PORPHYRY’S PEOPLE
Vegan group based in Christchurch, New Zealand, promoting veganism to further ethical, health and ecological goals.
THE HEALTHY EATING PYRAMID: EPIDEMIOLOGY SUPPORTS THE VEGAN DIET
Scientific nutrition is becoming increasingly supportive of the vegan diet and this is most evident in what is arguably the most important popular book on human nutrition for decades. Eat, Drink and be Healthy: The Harvard Medical School Guide to Healthy Eating 1, the controversial book written by Walter Willett, Chairman of the Department of Nutrition at the Harvard School of Public Health, is so important because it is based on recent discoveries in nutritional epidemiology rather than on laboratory experiments.
Epidemiology is the study of the patterns of disease in human populations and nutritional epidemiology is the study of the relationship between diet and disease. It is the study of the natural experiments that occur when people and populations adopt differing diets and lifestyles and in consequence suffer differing rates of disease. Typically, in a prospective cohort study, tens of thousands of people answer a questionnaire on their usual dietary habits and then their health status is followed up for a number of years to determine the relationship between their diets and which illnesses they subsequently develop.
For example, one such study of 30,000 Californian Seventh Day Adventists over a period of 6 years made the startling discovery that those who ate nuts at least 5 times a week had a 50% reduction in heart disease2 compared to those who rarely ate nuts, and later found that the nut-eaters lived about two years longer on average3. The beneficial effects of nut consumption have subsequently been confirmed by other such studies on other large groups of people. The Adventist study has also found that vegetarians live about two years longer than meat-eaters and that the combined benefits of being vegetarian, eating plenty of nuts, vigorous exercise, maintaining a mid-range body mass index and never having smoked add up to about 10 extra years of life3.
In another example of nutritional epidemiology, the Oxford Vegetarian Study has found that consumption of eggs, cheese, total animal fat, saturated fat and dietary cholesterol each significantly increase the death rate from ischaemic heart disease and that non-meat-eaters have a 20% lower death rate from all causes than do meat-eaters4.