Contemporary diets in Western countries are largely acid-inducing and deficient in potassium alkali salts, resulting in low-grade metabolic acidosis. The chronic consumption of acidogenic diets abundant in animal-based foods (meats, dairy, cheese and eggs) poses a substantial challenge to the human body's buffering capacities and chronic retention of acid wherein the progressive loss of bicarbonate stores can cause cellular and tissue damage. An elevated dietary acid load (DAL) has been associated with systemic inflammation and other adverse metabolic conditions. In this narrative review, we examine DAL quantification methods and index observational and clinical evidence on the role of plant-based diets, chiefly vegetarian and vegan, in reducing DAL. Quantitation of protein and amino acid composition and of intake of alkalising organic potassium salts and magnesium show that plant-based diets are most effective at reducing DAL. Results from clinical studies and recommendations in the form of expert committee opinions suggest that for a number of common illnesses, wherein metabolic acidosis is a contributing factor, the regular inclusion of plant-based foods offers measurable benefits for disease prevention and management. Based on available evidence, dietary shifts toward plant-based nutrition effectively reduces dietary-induced, low-grade metabolic acidosis.

Plant-based, i.e. vegetarian (without meat and fish) or vegan (exclusively plant-based foods) diets are in trend also among children and adolescents, but data on food intake in this group are lacking. Here, we compare the consumption of food groups of vegetarian (n 145), vegan (n 110) and omnivore (n 135) children and adolescents (6–18 years) in Germany using data of the VeChi Youth Study. Each food item reported in 3 d weighed dietary records was assigned to one of eighteen food groups and individual mean intake per day (g/MJ) was calculated. Group differences were assessed using covariance analyses adjusted for age, sex and other covariates. For food groups with a high number of non-consumers, non-parametric Kruskal–Wallis tests were run. Pairwise comparison of vegetarian and vegan groups indicated significantly higher intakes of legumes, nuts, milk alternatives (all P = 0·0003) and meat alternatives (P = 0·0065) among vegan subjects. Intake of these food groups of omnivore participants was low (Q3:0·0 g/MJ for legumes, milk alternatives and meat alternatives, 0·5 g/MJ for nuts). Dairy intake of vegetarians (11·6 g/MJ) was significantly lower than of omnivore subjects (24·7 g/MJ) (P = 0·0003). Intake of fats/oils and sweet foods was lowest in vegan compared with vegetarian and omnivore participants (P< 0·05). Whole grain intake was higher in vegan participants (14·5 g/MJ) than of vegetarian (9·1 g/MJ) and omnivore (6·5 g/MJ) participants (P = 0·0003). Longitudinal studies are necessary to evaluate the long-term health consequences of vegetarian, vegan and omnivore food patterns, especially in childhood and adolescence.

In parallel with increased public awareness of the health and environmental benefits of consuming a plant-based diet, the numbers of people who identify as vegan has increased sharply. The question of whether vegetarian and vegan diets are appropriate for children is a longstanding and unresolved controversy. The more restrictive the diet and the younger the child, the greater the risk of nutritional deficiency. Nutrients of potential concern are protein quantity and quality, iron, zinc, selenium, calcium, riboflavin, vitamins A, D, B12 and essential fatty acids. Although intakes and status of some nutrients (e.g. vitamin D and iron) are low in many children, vegan children are particularly susceptible due to inadequate supply and/or excess dietary fibre as well as other components that limit bioavailability. Although position papers from North America state that well-planned vegetarian and vegan diets, supplemented appropriately, are suitable for all life stages, European statements include strong recommendations to parents that vegan diets should not be adopted by children without medical and dietetic supervision. Case histories of malnutrition and serious harm persist, including irreversible neurological damage due to vitamin B12 deficiency among un-supplemented children. The evidence available to evaluate the nutritional appropriateness of vegetarian diets for children is inadequate and dated. Although nutritionally adequate vegetarian diets are more easily achieved, successful provision of a complete vegan diet for a young child requires substantial commitment, expert guidance, planning, resources and supplementation.

CVD are the main cause of death especially in high-income countries. Previously, research focused on single nutrients including saturated and MUFA, sodium and dietary fibre, or specific foods such as fish, fruit and vegetables, and olive oil, in the aetiology of CVD. In recent years, however, the effects of complete dietary patterns on the prevention of CVD have gained interest, to account for diet heterogeneity and food–nutrient interactions. Several dietary patterns have been investigated, such as the Paleolithic diet, the vegetarian and vegan diets, the Diet Approaches to Stop Hypertension (DASH), the Nordic and Mediterranean diets, with many contradictions remaining. The aim of this review is to give an overview of the effects of these dietary patterns on CVD risk, to discuss their overall nutrient adequacy and briefly discuss their environmental impact.

Meat consumption in high-income countries is increasingly discussed due to its impact on environment and health as well as ethical considerations. The present paper aims to provide information on meat consumption behaviour, sociodemographic factors related to meat consumption and its associations with health and nutritional behaviour, based on the German National Nutrition Survey II. For 12 915 participants aged 18–80 years, food consumption was assessed by two 24-h recalls and further data by interviews. Participants were distinguished in non-meat consumers and meat consumers; meat consumers were further differentiated as low and high meat consumers (<86 g/d and ≥86 g/d). Group differences were analysed using binary logistic and linear regression models. More non-meat consumers were found among women, young and more educated persons. They showed equal or more preferable health characteristics, had a similar energy intake but ate more plant-based foods compared with meat consumers. More high meat consumers were found among men, young and middle-aged and lower-educated persons. Compared with low meat consumers, they showed equal or less preferable health characteristics, had a higher energy intake and ate more potatoes and sauces/spices and less of most other food groups in relation to their energy intake. To conclude, sociodemographic groups differ in their meat consumption and differences in meat consumption go together with differences in health behaviour and other food consumption.

Previous studies have suggested that vegetarianism can result in a reduction of vitamin B12 circulating levels. The aim of the present study was to investigate the effects of a 3-month dietary intervention with a lacto-ovo-vegetarian diet (VD) on the levels of circulating vitamin B12 in a group of omnivores. We analysed fifty-four omnivorous subjects who followed a VD as a first dietary intervention within the CARDIVEG (Cardiovascular Prevention with Vegetarian Diet) study, a dietary intervention study. VD resulted in a significant reduction (P<0·001) of 51·2 % of vitamin B12 intake and in a significant reduction (P=0·005) of 6·2 % of the circulating levels of vitamin B12 (–24·5 pg/ml). Changes in vitamin B12 intake were significantly correlated with changes in circulating levels of vitamin B12 (R 0·61, P<0·001). Subgroup analyses showed that reduction in circulating vitamin B12 levels was more evident in participants who were younger, overweight, non-smokers and had hypercholesterolaemia. A logistic regression analysis showed that a reduction in vitamin B12 intake greater than the first quartile of the delta changes obtained in the study population (–28·5 %) conferred a significantly higher risk of experiencing a decrease in circulating vitamin B12 levels (OR 10·1; 95 % CI 1·3, 76·1). In conclusion, a 3-month VD period determined a significant reduction in circulating levels of vitamin B12, being significantly correlated with the reduction in vitamin B12 intake. Although a well-planned VD can provide adequate nutrition across all life stages, special care must be taken to ensure adequate vitamin B12 intake and to help prevent deficiency.

The vegetarian dietary pattern is traditionally a plant-based diet that includes fruits, vegetables, cereals, legumes, nuts, vegetable oils, soya, and possibly dairy products and/or eggs. Vegetarians and other populations who follow a plant-based dietary pattern enjoy longevity. Specifically, vegetarian dietary patterns have been associated with a lower risk for developing IHD, type 2 diabetes, hypertension, specific cancers, lower all-cause mortality and reduction in cause-specific mortality. The prevalence of the metabolic syndrome (MetS) in the USA is approximately 20 % and is currently increasing in developing countries in line with the obesity epidemic. The health care costs associated with the MetS are on a magnitude of 1·6 overall compared with healthy individuals, which makes it an important public health problem. Current evidence from several cross-sectional and case–control studies shows an association between consumption of a vegetarian dietary pattern and a reduced prevalence or risk of developing the MetS. There is a need for further research to be conducted, particularly prospective cohort studies to evaluate the effect of vegetarian dietary patterns on reducing the incidence of the MetS and, clinical trials should be designed to explore vegetarian dietary patterns for the reversal of the MetS in high-risk populations. This research could contribute to reduce the societal and economic burdens associated with the disorder.

A dog's nutrient requirements can theoretically be met from a properly balanced meat-free diet; however, proof for this is lacking. Exercise places additional demands on the body, and dogs fed a meat-free diet may be at increased risk of developing sports anaemia. We hypothesised that exercising dogs would remain in good health and not develop anaemia when fed a nutritionally balanced meat-free diet. To this end, twelve sprint-racing Siberian huskies were fed either a commercial diet recommended for active dogs (n 6), or a meat-free diet formulated to the same nutrient specifications (n 6). The commercial diet contained 43 % poultry meal, whereas soyabean meal and maize gluten made up 43 % of the meat-free diet, as the main protein ingredients. Dogs were fed these diets as their sole nutrient intake for 16 weeks, including 10 weeks of competitive racing. Blood samples were collected at weeks 0, 3, 8 and 16, and veterinary health checks were conducted at weeks 0, 8 and 16. Haematology results for all dogs, irrespective of diet, were within normal range throughout the study and the consulting veterinarian assessed all dogs to be in excellent physical condition. No dogs in the present study developed anaemia. On the contrary, erythrocyte counts and Hb values increased significantly over time (P < 0·01) in both groups of dogs. The present study is the first to demonstrate that a carefully balanced meat-free diet can maintain normal haematological values in exercising dogs.

The impact of nutrition on the epigenetic machinery has increasingly attracted interest. The aim of the present study was to demonstrate the effects of various diets on methylation and gene expression. The antioxidative enzyme mitochondrial superoxide dismutase (MnSOD) was chosen as the model system because epigenetic regulation has been previously shown in cell lines for this gene. Promoter methylation and gene expression of MnSOD in buccal swabs from three sample groups were analysed. The three groups included: (1) forty vegetarians (aged 20–30 years); (2) age-matched omnivores; (3) elderly omnivores (aged>85 years). A 3-fold increase in the expression of the MnSOD gene was associated with decreased CpG methylation of the analysed promoter region in the vegetarian group compared with the age-matched omnivores group. Expression and promoter methylation of the MnSOD gene in elderly omnivores showed no significant differences compared with younger omnivores. In accordance with previous findings in various tissues, DNA global methylation was found to be significantly higher (30 %) in buccal swabs of younger subjects (independent of the diet), than in those of elderly omnivores. In the control experiment which was designed to verify the findings of the human buccal swab studies, the Caco-2 cell line was treated with zebularine. Results of the control study showed a 6-fold increase of MnSOD expression, an approximately 40 % decreased methylation of specified CpG in the MnSOD promoter and a 50 % reduction of global DNA methylation. These results indicate that diet affects the epigenetic regulation of human MnSOD.

Certain dietary patterns may be related to the risk of CVD. We hypothesised that a plant-centred dietary pattern would be associated with a reduced risk of first myocardial infarction (MI). A case–control study of Norwegian men and postmenopausal women (age 45–75 years) was performed. A FFQ was administered, generally within 3 d after incident MI (n 106 cases). Controls (n 105) were frequency matched on sex, age and geographic location. On the FFQ, 190 items were categorised into thirty-five food groups and an a priori healthy diet pattern score was created. We estimated OR using logistic regression with adjustment for energy intake, family history of heart disease, marital status, current smoking, education and age. Among food groups, the risk of MI was significantly higher per sd of butter and margarine (OR 1·66 (95 % CI 1·12, 2·46)), and lower per sd of tomatoes (OR 0·53 (95 % CI 0·35, 0·79)), high-fat fish (OR 0·57 (95 % CI 0·38, 0·86)), wine (OR 0·58 (95 % CI 0·41, 0·83)), salad (OR 0·59 (95 % CI 0·40, 0·87)), wholegrain breakfast cereals (OR 0·64 (95 % CI 0·45, 0·90)), cruciferous vegetables (OR 0·66 (95 % CI 0·47, 0·93)) and non-hydrogenated vegetable oil (OR 0·68 (95 % CI 0·49, 0·95)). An abundance of cases were found to have a low a priori healthy diet pattern score. A dietary pattern emphasising nutrient-rich plant foods and high-fat fish and low in trans fatty acids was associated with decreased risk of MI among Norwegians.

The Orthodox Christian diet is unique in regularly interchanging from an omnivore to a vegetarian-type diet, and no study to date has focused on the impact of this on Fe status. Thirty-five Greek Orthodox Christian strict fasters (n 17 male, n 18 female; mean age 43·6±13·2 years) and twenty-four controls (n 11 male, n 13 female; mean age 39·8±7·6 years) were studied before (pre) and near completion (end) of the Christmas fasting (CF) period (40 d), during which meat and dairy products are prohibited. Fe status was assessed using standard haematological parameters, and Fe deficiency was determined via serum ferritin levels (<12 ng/ml) and the tri-index model. While fasters had marginally poorer pre haematological indicators, values were well above the cut-off levels, suggesting that intermittent fasting for a mean of 22·5±15·5 years did not have any substantial adverse effects on Fe status. During the CF period the changes in Fe status indices were more beneficial for fasters than for control subjects. In particular, fasters increased their ferritin levels (P=0·02) and decreased their total Fe-binding capacity (P<0·001). Compared with males, the effect of CF was more pronounced in female fasters. No subjects were detected with Fe deficiency at the end of the CF period. End dietary Fe and fibre intake were significantly higher in the fasters as compared with the control group (P=0·038 and P=0·001, respectively). Adherence to the Orthodox Christian dietary guidelines does not have a major impact on Fe status and is not associated with a significantly greater degree of Fe deficiency.

The efficacy of insulin in stimulating whole-body glucose disposal (insulin sensitivity) was quantified using direct methodology in thirty lacto-ovo vegetarians and in thirty meat-eaters. All subjects were adult, lean (BMI <23 kg/m2), healthy and glucose tolerant. Lacto-ovo vegetarians were more insulin sensitive than meat-eaters, with a steady-state plasma glucose (mmol/l) of 4·1 (95 % CI 3·5, 5·0) v. 6·9 (95 % CI 5·2, 7·5; P=0·0028) respectively. In addition, lacto-ovo vegetarians had lower body Fe stores, as indicated by a serum ferritin concentration (μg/l) of 35 (95 % CI 21, 49) compared with 72 (95 % CI 45, 100) for meat-eaters (P=0·0012). To test whether or not Fe status might modulate insulin sensitivity, body Fe was lowered by phlebotomy in six male meat-eaters to levels similar to that seen in vegetarians, with a resultant approximately 40 % enhancement of insulin-mediated glucose disposal (P=0·0008). Our results demonstrate that lacto-ovo vegetarians are more insulin sensitive and have lower Fe stores than meat-eaters. In addition, it seems that reduced insulin sensitivity in meat-eaters is amenable to improvement by reducing body Fe. The latter finding is in agreement with results from animal studies where, no matter how induced, Fe depletion consistently enhanced glucose disposal.

Urinary Mg is suggested to be an effective inhibitor of the formation and growth of calcium oxalate stones. In order to examine the influence of variations in dietary Mg on urinary Mg excretion, ten healthy male subjects were kept on two different standard diets for 5 d each. In the course of the test period, 24 h urine samples were collected. Diets 1 and 2 were calculated according to the dietary recommendations of the German Society of Nutrition (Deutsche Gesellschaft für Ernährung, 1986). Diet 1 was established as a model of a balanced mixed diet, whereas diet 2 represented an ovo-lacto-vegetarian meal plan. Diets 1 and 2 were isoenergetic with equal amounts of the main nutrients, estimated from food tables, and a constant fluid intake. In contrast to the content of Mg (336 mg) and dietary fibre (28 g) of diet 1, diet 2 was rich in Mg (553 mg) and dietary fibre (52 g). On the ingestion of diet 1, renal Mg excretion was 5·09 (SEM 0·35) mmol on the control day and increased slightly but not significantly to 5·40 (SEM 0·52) mmol on the corresponding day on diet 2. Urinary Mg excretion as a percentage of estimated dietary intake was about double on the balanced mixed diet (37%) than on the Mg-rich vegetarian diet (24%). As both diets contained equal amounts of most nutrients, these results indicate a lower excretion rate of Mg from the vegetarian diet than from the mixed diet. This would appear to be primarily due to the higher Mg and fibre contents and to the lower Mg utilization, that are important factors in decreasing Mg absorption and consequently urinary excretion rate.

In a controlled clinical trial we have recently shown that patients with rheumatoid arthritis (RA) improved after fasting for 7–10 d and that the improvement could be sustained through 3.5 months with a vegan, diet and 9 months with a lactovegetarian diet. Other studies have indicated that the inflammatory process in R A can be reduced through manipulation of dietary fatty acids. A switch to a vegetarian diet significantly alters the intake of fatty acids. Therefore, we have analysed the changes in fatty acid profiles of the plasma phospholipid fraction and related these changes to disease activity. The concentrations of the fatty acids 20: 3n-6 and 20: 4n-6 were significantly reduced after 3.5 months with a vegan diet (P < 0.0001 and P < 0.01 respectively), but the concentration increased to baseline values with a lactovegetarian diet. The concentration of 20: 5n-3 was significantly reduced after the vegan diet (P < 0.0001) and the lactovegetarian diet periods (P < 0.01). There was no significant difference in fatty acid concentrations between diet responders and diet non-responders after the vegan or lactovegetarian diet periods. Our results indicate that the changes in the fatty acid profiles cannot explain the clinical improvement.