Pros & cons of a vegan diet

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Vegan diet and diabetes

Veganism has become a very popular dietary trend recently with many people subscribing to this way of eating. Vegan has almost become synonymous with healthy. As a result, I wanted to write today about the pro’s and cons of such dietary interventions. I will not get political and thus will avoid topics of morality when choosing a vegan diet. If you are following a vegan diet because you disagree with practices of animal domestication this is not my argument. I am speaking purely from nutritional stand point.

What is a vegan diet?

Vegan diets avoid any food directly derived from an animal of any kind. This includes fairly foods such as meat and fish but stretches further to any animal produce such as eggs or milk. Therefore, vegan diets are mostly plant based. The diet primarily consists of fruits, vegetables, nuts, beans, pulses, lentils and starchy carbohydrates. Consequently, vegan diets are typically low in fat. Therefore, they can be quite low energy. It is no surprise then that vegan diets have become synonymous with healthy eating.

The pros of a vegan diet

Vegan diets can be quite low calorie and therefore help in weight management. Fruits, vegetables and wholegrain are also high in fibre, which helps with controlling cholesterol levels (a topic I previously wrote about – here).  They can help improve gut health and help to slow digestion of foods from the gut through the gastrointestinal tract. Fruits, vegetables and wholegrain starchy carbohydrates are also quite nutrient rich. Therefore vegan diets can be high in vitamins and minerals.  Vegan diets are can also be high in antioxidant levels, which can help protect against developing diseases.

The cons of a vegan diet

Often when diets are discussed in the media the focus is paid to only one component of health. Usually this is weight loss. As a dietitian we try to consider the overall picture. For all the benefits of a vegan diet, there are many nutrients which the diet is low in. Vitamin B12, calcium, iron, iodine, omega 3 fats and zinc are the more common nutrients we focus on when encountering a patient following a vegan diet. These nutrients are most abundantly found in animal produce such as meat, fish and milk/dairy products. Therefore, you can see how by cutting these foods from the diet, it is easy to become deficient.

Alternatives for a vegan

Although having a balanced diet as a vegan can be difficult and require prior planning it is not impossible. Several alternatives exist for a vegan to get their nutrients but they may find they are still short of the recommended daily intake.

Vegan diet & Vitamin B12

B12 helps to maintain healthy blood and a healthy nervous system. Vitamin B12 is only found naturally in foods from animal sources. Sources for vegans are therefore limited and a vitamin B12 supplement may be needed. Sources of vitamin B12 for vegans include fortified breakfast cereals fortified, fortidied unsweetened soya drinks and yeast extract such as Marmite, which is fortified with vitamin B12.

Vegan diet & Calcium

Meeting the daily recommended intakes for calcium is important for many bodily functions. The most well known is no doubt for bone health. Dairy products are the best source of calcium but there are many easy alternatives. Examples include fortified rice, soya and oat drinks and yogurts, beans, leafy green vegetables and dried fruits, brown and white breads, fish – particularly boney fish and/or whitebait, 150ml of orange juice and calcium containing tofu.

Vegan diet & Iron

Iron comes in two forms. Haem and non-haem sources. Haem sources, found in meat products such as red meat, are best absorbed by the body.  Conversely non haem sources found in plants are not easily absorbed. Therefore, iron levels in vegans can be tricky as even if meeting the daily recommended intakes for iron, the absorption of the nutrient is not great. Nonetheless, vegan alternatives for iron are plentiful. Examples include beans, fortified cereals, fortified wholemeal bread and flour, dark green leafy vegetables such as spinach, broccoli and spring greens, nuts and seeds (sesame seeds are a particularly good source), dried fruits, fortified eggs and steamed tofu. Be careful with dried fruits from a diabetes perspective because these can have a big impact on your blood glucose levels. Having rich sources of vitamin C alongside iron containing foods can also help the absorption. Therefore, perhaps adding a small portion of fruit following a meal may help to increase the absorptive capacity of the iron made available to the body. Also avoid drinking tea when eating iron containing foods. The tannins found in tea can disrupt the absorption of iron.

Vegan diet & Iodine

Iodine helps in the development of thyroid hormones. These hormones are needed for growth, metabolism and the development of a babies brain during pregnancy. The best sources commonly found in the diet are milk products and fish. Therefore, vegan diets can be deficient in this nutrient. Soya milk and milk alternatives are not always fortified with iodine. Therefore it is important to check the label. Seaweed is a concentrated source of iodine. This may help in ensuring you get enough iodine in your diet. However, due to it’s concentrated nature, we do not recommend having this more than once weekly. If supplementing iodine in your diet, avoid seaweed based supplements as these can provide excessive quantities.

Vegan diet & Omega 3 fatty acids

Omega 3 fatty acids are one of the essential fatty acids.. In other words, the only source of this available to the body is through our diet. Omega 3 is associated with reducing inflammation in the body and helping to lower bad LDL cholesterol. Oily fish is the most common source of omega 3 fatty acids but a vegan can replace this with alternatives.  Examples include nuts and seeds e.g. walnuts and pumpkin seeds, vegetable oils e.g. rapeseed and linseed, soya and soya products e.g. beans, milk and tofu, and green leafy vegetables.


Phytates found in plant foods such as wholegrains and beans reduce zinc absorption, so it’s important to eat good sources of zinc-containing foods. Ways of reducing this effect are by eating fermented soya. Examples, such as tempeh and miso, beans (soak dried beans then rinse before cooking to increase zinc absorption), wholegrain, nuts, seeds and some fortified breakfast cereals – although be careful with your blood glucose levels here.


Protein acts as the building blocks of the body. Proteins are made up of amino acids. If a finished protein molecule was a house, the amino acids would be the bricks. There are 20 different types of amino acids. 8 of these are indispensable or essential to the body. In other words, we can’t make them in our body. We have to eat them. The best protein sources in our diet are animal based. They have all the essential amino acids and they are the best absorbed once inside our body. However, there’s an easy workaround with this on a vegan diet. Beans, pulses, lentils, chickpeas and meat replacements like soya, tofu and Quorn all have the 8 essential amino acids. Therefore, ensuring these feature in your diet is important because otherwise you might not be quite getting what you need.


If considering going vegan for reasons other than morality, I hope this article has provided some more insight into the pros and cons of following a vegan diet. As mentioned, when examining diets dietitians look at the whole picture of nutrition. We try to avoid focusing on individual outcomes such as weight loss. Weight loss does not always translate into optimal health. So it is always worth considering whether the diet you are following is nutritionally complete. A good example of nutritional deficiencies leading to ill health is the tale of sailors who developed scurvy when at sea. It was finally found they were deficient in vitamin C and therefore began taking limes on board to help supplement their intake. Hence the nickname, ‘Limeys’. My point is, nutritional deficiencies are a very real thing and therefore a balanced diet is important. Vegan diets can be healthy. However, as you can see there remains some nutrients such as iodine and B12 where it can be difficult to obtain appropriate sources. Therefore, we typically recommend anyone following a vegan diet takes a daily multivitamin and mineral supplement.

Vegan diet and diabetes

People following a vegan diet loaded with vegetables, fruits and wholegrains, this can translate into very good glucose control. On the other hand, if opting for a predominately starchy carbohydrate based vegan diet, you may find your blood glucose levels actually worsen as the starch is converted into glucose in the body. My personal take on the subject is a vegetarian diet would be a much more sustainable alternative. Vegetarian diets provide all the nutrients your body requires. However, I do understand most peoples reasoning for following a vegan diet. Hopefully this gives you enough information to make an educated decision and if following a vegan diet and you have any questions, please do get in touch. For more information on the subject click NHS CHOICES LINK HERE .

Need more help

If you need more support we offer a range of 1:1 consultancy services and online programmes focused on helping you improve your glucose control and health for the long term. These include our type 2 diabetes recovery programme, type 1 glucose stability programme and winning weight loss programme. Go to the pages using the links above or in the headers or get in touch if you have questions.

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