Many of us are familiar with the health and environmental benefits of eating less meat, but what’s less clear is how different types of plant-based and plant-forward diets compare to each other.
This article will focus on three major “reducetarian” dietary patterns: vegan, vegetarian, and pescatarian diets.
As a registered dietitian, I’ll break down the differences, comparing their impacts on health, longevity, and the environment, in addition to ethical considerations. Whether you’re considering a dietary shift or simply curious about how these dietary patterns stack up, this guide will help you make an informed choice.
Vegan, vegetarian, & pescatarian diets: a brief overview
Vegan, vegetarian, and pescatarian diets are all dietary patterns that avoid meat and poultry. For the purposes of this article, “meat” refers to flesh from land-dwelling mammals.
Vegans aim to avoid the exploitation of animals for human benefit by consuming a 100% plant-based diet. Vegans avoid all animal-based foods, including meat, poultry, seafood, dairy, eggs, and honey. They also avoid ingredients derived from animals, such as gelatin, and foods processed with animal-based ingredients. An example is white sugar filtered through animal bone char.
Vegetarians also avoid meat, poultry, and seafood, but often consume dairy products and eggs. For vegetarians, the goal is to avoid the killing of animals for food. Milk and eggs are acceptable since they can be obtained without slaughtering the animal.
Pescatarians are similar to vegetarians with the exception that their diet includes fish and seafood, often for the protein and omega-3 fatty acid content.
Nutritional adequacy
Meat and poultry are not necessary components of a healthy, balanced diet, and therefore vegan, vegetarian, and pescatarian diets can all be nutritionally adequate.
According to the Academy of Nutrition and Dietetics1, vegan and vegetarian diets can meet the nutritional needs of people of all ages and life stages, including infants, pregnancy, athletes, and older adults, as long as meals are well-planned.
It bears mentioning that this goes for any type of dietary pattern, not just plant-based diets. Whatever the diet, including a good balance of protein-rich foods, whole grains, fruits, vegetables, and healthy fats is essential for good health.
For vegans, this means including plant-based protein from beans, lentils, soy foods, nuts, seeds, and whole grains. Vegetarians can also get protein from dairy and eggs.
Vegans do need to be aware of a couple key nutrients:
- Vitamin B12: This is the only nutrient absent in plant-based foods. Fortunately, vegans can get vitamin B12 from supplements or fortified foods like nutritional yeast and some brands of non-dairy milk.
- Iodine: Vegans should also cook with iodized salt or consume other vegan sources of iodine.
A nutrient that can be low in both vegan and vegetarian diets is omega-3 fatty acids, particularly the DHA and EPA forms found in seafood.
Those who avoid fish can get ALA omega-3 fats from foods like walnuts, flax seeds, and chia seeds. ALA is important, but only a small amount of this is converted to DHA and EPA. Luckily, algae-based DHA/EPA supplements are available.
Of course, the nutrient density of any diet depends on a person’s food choices. A plant-based diet that is rich in fruits, vegetables, whole grains, beans, nuts, and seeds will be more nutrient-dense than one that is excessively high in refined grains and sweets and low in whole or minimally processed plant foods.
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Health benefits
All three of these dietary patterns can have positive effects on our health when compared to diets high in meat (especially red and processed meats) and low in plant foods. Let’s discuss a few of the most significant benefits.
Improved heart health
Because plant-based diets tend to be lower in saturated fat and higher in dietary fiber and phytonutrients, they’re associated with better blood pressure and lower LDL cholesterol levels. This link is particularly strong with vegan diets1.
The DHA/EPA omega-3 fats in fish also support heart health. These same omega-3s are sourced from algae for vegan-friendly supplements.
Weight management
Many studies have shown that obesity is less prevalent in people following plant-based diets and appears to be the least prevalent in vegans1.
This is likely explained by the fact that plant-based foods are lower in calories and higher in dietary fiber than meat and dairy, making it easier not to eat more calories than your body needs.
The dietary fiber in plants has a satiating effect because it helps the stomach empty gradually. When combined with protein-rich foods (like soy and beans) and a moderate amount of healthy fats, balanced plant-based meals are filling and satisfying while being lower in calories.
Reduced cancer risk
Some cancers are primarily genetic, but many are linked to lifestyle. The risk of colorectal cancer is increased when consuming high amounts and red and processed meat, for example.
The American Institute for Cancer Research (AICR) recommends 10 lifestyle strategies for cancer prevention. The nutrition-related guidelines most relevant to this blog post include:
- Maintaining a healthy weight
- Eating a diet rich in whole grains, vegetables, fruits, and beans
- Limiting consumption of red and processed meat
- Limiting consumption of “fast foods” and other processed foods that are high in fat, starches, or sugars
As we just saw, plant-based diets are an effective way to maintain a healthy body weight.
They also encourage the consumption of whole plant foods and are inherently low in red and processed meats. Processed meats have been classified by the World Health Organization (WHO) as carcinogens, while red meats are classified as probable carcinogens.
Of course, people following pescatarian or plant-based diets will still need to watch their intake of fast food and processed foods high in fat, starch, and sugar. However, it’s clear that well-planned diets rich in plant foods can help reduce the risk of certain cancers.
Reduced risk of type 2 diabetes
Diets high in saturated fat and low in fiber have been linked to the development of insulin resistance, which in turn leads to high blood sugar levels and damage to blood vessels. Fiber, on the other hand, helps reduce the risk of chronic diseases, including type 2 diabetes.
This effect has been seen with vegan, vegetarian, and pescatarian diets, although vegan diets may be the most protective, according to a 2018 review2.
Longevity
Vegan, vegetarian, and pescatarian diets are associated with longer, disease-free life spans because they help reduce the risk of chronic diseases. Vegetarian and vegan diets, in particular, have been linked to lower risks of obesity, type 2 diabetes, heart disease, and certain cancers, as we’ve already discussed.
One explanation for this is that plant-based and pescatarian diets are higher in heart-healthy monounsaturated (MUFAs) and polyunsaturated fats (PUFAs) and lower in saturated fat.
Replacing saturated fat with MUFAs and PUFAs, especially from plant-based sources, helps reduce the risk3 of heart disease and mortality. These diets are also higher in antioxidants and phytochemicals that fight oxidative stress in the body and brain.
At this point, researchers can’t say with certainty which of these three diets is the best for longevity.
Overall, it appears that high consumption of antioxidant-rich, nutrient-dense plant foods and limited consumption of added sugars and sodium are important, as are exercising, avoiding alcohol or consuming it in moderation (one drink per day for women and two drinks per day for men), and maintaining a healthy body weight.
RELATED: Do Vegans Age Faster?
Sustainability
Vegan, vegetarian, and pescatarian diets each tend to be better for the environment than meat-heavy diets. That said, they differ significantly in their impact.
According to a 2023 research study4 published in Nature Food, the more animal-based foods a diet contains, the more damaging its impact on the environment. This is because it takes much more land and water to support animal agriculture, which is also linked with higher greenhouse gas emissions and lower biodiversity.
Even grass-fed, pasture-raised agriculture has its issues as it takes longer for these animals to put on the same amount of weight as factory farmed animals, requiring more food and water over time.
Considering that vegan diets contain no animal products, it’s clear that they have the greatest benefits for the planet.
Fish consumption faces an additional sustainability challenge: overfishing. Overfishing is a big problem, considered by experts to be the top threat to marine biodiversity5. This means that even with pescatarian diets, it’s important to include plant-based proteins like beans, soy, and nuts.
Ethics & Motivation
Ethical considerations are one of the primary drivers for individuals choosing between these diets.
Many vegetarians choose not to eat fish because they don’t want to contribute to the killing of living creatures. Many view fishing as inhumane, considering fish suffocate slowly once taken out of the sea.
Similarly, most vegans choose a plant-based diet because they don’t want to support factory farms. Recognizing the cruel practices6 that occur in the dairy and egg industries, vegans take things one step further by avoiding these foods that may not contribute directly to animal slaughter but are often produced by subjecting animals to poor living conditions.
RELATED: The 3 Types of Vegans
Final thoughts
Reducing your meat consumption while eating more whole, minimally processed plant foods is one of the most effective ways to support long-term health, reduce the risk of chronic diseases, and promote longevity.
All are better for the environment than meat-heavy diets. Diets with the highest proportions of plant-based foods appear to be the most environmentally friendly and avoid the ethical issues that come from factory farming.
Whichever dietary pattern you follow, it’s important to consume balanced meals rich in nutrient-dense plant-based foods like beans, soy, whole grains, fruits, vegetables, and healthy fats.
The scientific information in this article was accurate at the time of publishing but may change over time as new research becomes available.
References
- Melina V, Craig W, Levin S. Position of the Academy of Nutrition and Dietetics: Vegetarian Diets. J Acad Nutr Diet. 2016;116(12):1970-1980. doi:10.1016/j.jand.2016.09.025
- Olfert MD, Wattick RA. Vegetarian Diets and the Risk of Diabetes. Curr Diab Rep. 2018;18(11):101. Published 2018 Sep 18. doi:10.1007/s11892-018-1070-9
- Hu FB. Diet strategies for promoting healthy aging and longevity: An epidemiological perspective. J Intern Med. 2024;295(4):508-531. doi:10.1111/joim.13728
- Scarborough P, Clark M, Cobiac L, et al. Vegans, vegetarians, fish-eaters and meat-eaters in the UK show discrepant environmental impacts. Nat Food. 2023;4(7):565-574. doi:10.1038/s43016-023-00795-w
- Yan HF, Kyne PM, Jabado RW, et al. Overfishing and habitat loss drive range contraction of iconic marine fishes to near extinction. Sci Adv. 2021;7(7):eabb6026. Published 2021 Feb 10. doi:10.1126/sciadv.abb6026
- Croney CC, Anthony R. Invited review: ruminating conscientiously: scientific and socio-ethical challenges for US dairy production. J Dairy Sci. 2011;94(2):539-546. doi:10.3168/jds.2010-3627
