Plant-based diets can be incredibly healthy when they are well planned. Eating more vegetables, fruits, beans, lentils, nuts, seeds, and wholegrains can support gut health, fibre intake, heart health and overall wellbeing.
However, when a diet excludes some or all animal foods, certain nutrients require extra attention.
This is not about criticising vegetarian or vegan diets. It is about ensuring people following these diets have the right information, especially during pregnancy, childhood, adolescence, and any stage of life when brain health, mood, energy, and development are a priority.
Some nutrients are simply harder to obtain, less bioavailable, or absent from a fully plant-based diet. If these gaps are not addressed, they may affect energy, mood, concentration, hormonal health, brain function, pregnancy health, and long-term well-being.
Why planning matters
A well-planned vegetarian or vegan diet can provide many health benefits. The challenge is that animal foods are naturally rich in several nutrients important for the brain and nervous system.
These include long-chain omega-3 fats, vitamin B12, iodine, choline, iron, zinc, vitamin D, vitamin A, vitamin K2, taurine and creatine.
Some of these nutrients can be obtained from plant foods. Others may need fortified foods or supplements, particularly for vegans.
This becomes especially important during pregnancy and childhood, when the brain and nervous system are developing rapidly.
Omega-3: Why plant sources are not always enough
Omega-3 is often discussed as a single nutrient, but there are different types.
The main plant-based omega-3 is ALA, which is found in foods such as flaxseeds, chia seeds, walnuts, pumpkin seeds and some seed oils.
These foods are valuable and can be part of a healthy diet, but ALA is not the same as DHA and EPA.
DHA and EPA are long-chain omega-3 fats. They are the forms most directly used by the brain, eyes, heart and immune system. DHA is especially important for brain development, while EPA is often discussed in relation to inflammation and mood.
The body can convert some ALA into EPA and DHA, but this conversion is often limited and unreliable. It can vary depending on genetics, age, sex, overall diet, omega-6 intake and nutrient status.
This means that relying only on flax, chia, or walnuts may not provide enough DHA, especially during pregnancy, childhood, adolescence or for people with mood or inflammatory concerns.
For people who do not eat fish or seafood, algae-based omega-3 can be a helpful option because algae provides DHA directly. Some algae supplements also contain EPA. It is important to check labels carefully, because some “vegan omega-3” products contain only ALA, which is not the same.
Vitamin B12: Essential for brain and nerve health
Vitamin B12 is one of the most important nutrients to consider in vegan diets because it is virtually absent from unfortified plant foods.
B12 is needed for normal brain and nerve function, red blood cell production, mood, memory and energy. A deficiency can cause serious problems, sometimes even before classic signs such as anaemia appear.
Vegans need to obtain B12 from fortified foods or supplements. Some vegetarians may also need to check their intake, especially if they eat little dairy or eggs.
B12 is not a nutrient to guess with. If someone is vegan, pregnant, breastfeeding, fatigued, experiencing pins and needles, low mood, brain fog or memory issues, B12 status should be considered.
Choline: Often overlooked but important
Choline does not get as much attention as B12 or iron, but it is very important for brain health.
It is involved in the structure of brain cell membranes and is needed to make acetylcholine, a neurotransmitter involved in memory, mood and mental function.
Choline is especially important during pregnancy and infancy because it supports normal brain development. Low intake during these stages may have long-term effects on cognition and behaviour.
The richest food sources of choline are animal foods, especially eggs, fish and meat. Some plant foods, such as cruciferous vegetables and certain beans, provide smaller amounts, making it difficult to meet optimal needs without careful planning.
Vegetarians who eat eggs may find it easier to obtain choline. Vegans may need to pay particular attention to choline-rich plant foods and, in some cases, consider whether additional support is needed.
Iodine: Vital for thyroid and brain development
Iodine is needed to make thyroid hormones. These hormones are essential for metabolism, energy, growth and brain development.
Iodine deficiency is one of the largest preventable causes of brain development problems worldwide.
In the UK, iodine can be a concern because milk, dairy and fish are key dietary sources. Vegans and some vegetarians who avoid dairy may be at higher risk of low iodine intake.
Seaweed can be a source of iodine, but it needs caution. Kelp and some brown seaweeds can contain very high and variable amounts of iodine. Too much iodine can also be harmful, particularly for thyroid health. For that reason, regular kelp use or kelp-based supplements are not always recommended unless guided by a qualified practitioner.
This is particularly important before and during pregnancy, when iodine needs increase.
Iron: Plant iron sources are less easily absorbed
Iron is essential for oxygen transport, energy, mood, sleep, concentration, and brain development.
Plant foods can contain iron, including lentils, beans, chickpeas, tofu, spinach, kale, pumpkin seeds, dried fruit and fortified foods. However, plant-based iron is non-haem iron, which is less easily absorbed than haem iron from animal foods.
This does not mean people cannot meet iron needs on a plant-based diet, but it does mean they need to be more intentional.
Vitamin C helps improve iron absorption, so it can be useful to combine plant iron foods with foods such as citrus fruits, berries, peppers, kiwi, broccoli or lemon juice.
Tea and coffee can reduce iron absorption when taken with meals, so it may be better to have them away from iron-rich meals, especially if iron status is low.
Women with heavy periods, pregnant women, athletes, teenagers and anyone experiencing fatigue, dizziness, restless legs or hair shedding may need to check iron and ferritin levels.
Zinc: important for immunity, hormones and mood
Zinc is needed for immune function, wound healing, hormone health, fertility, growth, brain function and mood.
Good animal sources include seafood, fish and meat. Plant sources include chickpeas, lentils, beans, cashews, pumpkin seeds, wholegrains and dark chocolate.
However, plant foods can also contain phytates, which reduce the absorption of zinc and other minerals. Soaking, sprouting, fermenting and using sourdough methods may help improve mineral availability.
A varied whole-food plant-based diet can provide zinc, but it is still worth considering, particularly for people with poor immunity, slow wound healing, low mood, fertility concerns, hair loss or restricted diets.
Vitamin D: Difficult for many people in the UK
Vitamin D is important for bones, teeth, immunity, mood and brain health.
This is not just an issue for vegans and vegetarians. In the UK, many people struggle to maintain adequate vitamin D, especially during autumn and winter.
The main natural source is sunlight on the skin, but this is limited for much of the year in the UK. People with darker skin, older adults, babies, people who cover most of their skin, and those who spend a lot of time indoors may be at higher risk of deficiency.
Vitamin D3 is usually animal-derived, although vegan D3 from lichen is now available. Vitamin D2 is plant-derived but may not raise levels as effectively as D3.
Testing vitamin D can be useful, especially if someone has fatigue, low mood, aches and pains, low immunity or bone health concerns.
Vitamin A: Conversion can vary
Vitamin A is important for growth, immune health, vision, skin health and brain function.
Animal foods provide pre-formed vitamin A, whereas plant foods provide carotenoids, such as beta-carotene, which the body has to convert into vitamin A.
Good plant sources include orange sweet potato, butternut squash, carrots, spinach, kale, spring greens and cantaloupe melon.
Many people can convert carotenoids adequately, but conversion varies between individuals. This means a varied intake of colourful vegetables is important, particularly orange and dark green vegetables.
Vitamin K2: Often low in plant-based diets
Vitamin K2 works alongside vitamin D and magnesium to help regulate calcium in the body.
It supports bone and dental health and may also be relevant for cardiovascular health, because it helps direct calcium into bones and teeth rather than soft tissues.
Vitamin K2 is found mainly in animal foods and fermented foods. Natto, a traditional Japanese fermented soy food, is one of the richest plant-based sources of vitamin K2, although it is not commonly eaten in the UK.
This is another nutrient that may be worth considering in long-term plant-based diets, especially where bone health is a concern.
Taurine and creatine
Taurine and creatine are compounds found mainly in animal foods. They are involved in brain and body function, including energy metabolism, muscle function and nervous system health.
The body can make some creatine and taurine, but dietary intake is usually lower in vegan and vegetarian diets.
Research is still developing in this area, but for some individuals, especially those with fatigue, low muscle mass, intensive exercise demands or cognitive concerns, these nutrients may be relevant to consider with professional guidance.
What should vegetarians and vegans focus on?
A healthy vegetarian or vegan diet is not just about removing animal foods. It needs to be built carefully.
Helpful foundations include:
A variety of beans, lentils, chickpeas, tofu, tempeh and edamame for protein, iron and zinc.
Nuts and seeds, especially chia, flax, hemp, walnuts and pumpkin seeds, for healthy fats and minerals.
Dark green leafy vegetables and orange vegetables for folate, magnesium, carotenoids and antioxidants.
Fortified foods where appropriate, especially for B12, iodine, vitamin D, K2 and calcium.
Algae-based DHA is particularly beneficial for those who do not eat fish or seafood.
Attention to protein at each meal, especially during pregnancy, childhood, menopause, active lifestyles and older age.
Regular blood testing, where appropriate, rather than guessing.
My view as a Registered Nutritionist
I support people eating more plant-based, whole foods. However, I also think we need to be honest that vegan and vegetarian diets require planning.
This is especially true during pregnancy, childhood, adolescence, perimenopause, older age, or when someone is struggling with metabolic health conditions, fatigue, low mood, brain fog, poor immunity, hair loss, hormone symptoms or fertility concerns.
The goal is not to scare people away from plant-based diets. The goal is to help them do it well.
A vegan or vegetarian diet can be healthy, but it should not rely heavily on ultra-processed meat alternatives, refined carbohydrates, or be missing nutrients. It should be nutrient-dense, varied, and carefully planned around the nutrients most likely to be low.
Final thoughts
Plant-based diets can be rich in fibre, antioxidants and many protective nutrients. But some nutrients crucial for the brain, mood, energy, thyroid function, and development are harder to obtain without animal foods.
The key nutrients to consider include omega-3 DHA and EPA, vitamin B12, iodine, choline, iron, zinc, vitamin D, vitamin A, vitamin K2, taurine and creatine.
The question is not whether a plant-based diet is “good” or “bad.”
The better question is:
“Is this diet giving my body and brain everything they need to function well?”
If you are a vegetarian, vegan, pregnant, planning pregnancy, raising a plant-based child, or simply unsure whether your diet is meeting your needs, personalised nutrition advice can be helpful. For further advice, please book a discovery call here.
BOOK A FREE CallThis blog is for general education only and does not replace personalised medical advice. If you are pregnant, breastfeeding, taking medication, have thyroid disease, have a diagnosed deficiency, or are considering supplements, please speak to your GP, midwife or healthcare practitioner.
This blog is based on the FAB Research vegetarian/vegan nutrition factsheet and plant-based omega-3 handouts. For more information visit.
