Crit Rev Food Sci Nutr. February 2016, issue 17:3640-3649,Vegetarian, vegan diets and multiple health outcomes: A systematic review with meta-analysis of observational studies.
Beneficial effects of vegetarian and vegan diets on health outcomes have been supposed in previous studies.
Aim of this study was to clarify the association between vegetarian, vegan diets, risk factors for chronic diseases, risk of all-cause mortality, incidence, and mortality from cardio-cerebrovascular diseases, total cancer and specific type of cancer (colorectal, breast, prostate and lung), through meta-analysis.
A comprehensive search of Medline, EMBASE, Scopus, The Cochrane Library, and Google Scholar was conducted.
Eighty-six cross-sectional and 10 cohort prospective studies were included. The overall analysis among cross-sectional studies reported significant reduced levels of body mass index, total cholesterol, LDL-cholesterol, and glucose levels in vegetarians and vegans versus omnivores. With regard to prospective cohort studies, the analysis showed a significant reduced risk of incidence and/or mortality from ischemic heart disease (RR 0.75; 95% CI, 0.68 to 0.82) and incidence of total cancer (RR 0.92; 95% CI 0.87 to 0.98) but not of total cardiovascular and cerebrovascular diseases, all-cause mortality and mortality from cancer. No significant association was evidenced when specific types of cancer were analyzed. The analysis conducted among vegans reported significant association with the risk of incidence from total cancer (RR 0.85; 95% CI, 0.75 to 0.95), despite obtained only in a limited number of studies.
This comprehensive meta-analysis reports a significant protective effect of a vegetarian diet versus the incidence and/or mortality from ischemic heart disease (-25%) and incidence from total cancer (-8%). Vegan diet conferred a significant reduced risk (-15%) of incidence from total cancer.
Mortality in British vegetarians: results from the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford).
Key TJ1, Appleby PN, Spencer EA, Travis RC, Roddam AW, Allen NE.
Am J Clin Nutr. 2009 May;89(5):1613S-1619S. doi: 10.3945/ajcn.2009.26736L. Epub 2009 Mar 18.
Few prospective studies have examined the mortality of vegetarians.
We present results on mortality among vegetarians and nonvegetarians in the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford).
We used a prospective study of men and women recruited throughout the United Kingdom in the 1990s.
Among 64,234 participants aged 20-89 y for whom diet group was known, 2965 had died before age 90 by 30 June 2007. The death rates of participants are much lower than average for the United Kingdom. The standardized mortality ratio for all causes of death was 52% (95% CI: 50%, 54%) and was identical in vegetarians and in nonvegetarians. Comparing vegetarians with meat eaters among the 47,254 participants who had no prevalent cardiovascular disease or malignant cancer at recruitment, the death rate ratios adjusted for age, sex, smoking, and alcohol consumption were 0.81 (95% CI: 0.57, 1.16) for ischemic heart disease and 1.03 (95% CI: 0.90, 1.16) for all causes of death.
The mortality of both the vegetarians and the nonvegetarians in this study is low compared with national rates. Within the study, mortality from circulatory diseases and all causes is not significantly different between vegetarians and meat eaters, but the study is not large enough to exclude small or moderate differences for specific causes of death, and more research on this topic is required.
Vegetarian dietary patterns and mortality in Adventist Health Study 2. Orlich MJ1, Singh PN, Sabaté J, Jaceldo-Siegl K, Fan J, Knutsen S, Beeson WL, Fraser GE.
JAMA Intern Med. 2013 Jul 8;173(13):1230-8. doi: 10.1001/jamainternmed.2013.6473.
Some evidence suggests vegetarian dietary patterns may be associated with reduced mortality, but the relationship is not well established.
To evaluate the association between vegetarian dietary patterns and mortality.
Prospective cohort study; mortality analysis by Cox proportional hazards regression, controlling for important demographic and lifestyle confounders.
Adventist Health Study 2 (AHS-2), a large North American cohort.
A total of 96,469 Seventh-day Adventist men and women recruited between 2002 and 2007, from which an analytic sample of 73,308 participants remained after exclusions.
Diet was assessed at baseline by a quantitative food frequency questionnaire and categorized into 5 dietary patterns: nonvegetarian, semi-vegetarian, pesco-vegetarian, lacto-ovo-vegetarian, and vegan.
MAIN OUTCOME AND MEASURE:
The relationship between vegetarian dietary patterns and all-cause and cause-specific mortality; deaths through 2009 were identified from the National Death Index.
There were 2570 deaths among 73,308 participants during a mean follow-up time of 5.79 years. The mortality rate was 6.05 (95% CI, 5.82-6.29) deaths per 1000 person-years. The adjusted hazard ratio (HR) for all-cause mortality in all vegetarians combined vs nonvegetarians was 0.88 (95% CI, 0.80-0.97). The adjusted HR for all-cause mortality in vegans was 0.85 (95% CI, 0.73-1.01); in lacto-ovo-vegetarians, 0.91 (95% CI, 0.82-1.00); in pesco-vegetarians, 0.81 (95% CI, 0.69-0.94); and in semi-vegetarians, 0.92 (95% CI, 0.75-1.13) compared with nonvegetarians. Significant associations with vegetarian diets were detected for cardiovascular mortality, noncardiovascular noncancer mortality, renal mortality, and endocrine mortality. Associations in men were larger and more often significant than were those in women.
CONCLUSIONS AND RELEVANCE:
Vegetarian diets are associated with lower all-cause mortality and with some reductions in cause-specific mortality. Results appeared to be more robust in males. These favorable associations should be considered carefully by those offering dietary guidance.
Cardiovascular disease mortality and cancer incidence in vegetarians: a meta-analysis and systematic review.
Ann Nutr Metab. 2012;60(4):233-40. doi: 10.1159/000337301. Epub 2012 Jun 1.
Huang T1, Yang B, Zheng J, Li G, Wahlqvist ML, Li D.
Prospective cohort studies have examined mortality and overall cancer incidence among vegetarians, but the results have been inconclusive.
The objective of the present meta-analysis was to investigate cardiovascular disease mortality and cancer incidence among vegetarians and nonvegetarians.
Medline, EMBASE and Web Of Science databases were searched for cohort studies published from inception to September 2011. Studies were included if they contained the relative risk (RR) and corresponding 95% CI. Participants were from the UK, Germany, California, USA, the Netherlands and Japan.
Seven studies with a total of 124,706 participants were included in this analysis. All-cause mortality in vegetarians was 9% lower than in nonvegetarians (RR = 0.91; 95% CI, 0.66-1.16). The mortality from ischemic heart disease was significantly lower in vegetarians than in nonvegetarians (RR = 0.71; 95% CI, 0.56-0.87). We observed a 16% lower mortality from circulatory diseases (RR = 0.84; 95% CI, 0.54-1.14) and a 12% lower mortality from cerebrovascular disease (RR = 0.88; 95% CI, 0.70-1.06) in vegetarians compared with nonvegetarians. Vegetarians had a significantly lower cancer incidence than nonvegetarians (RR = 0.82; 95% CI, 0.67-0.97).
Our results suggest that vegetarians have a significantly lower ischemic heart disease mortality (29%) and overall cancer incidence (18%) than nonvegetarians.
[Nutrition and health--potential health benefits and risks of vegetarianism and limited consumption of meat in the Netherlands].
Ned Tijdschr Geneeskd. 2003 Jul 5;147(27):1308-13.
In the latest Dutch national food consumption survey (1998) just over 1% of subjects (about 150,000 persons) claimed to be vegetarians; however, a much larger group (6% or approximately 1 million persons) ate meat < or = once a week. Vegetarianism can be subdivided into lacto-vegetarianism (a diet without meat and fish) and veganism (a diet without any animal foods whatsoever, including dairy products and eggs). A recent meta-analysis showed that vegetarians had a lower mortality from ischaemic heart disease than omniovorous subjects; however, cancer mortality and total mortality did not differ. Although a high consumption of red meat, which is rich in haeme iron and saturated fat, may increase the risk of cardiovascular disease and some types of cancer, this does not apply to white meat and fish. In fact, the most important protective effect would seem to be derived from the consumption of unrefined vegetable products (whole-grain cereals, vegetables, fruits, nuts and legumes) and fish. In other words, a prudent, omnivorous diet with moderate amounts of animal products, in which red meat is partly replaced by white meat and fish (especially fatty fish), together with the consumption of ample amounts of unrefined vegetable products, is thought to be just as protective as a vegetarian diet. On the other hand, the omission of meat and fish from the dietincreases the risk of nutritional deficiencies. A vegan diet, in particular, leads to a strongly increased risk of deficiencies of vitamin B12, vitamin B2 and several minerals, such as calcium, iron and zinc. However, even a lacto-vegetarian diet produces an increased risk of deficiencies of vitamin B12 and possibly certain minerals, such as iron. Data from the latest Dutch food consumption survey suggest that 5-10% of all inhabitants of the Netherlands (up to 1 million persons) actually have a vitamin B12 intake below recommended daily levels. In medical practice, the possibility of vitamin B12 deficiency in subjects consuming meat or fish < or = once a week deserves serious consideration. In case of doubt, evaluation is indicated using sensitive and specific deficiency markers such as the levels of methylmalonic acid in plasma or urine. Alternative dietary sources of vitamin B12 instead of meat are fish (especially fatty fish is a good source of vitamin B12), or a vitamin-B12-supplement.
Health effects of vegetarian and vegan diets.
Proc Nutr Soc. 2006 Feb;65(1):35-41.
Key TJ1, Appleby PN, Rosell MS.
Vegetarian diets do not contain meat, poultry or fish; vegan diets further exclude dairy products and eggs. Vegetarian and vegan diets can vary widely, but the empirical evidence largely relates to the nutritional content and health effects of the average diet of well-educated vegetarians living in Western countries, together with some information on vegetarians in non-Western countries. In general, vegetarian diets provide relatively large amounts of cereals, pulses, nuts, fruits and vegetables. In terms of nutrients, vegetarian diets are usually rich in carbohydrates, n-6 fatty acids, dietary fibre, carotenoids, folic acid, vitamin C, vitamin E and Mg, and relatively low in protein, saturated fat, long-chain n-3 fatty acids, retinol, vitamin B(12) and Zn; vegans may have particularly low intakes of vitamin B(12) and low intakes of Ca. Cross-sectional studies of vegetarians and vegans have shown that on average they have a relatively low BMI and a low plasma cholesterol concentration; recent studies have also shown higher plasma homocysteine concentrations than in non-vegetarians. Cohort studies of vegetarians have shown a moderate reduction in mortality from IHD but little difference in other major causes of death or all-cause mortality in comparison with health-conscious non-vegetarians from the same population. Studies of cancer have not shown clear differences in cancer rates between vegetarians and non-vegetarians. More data are needed, particularly on the health of vegans and on the possible impacts on health of low intakes of long-chain n-3 fatty acids and vitamin B(12). Overall, the data suggest that the health of Western vegetarians is good and similar to that of comparable non-vegetarian.
Micronutrient status and intake in omnivores, vegetarians and vegans in Switzerland.
Eur J Nutr. 2017 Feb;56(1):283-293. doi: 10.1007/s00394-015-1079-7. Epub 2015 Oct 26.
Schüpbach R1, Wegmüller R1,2, Berguerand C3, Bui M3, Herter-Aeberli I4.
Vegetarian and vegan diets have gained popularity in Switzerland. The nutritional status of individuals who have adopted such diets, however, has not been investigated. The aim of this study was to assess the intake and status of selected vitamins and minerals among vegetarian and vegan adults living in Switzerland.
Healthy adults [omnivores (OVs), n OV = 100; vegetarians (VGs), n VG = 53; vegans (VNs), n VN = 53] aged 18-50 years were recruited, and their weight and height were measured. Plasma concentrations of the vitamins A, C, E, B1, B2, B6, B12, folic acid, pantothenic acid, niacin, biotin and β-carotene and of the minerals Fe, Mg and Zn and urinary iodine concentration were determined. Dietary intake was assessed using a three-day weighed food record, and questionnaires were issued in order to assess the physical activity and lifestyle of the subjects.
Omnivores had the lowest intake of Mg, vitamin C, vitamin E, niacin and folic acid. Vegans reported low intakes of Ca and a marginal consumption of the vitamins D and B12. The highest prevalence for vitamin and mineral deficiencies in each group was as follows: in the omnivorous group, for folic acid (58 %); in the vegetarian group, for vitamin B6 and niacin (58 and 34 %, respectively); and in the vegan group, for Zn (47 %). Despite negligible dietary vitamin B12 intake in the vegan group, deficiency of this particular vitamin was low in all groups thanks to widespread use of supplements. Prevalence of Fe deficiency was comparable across all diet groups.
Despite substantial differences in intake and deficiency between groups, our results indicate that by consuming a well-balanced diet including supplements or fortified products, all three types of diet can potentially fulfill requirements for vitamin and mineral consumption.