Flexitarian, vegetarian and vegan diets are increasingly popular, particularly amongst young adults. This is the first randomised dietary intervention to investigate the health, wellbeing, and behavioural implications of consuming a basal vegetarian diet that additionally includes low-to-moderate amounts of red meat compared to one containing plant-based meat alternatives (PBMAs) in young adults (NCT04869163)(1). The objective for the current analysis is to measure adherence to the intervention, nutrition behaviours, and participants’ experience with their allocated dietary group. Eighty healthy young adults participated in this 10-week dietary intervention as household pairs. Household pairs were randomised to receive approximately three serves of beef and lamb meat (average of 390 g total cooked weight per person per week, flexitarian group) or PBMAs (350–400 g, vegetarian group) on top of a basal vegetarian diet. Participants were supported to adopt healthy eating behaviours, and this intervention was developed and implemented using a behaviour change framework(2). Diet adherence (eating allocated meat or PBMA, abstaining from animal-based foods not provided by researchers) was monitored daily, with total scores calculated at the end of the 10-week intervention period. Eating experiences were measured by the Positive Eating Scale and a purpose-designed exit survey, and a food frequency questionnaire measured dietary intake. Analyses used mixed effects modelling taking household clustering into account. The average total adherence score was 91.5 (SD = 9.0) out of a possible 100, with participants in the flexitarian group scoring higher (96.1, SD = 4.6, compared to 86.7, SD = 10.0; p < 0.001). Those receiving meat were generally more satisfied with this allocation compared to those receiving the PBMAs, even though a leading motivation for participants joining the study was an opportunity to try plant-based eating (35% expressed that that interest). Participants in both intervention groups had increased vegetable intake (p < 0.001), and reported more positive eating experiences (p = 0.020) and satisfaction with eating (p = 0.021) at the end of the 10-week intervention relative to baseline values. Behavioural methods to encourage engagement with the trial were successful, as participants demonstrated excellent adherence to the intervention. The flexitarian and vegetarian diets elicited different responses in adherence and eating experience. This holds relevance for the inclusion of red meat and PBMAs in healthy, sustainable dietary patterns beyond this study alone.

The adoption of dietary patterns emphasising higher intakes of plant foods and lower intakes of animal foods (plant-based diets, PBDs), continue to rise worldwide. PBDs have been associated with a lower risk of cardiovascular morbidity and mortality as well as major risk factors such as overweight/obesity and type 2 diabetes. Evidence regarding the dietary profile and disease risk associated with various PBDs in comparison to traditional meat-eating diets are scarce within the Australian population. The aim of this study is to investigate the 5-year and 10-year risk of developing cardiovascular disease (CVD) among Australians habitually following various PBDs compared to a regular meat diet (RMD). The Plant-based Diet (PBD) Study is a cross-sectional study consisting of healthy adults between aged 30-75 years from the Hunter Region (NSW) between 2021-2023. A validated FFQ was used to assess eligibility and categorise individuals who were habitually consuming one of five dietary patterns for at least 6 months into the following groups: vegan (nil animal products), lacto-vegetarian (LOV, including eggs and dairy), pesco-vegetarian (PV, including seafood with/without dairy and eggs), semi-vegetarian (SV, minimal consumption of animal products) or RMDs (including animal meat daily or multiple times/day)(1). 5-year and 10-year CVD risk was quantified using the Framingham Risk Equation(2) and the Australian Absolute CVD risk calculator, respectively. CVD risk and other quantitative measures was compared using One-way ANOVA or Kruskal Wallis, and Chi-square or Fisher’s Exact for qualitative data. Directed acyclic graphs displayed confounding variables and mediators and a regression model was used to adjust for these. A total of 240 participants (median age 55(16), 77.5% female) with 48 participants in each group showed a significant difference in predicted 5-year risk of CVD (P<0.05), however 10-year risk did not significantly differ across groups. 5-year CVD risk was significantly lower in the vegan group (1%) compared to the RMD, SV, PV, and LOV diet groups (all 2%). In comparison to a vegan diet, crude association showed those consuming a RMD had a 2.4% (95% CI 0.7, 4.1) higher 5-year risk of developing CVD, followed by 1.7% in LOV (95% CI 0.6, 2.9), 1.8% in PV (95% CI 0.5, 3), and 1.1% in SV (95% CI 0.2, 2.1). Significance was lost after adjusting for confounders such as age, gender, smoking status, alcohol intake, physical activity levels and BMI. This is the first study to purposefully sample Australians habitually following PBD, presenting novel population-based evidence for CVD risk. These findings suggest more restrictive PBDs such as vegan diets when compared to RMD may lead to lower CVD risk, however population-based longitudinal studies primary investigating the development of CVDs in the context of PBDs are warranted.

Maternal diet influences breast milk nutritional profile; however, it is unclear which nutrients and contaminants are particularly responsive to short- and long-term changes in maternal intake, and the impact of specific exclusion diets, such as vegan or vegetarian. This study systematically reviewed the literature on the effects of maternal nutrient intake, including exclusion diets, on both the nutrient and contaminant content of breast milk. The electronic databases, PubMed, CENTRAL, Web of Science and CINALH were systematically searched until 4 June 2023, with additionally searches of reference lists (PROSPERO, CRD42020221577). The quality of the studies was examined using Cochrane Risk of Bias tool and Newcastle–Ottawa scale. Eighty-eight studies (n 6577) met the search criteria. Due to high heterogeneity, meta-analysis was not possible. There was strong evidence of response to maternal intakes for DHA and EPA, vitamins A, E and K, iodine and Se in breast milk composition, some evidence of response for α-linolenic acid, B vitamins, vitamin C and D, ovalbumin, tyrosine and contaminants, and insufficient evidence to identify the effects arachidonic acid, Cu, Fe, Zn and choline. The paucity of evidence and high heterogeneity among studies reflects the need for more high-quality trials. However, this review identified the importance of maternal intake in the nutritional content of breast milk for a wide range of nutrients and supports the recommendation for supplementation of DHA and vitamin B12 for those on restrictive diets.

Plant-based substitutes (PBS) are seen as a convenient way to transition to a more plant-based diet, but their potential health benefits and nutritional concerns remain debated. Based on a review of the literature, it is concluded here that the primary risk of insufficient nutrient intake with PBS concerns iron and calcium, which are critical to the nutritional value of PBS. Other risks were identified but these would depend on the characteristics of the overall diet, as is the case for iodine in a diet containing no seafood or dairy, and vitamin B12 in a vegetarian/vegan diet. Conversely, the use of PBS is also expected to confer some benefits for long-term health because it would result in higher fibre intakes (in the case of meat PBS) and lower SFA intakes (but higher PUFA/MUFA intakes), but attention should be paid to a potential increase in sodium intake with PBS of meat products. In fact, a recurring finding in this review was that PBS is a very heterogeneous food category involving considerable variations in ingredient and nutrient composition, and whose design could be improved in order to foster nutritional and health benefits. The latter also depend on the animal food that is being replaced and are only deemed likely when PBS replace red meat. The fortification of PBS with key nutrients such as iron and calcium may constitute an actionable public health solution to further shift the balance in favour of PBS in the context of the current dietary transition in western countries.

Vegan and vegetarian diets are widely supported and adopted, but individuals following such diets remain at greater risk of iodine deficiency. This systematic review and meta-analysis was conducted to assess the iodine intake and status in adults following a vegan or vegetarian diet in the modern day. A systematic review and quality assessment were conducted from October 2020 to December 2022 according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidance. Studies were identified in Ovid MEDLINE, Web of Science, PubMed, and Scopus. Eleven articles were eligible for review containing 4421 adults (aged ≥ 18 years). Vegan groups had the lowest median urinary iodine concentration (mUIC) (12·2/l). None of the dietary groups had mUIC within the optimal range for iodine status (100–200 µg/l) (WHO). Vegan diets had the poorest iodine intake (17·3 µg/d) and were strongly associated with lower iodine intake (P = < 0·001) compared with omnivorous diets. Lower intake in vegan diets was influenced by sex (P = 0·007), the presence of voluntary or absence of Universal Salt Iodisation (USI) programmes (P = 0·01 & P = < 0·001), and living in a country with adequate iodine nutrition (P = < 0·001). Vegetarians and particularly vegans living in countries with no current USI programme continue to have increased risk of low iodine status, iodine deficiency and inadequate iodine intake. Further research into the usefulness of mandatory fortification of vegan appropriate foods is required.

Iodine is essential for thyroid hormone synthesis. Individuals adhering to vegan and vegetarian diets have been found to be vulnerable to iodine deficiency. Yet, iodine has not been monitored in these groups across time. This study aims to investigate iodine status, intake and knowledge in vegans, vegetarians and omnivores and determine changes between 2016–2017 and 2019. Dietary intake (µg/d) was estimated by 3-d food diaries and iodine FFQ. Urinary iodine concentration, analysed by inductively coupled plasma mass spectrometry, assessed iodine status according to WHO criteria. Iodine knowledge was scored by an adapted questionnaire. IBM SPSS was used for statistical analysis. Ninety-six adults (18–60 years) were recruited in October 2016–2017 (vegans: 12; vegetarians: 5; omnivores: 43) and June 2019 (vegans: 7; vegetarians: 10;omnivores: 19). Median dietary iodine was below the Reference Nutrient Intake for all groups. Vegans and vegetarians had the lowest iodine intake. Vegans had significantly lower iodine intake than omnivores (2016–2017, P = 0 032; 2019, P = 0 001). Omnivores had the highest iodine status (2016–2017, 79 4 µg/l; 2019, 72 4 µg/l) and vegans the lowest (2016–2017, 31 2 µg/l; 2019, 12 2 µg/l). Iodine knowledge was poor but did not differ between dietary groups (2016–2017, P = 0 219; 2019, P = 0 532). Vegans and vegetarians continue to be at risk of iodine deficiency. Further, iodine intake in the UK is poor independent of dietary choice. Iodine education is needed along with research into improving iodine nutrition at national level.

Plant-based (PB) diets are associated with good health and are also recommended for environmental sustainability. The present review aimed to summarise the definitions of PB diets globally and to investigate the nutritional role of PB diets in adults. This review found that there is a wide range of PB definitions ranging from the traditional vegetarian diets (including vegan) to semi-vegetarian/flexitarian diets. Furthermore, other diets which were originally developed due to their associations with positive health outcomes, such as the portfolio, Mediterranean-style, DASH, healthy US-style, planetary health and Nordic-style diets, have been encompassed in PB definitions due to their emphasis on certain PB components. This review has highlighted that those consuming a PB diet are more likely to meet recommended intakes for carbohydrate, dietary fibre and vitamin E and are less likely to meet recommendations for protein, vitamin B12 and iodine compared to omnivores. Regardless of consumer type, neither PB consumers nor omnivores met recommendations for intakes of vitamin D, calcium and sodium. While intakes of protein, n-3, iron and zinc were generally sufficient from the PB diet, it is important to acknowledge the lower bioavailability of these nutrients from PB foods compared to animal-derived products. As dietary patterns shift towards a more PB diet, there is a need for further studies to investigate the role of PB diets for nutritional adequacy and status in populations currently accustomed to consuming a primarily omnivorous diet.

The concept of plant-based diets has become popular due to the purported benefits for both human health and environmental impact. Although ‘plant-based’ is sometimes used to indicate omnivorous diets with a relatively small component of animal foods, here we take it to mean either vegetarian (plant-based plus dairy products and/or eggs) or vegan (100% plant-based). Important characteristics of plant-based diets which would be expected to be beneficial for long-term health are low intakes of saturated fat and high intakes of dietary fibre, whereas potentially deleterious characteristics are the risk of low intakes of some micronutrients such as vitamin B12, vitamin D, calcium and iodine, particularly in vegans. Vegetarians and vegans typically have lower BMI, serum LDL cholesterol and blood pressure than comparable regular meat-eaters, as well as lower bone mineral density. Vegetarians in the EPIC-Oxford study have a relatively low risk of IHD, diabetes, diverticular disease, kidney stones, cataracts and possibly some cancers, but a relatively high risk of stroke (principally haemorrhagic stroke) and bone fractures, in comparison with meat-eaters. Vegans in EPIC-Oxford have a lower risk of diabetes, diverticular disease and cataracts and a higher risk of fractures, but there are insufficient data for other conditions to draw conclusions. Overall, the health of people following plant-based diets appears to be generally good, with advantages but also some risks, and the extent to which the risks may be mitigated by optimal food choices, fortification and supplementation is not yet known.

From health and sustainability perspectives, reduction in the consumption of animal-based foods, especially red meat, is a key strategy. The present study examined the prevalence, sociodemographic and lifestyle factors, food consumption and food choice motives of vegetarians and consumers of low and high amounts of red and processed meat (RPM) among Finnish adults. We applied the data from three national health studies: FINRISK 2007 (n 4874), FINRISK 2012 (n 4812) and FinHealth 2017 (n 4442). Participants addressed their food consumption with a FFQ and answered other questionnaires about sociodemographic and lifestyle factors, as well as food choice motives. The prevalence of vegetarianism increased from 0·7 % in 2012 to 1·8 % in 2017, and median daily RPM consumption decreased from 128 g in 2007 to 119 g in 2012 and to 96 g in 2017. Vegetarians and members of the low-RPM group were more often women, younger and more highly educated than the high-RPM group, both in 2007 and 2017. Still, the importance of sex for the probability of a vegetarian diet decreased, while its importance for high-RPM consumption increased. Vegetarians consumed more fruit, vegetables, legumes, nuts and seeds than either the low- or high-RPM groups. The high-RPM group had the lowest scores in several aspects of healthy and sustainable diet, healthy food choice motives and healthy lifestyle. Vegetarians and groups differing in their RPM consumption levels might benefit from differing interventions and nutrition information taking into account their other dietary habits, food choice motives and lifestyle factors.

It is now fashionable in many circles to advocate vegetarianism, and many activist groups are vocal in their aim to convert the human race to vegetarians. What would be the economic costs and benefits of a shift away from meat consumption? In this article we provide some partial answers to this question. In three separate analyses we show (i) that it is much more costly to produce energy and protein from animal-based sources than from some plant-based sources, (ii) that sizable demand shifts away from meat consumption would result in significantly lower corn prices and production, and (iii) that the average U.S. consumer places a higher value on having meat in his or her diet than having any other food group. This information should help move forward our understanding of the economics of vegetarianism and provide an objective stance from which to evaluate the claims being made by advocates of vegetarianism.

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.