The Vegetarian Diet: Everything you need to know

Table laid with vegetarian diet food
(Image credit: Getty Images)

Considering switching to a vegetarian diet, but not sure whether it is a good idea, or how to best handle it? Rest assured you’re not alone. With plant-based diets rocketing in popularity, an increasing number of people are choosing to give up meat, fish and poultry. A well balanced vegetarian diet can be very healthy, but if you want to reap all the benefits, you may need to pay more attention to what and how much you eat. 

Vegetarian diets can not only be good for our health and animal welfare, they can also benefit the environment. According to the Vegetarian Society, a meat-based diet generates nearly three times the amount of carbon emissions compared with a plant-based diet. It also uses many more natural resources. In fact, switching to a vegetarian diet could reduce your water consumption by up to 41%, as well as saving on land use. 

But the transition to vegetarianism may not be easy. To make sure it goes smoothly, we’ve put together a guide on how to enjoy a well-balanced vegetarian diet, including foods to eat, foods to avoid, and potential supplements. And if you are wondering whether veganism may be a better option, our article on veganism vs vegetarianism should answer all of your questions. Of course, any change to your dietary routine should be first consulted with your doctor or a registered dietician. 

What is a vegetarian diet?

According to the Vegetarian Society, vegetarians do not eat animal-based products like fish, meat and chicken. They also avoid by-products of slaughter like gelatine and animal rennet. 

Vegetarian diets come in several different forms, including:

  • Lacto-ovo-vegetarian diet: Eliminates meat, fish and poultry but allows eggs and dairy products.
  • Lacto-vegetarian diet: Eliminates meat, fish, poultry and eggs but allows dairy products.
  • Ovo-vegetarian diet: Eliminates meat, fish, poultry and dairy products but allows eggs.
  • Pescetarian diet: Eliminates meat and poultry but allows fish.
  • Vegan diet: Eliminates all animal-based and animal-derived products.

avocado and poached egg on toast for breakfast

(Image credit: Getty Images)

What are the potential benefits of a vegetarian diet?

Weight loss

According to the Journal of the Academy of Nutrition and Dietetics, vegetarian diets may promote weight loss and help maintain these results in the long term. Scientists have pulled together the results from intervention trials that did not include calorie restriction and lasted more than four weeks. They found that vegetarian diets resulted in an average weight loss of 3.4kg to 4.6kg, depending on the analysis method. Observational studies have also shown that vegetarians tend to have lower body weight than omnivores, which suggests that plant-based diets may protect against obesity in the long term. 

Cardiovascular health

Vegetarian diets may also have a beneficial effect on our cardiovascular health. According to a meta-analysis published in the Nutrients journal, vegetarians tend to have a significantly lower systolic and diastolic blood pressure compared with omnivores. Plant-based diets may also help regulate blood lipid levels. As stated in the Clinical Nutrition journal, there is convincing evidence that vegetarian diets lead to lower concentration of total cholesterol, LDL-cholesterol and HDL-cholesterol — factors that may contribute to the narrowing of the arteries. 

Type 2 diabetes

Vegetarian diets may help regulate blood glucose metabolism. According to the Clinical Nutrition journal, plant-based foods enhance insulin sensitivity, while animal protein intake contributes to insulin resistance. This effect can be observed in both healthy subjects and patients with diabetes. Multiple studies have also demonstrated that vegetarian diets significantly decrease the likelihood of developing type 2 diabetes.     

Woman checking blood sugar level while sitting on bench. Maskot via Getty Images

(Image credit: Maskot via Getty Images)

Gut health

Good gut health is crucial to the proper functioning of multiple systems in our bodies. The evidence is growing that vegetarian diets may have a beneficial effect on the composition of our gut microbes. According to the Frontiers in Nutrition journal, people who follow vegan and vegetarian diets tend to have a significantly higher count of the ‘good’ Bacteroidetes and lactic acid bacteria, and lower count of the ‘bad’ Clostridium and Enterococcus species. 

Scientists suggest that this effect is partly caused by the abundance of fiber and polyphenols present in plant-based foods. A high fiber intake promotes the growth of microbial strains that ferment fiber into metabolites like short-chain fatty acids (SCFAs). SCFAs have been shown to boost our immunity, improve the integrity of the blood-brain barrier and regulate the intestinal environment. 

Exercise performance

Contrary to popular belief, vegetarian diets may also help to elevate your exercise performance. According to the Nutrients journal, studies have shown that there are not any consistent differences between omnivores and vegetarians when it comes to endurance and muscle strength. In fact, the evidence suggests that vegetarian diets may be superior in that regard. Scientists suggest that it is because plant-based diets alter molecular signaling and gut microbiome, contributing to better muscle adaptation. 

Foods to enjoy on a vegetarian diet

  • Vegetables and fruits
  • Grains, including quinoa, rice and oats
  • Legumes, such as beans, peas and lentils 
  • Nuts and seeds
  • Plant-based fats, such as olive oil and avocados
  • Plant-based proteins, such as tofu, tempeh, seitan and spirulina
  • Eggs
  • Dairy products
  • Honey
  • Plant-based meat alternatives

Bowl of vegetarian food

(Image credit: Getty Images)

What foods should you avoid if you’re vegetarian?

  • Meat or poultry
  • Fish or seafood
  • Animal-derived ingredients, such as gelatine, stock, animal rennet, lard, carmine and oleic acid
  • Insects

If you are a vegan or lacto-vegetarian, you should also avoid eggs. If you are a vegan or ovo-vegetarian, you should also avoid dairy products. And if you are vegan, you should also avoid other animal by-products, such as honey, beeswax and pollen. 

Are there any risks to a vegetarian diet?

Balanced plant-based diets can be healthy and nutritious. However, due to their restrictive nature, vegetarian diets can also increase the risk of certain nutritional deficiencies. 

To start with, animal-based foods are a rich source of essential amino acids — protein ‘building blocks’ that our bodies are unable to produce themselves. Plant-based foods tend to lack one or more of these compounds, and as such are considered to be incomplete protein sources. 

Tofu salad

(Image credit: Getty Images)

But that does not mean that vegetarians are unable to get good quality protein. Eating a variety of legumes, nuts, seeds and grains will help you to obtain a complete amino acid profile. Another solution is to consume more complete vegan protein sources, such as tofu and seitan. Lastly, including more eggs and dairy products in your diet can also help bridge the gap.   

Vegetarian diets may also contain insufficient amounts of omega-3 fatty acids, vitamin D, vitamin B12, iron, calcium, and zinc, as stated in the Current Nutrition Reports journal. According to the Clinical Nutrition journal, vegetarians are at particular risk for vitamin B12 deficiency. 

What’s more, there is evidence that plant-based diets may affect dental health. According to a review published in the Community Dentistry and Oral Epidemiology, vegetarians may be at higher risk of developing dental erosion. 

Do you need to supplement on a vegetarian diet?

Vitamin B12

Vitamin B12 is essential for our health and getting enough of this vital micronutrient may result in unintentional weight loss, lack of appetite, fatigue, depression and cognitive problems. Since the majority of sources of vitamin B12 are animal-based foods, those following plant-based diets are at high risk of deficiency. Scientists from the Nutrients journal advise vegetarians to increase their intake of B12-fortified foods and/or to supplement.


Zinc is another nutrient that may need to be supplemented on vegetarian diets. According to the Journal of the Science of Food and Agriculture, vegetarians tend to have much lower dietary zinc intakes and serum zinc levels than omnivores. Although there are many plant-based sources of this crucial nutrient, their bioavailability may be hampered by the presence of phytates. Phytates are found in a range of seeds, nuts and legumes, and may bind to zinc and prevent it from absorption in the gastrointestinal system. Therefore researchers advise vegetarians to increase their consumption of zinc-fortified foods, or to take low-dose zinc supplements. 


Omega-3 fatty acids, such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid, have been shown to provide multiple health benefits. These vital compounds are mostly found in fish, so vegetarians may struggle to obtain enough of them from plant-based foods. 

According to the Nutrients journal, plant-based omega-3 sources like walnuts, flaxseed, spirulina and chlorella contain mostly alpha-linolenic acid (ALA), which in humans may not be sufficiently converted into EPA and DHA acids. Therefore scientists advise vegetarians to increase their consumption of plant-based ALA foods, or take algae-based EPA and DHA supplements.

This article is for informational purposes only and is not meant to offer medical advice.

Anna Gora
Health Writer

Anna Gora is a health writer at Live Science, having previously worked across Coach, Fit&Well, T3, TechRadar and Tom's Guide. She is a certified personal trainer, nutritionist and health coach with nearly 10 years of professional experience. Anna holds a Bachelor's degree in Nutrition from the Warsaw University of Life Sciences, a Master’s degree in Nutrition, Physical Activity & Public Health from the University of Bristol, as well as various health coaching certificates. She is passionate about empowering people to live a healthy lifestyle and promoting the benefits of a plant-based diet.