Growth and development of vegans and vegetarians...

A well-planned vegetarian diet is considered to be adequate for all stages of the life cycle including infancy,

childhood and adolescence (American Dietetic Association and Dietitians of Canada, 2003), but epidemiological data on growth and development in vegetarians are still sparse. Recent data on 390 lifelong vegetarians in EPIC-Oxford (Rosell et al. 2005a) show no significant differences in height in men or women, or in age at menarche in women, between lifelong vegetarians and those who became vegetarian at age ‡20 years.

Obesity

Studies of Western vegetarians have consistently reported that vegetarians have a lower BMI than comparable non-vegetarians, with differences in mean BMI of about 1 kg/m2 the proportion of vegetarians who are obese is correspondingly lower than that among non-vegetarians. The reasons for this difference are not well understood, but may include differences in the composition of the diet such as a higher fibre intake and a lower protein intake. 

Follow-up of body weight among 21 966 individuals in EPIC-Oxford shows a mean body-weight increase of approximately 400 g/year overall, with nificantly lower weight gain in vegans, but not in vegetarians, than in meat-eaters (Rosell et al. 2005b). Despite these consistently-observed differences in BMI between vegetarians and non-vegetarians, obesity is common among some populations that follow largely vegetarian diets, such as Indians living in the UK and in India.

CVD

Plasma cholesterol Studies have consistently reported that total plasma cholesterol is lower in vegetarians than in non-vegetarians, e.g. by 0.61 mmol/l in the Health Food Shoppers Study, 0.43 mmol/l in the Oxford Vegetarian Study and 0.39 mmol/l and 0.35 mmol/l in men and women respectively in EPIC-Oxford (Key et al. 1999b). 

The effect of a vegetarian diet on plasma cholesterol is dependent on the exact composition of the diet, particularly in relation to saturated and unsaturated fatty acids, and have shown that a vegetarian diet including a portfolio of cholesterol-lowering foods such as soyabean and nuts reduces serum LDL-cholesterol substantially more than a control vegetarian diet. Hypertension 

The main diet-related determinants of ypertension are high salt intake, obesity and excess alcohol consumption (Scientific Advisory Committee on Nutrition, 2003). Some early studies have suggested that vegetarians have a lower blood pressure than similar non-vegetarians, with differences of 2–10mmHg in systolic or diastolic pressure (Beilin et al. 1988). 

However, analyses of blood pressure among 11 004 men and women in EPIC-Oxford indicate very little difference in blood pressure between vegetarians and meat-eaters (£1 mmHg); blood pressure was observed to be 2–3mmHg lower in vegans than in meat-eaters, largely associated with the lower BMI of the vegans (Appleby et al. 2002). In this study the very small differences in blood pressure between the dietary groups would not be expected to cause a detectable difference in rates of CVD.

Growth and development of vegans and vegetarians

IHD

Collaborative re-analysis of five prospective studies, each including a large proportion of vegetarians, has shown the mortality from IHD to be 24 (95% CI 6, 38) % lower in vegetarians than in non-vegetarians. Results published subsequently are similar; a death rate ratio of 0.75 (95% CI 0.4, 1.37) in the first analysis of EPIC-Oxford (Key et al. 2003) and 0.70 (95% CI 0.41, 1.18) in the extended follow-up of the cohort in Germany. 

In a case–control study among Indians in Bangalore the risk for myocardial infarction in vegetarians compared with non-vegetarians has been reported to be 0.81 (95% CI 0.46, 1.43; Pais et al. 1996). Law et al. (1994) have estimated that a reduction in total serum cholesterol of 0.6 mmol/l would reduce mortality from IHD by 27%; therefore, the observed differences in cholesterol between vegetarians and non-vegetarians of approximately 0.4 mmol/l would be expected to reduce mortality from IHD by approximately 20%. 

The observed difference in mortality of about 24% is therefore of the magnitude that might be predicted from the difference in serum cholesterol. The lower BMI of vegetarians would also be expected to cause a small reduction in mortality from IHD. Stroke The main known risk factor for stroke is high blood pressure. 

The only data on stroke mortality in vegetarians comes from the five prospective studies, pooled analysis of which shows a death rate ratio for stroke in vegetarians compared with non-vegetarians of 0.93 (95% CI 0.74,1.17; Key et al. 1999b).