Vitamins and vegans: the nutrients lacking in a plant-based diet

The Vitl Nutrition Team / 7 Sept 2021

Our in-house nutritionist discusses which nutrients are commonly lacking in a plant-based diet.


Vegetarians choose not to consume animal flesh, such as meat and fish. However, not all vegetarians eat the same things; requirements can vary depending on preferences. Vegans, for example, do not consume any product that is derived from animals (including dairy and honey), while pescatarians choose not to consume red meat or poultry, but do eat fish. Whatever the preference, it is important to ensure that you are receiving all the nutrients that you would otherwise derive from meat or meat products. Key nutrients easily derived from animal products include: protein, haem iron, DHA & EPA (omega-3), vitamin B12, vitamin D, calcium and iodine. Let's take a look at some of these now:

DHA & EPA (omega-3): The consumption of omega 3 fatty acids tends to be low in a vegan diet. Some can be obtained from ALA (alpha-linolenic acid) that is found in abundance in plants. ALA, then, converts to the essential fatty acids EPA and DHA, which are crucial components of our cell membranes (and can be found in fish sources). However, the conversion rate (how quickly ALA is converted to EPA and DHA) is very inefficient, making vegans and vegetarians at a higher risk of inadequate EPA and DHA status, compared to e.g. pescatarians or those who consume meat.  

Protein: Individual plant proteins have a lower biological value, or bioavailability, than animal proteins. (Bioavailability = proportion of the nutrient that is absorbed from the diet or supplements and used for normal body functions). However, when a variety of plant-based foods are combined, the amino-acid profile in the different plant proteins complement each other. You should therefore consume a variety of vegetables - as well as natural meat alternatives - to maintain a healthy protein status, such as beans, lentils, chickpeas, soy and soy products, seeds, nuts, butters, wheat, rice and maize. Including at least one protein source at every meal is a good way of ensuring you are eating enough protein, and will keep you feeling fuller for longer as it takes longer to digest than carbohydrates.

Iron: Haem iron, found in meat, is more bioavailable than non-haem iron, found in plant-based foods. This means vegetarians/vegans are at an increased risk of developing iron deficiency anaemia, so it is important to consume foods rich in non-haem iron regularly. It may also be worth taking iron supplements (unless otherwise advised). Good sources of non-haem iron include: wheat, pulses, dark leafy vegetables, fortified cereals and dried fruits.

Vitamin B12: Meat provides an easy source of vitamin B12. Vegetarians/vegans, therefore, are more likely to develop a vitamin B12 deficiency, which can lead to megaloblastic anaemia and neurological symptoms. Some plant-based sources of vitamin B12 include: egg, milk, cheese, Marmite, soy milk and fortified cereals. Supplementation is also frequently considered (unless otherwise advised).

Vitamin D: Vegetarians/vegans are also at a greater risk of developing a vitamin D deficiency - particularly those with limited sun exposure (in which case vitamin D supplements are recommended). Vitamin D can be found in eggs and fortified foods, but the main source remains the sun. 

Calcium: Any vitamin D deficiency - a common problem for vegetarians/vegans - will lessen the bioavailability of calcium. This, in turn, can affect bone health. Vegans are at an even greater risk as their diet restricts the consumption of dairy products, such as milk. In this case, It is especially important to ingest calcium from plant-based alternatives, such as spinach, soybeans, and tofu. If necessary, calcium supplements might be considered. 

Zinc: Zinc is important for supporting healthy immune function and DNA synthesis, and vegans tend to consume lower amounts of zinc than their meat-eating counterparts. The effect of a higher phytate consumption (as found with vegan diets) on the bioavailability of zinc is a cause for concern. Suitable sources include legumes, nuts, seeds and soya products.

In conclusion, a vegan diet may need to be supplemented with vitamins and minerals; such as vitamin B12, iron, omega-3, vitamin D and calcium. Children following a vegan diet need to be particularly attentive to their nutritional status.

Other related articles:

I am vegan; do I need to take omega-3?

Nutrients depleted by alcohol and drugs

Fasting and exercise: should I work out on an empty stomach?