Plant-Based Diet Gaps Putting Health At Risk


A new research review published in the academic journal, Food Science & Nutrition,[1] and commissioned by the Health and Food Supplements Information Service (HSIS,, has revealed the popular trend to adopt plant-based diets could actually be putting our health at risk.

Despite evidence suggesting that plant-based diets are linked with a lower risk of cancer, heart disease and obesity, there is now a growing number of studies on vegans and vegetarians which report that giving up meat, fish and eggs leaves a worrying gap in terms of vitamins and minerals.

Lead author and nutritionist, Dr Emma Derbyshire from HSIS, searched for meta-analyses, multicentre trials, comparative and observational studies published in the past 10 years, whittling down the initial large number of studies to 11 key publications which met the inclusion criteria. Six of these were observational studies, reporting on the diets of 16,262 participants.

The results from the five meta-analyses, which combined results from up to 34 different studies, found that vegetarians and vegans typically lack iron, vitamin B12, zinc and vitamin D. Evidence related both to dietary intakes and the more accurate marker of blood tests. Zinc and vitamin D are needed for normal immune function, while B12 is important for energy release from food, and iron is essential for normal cognitive function and oxygen transport via our red blood cells.

Looking at the observational studies, there were clear associations between avoiding animal foods and having lower intakes of B vitamins, vitamin D, zinc, iodine and selenium. Shockingly, in one study of Danish vegans[2], no vitamin B12 or vitamin D was recorded during the four-day weighed food records, highlighting the risks of highly-restrictive vegan diets.

Commenting on the new review, HSIS author Dr Derbyshire said: “The trend for plant-based diets is encouraging from an environmental perspective but will worry many nutritionists, given that people often don’t plan their new vegetarian and vegan diets.

“Plant foods are rich in vitamin C and fibre but typically lack the full range of nutrients found in meat, poultry, fish and eggs. This puts people at risk from inadequate intakes of vitamins and minerals, especially vitamin B12, iodine, zinc and vitamin D which are all vital for optimal health. Chronically low levels of vitamins, minerals and marine omega-3 fats have been linked with health issues, such as bone fractures, respiratory illnesses, fatigue, poor cognitive function and inflammation.”

The review also detailed a 2020 Omnibus survey of more than 1,000 UK adults which revealed that 44 per cent of those planning to switch to a plant-based diet had never researched which nutrients they would need, while one in five didn’t realise that vegan diets could lack specific nutrients. In addition, only half were currently taking a multivitamin or mineral supplement.

In summary, Dr Derbyshire adds: “When planning to switch to a fully plant-based diet, it’s essential to consider the nutrients you might be missing and ensuring these are supplied from fortified foods and dietary supplements – for example a multivitamin and multimineral and algae-sourced omega-3 supplement. Simply avoiding animal-sourced foods will not necessarily provide a healthy, balanced diet and it’s also worth checking food labels to ensure that vegan replacements for milk, spreads and snacks are fortified with extra nutrients.”What is a plant-based diet? The British Dietetic Association (BDA) defines a plant-based diet as one “based on foods derived from plants, including vegetables, wholegrains, legumes, nuts, seeds and fruits, with few or no animal products”.[3] Other ‘official’ definitions can be found in Table 1. Key to the BDA definition is that it simply spells out plant based in an uncomplicated way. The definition also clearly states that the plant-based diet can be devoid of animal products or can contain a few.

Note to editors:

Table 1: Definitions of plant-based diets.

British Dietetic Association (2020)

“A plant-based diet is based on foods derived from plants, including vegetables, wholegrains, legumes, nuts, seeds and fruits, with few or no animal products”.


EAT-Lancet Commission (2019)

“The volume of approximately half a plate should be vegetables and fruits whilst the other half should consist of primarily whole grains, plant protein sources, unsaturated plant oils, and (optionally) modest amounts of animal sources of protein.”


McManus (2018) Harvard Medical School

“Plant-based or plant-forward eating patterns focus on foods primarily from plants. This includes not only fruits and vegetables, but also nuts, seeds, oils, whole grains, legumes, and beans. It doesn’t mean that you are vegetarian or vegan and never eat meat or dairy. Rather, you are proportionately choosing more of your foods from plant sources”.


Tuso et al. (2013) Definition for Physicians

“A regimen that encourages whole, plant-based foods and discourages meats, dairy products, and eggs as well as all refined and processed foods.”


[1] Journal of Food Science & Nutrition; Plant-Based Diets – Environmental Benefits but Better Awareness Needed to Prevent Future Micronutrient Shortcomings; Dr Emmer Derbyshire; Publication September 2020