Check out this answer from Consensus:
Transitioning from a vegetarian to a vegan diet may offer additional health benefits, including greater protection against obesity, hypertension, type-2 diabetes, and certain types of cancer. Vegan diets also promote a healthier gut microbiota and are more environmentally sustainable. However, the impact on mental health is less clear and warrants further research. Overall, a well-planned vegan diet can be a healthful and sustainable choice for many individuals.
The debate between vegetarian and vegan diets has garnered significant attention in recent years, with many individuals transitioning from vegetarianism to veganism in pursuit of better health outcomes. This article aims to explore whether there are significant health benefits associated with making the switch from a vegetarian to a vegan diet, drawing on evidence from multiple research studies.
Health Benefits of Vegetarian and Vegan Diets
Both vegetarian and vegan diets have been associated with numerous health benefits. A comprehensive meta-analysis of observational studies found that both diets are linked to lower body mass index (BMI), total cholesterol, LDL-cholesterol, and glucose levels compared to omnivorous diets1. Additionally, these diets are associated with a reduced risk of ischemic heart disease and certain types of cancer1.
The Academy of Nutrition and Dietetics also supports the health benefits of well-planned vegetarian and vegan diets, noting their potential to prevent and treat various chronic diseases, including ischemic heart disease, type 2 diabetes, hypertension, and obesity2. These diets are rich in fiber, phytochemicals, and low in saturated fat, contributing to better serum glucose control and lower cholesterol levels2.
Specific Benefits of Vegan Diets
While both vegetarian and vegan diets offer health benefits, some studies suggest that vegan diets may provide additional advantages. For instance, a review of the Adventist Health Studies indicated that vegan diets offer greater protection against obesity, hypertension, type-2 diabetes, and cardiovascular mortality compared to lacto-ovo-vegetarian diets6. This suggests that eliminating all animal products, including dairy and eggs, may confer extra health benefits.
Moreover, a systematic review highlighted that vegans have a significantly reduced risk of total cancer incidence compared to vegetarians and omnivores1. This protective effect is attributed to the higher intake of plant-based foods, which are rich in antioxidants and other bioactive compounds that may reduce cancer risk1.
Mental Health and Cognitive Outcomes
The relationship between diet and mental health is complex. A meta-analysis examining the impact of vegetarian and vegan diets on mental health found no significant differences in depression, stress, well-being, or cognitive impairment between the two diets3. However, vegans and vegetarians were at a higher risk for depression but had lower anxiety scores compared to omnivores3. These findings suggest that while vegan diets may offer physical health benefits, their impact on mental health requires further investigation.
Gut Microbiota and Overall Health
The composition of gut microbiota is another area where vegan diets may offer advantages. A review of the effects of vegetarian and vegan diets on gut microbiota found that plant-based diets promote a more diverse and stable microbial system, which is beneficial for overall health8. Vegans and vegetarians have higher counts of beneficial bacteria, such as Bacteroidetes, which are associated with anti-inflammatory effects and improved cardiovascular health8.
Environmental and Planetary Health
Beyond individual health benefits, vegan diets are also more environmentally sustainable. A review article highlighted that vegan diets result in significantly lower greenhouse gas emissions and use fewer natural resources compared to omnivorous diets9. This alignment of health and environmental benefits makes vegan diets an attractive option for those concerned about planetary health.
Are there significant health benefits going from vegetarian to vegan?
Ben De Groeve has answered Uncertain
An expert from Ghent University in Communication and Media, Social Sciences, Environmental Science, Evolutionary Biology
Based on the sources below and my own (limited) expertise on the communication of meat-reduction diets (my own relevant peer-reviewed article), I am uncertain about the health benefits of going from vegetarian to vegan.
On some health outcome measures, vegan diets score higher, but the health benefits also depends on how the diets are performed. In the future, health benefits of going vegan may be more likely (because of technological developments and increasing health awareness), on the condition that vegans consume reliable sources of vitamin B-12, such as fortified foods or supplements.
Sources below:
The negative health impacts are functions of the amount of animal products consumed. Simplifying matters, we can draw a J-shaped curve to represent this negative health impact. Our current situation is on the far right of the curve, where the harm or negative impact is high and there is a sharp increase in negative impact if we move further to the right. The vegan situation is on the far left. The question is: where is the minimum of this J-curve? What level of animal consumption minimizes the negative health impact? This minimum level is the one that optimizes our health.
In the past, the optimal level of animal consumption was probably higher than zero: consumers needed meat because other, plant-based or vegan sources of essential nutrients were lacking. But at this moment the situation is less clear. There is an abundance of vegan sources of essential nutrients, wrapped in healthy fibers and phytonutrients instead of unhealthy saturated fats and carcinogens. Technological developments result in a downward shift of our J-shaped curve, because these technologies reduce negative impacts. But also the minimum of the J-shape is shifting to the left. The J-shape becomes more like a forward slash shape (/). Eventually, the minimum level may be at zero consumption of animal products.
Source: https://stijnbruers.wordpress.com/2018/03/23/is-a-vegan-diet-optimal-for-our-health-and-the-environment/
A 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.
Source: Dinu, M., Abbate, R., Gensini, G. F., Casini, A., & Sofi, F. (2017). Vegetarian, vegan diets and multiple health outcomes: a systematic review with meta-analysis of observational studies. Critical reviews in food science and nutrition, 57(17), 3640-3649.
Moving to diets with fewer animal-sourced foods would have major health benefits. Compared with the reference scenario, we project that adoption of global dietary guidelines (HGD) would result in 5.1 million avoided deaths per year [95% confidence interval (CI), 4.8–5.5 million] and 79 million years of life saved (CI, 75–83 million). The equivalent figures for the vegetarian diet (VGT) are 7.3 million avoided deaths (CI, 7.0–7.6 million) and 114 million life years saved (CI, 111–118 million) and for the vegan diet (VEG) 8.1 million avoided deaths (CI, 7.8–8.5 million) and 129 million life years saved (CI, 125–133 million). Adopting these nonreference diets are estimated to reduce the combined number of deaths per year from coronary heart disease, stroke, cancer, and type 2 diabetes mellitus in 2050 by 12% (HGD), 17% (VGT), and 19% (VEG) and the overall number of deaths from all causes by 6% (HGD), 9% (VGT), and 10% (VEG) (SI Appendix, Table S8 ).
Source: Springmann, M., Godfray, H. C. J., Rayner, M., & Scarborough, P. (2016). Analysis and valuation of the health and climate change cobenefits of dietary change. Proceedings of the National Academy of Sciences, 113(15), 4146-4151.
Vegetarians and vegans are at reduced risk of certain health conditions, including ischemic heart disease, type 2 diabetes, hypertension, certain types of cancer, and obesity. Low intake of saturated fat and high intakes of vegetables, fruits, whole grains, legumes, soy products, nuts, and seeds (all rich in fiber and phytochemicals) are characteristics of vegetarian and vegan diets that produce lower total and low-density lipoprotein cholesterol levels and better serum glucose control. These factors contribute to reduction of chronic disease. Vegans need reliable sources of vitamin B-12, such as fortified foods or supplements.
Source: Melina, V., Craig, W., & Levin, S. (2016). Position of the Academy of Nutrition and Dietetics: vegetarian diets. Journal of the Academy of Nutrition and Dietetics, 116(12), 1970-1980.