Mortality among German vegetarians: first results after five years of follow-up

Vegetarianism, Microbiota and Cardiovascular health: Looking back, and forward

Cardiovascular diseases (CVD) are the leading cause of death globally, with over 17.9 million attributed deaths in 2019. Unhealthy diet is an often-overlooked major modifiable risk factor for CVD. Global Burden of Disease (GBD) estimates suggest that unhealthy diets account for nearly 26% of all deaths, of which 84% were attributed to CVD. Plant-based diets (PBDs), which are a diverse group of dietary patterns focused on plant produce, with flexibility for varying levels of vegetarianism, have been suggested to decrease the incidence of various cardiovascular and cardiometabolic diseases. In this review, we aim to delve into the spectrum of PBDs, revisit objective definitions and classifications, and compare them with standard non-vegetarian diets. We examine plausible mechanisms underlying the cardiovascular benefits of PBDs with a particular focus on the dietary manipulation of gut microbiota-host interaction and its effect on energy metabolism, and local and systemic inflammation. In addition, we explore the evidence on the impact of PBDs on cardiovascular disease, examine the challenges and limitations associated with dietary intervention studies, and devise strategies to draw valid conclusions. Dietary interventions, such as PBDs are one of the most powerful, attainable, cost-effective tools for health and environmental protection at the population level. We conclude with a clear appreciation for PBDs in environmental sustainability, climate change, and animal welfare.

The long-term health of vegetarians and vegans

Vegetarians, who do not eat any meat, poultry or fish, constitute a significant minority of the world's population. Lacto-ovo-vegetarians consume dairy products and/or eggs, whereas vegans do not eat any foods derived wholly or partly from animals. Concerns over the health, environmental and economic consequences of a diet rich in meat and other animal products have focussed attention on those who exclude some or all of these foods from their diet. There has been extensive research into the nutritional adequacy of vegetarian diets, but less is known about the long-term health of vegetarians and vegans. We summarise the main findings from large cross-sectional and prospective cohort studies in western countries with a high proportion of vegetarian participants. Vegetarians have a lower prevalence of overweight and obesity and a lower risk of IHD compared with non-vegetarians from a similar background, whereas the data are equivocal for stroke. For cancer, there is some evidence that the risk for all cancer sites combined is slightly lower in vegetarians than in non-vegetarians, but findings for individual cancer sites are inconclusive. Vegetarians have also been found to have lower risks for diabetes, diverticular disease and eye cataract. Overall mortality is similar for vegetarians and comparable non-vegetarians, but vegetarian groups compare favourably with the general population. The long-term health of vegetarians appears to be generally good, and for some diseases and medical conditions it may be better than that of comparable omnivores. Much more research is needed, particularly on the long-term health of vegans.

The Netherlands Cohort Study−Meat Investigation Cohort; a population-based cohort over-represented with vegetarians, pescetarians and low meat consumers

BACKGROUND

Vegetarian diets have been associated with lower risk of chronic disease, but little is known about the health effects of low meat diets and the reliability of self-reported vegetarian status. We aimed to establish an analytical cohort over-represented with vegetarians, pescetarians and 1 day/week meat consumers, and to describe their lifestyle and dietary characteristics. In addition, we were able to compare self-reported vegetarians with vegetarians whose status has been confirmed by their response on the extensive food frequency questionnaire (FFQ).

STUDY METHODS

Embedded within the Netherlands Cohort Study (n = 120,852; including 1150 self-reported vegetarians), the NLCS-Meat Investigation Cohort (NLCS-MIC) was defined by combining all FFQ-confirmed-vegetarians (n = 702), pescetarians (n = 394), and 1 day/week meat consumers (n = 1,396) from the total cohort with a random sample of 2-5 days/week- and 6-7 days/week meat consumers (n = 2,965 and 5,648, respectively).

RESULTS

Vegetarians, pescetarians, and 1 day/week meat consumers had more favorable dietary intakes (e.g., higher fiber/vegetables) and lifestyle characteristics (e.g. lower smoking rates) compared to regular meat consumers in both sexes. Vegetarians adhered to their diet longer than pescetarians and 1 day/week meat consumers. 75% of vegetarians with a prevalent cancer at baseline had changed to this diet after diagnosis. 50% of self-reported vegetarians reported meat or fish consumption on the FFQ. Although the misclassification that occurred in terms of diet and lifestyle when merely relying on self-reporting was relatively small, the impact on associations with disease risk remains to be studied.

CONCLUSION

We established an analytical cohort over-represented with persons at the lower end of the meat consumption spectrum which should facilitate prospective studies of major cancers and causes of death using ≥20.3 years of follow-up.

Vegetarian diets, low-meat diets and health: a review

OBJECTIVE

To review the epidemiological evidence for vegetarian diets, low-meat dietary patterns and their association with health status in adults.

DESIGN

Published literature review focusing primarily on prospective studies and meta-analyses examining the association between vegetarian diets and health outcomes.

RESULTS

Both vegetarian diets and prudent diets allowing small amounts of red meat are associated with reduced risk of diseases, particularly CHD and type 2 diabetes. There is limited evidence of an association between vegetarian diets and cancer prevention. Evidence linking red meat intake, particularly processed meat, and increased risk of CHD, cancer and type 2 diabetes is convincing and provides indirect support for consumption of a plant-based diet.

CONCLUSIONS

The health benefits of vegetarian diets are not unique. Prudent plant-based dietary patterns which also allow small intakes of red meat, fish and dairy products have demonstrated significant improvements in health status as well. At this time an optimal dietary intake for health status is unknown. Plant-based diets contain a host of food and nutrients known to have independent health benefits. While vegetarian diets have not shown any adverse effects on health, restrictive and monotonous vegetarian diets may result in nutrient deficiencies with deleterious effects on health. For this reason, appropriate advice is important to ensure a vegetarian diet is nutritionally adequate especially for vulnerable groups.

Vegetarian diets: what do we know of their effects on common chronic diseases?

A number of studies have evaluated the health of vegetarians. Others have studied the health effects of foods that are preferred or avoided by vegetarians. The purpose of this review is to look critically at the evidence on the health effects of vegetarian diets and to seek possible explanations where results appear to conflict. There is convincing evidence that vegetarians have lower rates of coronary heart disease, largely explained by low LDL cholesterol, probable lower rates of hypertension and diabetes mellitus, and lower prevalence of obesity. Overall, their cancer rates appear to be moderately lower than others living in the same communities, and life expectancy appears to be greater. However, results for specific cancers are much less convincing and require more study. There is evidence that risk of colorectal cancer is lower in vegetarians and in those who eat less meat; however, results from British vegetarians presently disagree, and this needs explanation. It is probable that using the label "vegetarian" as a dietary category is too broad and that our understanding will be served well by dividing vegetarians into more descriptive subtypes. Although vegetarian diets are healthful and are associated with lower risk of several chronic diseases, different types of vegetarians may not experience the same effects on health.

Gluten-free vegan diet induces decreased LDL and oxidized LDL levels and raised atheroprotective natural antibodies against phosphorylcholine in patients with rheumatoid arthritis: a randomized study

Introduction

The purpose of this study was to investigate the effects of vegan diet in patients with rheumatoid arthritis (RA) on blood lipids oxidized low-density lipoprotein (oxLDL) and natural atheroprotective antibodies against phosphorylcholine (anti-PCs).

Methods

Sixty-six patients with active RA were randomly assigned to either a vegan diet free of gluten (38 patients) or a well-balanced non-vegan diet (28 patients) for 1 year. Thirty patients in the vegan group completed more than 3 months on the diet regimen. Blood lipids were analyzed by routine methods, and oxLDL and anti-PCs were analyzed by enzyme-linked immunosorbent assay. Data and serum samples were obtained at baseline and after 3 and 12 months.

Results

Mean ages were 50.0 years for the vegan group and 50.8 years for controls. Gluten-free vegan diet induced lower body mass index (BMI) and low-density lipoprotein (LDL) and higher anti-PC IgM than control diet (p < 0.005). In the vegan group, BMI, LDL, and cholesterol decreased after both 3 and 12 months (p < 0.01) and oxLDL after 3 months (p = 0.021) and trendwise after 12 months (p = 0.090). Triglycerides and high-density lipoprotein did not change. IgA anti-PC levels increased after 3 months (p = 0.027) and IgM anti-PC levels increased trendwise after 12 months (p = 0.057). There was no difference in IgG anti-PC levels. In the control diet group, IgM anti-PC levels decreased both after 3 and 12 months (p < 0.01). When separating vegan patients into clinical responders and non-responders at 12 months, the effects on oxLDL and anti-PC IgA were seen only in responders (p < 0.05).

Conclusion

A gluten-free vegan diet in RA induces changes that are potentially atheroprotective and anti-inflammatory, including decreased LDL and oxLDL levels and raised anti-PC IgM and IgA levels.

Dietary Patterns and Survival After Breast Cancer Diagnosis

Purpose

There is little prior study of major dietary patterns and breast cancer survival.

Methods

Patients included 2,619 Nurses' Health Study participants who were diagnosed with invasive breast cancer between 1982 and 1998 and completed a dietary questionnaire more than 1 year after diagnosis. Participants were followed through 2002 (median = 9 years). During follow-up, 414 patients died of any cause, 242 patients died of breast cancer, and 172 patients died from causes other than breast cancer. Women with in situ or metastatic disease at diagnosis were excluded. We used Cox proportional hazards models to evaluate prospective associations of prudent and Western dietary patterns assessed both before and after diagnosis with time to event after diagnosis.

Results

In multivariate-adjusted analyses assessed after diagnosis, the Western and prudent dietary patterns were unrelated to all-cause or breast cancer mortality. However, compared with women with the lowest intake of the prudent dietary pattern, the relative risks (and 95% CIs) of death from causes other than breast cancer were 0.85 (95% CI, 0.53 to 1.35), 0.74 (95% CI, 0.45 to 1.21), 0.70 (95% CI, 0.42 to 1.17), and 0.54 (95% CI, 0.31 to 0.95; P = .03, from lowest to highest quintile of intake). In contrast, the Western dietary pattern was positively associated with this outcome (P = .04). Results for the assessment of dietary patterns before diagnosis were similar, except the prudent dietary pattern was unrelated to mortality.

Conclusion

A higher intake of the prudent pattern and a lower intake of the Western pattern may protect against mortality from causes unrelated to breast cancer.

Lifestyle determinants and mortality in German vegetarians and health-conscious persons: results of a 21-year follow-up

BACKGROUND

The long-term observation of vegetarians in affluent countries can provide insight into the relative effects of a vegetarian diet and lifestyle factors on mortality.

METHODS

A cohort study of vegetarians and health-conscious persons in Germany was followed-up prospectively for 21 years, including 1,225 vegetarians and 679 health-conscious nonvegetarians. Standardized mortality ratios compared with the German general population were calculated for all causes and specific causes. Within the cohort, Poisson regression modeling was used to investigate the joint effects of several risk factors on overall and cause-specific mortality.

RESULTS

Standardized mortality ratios for all-cause mortality was significantly below 100: 59 [95% confidence interval (95% CI), 54-64], predominantly due to a deficit of deaths from circulatory diseases. Within the cohort, vegetarian compared with nonvegetarian diet had no effect on overall mortality [rate ratio (RR), 1.10; 95% CI, 0.89-1.36], whereas moderate and high physical activity significantly reduced risk of death (RR, 0.62, 0.64), adjusted for age, sex, smoking, alcohol intake, body mass index, and educational level. Vegetarian diet was however associated with a reduced RR of 0.70 (95% CI, 0.41-1.18) for ischemic heart disease, which could partly be related to avoidance of meat.

CONCLUSIONS

Both vegetarians and nonvegetarian health-conscious persons in this study have reduced mortality compared with the general population. Within the study, low prevalence of smoking and moderate or high level of physical activity but not strictly vegetarian diet was associated with reduced overall mortality. The nonsignificant reduction in mortality from ischemic heart diseases in vegetarians compared with health-conscious persons could be explained in part by avoidance of meat intake.

Veganism and its relationship with insulin resistance and intramyocellular lipid

OBJECTIVE

To test the hypothesis that dietary factors in the vegan diet lead to improved insulin sensitivity and lower intramyocellular lipid (IMCL) storage.

DESIGN

Case-control study.

SETTING

Imperial College School of Medicine, Hammersmith Hospital Campus, London, UK.

SUBJECTS

A total of 24 vegans and 25 omnivores participated in this study; three vegan subjects could not be matched therefore the matched results are shown for 21 vegans and 25 omnivores. The subjects were matched for gender, age and body mass index (BMI).

INTERVENTIONS

Full anthropometry, 7-day dietary assessment and physical activity levels were obtained. Insulin sensitivity (%S) and beta-cell function (%B) were determined using the homeostatic model assessment (HOMA). IMCL levels were determined using in vivo proton magnetic resonance spectroscopy; total body fat content was assessed by bioelectrical impedance.

RESULTS

There was no difference between the groups in sex, age, BMI, waist measurement, percentage body fat, activity levels and energy intake. Vegans had a significantly lower systolic blood pressure (-11.0 mmHg, CI -20.6 to -1.3, P=0.027) and higher dietary intake of carbohydrate (10.7%, CI 6.8-14.5, P<0.001), nonstarch polysaccharides (20.7 g, CI 15.8-25.6, P<0.001) and polyunsaturated fat (2.8%, CI 1.0-4.6, P=0.003), with a significantly lower glycaemic index (-3.7, CI -6.7 to -0.7, P=0.01). Also, vegans had lower fasting plasma triacylglycerol (-0.7 mmol/l, CI -0.9 to -0.4, P<0.001) and glucose (-0.4 mmol/l, CI -0.7 to -0.09, P=0.05) concentrations. There was no significant difference in HOMA %S but there was with HOMA %B (32.1%, CI 10.3-53.9, P=0.005), while IMCL levels were significantly lower in the soleus muscle (-9.7, CI -16.2 to -3.3, P=0.01).

CONCLUSION

Vegans have a food intake and a biochemical profile that will be expected to be cardioprotective, with lower IMCL accumulation and beta-cell protective.

Relative weight, weight loss efforts and nutrient intakes among health-conscious vegetarian, past vegetarian and nonvegetarian women ages 18 to 50

OBJECTIVE

To compare relative weight, weight loss efforts and nutrient intakes among similarly health-conscious vegetarian, past vegetarian and nonvegetarian premenopausal women.

METHODS

Demographic data, lifestyle practices and weight loss efforts (by questionnaire), body mass index (BMI;kg/m2) and dietary intake (via multiple-pass 24-hour diet recall) were compared in a convenience sample of 90 current vegetarians, 35 past vegetarians and 68 nonvegetarians.

RESULTS

Age (31.9 +/- 8.8), educational attainment, smoking status, alcohol use, physical activity and perceived health status were similar among the three groups of women. BMI did not differ by dietary pattern and averaged 23.7 +/- 4.7 for all women combined. Participants had intentionally lost > or = 10 pounds a mean of 2.1 times, and 39% of women perceived themselves to be overweight; again, no differences were observed among dietary groups. Dietary intakes of vegetarians and current nonvegetarians were consistent with current recommendations for macronutrient composition (< 30% fat, < 10% saturates). Compared to current nonvegetarians, current vegetarians had lower intakes of protein, saturated fat, cholesterol, niacin, vitamins B12 and D, and higher fiber and magnesium intakes. Vegetarians' mean vitamin B12 and D intakes were well below recommendations.

CONCLUSIONS

Relative weight and weight loss efforts do not differ by dietary pattern among similarly health-conscious vegetarian and nonvegetarian women. The only differences in nutrient intake with potential health implications were vitamins D and B12.

Mortality in vegetarians and nonvegetarians: detailed findings from a collaborative analysis of 5 prospective studies

We combined data from 5 prospective studies to compare the death rates from common diseases of vegetarians with those of nonvegetarians with similar lifestyles. A summary of these results was reported previously; we report here more details of the findings. Data for 76172 men and women were available. Vegetarians were those who did not eat any meat or fish (n = 27808). Death rate ratios at ages 16-89 y were calculated by Poisson regression and all results were adjusted for age, sex, and smoking status. A random-effects model was used to calculate pooled estimates of effect for all studies combined. There were 8330 deaths after a mean of 10.6 y of follow-up. Mortality from ischemic heart disease was 24% lower in vegetarians than in nonvegetarians (death rate ratio: 0.76; 95% CI: 0.62, 0.94; P<0.01). The lower mortality from ischemic heart disease among vegetarians was greater at younger ages and was restricted to those who had followed their current diet for >5 y. Further categorization of diets showed that, in comparison with regular meat eaters, mortality from ischemic heart disease was 20% lower in occasional meat eaters, 34% lower in people who ate fish but not meat, 34% lower in lactoovovegetarians, and 26% lower in vegans. There were no significant differences between vegetarians and nonvegetarians in mortality from cerebrovascular disease, stomach cancer, colorectal cancer, lung cancer, breast cancer, prostate cancer, or all other causes combined.

Long-term effects of a vegetarian diet on the nutritional status of elderly people (Dutch Nutrition Surveillance System)

The health and nutritional status (anthropometry, and blood and urine biochemistry) of 44 Dutch apparently healthy vegetarians, aged 65-97 years, refraining from meat, fish, and poultry consumption, was assessed for insight into long-term consequences of ovo-lacto- or lacto-vegetarianism. The results indicate that in comparison to omnivorous elderly the vegetarian elderly (especially men) have aged successfully with respect to cardiovascular risk factors. In contrast, vegetarian elderly are at a higher risk for a marginal iron, zinc, and vitamin B12 status. Although several vegetarian elderly showed low levels of 25-hydroxyvitamin D in plasma and many had low values of 24-hr urine volume (per kg body weight), these values are not likely the result of a vegetarian diet per se. It is concluded that, although some nutrition-related risks are prevalent among vegetarian elderly, these risks can probably be prevented by lifestyle changes.

Pickles, peptide hormones and pregnancy: a hypothesis

In western societies a high frequency of heartburn, nausea and vomiting occur during pregnancy. The causes and mechanisms of these clinical symptoms remain poorly understood. Evidence suggests steroid hormones modulate gastrointestinal transit time and plasma peptide hormones, while peptide hormone modulated food intake and preferences. Since diurnal and episodic release of steroid and peptide hormones occur, it is postulated that heartburn and other digestive dysfunction during pregnancy are associated with elevated steroid and peptide (beta-endorphin, NPY) hormone interaction with innate biological rhythms controlling the gastrointestinal tract.

Adequacy of a vegetarian diet at old age (Dutch Nutrition Surveillance System)

To assess the adequacy of a vegetarian diet at old age, the dietary intake (assessed through dietary history with cross-check) of 44 apparently healthy lacto-(ovo-)vegetarians, aged 65-97 years, was evaluated. Adequacy was assessed by a comparison of nutrient intake with (Dutch) recommendations and by evaluating data on nutritional status. The results were also compared with data of elderly omnivores. In contrast to elderly omnivores, percentages of energy from protein (13%), fat (37%), and carbohydrates (50%) as well as P/S ratio (0.63) were close to or within the range of Dutch guidelines regarding a healthy diet (percentages of energy from protein, fat, and carbohydrates 10-15, 30-35, and 55%, respectively: P/S ratio 0.5-1.0). For most of the micronutrients studied intake was adequate, and nutrient density of the vegetarian diet was higher than of the omnivorous diet. However, the supply of zinc (average daily intake 8.5 and 7.6 mg for men and women, respectively), iron (because of lower bioavailability of nonheme iron), vitamin B12 (women only: intake 2.3 micrograms/day), and water (daily intake less than 1600 ml for 30% of the vegetarians) need special attention, considering the relatively high prevalence of a marginal status of these nutrients. In conclusion, a lacto-(ovo-)vegetarian diet can be adequate at old age, provided that it is carefully planned, especially with respect to the supply of iron, zinc, and vitamin B12.

Natural killer cells, vitamins, and other blood components of vegetarian and omnivorous men

The study population consisted of male vegetarians (aged 28-50 years), who were recruited from the vegetarian cohort being followed by the Department of Epidemiology (German Cancer Research Center, Heidelberg, FRG), and the same number of age- and sex-matched controls from the personnel of the same center. Among the vitamins tested, only the level of carotene was significantly higher in vegetarians; the levels of vitamin A, K, and E were not elevated. Among the other blood parameters tested, only creatinine and glutamine-transferase levels were significantly lower in vegetarians. The natural cytotoxicity of peripheral blood lymphocytes was measured using a chromium-release test. Cytotoxic activity, which is expressed as lytic units, was significantly higher in vegetarians than in their omnivorous controls by a factor of 2. The total number of white blood cells, lymphocytes, and other subpopulations did not differ between vegetarians and nonvegetarians. The enhanced natural cytotoxicity may be one of the factors contributing to the lower cancer risk shown by vegetarians.