The aim of this study was to describe the dietary intake of British vegetarians according to the Nova classification and to evaluate the association between the consumption of ultra-processed foods and the nutritional quality of the diet. We used data from the UK national survey (2008/2019). Food collected through a 4-d record were classified according to the Nova system. In all tertiles of the energy contribution of ultra-processed foods, differences in the average nutrient intake, as well as in the prevalence of inadequate intake, were analysed, considering the values recommended by international authorities. Ultra-processed foods had the highest dietary contribution (56·3 % of energy intake), followed by fresh or minimally processed foods (29·2 %), processed foods (9·4 %) and culinary ingredients (5 %). A positive linear trend was found between the contribution tertiles of ultra-processed foods and the content of free sugars (β 0·25, P < 0·001), while an inverse relationship was observed for dietary fibre (β –0·26, P = 0·002), potassium (β –0·38, P < 0·001), Mg (β –0·31, P < 0·001), Cu (β –0·22, P < 0·003), vitamin A (β –0·37, P < 0·001) and vitamin C (β –0·22, P < 0·001). As the contribution of ultra-processed foods to total energy intake increased (from the first to the last tertile of consumption), the prevalence of inadequate intake of free sugars increased (from 32·9 % to 60·7 %, respectively), as well as the prevalence of inadequate fibre intake (from 26·1 % to 47·5 %). The influence of ultra-processed foods on the vegetarian diet in the UK is of considerable magnitude, and the consumption of this food was associated with poorer diet quality.

Plant-based diets may increase the risk of vitamin B12 deficiency due to limited intake of animal-source foods, while dietary folate increases when adhering to plant-based diets. In this cross-sectional study, we evaluated the B12 and folate status of Norwegian vegans and vegetarians using dietary B12 intake, B12 and folic acid supplement use, and biomarkers (serum B12 (B12), plasma total homocysteine (tHcy), plasma methylmalonic acid (MMA) and serum folate). Vegans (n 115) and vegetarians (n 90) completed a 24-h dietary recall and a FFQ and provided a non-fasting blood sample. cB12, a combined indicator for evaluation of B12 status, was calculated. B12 status was adequate in both vegans and vegetarians according to the cB12 indicator; however 4 % had elevated B12. Serum B12, tHcy, MMA concentrations and the cB12 indicator (overall median: 357 pmol/l, 9·0 µmol/l, 0·18 µmol/l, 1·30 (cB12)) did not differ between vegans and vegetarians, unlike for folate (vegans: 25·8 nmol/l, vegetarians: 21·6 nmol/l, P = 0·027). Serum B12 concentration < 221 pmol/l was found in 14 % of all participants. Vegetarians revealed the highest proportion of participants below the recommended daily intake of 2 µg/d including supplements (40 v. 18 %, P < 0·001). Predictors of higher serum B12 concentrations were average daily supplement use and older age. Folate deficiency (< 10 nmol/l) was uncommon overall (< 2·5 %). The combined indicator cB12 suggested that none of the participants was B12-depleted; however, low serum B12 concentration was found in 14 % of the participants. Folate concentrations were adequate, indicating adequate folate intake in Norwegian vegans and vegetarians.

We critically review potential involvement of trimethylamine N-oxide (TMAO) as a link between diet, the gut microbiota and CVD. Generated primarily from dietary choline and carnitine by gut bacteria and hepatic flavin-containing mono-oxygenase (FMO) activity, TMAO could promote cardiometabolic disease when chronically elevated. However, control of circulating TMAO is poorly understood, and diet, age, body mass, sex hormones, renal clearance, FMO3 expression and genetic background may explain as little as 25 % of TMAO variance. The basis of elevations with obesity, diabetes, atherosclerosis or CHD is similarly ill-defined, although gut microbiota profiles/remodelling appear critical. Elevated TMAO could promote CVD via inflammation, oxidative stress, scavenger receptor up-regulation, reverse cholesterol transport (RCT) inhibition, and cardiovascular dysfunction. However, concentrations influencing inflammation, scavenger receptors and RCT (≥100 µm) are only achieved in advanced heart failure or chronic kidney disease (CKD), and greatly exceed pathogenicity of <1–5 µm levels implied in some TMAO–CVD associations. There is also evidence that CVD risk is insensitive to TMAO variance beyond these levels in omnivores and vegetarians, and that major TMAO sources are cardioprotective. Assessing available evidence suggests that modest elevations in TMAO (≤10 µm) are a non-pathogenic consequence of diverse risk factors (ageing, obesity, dyslipidaemia, insulin resistance/diabetes, renal dysfunction), indirectly reflecting CVD risk without participating mechanistically. Nonetheless, TMAO may surpass a pathogenic threshold as a consequence of CVD/CKD, secondarily promoting disease progression. TMAO might thus reflect early CVD risk while providing a prognostic biomarker or secondary target in established disease, although mechanistic contributions to CVD await confirmation.

Studies on the nutritional status of vegetarians in Spain are lacking. Prevention of vitamin B12 deficiency is the main concern, as dietary sources are of animal origin. The present study aimed to evaluate vitamin B12 and folate status of Spanish vegetarians using classical markers and functional markers. Participants were adult and healthy lacto-ovo vegetarians (forty-nine subjects) and vegans (fifty-four subjects) who underwent blood analyses and completed a FFQ. Serum vitamin B12, homocysteine (Hcy), methylmalonic acid (MMA), erythrocyte folate and haematological parameters were determined. The effects of the type of plant-based diet, and the intake of supplements and foods were studied by a FFQ. Mean erythrocyte folate was 1704 (sd 609) nmol/l. Clinical or subclinical vitamin B12 deficiency was detected in 11 % of the subjects (MMA>271 nmol/l) and 33 % of the participants showed hyperhomocysteinaemia (Hcy>15 µmol/l). Regarding plant-based diet type, significantly higher Hcy was observed in lacto-ovo vegetarians compared with vegans (P = 0·019). Moreover, use of vitamin B12 supplements involved an improvement of vitamin B12 status but further increase in erythrocyte folate (P = 0·024). Consumption of yoghurts was weakly associated with serum vitamin B12 adequacy (P = 0·049) and that of eggs with lower Hcy (P = 0·030). In conclusion, Spanish vegetarians present high folate status but vitamin B12 subclinical deficiency was demonstrated using functional markers. The lack of influence of dietary sources on functional markers and the strong effect of vitamin B12 supplement intake emphasise the need of cobalamin supplementation in both lacto-ovo vegetarians and vegans.

Evidence suggests a relationship between polyphenol intake and health benefits. Polyphenol intake among a large US cohort with diverse dietary practices ranging from meatless to omnivorous diets has not been previously evaluated. The primary aim of this study was to compare polyphenol intakes of several vegetarian and non-vegetarian dietary patterns and to assess phenolic intake by food source. To characterise dietary intake, a FFQ was administered to 77 441 participants of the Adventist Health Study-2. Dietary patterns were defined based on the absence of animal food consumption as vegan, lacto-ovo-vegetarian, pesco-vegetarian, semi-vegetarian and non-vegetarian. Polyphenol intakes were calculated based on chromatography-derived polyphenol content data of foods from Phenol-Explorer, US Department of Agriculture databases and relevant literature. Results revealed a mean unadjusted total polyphenol intake of 801 (sd 356) mg/d, and the main foods contributing to polyphenol intakes were coffee, fruits and fruit juices. Total polyphenol intake differed significantly between dietary patterns, with phenolic acids from coffee contributing the greatest variation. The dominant classes and sources of dietary polyphenols differed between vegetarian and non-vegetarian diets. Flavonoid intake was the highest among pesco-vegetarians, and phenolic acid intake was the highest among non-vegetarians. In addition, coffee consumers appeared to have a different dietary profile than non-coffee consumers, including greatly reduced contribution of fruits, vegetables and legumes to total phenolic intake. Coffee drinkers were more likely to be non-vegetarians, which explained several of these observations. Further evaluating these differences may be important in identifying relationships between plant-based diets and health outcomes.

Among cancers in American women, breast cancer (BC) has the second highest incidence and mortality. The association of BC with diet has been inconsistent. Studies that evaluate associations with dietary patterns are less common and reflect an individual’s whole diet. We associated dietary patterns with the risk of BC in American women of the Adventist Health Study-2 (AHS-2), a prospective cohort of 96 001 subjects recruited between 2002 and 2007. Answers to a previously validated FFQ were used to classify subjects to vegan, lacto-ovo-vegetarian, pesco-vegetarian, semi-vegetarian and non-vegetarian dietary patterns. Incident BC were identified by matching AHS-2 subjects to data from forty-eight state cancer registries. Statistical analyses used proportional hazard regression analyses with covariates that were chosen a priori. From 50 404 female participants (26 193 vegetarians), we identified 892 incident BC cases, with 478 cases among vegetarians. As compared with non-vegetarians, all vegetarians combined did not have a significantly lower risk (hazard ratio (HR) 0·97; CI 0·84, 1·11; P=0·64). However, vegans showed consistently lower (but non-significant) point estimates when compared with non-vegetarians (all cases: HR 0·78; CI 0·58, 1·05; P=0·09). In summary, participants in this cohort who follow a vegetarian dietary pattern did not experience a lower risk of BC as compared with non-vegetarians, although lower risk in vegans is possible. These findings add to the very limited literature associating vegetarian diets with BC risk and can assist nutritionists when evaluating the impact of these diets. The findings will also motivate further evaluation of vegan diets and their special characteristics.

Vegetarian dietary patterns have been reported to be associated with a number of favourable health outcomes in epidemiological studies, including the Adventist Health Study 2 (AHS-2). Such dietary patterns may vary and need further characterisation regarding foods consumed. The aims of the present study were to characterise and compare the food consumption patterns of several vegetarian and non-vegetarian diets. Dietary intake was measured using an FFQ among more than 89 000 members of the AHS-2 cohort. Vegetarian dietary patterns were defined a priori, based on the absence of certain animal foods in the diet. Foods were categorised into fifty-eight minor food groups comprising seventeen major food groups. The adjusted mean consumption of each food group for the vegetarian dietary patterns was compared with that for the non-vegetarian dietary pattern. Mean consumption was found to differ significantly across the dietary patterns for all food groups. Increased consumption of many plant foods including fruits, vegetables, avocados, non-fried potatoes, whole grains, legumes, soya foods, nuts and seeds was observed among vegetarians. Conversely, reduced consumption of meats, dairy products, eggs, refined grains, added fats, sweets, snack foods and non-water beverages was observed among vegetarians. Thus, although vegetarian dietary patterns in the AHS-2 have been defined based on the absence of animal foods in the diet, they differ greatly with respect to the consumption of many other food groups. These differences in food consumption patterns may be important in helping to explain the association of vegetarian diets with several important health outcomes.

There is strong evidence indicating that elevated plasma total homocysteine (tHcy) levels are a major independent biomarker and/or a contributor to chronic conditions, such as CVD. A deficiency of vitamin B12 can elevate homocysteine. Vegetarians are a group of the population who are potentially at greater risk of vitamin B12 deficiency than omnivores. This is the first systematic review and meta-analysis to appraise a range of studies that compared the homocysteine and vitamin B12 levels of vegetarians and omnivores. The search methods employed identified 443 entries, from which, by screening using set inclusion and exclusion criteria, six eligible cohort case studies and eleven cross-sectional studies from 1999 to 2010 were revealed, which compared concentrations of plasma tHcy and serum vitamin B12 of omnivores, lactovegetarians or lacto-ovovegetarians and vegans. Of the identified seventeen studies (3230 participants), only two studies reported that vegan concentrations of plasma tHcy and serum vitamin B12 did not differ from omnivores. The present study confirmed that an inverse relationship exists between plasma tHcy and serum vitamin B12, from which it can be concluded that the usual dietary source of vitamin B12 is animal products and those who choose to omit or restrict these products are destined to become vitamin B12 deficient. At present, the available supplement, which is usually used for fortification of food, is the unreliable cyanocobalamin. A well-designed study is needed to investigate a reliable and suitable supplement to normalise the elevated plasma tHcy of a high majority of vegetarians. This would fill the gaps in the present nutritional scientific knowledge.

The association of plasma phospholipid (PL) fatty acid composition with plasma homocysteine (Hcy) in Chinese vegetarians is not understood. The main aim of the present study was to investigate the plasma PL fatty acid status, and its association with plasma Hcy in Chinese vegetarians and omnivores. A total of 103 male vegetarians and 128 male omnivores were recruited in Linyin Temple, Hangzhou. Plasma Hcy and PL fatty acid concentrations were determined by standard methods. Compared with omnivores, plasma PL n-3 PUFA (P< 0·001), 22 : 6n-3 (P< 0·001), 22 : 5n-6 (P= 0·021), 22 : 2n-6 (P< 0·001) and SFA (P= 0·017) were significantly lower, while plasma PL n-6 PUFA (P= 0·007) and total PUFA (P< 0·001) were significantly higher in vegetarians. The prevalence of hyperhomocysteinaemia (HHcy) in vegetarians (26·47 %) was significantly higher than that in omnivores (13·28 %). In vegetarians, plasma PL 22 : 6n-3 (r − 0·257, P= 0·046) was significantly negatively associated with plasma Hcy. In omnivores, plasma PL 18 : 1n-7 (r 0·237, P= 0·030) was significantly positively associated with plasma Hcy. Plasma PL 22 : 6n-3 (r − 0·217, P= 0·048) was negatively associated with plasma Hcy in omnivores. Plasma PL SFA were positively associated with the prevalence of HHcy. It would seem appropriate for vegetarians to increase their dietary n-3 PUFA and decrease dietary SFA, and thus reduce the risk of HHcy.

The present study examines the prevalence and characteristics of vegetarians in the Taiwanese elderly. We analysed data from the Elderly Nutrition and Health Survey in Taiwan (1999–2000), which used a multi-staged, stratified, clustered probability sampling design. Community-dwelling elderly (n 1071), aged 65 years and older, were included. Sociodemographic, anthropometric, lifestyle and metabolic variables, and eating habits were obtained through household interviews and health examinations. Nutrient intake was assessed using a 24 h dietary recall. Multivariable logistic regression analysis was performed to examine factors significantly and independently associated with vegetarian status and to estimate the OR of the hypertension and the metabolic syndrome (MS) for vegetarians compared with omnivores. About 25 % of the Taiwanese elderly persons were vegetarians. Systolic pressure (OR 1·01, 95 % CI 1, 1·02, P = 0·038), female sex (OR 5·02, 95 % CI 3·11, 8·1, P < 0·001), smoking status (P = 0·034; current smoker (OR 0·45, 95 % CI 0·24, 0·85, P = 0·014)) and regular exercise (OR 1·87, 95 % CI 1·37, 2·56, P < 0·001) were independently associated with vegetarian status among Taiwanese elderly persons. Vegetarians consumed significantly lower daily total energy (P < 0·001), lower cholesterol (P = 0·002), a higher percentage of fat as PUFA (P = 0·022), higher Ca (P < 0·001) and higher crude fibres (P = 0·041) compared with omnivores. Between the two vegetarian diets, ovo- or lacto-vegetarian diets contained more beneficial micronutrients, such as K, Ca and Mg, and higher crude fibres than vegan diets (all P < 0·05). The likelihood of having hypertension and the MS was not significantly different between vegetarians and omnivores as examined by sex- or multivariate-adjusted logistic regression.

Creatine when combined with P forms phosphocreatine that acts as a reserve of high-energy phosphate. Creatine is found mostly in meat, fish and other animal products, and the levels of muscle creatine are known to be lower in vegetarians. Creatine supplementation influences brain functioning as indicated by imaging studies and the measurement of oxygenated Hb. Given the key role played by creatine in the provision of energy, the influence of its supplementation on cognitive functioning was examined, contrasting the effect in omnivores and vegetarians. Young adult females (n 128) were separated into those who were and were not vegetarian. Randomly and under a double-blind procedure, subjects consumed either a placebo or 20 g of creatine supplement for 5 d. Creatine supplementation did not influence measures of verbal fluency and vigilance. However, in vegetarians rather than in those who consume meat, creatine supplementation resulted in better memory. Irrespective of dietary style, the supplementation of creatine decreased the variability in the responses to a choice reaction-time task.

Compared with non-vegetarians, Western vegetarians have a lower mean BMI (by about 1 kg/m2), a lower mean plasma total cholesterol concentration (by about 0.5 mmol/l), and a lower mortality from IHD (by about 25 %). They may also have a lower risk for some other diseases such as constipation, diverticular disease, gallstones and appendicitis. No differences in mortality from common cancers have been established. There is no evidence of adverse effects on mortality. Much more information is needed, particularly on other causes of death, other morbidity including osteoporosis, and long-term health in vegans. The evidence available suggests that widespread adoption of a vegetarian diet could prevent approximately 40 000 deaths from IHD in Britain each year.

The nutritional adequacy of plant-based diets is discussed. Energy and protein intakes are similar for plant-based diets compared with those containing meat. Fe and vitamin B12 are the nutrients most likely to be found lacking in such diets. Bioactive substances present in foods of plant origin significantly influence the bioavailability of minerals and requirements for vitamins. Well-balanced vegetarian diets are able to support normal growth and development. It is concluded that meat is an optional rather than an essential constituent of human diets.

Vegetarians have a lower incidence of many chronic diseases than omnivores. However, vegetarian diets could potentially result in lower intakes of some minerals, particularly Zn. In a cross-sectional study, dietary Zn intake was measured using 12 d weighed records in ninety-nine vegetarians (ten vegans) aged 18–50 years and forty-nine age- and sex-matched omnivores. In men, the mean daily Zn intake and Zn density values were similar in omnivores, ovolactovegetarians and vegans, but in women they were significantly lower in vegetarians (mean intake 6·8 mg v. 8·4 mg in omnivores) and few achieved the recommended intake. Significantly more vegetarian than omnivorous women had a daily Zn intake < 6 mg (44 % v. 13 %). Mean serum Zn concentrations were similar in female omnivores and vegetarians, despite the differences in intake. However, omnivorous men had a lower mean serum Zn concentration (0·85 μg/ml v. 0·95 μg/ml) and more subjects had levels below the reference range of 0·72–1·44 μg/ml than ovolactovegetarians (P < 0·01). Overall more women than men had low Zn concentrations; and these women generally had intakes below 6 mg/d. There was a significant correlation between serum Zn concentration and dietary Zn density in vegetarians, especially females (P < 0·001), but not in omnivores. Ovolactovegetarians did not have a significantly greater risk of low Zn status than omnivores.

Observational studies primarily based on diet questionnaires or food records have reported that vegetarians can have a very low I intake. However, analytically ascertained data on the possible degree of I deficiency with this form of diet is lacking. Six healthy adult volunteers participated in the present controlled experimental diet study carried out in four separate 5 d diet periods. The study diets, normal, protein-rich, lactovegetarian, and repeat of the initial normal diet, were almost isoenergetic and contained no fish, sea food, iodized salt or processed foods fortified with I. During the last 48 h of each diet period two 24 h urine samples were obtained from each subject. I analyses were performed in the urine samples and in representative samples taken from all ingested diets. Urinary I excretion was significantly lower with the lactovegetarian diet (36·6 (sd 8·8) μg/d) than with the normal and the protein-rich diets (50·2 (sd 14·0) and 61·0 (sd 8·0) μg/d respectively). Accordingly, a markedly reduced I intake was confirmed analytically for the lactovegetarian diet (15·6 μg/d v. 35·2 and 44·5 μg/d respectively). Our results provide experimental confirmation of literature findings indicating that I supply is higher with non-vegetarian than with vegetarian diets. Specifically, the extremely low intake and urinary output of I as analytically determined for one exemplary vegetarian diet, demonstrate that dietary I may be limiting when strict forms of vegetarian dietary practices (no iodized salt, no I supplements) are followed. The present study is, therefore, the first diet-experiment-based pointer to the potential danger of I deficiency disorders due to strict forms of vegetarian nutrition, especially when fruits and vegetables grown in soils with low I levels are ingested.

Faecal bulk, pH, water content, the concentrations of neutral sterols and bile acids and dietary intakes were measured in twenty-two Indian vegetarian, twenty-two white omnivorous and eighteen white vegetarian premenopausal women. Faecal bulk and water content were greater and pH lower in the Indian vegetarians. Total faecal animal sterol and coprostanol concentrations expressed on a dry-weight basis were lower in the vegetarians compared with the omnivores. The faecal sterol concentrations were correlated with dietary cholesterol intake. Primary bile acids were detected in six Indian vegetarians, two white vegetarians and two white omnivores; secondary bile acids were detected in all the white omnivore and vegetarian subjects but not in two of the Indian vegetarians. Total faecal free bile acid and conjugated bile acid concentrations were lower in the white vegetarians compared with the omnivores. Faecal lithocholic acid concentrations were lower in both Indian and white vegetarians. The lithocholic: deoxycholic acid ratio and coprostanol: total animal sterols ratio were significantly lower in the Indian vegetarians compared with the omnivores. Both ratios were positively correlated with faecal pH. Stepwise multiple regression analyses were undertaken in order to identify which nutrients influenced faecal pH, lithocholic and deoxycholic acid concentrations. The intakes of starch and dietary fibre were negatively associated with faecal concentrations of lithocholic and deoxycholic acid. Starch intake alone was negatively associated with faecal pH. The results of this study confirm that diets high in dietary fibre decrease faecal bile acid concentrations and suggest that the complex carbohydrates present in Indian vegetarian diets influence faecal pH and inhibit the degradation of faecal steroids.

The effect of long-term differences in diet composition on whole-body acid–base status was examined in thirty-three young healthy females. The volunteers were recruited from two separate groups matched approximately for age, height and weight; one group regularly ate meat (omnivores; n 20) and one group did not (vegetarians; n 13). All subjects completed a 7 d weighed intake of food, and from their dietary records, total energy, carbohydrate (CHO), fat and protein content were estimated using computer-based food composition tables. During this week they reported to the laboratory on two occasions, following an overnight fast and separated by at least 48h. Arterialized venous blood samples were obtained on each visit and these were analysed for blood acid–base status. Haemoglobin and packed cell volume, serum total cholesterol and HDL-cholesterol, serum albumin and total protein were also determined. Two 24 h urine collections were completed; the volume was recorded and samples were analysed for pH, titratable acid and Mg and Ca concentration. Total energy intake of the omnivores was greater (P = 0.0003) than that of the vegetarian group. Dietary intake of CHO (P = 0.024), fat (P = 0.0054) and protein (P = 0.0002) were higher in the omnivorous group than in the vegetarians. There were no differences between the two groups with respect to blood CO2 partial pressure, plasma HCO3- and blood base excess, but blood pH was slightly higher in the omnivores (P = 0.064). Measures of urine acid–base status suggested a lower pH in the omnivore group, but this difference was not statistically significant; a greater titratable acid output was observed with the omnivorous group compared with the vegetarians (48.9 (se 20.3) ν. 35.3 (se 23.3) mEq/24h; P = 0.018). Although the dietary intake of Ca was not different between the two groups, urinary Ca excretion of the omnivores was significantly higher (3.87 (sd 1.34) ν. 3.22 (sd 1.20) mmol/24h) than that of the vegetarians (P = 0.014). It is suggested that the higher protein intake of the omnivores resulted in an increase in urinary total acid excretion, which may explain the higher rate of Ca excretion.