Supplements on a Plant-Based Diet


A dietary supplement is “A product containing one or more vitamins, herbs, enzymes, amino acids, or other ingredients, that is taken orally to supplement one's diet, as by providing a missing nutrient”. The global supplement industry growing rapidly, and will be worth nearly €300 billion by 2024. According to nutritional research, it is necessary to supplement certain nutrients on a plant-based diet. The reasons for this are detailed below. You may come across online articles, plant-based guru's or social media personalities who state otherwise. This is their opinion, and as it is not based on any credible scientific research, it should be disregarded.

Why You Need Supplements

You may at this point be asking why, if a plant-based or diet is the healthiest diet we know of, one must supplement the diet. It does seem contradictory that the diet is advocated for its superior nutrient content and yet is nutritionally incomplete. Firstly, the standard western diet is not nutritionally complete to begin with. In the US, 97% of the population are deficient in the nutrient of fiber. Only 3% meet the daily minimum requirement for fiber intake. If you do not know by now, fiber is only found in plants. Less than 2% of Americans meet the minimum daily requirement for potassium, which again is highest in plant foods. Water, like potassium, is required by every cell in our body to function correctly; 75% of US adults are also chronically dehydrated. Water is found in either liquid form, or in food. Animal products contain no water, again, it is only found in fresh fruits and vegetables. B12 deficiencies are common in Vegans and meat eaters alike, and is explored further below. It is recommended that all adults over 50 should be taking a B12 supplement, regardless of meat consumption or not.

Secondly, our food, in this case fruits and vegetables, is grown by the agri-food industry; not nature. Food grown in nature is nurtured in vastly bio-diverse ecosystems, where soil is naturally rich in minerals and vitamins. The agri-food industry on the other hand grows food on an industrial scale with yield, profit, demand and low cost production at top of mind. As with all industries, profit maximization is the goal, while nutritional content is an afterthought. In nature, a piece of fruit falls from a tree when it is perfectly ripe; we harvest before it is ready, which leads to lower nutritional content. The nutritional content of a plant is dependent on the nutrient content of the soil, air, and water in which the plant is grown. If there is low nutrients in its environment, the plant itself will be of low nutritional value. Sadly, industrialization of farming and mono crop cultures (the growing of only one crop repeatedly in the same field) has resulted in soil so depleted of nutrients that the UK, our nearest neighbour, has only 100 harvests left in its soil as nutrient content sharply declines & bio diversity is lost. Eat organic fruits and vegetables where possible. If it is outside your budget, aspire to eat partially or wholly organic one day.


Below is the recommended supplements to avoid common deficiencies on a plant based diet. One should note that this is simply a guide; regular blood tests should be used as an individual marker to spot any nutrients which your body requires. Activity levelslifestyle factorsphysiological and genetic differences, and even an individual’s internal bodily environment mean some may require more of a supplement than others, as nutrient absorption differs. Instruct the nurse or doctor that you are following a diet free of animal products and are taking a blood test to check nutrient levels:


Seen as meat eaters as the defect in a plant-based diet, vitamin B12 is found almost exclusively in animal products. There are 2 types, Cyanocobalamin and Methylcobalamin. Methylcobalamin is more readily absorbed, and will end up dominating the B12 market. B12 deficiencies only appear over time (4-6 years) on a plant-based diet. Supplementation and blood tests are essential for this nutrient.


Heme Iron from meat is more bio-available than non-heme iron in plants. However, the absorption of non-heme iron increases 3 fold when consumed with vitamin C, surpassing the absorbability of heme iron. Squeezing the juice of 1 lemon onto fresh leafy greens (for example, 50g spinach) will increase Iron absorption. Alternatively, Floradix Iron tonic is plant-based, includes vitamin C for absorption, and also includes B12.

Vitamin D

Vitamin D is made by our skin when in contact with UVB radiation in sunlight. Deficiency is not a vegan exclusive issue, but affecting the wider population who live in climates with less sunlight or spend most time indoors. In Ireland, for example, everyone should be supplementing with Vitamin D.

Omega 3's

As seen in the previous post on fat, plant-based omega sources, walnuts, flax, spirulina and chlorella, should be consumed daily.


A study has shown that vegetarians have lower average zinc levels than meat eaters, as zinc from animal products is easier absorbed vs. plants. Males are at particular risk of being lower in this trace mineral, as some is lost in semen ejaculation. The best plant sources, whole-grains, beans and nuts should be consumed daily. If a blood test indicates a deficiency, a zinc supplement should be taken.


Iodine is essential for normal thyroid function. Vegans have been found to have low levels of Iodine compared to vegetarians and meat eaters. Salt was the world's first fortified food, and was used as a vehicle to increase iodine consumption in the US. European salt is less iodized, and European vegans are more at risk to deficiency as a result. Kelp is a good plant source and should be consumed infrequently.


A growing body of research is repeatedly showing that dairy, the largest dietary source of calcium, is harmful to bones. However, one should not overlook the importance of calcium in bone health. One must consume at least 500mg of calcium a day to avoid increased risk of fracture. Spinach, kale, almonds, soybeans, and white beans are all excellent plant-based calcium sources. 250g of boiled & drained spinach provides enough calcium for a day.

Key Take-Away

It is somewhat ironic that a common concern for individuals switching to a plant-based diet is fear of not obtaining adequate levels of certain nutrients, when their existing diet is causing chronic deficiencies in water, fibre, potassium, and B12, to name but a few. Additionally, although no hard data currently exists, low levels of fresh fruit and vegetable consumption (only 27% of people in Ireland get the recommended 5 a day) mean it is not unreasonable to assume deficiencies in over 100,000 phyto (plant) nutrients. If one simply eats a variety whole foods in the form of fresh ripe fruits, vegetables, nuts and legumes, an abundance of macro, micro, and phytonutrients will be consumed, along with adequate fibre and water. Blood tests every 2/3 months will safeguard and highlight any deficiencies developing over time. Should a blood test show a particular nutrient deficiency, don’t panic. Take a supplement immediately to halt and reverse the deficiency, while you research the best plant sources of the deficient nutrient, and add said plants to your diet. The next post will give you a framework on which to build your diet, and what exactly you should be eating every day to maximize nutrient intake and health.


One should note that this is simply a guide; regular blood tests should be used as an individual marker to spot any nutrients which your body requires