of sugar in health and disease.

NEW SCIENTIFIC KNOWLEDGE

The past thirty-plus years of intensive research into sugars, carbohydrates and dietary fibres has led to significant strides in our understanding of the metabolism and physiological effects of these dietary components. Epidemiological studies have delved into the relationships between food consumption, including that of sugars, and health status, and earlier concerns have been clarified. Our understanding of dietary behaviours in different food situations and among different populations and age groups has also increased dramatically during this time. To bring these new findings together and make use of them for nutrition improvement and maintaining health, FAO and WHO convened the joint Expert Consultation on Carbohydrates in Human Nutrition in Rome in April 1997.

In preparation for this consultation extensive literature reviews on non-communicable diseases and all aspects of carbohydrate digestion, absorption, metabolism, and behaviour were examined by a group of experts from thirteen countries. These examinations included sucrose (table sugar) and the different sugars contained in the myriad of foods in world diets. In brief, the results, based on solid scientific grounds, dispelled the generally negative myths about the consequences of sugar consumption. The Report of the Consultation and its Recommendations were given world-wide dissemination through the Nutrition site of the FAO Homepage on the Internet (www.fao.org). They will be circulated through other channels once the Report is published.

Selected findings from this and other sources are discussed as follows:

Sugar does not make people fat

In high-income countries there is great public health concern about the rising percentage of obesity as expressed in high body fat accumulation. In the richest countries, more than 25% of the population can be considered obese, but its prevalence is also rising in the developing countries, even among the poor income instances. Since obesity is a key factor in the aetiology of several degenerative diseases, the understanding of the role of sugar as a food energy source is therefore of great importance.

Maintaining stable body weight requires that total energy consumed be balanced against total energy spent. Therefore, excess energy consumption in any form will promote body fat accumulation. When it is realised that dietary fats and oils have over twice the food energy value of sugars, it becomes clear that the major risk factor for obesity is excess dietary fat, not carbohydrates or sugar. Coupled with this unequal energy contribution is the fact that carbohydrate, including sugar, is the preferential energy source for the body. That is, carbohydrates are oxidised first and leave the more easily accumulated fat as the excess energy source.

Interestingly, findings generally show an inverse association between the intake of sugars (total sugars) and obesity and fat intake. Indeed, epidemiological data from a number of countries show that people with higher sugar intakes are less likely to be obese than those with lower sugar intakes. Also, there is no conclusive evidence indicating that the sweetness of sugar contributes to increased appetite. In fact, the opposite is generally true: the body tends to have a much better appetite-reduction response to carbohydrates and sugar than it does to dietary fat.

In summary, the consultation found no evidence to implicate either sugar or starch in the promotion of obesity other than their contribution to total energy intakes.

Sugar does not cause diabetes

Table sugar, or sucrose, is made up of one molecule of glucose linked with one molecule of fructose. Once eaten, the chemical bond is split and both sugars follow different absorption paths: glucose is absorbed via a dynamic process whereas fructose enters through a passive mechanism. Following ingestion of carbohydrate, glucose increases blood glucose and stimulates the release of insulin. The latter hormone signals to the cells of the body to absorb glucose, thus reducing its concentration in blood. In diabetes patients this control mechanism is impaired, and historically much attention had been given to helping such patients regulate their sugar intake.

Many factors influence the rate of serum glucose increase following consumption of carbohydrate, ranging from the type of carbohydrate and other nutrients consumed to physical activity levels. Among the more important discoveries about carbohydrate over the past twenty years has been that some of it is not absorbed at all in the small intestine and becomes fermented in the colon. This carbohydrate that goes to the colon contributes little energy and is not glycemic.

A system, called the glycemic index (GI), has been devised to rank foods empirically on the basis of their ability to contribute to increased blood glucose levels. It is particularly interesting to note that while pure glucose is the most glycemic food, sucrose is not highly glycemic. In fact, it is often surprising to learn that sucrose is rated below maize, rice, wheat and potatoes. This is due to the high amount of fructose, which has a very low GI, present in sucrose. The use of the GI has totally transformed dietary advice for many diabetics who are generally encouraged to consume foods with a low glycemic index. As a result, diabetics are allowed to consume even sugar, generally up to 50 grams per day.

The cause for non-insulin-dependent diabetes (NIDDM) is insulin resistance at the cellular level, also referred to as glucose intolerance. Sugar intake is not the cause of the development of this clinical state. In fact, the most important contributing factor towards the development of NIDDM is obesity.

Epidemiological studies show that high percentages of non-insulin dependent diabetes (NIDDM) are found in all population groups undergoing rapid cultural changes and changes from traditional diets. There is no doubt that genetic factors are involved even though the precise mode of inheritance has not yet been established. Diet and lifestyle-related conditions, which lead to obesity, will clearly influence the risk of non-insulin deficient diabetes.

The main disease management feature for this condition focuses on reduction of weight, avoidance of obesity and, strengthening low fat diets including a wide range of cereals, vegetables and fruits with emphasis on low glycemic index. Sucrose and other sugars have not been directly involved in the aetiology of non-insulin dependent diabetes and key dietary advice for diabetics has been to distribute the intake of carbohydrates throughout the day.

Sugar does not cause cardiovascular diseases

Understanding the results of early studies on the metabolism of sugar resulted in the concern that glucose was not being used for the production of glycogen, i.e. energy storage in the body, but rather for the production of fatty acids and triglycerides. It appears, however, that carbohydrate is not readily transformed to fat by the body but contributes to obesity through a fat-sparing mechanism. In other words, carbohydrate is the first choice of the body as a source of energy and is preferentially oxidised. Fat tends to be oxidised only when available carbohydrate has been oxidised first. Ingested fat also directly contributes to fat stores, by contrast to carbohydrate.

The expert consultation reported that genetic factors are involved in the aetiology of coronary heart diseases and influence both the atherosclerotic and thrombotic processes underlying clinical manifestations of this disease. Dietary factors may influence these processes directly or via a range of cardiovascular disease risk factors. Obesity, particularly when centrally distributed in the body, is associated with an appreciable increase in the risk of coronary heart disease. There is also evidence implicating specific nutrients and, in particular, the high intake of some saturated fatty acids, which appear to be promoters of coronary heart disease. On the other hand, there is increasing evidence that a range of antioxidant nutrients provide strong, protective effects. Increasing carbohydrate intake can assist in the reduction of saturated fat, and many fruits and vegetables, rich in carbohydrates, are also rich in several antioxidants. Cereal foods rich in non-starch polysaccharides have been shown to be protective against coronary heart disease in a series of prospective studies. There is no evidence that sucrose plays a causal role in the aetiology of coronary heart disease.

The cornerstone of dietary advice aimed at reducing the risk of coronary heart disease is to increase the intake of carbohydrate-rich foods, especially cereals, vegetables and fruits rich in non-starch polysaccharide, while reducing the intake of fat. Among the overweight and obese, it is important to reduce total fat intake while encouraging the consumption of appropriate carbohydrate-containing foods. There has been concern that a substantial increase in carbohydrate-containing foods at the expense of fat might result in a decrease in high-density lipoprotein and an increase in very low-density lipoprotein and triglycerides in the blood. There is, however, no evidence that this occurs when the increase in carbohydrate results from increased consumption of vegetables, fruits and appropriately processed cereals, over prolonged periods.

Sugar intake does not lead to micronutrient deficiencies

Table sugar, i.e. sucrose, has been labelled a food or a nutrient consisting of only "empty calories". It is believed that, if used in substantial quantities, it might replace other nutrients in the food or diet. While it is, of course, true that refined sugar does not contain micronutrients, examination of data looking at nutrient intake data, for example, men of different ages in the United States, consuming widely differing amounts of sugar (less than 26g, up to more than 60 g/1000 kcal/day), show that there is no risk of becoming mineral or vitamin deficient even when higher intakes are recorded. Only fibre intake was reduced slightly in high sugar diets. In fact, high sugar consumers are more likely to reach at least two-thirds of their recommended dietary allowance of essential vitamins and minerals than are low sugar consumers.

As to fat intake, the data showed a marked decrease in the higher intake group. The supposition that sugar automatically replaces foods rich in micronutrients, adversely altering micronutrient intake, therefore, is without foundation. Common sense would indicate this since there appears to be a limit to total daily sugar intake, and sugar intake has to be seen as an integral part of the whole diet.

Sugar does not cause hyperactivity in children

The notion that sugar adversely affects human behaviour has circulated since the 1920s. By mid-century sugar was associated with the condition called "tension fatigue syndrome". Twenty-five years ago sugar consumption was related to a condition called "functional reactive hypoglycaemia". The strong belief in the relationship between sugar and anti-social behaviour has resulted in studies to demonstrate a correlation between sugar intake in children and hyperactive behaviour. Double blind studies followed earlier less rigidly controlled ones, and a meta-analysis was undertaken including a look at the claim that sugar intake improves cognitive performance.

The experts of the consultation, however, after discussing this extensive review of the scientific literature on sugar and behaviour produced for the meeting, declared that there was no evidence to support the claim that refined sugar intake has any significant influence on either behaviour or cognitive performance in children.

Sugar consumption can lead to dental caries

Dental caries affect the hard tissues of the teeth. Bacteria-producing plaque (the accumulation of sugar and other carbohydrate foods in a dense mass on the teeth) are responsible for the formation of acids which demineralise the hard tissue of the teeth.

The expert consultation confirmed that the incidence of dental caries is influenced by a number of factors. Foods containing sugars or starches may be easily broken down by alpha-amylase and bacteria in the mouth and can produce acid, which increases the risk of caries. Foods with a high glycemic index produce more pronounced changes in plaque pH than low glycemic index carbohydrate foods. However, the impact of these carbohydrates on caries is dependent on the type of food, frequency of consumption, degree of oral hygiene performed, availability of fluoride, salivary function and genetic factors.

Regarding dental health, the most important observations emerging from the recent epidemiological studies and reviews is "that more and more populations are characterised by a decreasing caries prevalence in the young generations, mostly independent from intake of sugars and other carbohydrates". All these findings call for a less biased and more rational approach to the relationship between sugar, carbohydrates and dental caries and clearly confirm that prevention programmes to control and eliminate dental caries should focus on fluoridation and adequate oral hygiene, rather than on sucrose intake alone.

THE MYTH REMAINS

The Joint FAO/WHO Expert Consultation brought to light strong evidence that a new and dispassionate voice is needed when speaking about sugar, its production, processing and consumption. Yet, it is difficult to translate the results of scientific endeavours into easily understood messages for the public. It is obvious that one expert consultation and continued scientific research, even with convincing results, will not immediately alter some people’s firmly held opinions about specific foods or the consequences of certain dietary intakes. For many, among both the public and some nutritionists, the myth regarding the dire consequences of sugar remains and will need time before it can be corrected.

This has significance for policymakers dealing with production and trade of food items, for the food industry attempting to expand their offered products, and for nutritionists and health professionals setting national dietary goals, establishing dietary guidelines and preparing nutrition education and information programmes for the public. The interesting difference of projections of sugar demand when based on general economic models or on habit formation models is only one example of how an equation can change when the human factor is included.

General food habits often change slowly, although rapid changes can also take place due to external and internal forces in the family. In Norway, for example, in spite of a concerted nutrition education programme, it took twenty-seven years (nearly a generation) to reduce energy intake from animal fat from 29% to 23% (1961-1988). It also took fourteen years to reduce total fat intake from 41% in 1975 to 35% in 1988.

Therefore, in order to dispel the widely-held "sugar is deadly" myth and to allow sugar to be recognised as a valuable component of people’s diets, creative and sustained nutrition education campaigns will be needed. At the heart of the matter is the simple notion that sugar is an inexpensive source of energy that helps make a variety of foods taste better. This can be of particular significance, for example, in regard to child feeding where energy density and taste are of paramount concern. Sugar can play an important role in improving child-feeding practices, but often concerted nutrition education programmes will be needed to overcome outmoded or prejudiced views about its appropriateness. Developing such nutrition education programmes will be challenging as they cannot, both for nutritional reasons and cost effectiveness, focus on only one food item. In fact, for all people of all cultures, it is the whole diet that must be addressed.

In line with this, FAO has developed a simple set of nutritional guidelines that are intended to stimulate the development of local nutrition education initiatives. This FAO initiative, entitled "Get the Best from Your Food," is based on the realisation that a variety of diets and dietary patterns are consistent with good health, and that there are no good or bad foods, per se, only good and bad diets and lifestyles. What this means is that there is no global, ideal diet or dietary pattern appropriate for all people, everywhere. It also means that the appropriateness of a given diet to meet one’s nutritional needs must be judged in light of a variety of individual requirements and local conditions.

The general messages promoted in the "Get the Best from Your Food" materials are: "Enjoy a variety of foods," "Eat to meet your needs," "Protect the quality and safety of your food, " and "Keep active and stay fit." These simple messages can be the key building blocks for national nutrition education campaigns designed to meet local needs and conditions.

FAO has actively been promoting the development of collaborative nutrition education campaigns involving governments and private sector partners. In fact, various elements of the food industry have generously supported the translation, adaptation, printing and introduction of local versions of the "Get the Best from Your Food" materials. There is considerable scope for increasing such co-operative arrangements, and we call upon both the food industry and those in government responsible for nutrition education to explore how they could best work together to develop appropriate education programmes for the public. Only in this way can new knowledge that will ultimately dispel the myth that sugar is deadly be disseminated consistently.

CONCLUSION

In recent years, the science of sugars and their metabolic and physiological effects has become better understood. Similarly, much of the public has become better informed as to the positive effects that sugar can have in their diets, after years of unnecessary fear and suspicion.

Simply stated: eating sugar is not deadly. It does not cause obesity, diabetes, cardiovascular disease, hypoglycaemia, hyperactivity, cancer or lead to micronutrient deficiencies. On a positive note, sugar is a tasty, low-cost energy source that helps make a variety of foods more palatable and desirable. Given the wide-spread prevalence of undernutrition (chronic energy deficiency) throughout the world, the positive contribution that sugar can make to increasing energy intakes among the poor should be stressed. Concurrently, the role that sugar can play in combating obesity by lowering the energy density of high-fat diets should also be noted.

It is unrealistic to expect that the results of a scientific review of carbohydrates and sugar, even one undertaken and reported by a Joint FAO/WHO Expert Consultation, can do much on its own to change the public’s misconceptions about sugar and health. To the contrary, correcting the years of misguided dietary advice will require concerted and consistent efforts in nutrition education. To be most effective, co-operative efforts among producers, food industry technologists, nutritionists, and health professionals will be needed.

The ultimate aim of nutrition education programmes is to promote adequate access to and consumption by all people of the food they need for an active and healthy life. Obviously, sugar can make a valuable contribution to meeting the energy needs of the population. However, it is also important to recognise that in many countries the sugar industry, itself, can make a valuable contribution to improved nutrition. This happens through the sugar industry’s impact on economic development and income generation which are necessary to alleviate poverty and provide the social services needed to promote better nutrition for all.