The Origin of ideas, myths and misinformation about food

Professor Mark L. Wahlqvist * and David R. Briggs (1991)#

Although the origin of many of our ideas about food and health is difficult to trace, we can isolate a number of factors behind some of these beliefs.

Food Availability

Many cultures restrict the eating of foods that are in limited supply, through either social or religious prohibitions. For example, the vegetarian or semi-vegetarian diet developed in cultural settings where meat was in short supply.

Availability may have played a role in the different allocation of food to mend and women and to adults and children in some cultures, though physiological meeds will also have played a part. Some communities also attempted to control fertility and population size by using particular foods for pregnant and lactating women, or for older members of society.

You may be able to trace the most likely reason for the association of particular foods with special occasions and celebrations that have become traditional in your family. Were these foods in short supply, and therefore more expensive, in your grandparents time? Do they have a special religious significance? Are there other factors involved?

It is a luxury of the affluent to be able to overturn food beliefs that in the past have controlled the distribution of scarce food.

Exploitation

Ideas about food and health are sometimes developed by those who seek power or money. These people may use a fragment of evidence or partial truth which they develop beyond all scientific justification, to enhance their credibility. They encourage people to believe that their health depends on having a certain food, so that they are more likely to buy that food or product. Such foods may have a place, even an important one, in a healthy diet, but it is also clear that many foods are not essential because the essential nutrients can be found in a range of foods. For example, 'health' food shops offer many foods such as whole grain cereals, legumes, dried fruits and nuts which are commendably lower in fat, particularly saturated fat, and contain less sugar and salt and more dietary fibre than many processed foods. However, these foods are also available in most supermarkets and generally at lower prices.

If people are persuaded that their diet is deficient in a particular vitamin or mineral or some other nutrient they may believe that they need nutrient supplements, like vitamin pills. Unfounded fears about the food supply in countries like Australia have contributed to the use, even abuse, of nutrient supplements on a regular basis by at least 20 percent of the adult population. In our society we can afford to demand high quality in our food supply. But we should not allow ourselves to be at the mercy of those who have much to gain financially from these fears.

Efforts to explain food preparation and its effects on people

Since food purchase, preparation and eating occupy a significant part of our lives, it is not surprising that there is a great deal of interest in food and in trying to explain the various phenomena associated with it.

What is the ecological place and function of an oyster? Given that seeds support the early life of plants, what nutritional properties might they have? What is happening to fruit as it ripens? To meat as it is barbecued? To bread as it bakes? What makes us feel hungry, or satisfied?

Science offers one way of explaining these phenomena. What distinguishes science from other systems of knowledge is the predicability of a particular outcome when a practice or event is repeated. Ideas are the starting point, but they are not enough. Observations must be repeatable. Explanations must be consistent, no matter how tested. The establishment of a scientific fact depends on well-designed, extensive and rigorous testing. Ideas and explanations must be able to stand up to full evaluation by other scientists.

Biological systems, including food and the human organism, are exceedingly complex. In seeking to understand such systems the scientist must unravel many interacting factors. The effect observed after a certain event may be modified, enhanced or diminished by other factors. For example, for a particular level of cigarette smoking the risk of lung cancer can be decreased by a regular intake of green leafy and yellow vegetables. The risk of cancer of the throat from cigarette smoking can be increased by regular intake of alcohol.

Pseudo-science is rife. Many people now use a scientific vocabulary, to inspire confidence in what they say or write. But careful analysis shows their case to be phoney.

For example, you might read that 'stomach enzymes do not work on vegetables and fish at the same time and therefore these foods should not be eaten together'. Sounds scientific! How should you examine such a statement? First you might note that most people at some time combine these foods, and that doctors and government health officials now recommend consumption of these foods to promote good health and a long life. You might still want to seek more information on the suggestion that combining the foods is not a good idea. The explanation offered is inaccurate. Firstly, the stomach is only one site of digestion, and much more digestion takes place in the small intestine under the action of pancreatic secretions and other digestive enzymes. Secondly, both vegetables and fish contain different nutrient components, such as protein, carbohydrate and fat, which must be digested. We do know that some plant foods contain substances that inhibit some of the enzymes that digest proteins or carbohydrates, but this is usually not of practical importance; and, if it were, it would affect digestion of both plant and animal-derived foods. Moreover, even if a particular food component is incompletely digested, this may not be a problem, and could even be an advantage. Some starch, for example from cereal and bananas, is not  digested in the small intestine, but is further processed by the bacteria in the large bowel, yielding gases like carbon dioxide, methane and hydrogen and other body fuels. These are used in the lining of the large bowel and are absorbed into the bloodstream for use in the liver and other tissues. These processes may play an important role in the function of the large bowel.

To come back to the original proposition about eating fish and vegetables together, so far there is not scientific evidence that combining vegetables and fish is a risk to human health. The point of this example is that biological and especially physiological knowledge is required to evaluate nutritional claims, and not just scientific jargon. Since such basic physiological knowledge is often lacking, many interested and well-meaning, even 'educated', individuals are prey to bogus nutritional claims.

Health

There is every reason to believe that the way we eat contributes to our health. At one extreme this simply means having enough food. Once the food supply is sufficient and affordable, people can begin to seek the most healthy diet for their lifestyles and circumstances. This has been happening for several decades in the more affluent Western societies. As more societies gain access to a wider range of foods, it is important that research in the area of food and nutrition is equal to the challenge, that the findings are available, and that they are interpreted in a scientifically sound way.

Nutrition researchers should also consider the experience of earlier and contemporary hunter-gatherer populations, because this is the longest food experience that humans have had. For example, the food culture of Aboriginal Australians was characterised by considerable variety of both plant and animal foods and the use of lean meat or fish. The diet was low in salt (sodium) and in added sugar, contained little or no alcohol, was combined with physical activity, and was associated with good life expectancies. Current national dietary guidelines embody many of the characteristics of the hunter-gatherer diet, modified for twentieth-century reality. When in doubt, or when radical dietary proposals are made, it is worth appealing to the longest human experience!

When considering food and health, food patterns that may help to prevent particular health problems need to be distinguished from foods that may help in the treatment of various diseases. The two are not necessarily the same. For example, a diet that helps to prevent cancer developing may be useless in treating cancer. As another example, dietary patterns that may contribute to the development of age-related diseases, such as coronary heart disease or mature-onset diabetes, do not necessarily have any connections with the ageing process, which is still poorly understood. It is wise to be sceptical about claims that a nutritional technique prolongs life, especially if it distorts an established food culture or tradition. At the same time, we continue to need sound research in this difficult area of human nutrition.

Logical errors

Errors in logic are sometimes the basis of mythology on food and nutrition.  For example:

1.  A simple association is mistaken for a cause-and-effect relationship.

'I was eating cucumber when I developed central chest pain which turned out to be a heart attack. The cucumber must have caused the heart attack'.

Analysis: It may have been pure chance that the heart attack occurred during consumption of the food in question. Many factors, including food factors, over an extended period of time contribute to heart attack. There may have been precipitating factors other then food consumption operating at the time of the heart attack, although these may not have been obvious to the person suffering the attack.

2.  The primary cause of a disease is mistaken for the only factor involved in becoming ill.

'Measles is caused by a virus, so the way children eat is not going to help them avoid measles'.

Analysis: In fact, protein-energy malnutrition is one of the factors which predisposes people, especially children, toward fatal measles infections. This is because a person's nutritional status determines, in part, their resistance to infection. 'Nutrition status' is the biological consequence of the way in which we eat (or, if we cannot eat, by vein or tube-feeding); it is reflected in how much muscle and fat we have, what our blood protein levels are, how well our body's defence system works, whether we can make blood cells and much more. Genetic and other factors are also involved in resistance to disease. Whether someone catches a particular disease almost always depends on the interaction of several factors, only one of which is their exposure to a particular disease-causing agent such as a virus. This partly explains why a particular agent or food or way of eating does not necessarily carry the same risk for all individuals.

3.  The amount of nutrient in a food is mistakenly thought to be the main factor determining the value of that food.

'Wholegrain cereals do not contain as much iron as meat, therefore vegetarians are at risk of iron deficiency'.

Analysis: The availability to the body of a particular nutrient (iron in this case) is affected by more than just the amount of that nutrient in a food or even the whole meal. For example, phytate found with dietary fibre, phytase (an enzyme from yeast), or tannin from tea affects the bioavailability of iron from our diet (the extent to which the iron in food can be utilised by the body). The food components that have no nutritive value must also be considered because they may react chemically with some nutrients, or have physiological effects. For example, phyto-oestrogens in some plants (substances with female sex hormone like properties) could modify the menstrual cycle and menstrual blood and iron loss in some women who ate these plants in sufficient quantity. It must be remembered that foods are chemically complex mixtures, and not simply sources of particular combinations of nutrients.

Chapter 1 from "Food Questions and Answers: Sort the facts from the fads to help you choose a healthy diet". Victoria, Australia: Penguin. (1991). ISBN: 014 008743 5. pp. 1-9.

* Mark L. Wahlqvist is Professor of Medicine at Monash University and current Chairperson of the Australian Nutrition Foundation Inc.

# David Briggs is a food scientist and Associate Professor in the Department of Human Nutrition at Deakin University

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[Date Modified: October 1999]