Optimising a plant-based diet

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Going plant-based this January? The Institute for Optimum Nutrition looks at what nutrients you should be thinking of and how to get them

Whether it’s for concerns about the environment, animal welfare, or just wanting to be healthier, increasing numbers of people are choosing a diet that minimises animal produce or cuts it out entirely.

But regardless of your reasons, if you are used to a ‘meat and two veg’ diet, making the switch can require a bit of thought, and there are some nutrients that will need to be included either through fortified foods or supplements.


Protein is essential for growth and tissue repair, and is also a source of energy. For the human body, it is the compounds found in proteins (called amino acids) that are important. Whilst meat, eggs and dairy products each contain all the amino acids that we need, and so are considered ‘complete’ foods, most plant sources do not — with the exception of quinoa, chia seeds, buckwheat, and soy.

But anyone on a plant-based diet can obtain all the amino acids they need without resorting to supplement bars and shakes. Combining protein sources creates a complete protein — for instance, eating wholemeal grains with legumes (think: rice or bulgur wheat with lentils or bean chilli).

Try to avoid relying on highly-processed fake meats. The odd veggie sausage won’t hurt, but it’s best to obtain protein from unprocessed or minimally processed whole foods such as lentils, beans, mushrooms and quinoa that don’t have artificial ingredients added.


Whilst animal produce is typically a source of haem (blood) iron, non-haem iron (from plant sources) is available from legumes such as chickpeas, lentils and beans; nuts and seeds such as cashew, almond, chia and pumpkin; and leafy green vegetables.

One of the problems with iron, however, may not be an issue of how much you consume but how much you absorb. Taking your iron source with a source of vitamin C can help absorption, as can avoiding tea (black or green) or coffee for about one hour either side of meals. This is because studies have shown that phenolic compounds in tea and coffee reduce iron absorption.


If you cut out dairy, sea fish and shellfish, you may need to consider other sources of iodine, such as seaweed or supplements. A small study comparing nutrient status between vegans and non-vegans found that instead of being deficient in vitamin B12 as expected, vegans had lower levels of iodine compared to people who ate a mixed diet; although both groups had below optimum levels.1

Iodine is important for healthy thyroid function, however taking supplements in excessive amounts may lead to thyroid problems. Anybody already taking medication for a thyroid problem should not increase their iodine intake without speaking to a GP.


Vitamin B12 is essential for nerve and brain health, and has been a particular area of concern for vegans because it is only naturally obtained through animal products. Vegan sources of B12 are found in nutritional yeast, fortified foods or supplements.


Although dairy is often considered the most important source of calcium, it is possible to get enough from a plant-based diet. Leafy green vegetables, broccoli, almonds and tahini are all good sources.

Omega-3 fatty acids

Omega-3 polyunsaturated fatty acids are important for a number of functions, including heart and brain health. There are three types: eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and alpha-linolenic acid (ALA), however it is DHA that is most critical for brain health.

Omega-3s are mainly found in oily fish. Whilst it is possible to obtain them through plant sources such as pumpkin seed oil, nuts, seeds (particularly flax and chia seeds), sprouted beans, squashes and blueberries, these mostly contain ALA, which is not as active in the body and must be converted to EPA and DHA to deliver the same health benefits.

And the body’s ability to convert ALA is limited. Studies have shown that about 5% of ALA is converted to EPA, while less than 0.5% is converted to DHA.2

Suitable for vegetarians and vegans, algae-derived EPA and DHA supplements are available — and although research on algae oil supplementation is limited, studies have so far suggested that its bioavailability and subsequent health benefits are comparable to that of fish or krill-based DHA and EPA sources.3

A personalised approach

Whilst there are some general dos and don’ts when adopting a plant-based diet, it can still take some fine tuning to ensure you’re getting the nutrients you need. A registered nutritional therapist can provide personalised recommendations to help you get the most from your food, and optimise your long term health.


Find a registered nutritional therapist to work with at the Institute for Optimum Nutrition’s innovative clinic and find out about all of ION’s services and courses at ion.ac.uk/thrive