Health and food safety
Although Animal Welfare has been the single most important reason for people becoming fully vegetarian, health reasons are probably playing an important part amongst semivegetarians. There are concerns about cardiovascular disease, cancer, Creutzfeldt Jacob disease, Salmonellosis and the consumption of hormones and antibiotics. At the other extreme it is widely held that strict vegetarianism can introduce health risks, especially for infants.
There is a strong emphasis on mental and bodily health in the vegetarian outlook. Oneness and wholeness are important abstract concepts in the vegetarian's perception of mental and physical health. Oneness means that the individual is at peace with nature. Nature is often considered more valuable than culture, and this outlook has helped sustain the Natural and Health Food Industries. The vegetarian outlook despises the way that modern culture has moved towards greater reliance on refinement, cooking and further processing of foods. In ardent vegetarianism, food is believed to be more "natural" if it is eaten raw, and choosing raw foods is seen as an escape from highly processed foods which are regarded as junk (false) foods. Whole foods, such as whole grains and whole nuts are seen as more full of life and vibrant. Their wholeness is synonymous with being unadulterated. Whereas, meat is regarded as a dead food which is in the process of decomposing and eating it is synonymous with ingesting death. Even amongst meat-eaters meat does not have an image of being a "health food", but it may be thought to be "good for health".
All this emphasises the point that "healthy eating" is based on cultural influences as much as pathophysiology or nutritional science, and so beliefs about healthiness of foods are not necessarily accurate. In Australia, about one fifth of all 16 year olds think that it is healthier to be vegetarian than a meat eater (Worsley and Skrzypiec, 1996a). An immediate impression might be that fat intake is the main concern.
A study conducted during the 1960s in Australia showed that vegetarians tended to eat less fat than non-vegetarians. Whether this is true today is not certain. A recent study in the United Kingdom showed that vegetarian children had similar fat intakes to non-vegetarian children (Nathan et al, 1994). The vegetarian children made up their fat intake by eating more margarine in association with bread. On average, fat intake amongst Australian children and adults varies between 34 and 40% of total energy intake (Margarey and Boulton, 1994; Skurray and Newell, 1993). It has been recommended that for adults it should be reduced to 30%.
In the United Kingdom, the public perception of risk factors for developing cardiovascular disease puts fat intake at a low priority (Silagy et al, 1993). Furthermore when a sample of meat-eaters were presented with the hypothetical situation that if the percentage of fat in meats was limited, would they increase their meat eating, the majority estimated that their meat eating would stay the same. This applied to both red meat eaters and red meat avoiders (Richardson et al, 1993). However, they thought that if beef contained polyunsaturated fat their meat eating habits would change.
The most important self criticisms in relation to cardiovascular disease are physical inactivity, followed by smoking, being overweight and then a high dietary fat intake. In reality, the most important factor influencing susceptibility to coronary disease is age. The older one is the greater the risk (Fraser, 1994). Nevertheless there could be benefits from certain types of vegetarian foods. For example, it is thought that nuts might have a protective effect against platelet adhesion and aggregation because of their polyunsaturated fatty acids. Two studies conducted in Australia have shown the advantage of vegetarianism on serum cholesterol levels. One was conducted in teenage Seventh Day Adventists (Ruys and Hickie, 1976) and the other was in 2 to 4 year old lacto-ovo-vegetarian children (Zed & Heywood, 1977). The lower serum cholesterol levels in the infants was associated with lower dietary intakes of saturated fat and cholesterol.
There is sound epidemiological and experimental evidence which shows that vegetarianism is associated with a lower blood pressure. Melby et al (1989) found that vegetarian Seventh Day Adventists had a lower blood pressure than non-vegetarian Seventh Day Adventists, even after adjustment for any differences in tendency to being overweight. Similarly, when lacto-ovo-vegetarian Seventh Day Adventists were compared with meat-eating Mormons in Western Australia, the prevalence of mild hypertension was only 2% in the vegetarians compared with 10% in the meat eaters (Beilin, 1993).
Cross-sectional studies such as this are only suggestive of cause and effect relationships. A number of controlled studies have been done in Australia where subjects were put onto a lacto-ovo-vegetarian diet for a period and then returned to their normal diet. When healthy meat eaters with normal blood pressure took up the vegetarian diet their blood pressure fell, and it rose again on return to the meat-eating diet (Rouse et al, 1983). The same effect was observed with meat eaters who were mildly hypertensive (Margetts et al, 1988). It was not clear which components of the vegetarian diet caused the reduction in blood pressure, but it was not attributable to a change in sodium or potassium intake. Similarly, the effects were independent of any change in body weight or energy intake (Beilin et al, 1988). Two of the largest dietary changes that occur on introducing a vegetarian diet are increases in polyunsaturated to saturated fat ratio and fibre intake. When intakes of these nutrients were increased (in isolation from other dietary changes) to levels seen in vegetarians, no effects on blood pressure were seen in subjects who had normal blood pressure. It is unlikely that it is meat protein which is responsible for the blood pressure differences observed in these studies (Beilin & Burke, 1995). In addition it is unlikely that the absence of meat in the vegetarian's diet is responsible for their lower blood pressure. There is no clear indication as to which nutrient or nutrients are responsible.
Comparisons between the health of vegetarians and non-vegetarians are often complicated by differences in lifestyle and habits and because of changes in eating pattern for reasons of existing illness. Only a few studies have attempted to exclude lifestyle differences, and some of the best evidence comes from medical reports on certain ethnic minorities and religious groups. A particularly useful group has been the Seventh Day Adventists. They usually refrain from smoking, drinking alcohol and coffee but they may or may not be vegetarian. Health records have shown that vegetarian Seventh Day Adventists have a lower prevalence of chronic disease in comparison with non-vegetarian Seventh Day Adventists (Knutsen, 1994). The risk of death from cancer has been shown to be lower in Seventh Day Adventists than in the general population (Mills et al, 1994), but there was no difference in the prevalence of cancer between vegetarian and non-vegetarian Seventh Day Adventists (Knutsen, 1994).
Thorogood et al (1994) examined the reasons for mortality in meat eaters and non-meat eaters over a 12 year period. The vegetarians in their study tended to be more health conscious and their mortality was about 20% lower than in the meat eating group. The vegetarians and fish eaters had a 40% reduction in mortality from cancer, which was independent of any associated difference in prevalence of smoking or other important lifestyle variable. It was concluded, however, that the results do not justify excluding meat since several features of a vegetarian diet apart from not eating meat might reduce the risk.
The risk factors contributing to colon cancer have been studied in some detail in a group of South Australian adults (Steinmetz & Potter, 1993). Colon cancer is the third most common cancer in males in South Australia and the second most common in females. The most striking feature of the results was the link between colon cancer and egg consumption in females. High consumption of red meat was weakly associated with increased risk of colon cancer in both sexes.
In general, vegetarians believe that they are healthier than non-vegetarians. In the United States of America, vegetarians use alcohol, tobacco and prescription drugs less than non-vegetarians (Freeland-Graves et al, 1986b). However, when they rated their own incidence of health problems it turned out to be the same as for non-vegetarians. This suggests that their perception of their own health may not be true. Vegetarians are more inclined to believe that ill-health is nutritionally related (Table 12), they have a higher frequency of bowel movements and they are more inclined to use purgatives. Meat is not the only food which they feel is hazardous to health. Those listed most frequently were: preservatives, sugar, unspecified food additives, foods containing pesticides and sprays, hormones thought to be used in meat production, and fats. White sugar is avoided because animal charcoal is sometimes used to bleach it. Despite their high sugar intakes, vegan children have been found to have low levels of dental caries (Saunders and Manning, 1992).
The BSE scare has undoubtedly helped to reinforce the vegetarian view that meat-eating can be hazardous. It is surprising however that such a large scale reaction against eating beef could arise from such a low prevalence of a human disorder. Amongst other meats, concerns about food poisoning apply most to fish and shellfish, and concerns about hormones apply most to meat products (Richardson et al, 1993).
Thirty years ago, becoming vegetarian was commonly regarded as raising serious health risks. This view has almost completely reversed and many people now associate meat eating with health risks. It is recognised within the medical profession that dietary inadequacies can develop in vegetarians, and that children are at more risk than adults. Their requirements are greater and they are less likely to exert the same control over what they eat in comparison with adults. Some of the more tragic consequences of strict vegetarianism have in fact occurred in infants.
Table 12 Percentage of vegetarians and non-vegetarians agreeing with the following statement on health
| Vegetarians | Non-vegetarians | p< | |
| Vegetarians are healthier than non-vegetarians | 85 | 30 | 0.001 |
| Doctors are lacking in nutritional knowledge | 80 | 66 | 0.05 |
| Disease is caused by an imbalance of nutrients | 75 | 57 | 0.05 |
| Disease can be cured by fasting | 49 | 12 | 0.001 |
(Freeland-Graves et al, 1986b)
Several studies have examined the growth of vegetarian babies and children (Shull et al, 1977; O'Connell et al, 1989; Saunders, 1988; Saunders and Manning, 1992). The general finding has been that during the first six months growth is usually satisfactory in breast-fed babies. Vegetarian parents often wean their babies later than non-vegetarians, and between 6 and 18 months growth can be retarded. Breast milk alone no longer supplies adequate nourishment, and instead the infant relies more on the weaning diet. Vegan infants normally start off on a relatively high fibre diet and this is thought to suppress digestibility of their dietary fat. This probably contributes to the slower growth, smaller stature and leaner bodies which they have by two years of age. After that time they catch up with non-vegetarian children, and by five years of age there is usually no difference. Another reason why vegan children are underweight is that they may experience more ailments during infancy. Quite a high proportion of vegan children are not immunised against whooping cough or polio, for ethical reasons, as the vaccines may be raised in animals (Saunders and Manning, 1992). Yet another cause is malnutrition. Pugliese et al (1987) reported the case histories of seven 7 to 22 month old infants which had stunted growth because of malnutrition. In all cases the principal cause had been the parents' concern about what the infants ate. There were fears about obesity and atherosclerosis, and a desire to avoid "junk food". Because of this the childrens' energy intakes were restricted and so their growth was curtailed. Their failure to thrive was reversed when they were put onto a more liberal diet. These cases are another reflection of society's obsession with being slim and trim and its fear of heart disease.
Most nutrients can be provided by plant foods provided enough of the food is eaten. Nutritional deficiencies which pose the greatest threat to infants on a strict vegetarian diet are:
- Vitamin B12
- Vitamin D
- Retinol
- C20-22 polyunsaturated fatty acids
Vitamin B12 is present in substantial amounts only in animal foods. It is present in milk, but not in plentiful amounts, and its concentration is greatly reduced if the milk is boiled. This vitamin is required for the synthesis of myelin which acts as an insulating sheath for nerves. Deficiencies of Vitamin B12 at critical stages of nervous tissue development during infancy can result in irreversible damage to the nervous system. This was reported in a baby at Adelaide Children's Hospital whose parents were lacto-vegetarians (Wrighton et al, 1979). The baby was normal at birth and for the first three months. He was breast-fed by his mother who became a strict vegan when the baby was born. After three months he deteriorated mentally and developed anaemia. Treatment for Vitamin B12 deficiency at nine months of age resolved the anaemia, but by 12 years of age he was retarded intellectually and socially.
Zed and Heywood (1977) investigated the Vitamin B12 status for 2 to 4 year old lacto-ovo-vegetarian children in Australia, and found that they had lower serum Vitamin B12 levels than normal. Plant foods cannot be relied upon as adequate dietary sources of the vitamin, and so the period following weaning can raise risks if there is inadequate supplementation or if a disease occurs which diminishes pancreatic and intestinal function. Some infants who have been introduced to vegan-like diets at this stage have failed to thrive (Dwyer, 1991), but generally, vegan families are aware of the risks and take adequate supplements. Resistance to taking vitamin supplements has occurred amongst Rastafarian vegans and this has led to clinical deficiencies (Campbell et al, 1982). Rastafarian vegetarians have also been known to develop Vitamin D deficiency, especially amongst inner city dwellers who experience limited exposure to the sun (Ward et al, 1982).
Parents of teenage children often become concerned when they learn that their daughter or son wants to become a vegetarian. The chief fear is whether they will receive enough protein and that they may develop a growth disorder, particularly if they are light eaters anyway. Generally, however, they are supportive in spite of those worries. Vegetarian children do in fact eat less protein than non-vegetarian children (Nathan et al, 1994). In addition, animal-based proteins have an advantage over plant sources of protein because they are generally of high quality, providing most of the essential and non-essential amino acids. However, the disadvantage of single plant protein sources can be overcome by combining different plant proteins. Deficiencies of protein or amino acids are unlikely in semivegetarians; semivegetarian men tend to eat more protein than vegetarian men (Draper and Wheeler, 1990).
The vegan diet is rich in polyunsaturated fatty acids as distinct from saturated fatty acids. Moreover, the ratio of linoleic/linolenic acid tends to be high and this is likely to inhibit the conversion of %-linolenic acid to docosahexaenoic acid. This may be important as docosahexaenoic acid is absent from vegan diets. This acid is believed to play a role in retina and nervous system function.
Risk analysis using data from the 1983 National Dietary Survey for Australia has shown that the only food group which had a strong influence on the risk of developing iron deficiency was the consumption of meat. Those at lowest risk of developing a deficiency obtained a greater proportion of their total iron intake from meat (Cobiac & Baghurst, 1993). On average about one third of the Australia's iron intake comes from meat, and, up to 31% of girls and 7% of boys have iron intakes below the recommended dietary intake (Magarey & Boulton, 1994). Almost half the women between 18 and 49 years of age have an iron intake which is less than the recommended daily intake.
There are two forms of dietary iron; haem iron which is present in animal products and nonhaem iron which is present in foods of animal and plant origin. Nonhaem iron is usually less well absorbed than haem iron, and vegetarians have limited intakes of the haem form. This introduces a risk of iron deficiency anaemia amongst vegetarians, especially for milk fed infants and for women who either are prone to losing more than usual amounts of iron during menstruation, or, have reduced iron intakes whilst dieting.
Vitamin C is thought to assist in the absorption of nonhaem iron by the gut and this may be an important feature for vegetarians. Phytates, tannins, phosphates, fibres and soybean protein which are common ingredients in the vegetarian diet have an opposing effect, as they inhibit iron absorption by the gut.
Meat is an important source of dietary zinc, but other useful sources are bread, milk, cheese and breakfast cereals. In a survey of Australian adults it was estimated that over a quarter of the men and 40% of the women had zinc intakes that were 30% below the recommended daily allowance. This threshold of intake is generally accepted as conferring significant risk.
Above all, healthy eating requires moderation and informed choice. It should not be necessary to totally eliminate a particular food group to sustain good health. Humankind has survived on an omnivorous diet since its origins, and premature death is more closely linked to accidental death than to eating meat. Although there is a growing minority who think that meat-eating is harmful, 70 to 80% of all teenagers in Australia agree with the view that meat is needed for good health (Worsley and Skrzypiec, 1996a).
Contact for Enquiries
Rural Affairs Coordinator
Sector Performance Policy
MAF Policy
Ministry of Agriculture and Forestry
PO Box 2526
Wellington
NEW ZEALAND
Phone: +64 4 894 0675
Fax: +64 4 4 894 0745
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