The pros and cons of going vegan: what research says

The VITL Nutrition Team / Nov 22, 2016

There are three and half times as many vegans in Britain as there were in 2006, making veganism one of Britain’s fastest growing lifestyle movements (1). Over half a million people in the UK follow a plant-based vegan diet, avoiding all animal foods including meat, fish, dairy, eggs, and honey.


Historically, vegans have been motivated by religious and spiritual ideas, believing that a diet free of animal products cleansed the body and helped them reach a spiritual state, where they could live in harmony with the earth (2) . Vegans often follow a plant-based diet for ethical reasons, avoiding animal products out of a concern for the environmental and social impacts of raising livestock for food. More recently, people are turning to a vegan diet for health reasons. Those wanting to follow a ‘cleaner’ way of eating, are doing so through plant-based diets, free from contaminants such as antibiotics, hormones and other pollutants that may be present in animal products.

What are the health benefits of a vegan diet?

  • A plant-based diet which is high in vegetable fibre has been shown to help prevent chronic disease (3).  Undigested fiber improves bulking and satiety, short chain fatty acid production and reduces glycaemic responses (4). Fibre can dilute possible carcinogens in faeces and increase their elimination speed, reducing exposure time and protecting against bowel cancer. Viscous fibre in starchy vegetables, and b- glutan in oats, barley, and whole grains, can contribute to lower cholesterol and therefore reduced rates of cardiovascular disease (CDV) (4).
  • Saturated fats found mainly in animal products have been linked to CDV and associated risk factors, such as obesity and high cholesterol. Research in this area, however, is controversial, and there is evidence to show that saturated fat can contribute to a healthy diet (5).
  • Vegan diets are often rich in healthy fats such as the monounsaturated fats found in nuts and avocados.
  • Vegans may have a lower calorific intake than non-vegans. A diet lower in calories can help prevent obesity, type 2 diabetes, heart disease and cancer.
  • Antioxidants are found in abundance in fruit and vegetables, which are prominent in a vegan diet. Vitamin C, E and beta-carotene are antioxidants that help defend against free radicals, which are highly reactive molecules said to be the cause of many diseases (6). 

What are the main problems with a vegan diet?

  • Essential fatty acids, omega-3, and omega-6 are chiefly obtained from fish and are not easily found in plant foods. They are important for growth and have lipid lowering and blood clot-reducing properties which protect against CDV (7).  However, it is argued that meat eaters do not consume enough essential fatty acids either, so would also benefit from supplementation (8). 
  • Animal-derived proteins are termed ‘first class’ as they are high in good quality amino acids, whereas vegetable proteins are incomplete, meaning that no individual vegetable protein contains all the amino acids that we need. Different vegetable proteins need to be combined to get a complete protein.
  • Consuming enough protein is absolutely essential for optimal health. This is something vegans need to be aware of by including a variety of legumes, whole grains, nuts, and seeds into their diet.
  • Fish, dairy, and eggs are the major sources of zinc. Zinc absorption is a concern amongst vegans, even if their intake is similar to omnivores. Increased levels of phytates and polyphenols, which are high in vegan diets, bind to zinc and prevent its absorption (9). 
  • Iron deficiency can be a problem for those following a vegan diet and is linked to anaemia and compromised immune function. There are two main sources of iron: haem iron found in animal-based products, and non-haem from vegetable sources. Haem iron is much more easily absorbed by the body, compared to non-haem.
  • B12 is only found in animal products so need to be supplemented in a vegan diet. Low energy, impaired memory and permanent nerve damage are just a few of the symptoms of low B12 supplies.
  • Calcium is most commonly found in dairy products, so a diet which restricts these will need to compensate with green vegetables, nuts, seeds, seaweeds, soy foods and other legumes.
  • Vitamin D is found in fish, meat, eggs and fortified milk which are all absent from a vegan diet. This vitamin is synthesized from cholesterol when the skin is exposed to sunlight, hence vitamin D deficiency is common amongst both vegans and omnivores due to lack of sunlight exposure.


A vegan diet definitely has its benefits. It is rich in antioxidants, folates, phytonutrients and fibre; and low in calories, saturated fats, and cholesterol. A plant-based diet can offer protection against high blood pressure, heart disease, diabetes and other degenerative diseases. However, the absence of certain essential fatty acids, zinc, B12 and low levels of calcium and vitamin D, can cause health problems. Supplementation is required to relieve deficiencies in a solely plant-based diet and it is important to seek advice from a qualified health practitioner if you are thinking about becoming a vegan. 

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