Embracing a vegan or vegetarian lifestyle may in part be driven by ethical considerations such as, animal welfare, environmental sustainability or health reasons. Research suggests whole unprocessed plant based diets are associated with reduced cardiovascular disease risk, certain cancers, inflammation, obesity and improved blood sugar regulation (1-4). However, adopting to these diets may cause nutritional challenges. Specific nutrients can be difficult to obtain when not sourced from animal foods, let’s explore this topic.

Understanding Vegan vs Vegetarian

  • A vegan diet abstains from all animal foods including meat, poultry, fish, shellfish, insects, eggs, dairy, honey and gelatine. Veganism often encompasses a holistic lifestyle approach, seeking to avoid all forms off animal cruelty, products and exploitation (5).
  • A vegetarian diet consists of grains, seeds, nuts, fruits, vegetables and excludes “by-products of slaughter” such as meat, poultry, fish, game, shellfish but may still include dairy and eggs (6).

Key nutritional deficiencies in vegan and vegetarian diets with plant based alternatives

  1. Protein: A macronutrient needed for muscle growth, repair, skin, hair, production of hormones and neurotransmitters. Plant sources are considered “incomplete” as they do not contain adequate amounts of all essential amino acids (proteins that cannot be made by the body, so must be acquired through food). Combining various plant sources, vegans and vegetarians can meet their protein needs consuming a wide amino acid profile per meal. Plant sources include lentils, pulses, beans, legumes, tofu, grains, nuts and seeds. UK government guidelines by weight are 0.75g protein per kg/d in adults 19-50 years (7 -9).
  2. Omega 3: An essential polyunsaturated fat that cannot be made by the body, so must be obtained from food. Vital for brain and nervous system function. Animal sources include fatty fish such as salmon, mackerel and sardines. For vegans and vegetarians, plant sources of omega 3 called alpha-linolenic acid (ALA) require an extra conversion into EPA and DHA (derivatives of ALA found in fish). Plant sources include flaxseed oil, soya, walnuts, leafy greens, chia, flax and hemp seeds. UK government guidelines are to consume no more than 35% of energy/d from total dietary fat intake in adults 19-50 years (7-9).
  3. Vitamin B12: Required for central nervous system function, energy production, red blood cell and DNA formation. Vegetarians and vegans in particular may struggle to consume B12 as it is predominately found in animal foods. Inadequate plant amounts are found in nori, spirulina, chlorella algae, and unfortified nutritional yeast. Fortified foods or supplementing may be required for maintaining optimal levels. UK government guidelines are 1.5mcg/d in adults 19+ years (7-9).
  4. Vitamin D: A hormone made by the body through sunlight exposure. Needed for bone health, immune system and mood regulation. Vitamin D receptors are found in almost all cells off the body. Plant sources are sundried shiitake mushrooms. Fortified foods or supplementing may be required for maintaining optimal levels. UK government guidelines are 10mcg/d in adults 18+ years (7-9). 
  5. Calcium: A mineral required for many functions including bone health and muscular contraction. Animal calcium sources are found in dairy products. Plant sources include dark green leafy vegetables, legumes, tofu and rhubarb. UK government guidelines are 700mg/d in adults 19+ years (7-9).
  6. Trace minerals: Needed in smaller amounts by the body which include: 
  • Iron: Essential for red blood cell formation, immune system and healthy brain function. Animal iron sources are found in offal, fish, red meat and eggs. Non-haem iron plant foods include dark green leafy vegetables, nuts, seeds, lentils, beans and apricots.Non-haem is more difficult for the body to absorb compared to haem iron found in meat. Combining with vitamin C foods may help with non-haem iron absorption. UK government guidelines are 8.7mg/d in males 19+ years and 14.8mg/d in females 19-50 years. 
  • Zinc: A essential cofactor for over 200 enzymes in the body, DNA synthesis, immune system function and wound healing. Animal zinc sources are found in oysters, red meat and poultry. Plant sources include leafy vegetables, whole grains and legumes. UK government guidelines are 9.5mg/d in males 18+ years and 7.0mg/d in females 18+ years (7-9).

Whether you’re a vegan, vegetarian or exploring plant based living, it is important to be mindful of nutritional requirements, which provide essential nutrients for normal functioning of the body and overall health quality. Consulting with a qualified nutritional therapist can provide personalised guidance to ensure nutritional needs and a well-balanced diet are met. It is important to note all suggestions are food based. If perusing supplementation please seek advice from a health care professional.

Aishling Hannigan-Murphy is a qualified nutritional therapist, continuing her studies in personalised nutrition and can be found on X as @Aishling_H_M.


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  2. Key TJ. Cancer risk and vegetarian diets. Vegetarian and Plant-Based Diets in Health and Disease Prevention [Internet]. 2017 [cited 6 January 2024];345–54. Available from:
  3. Sutliffe JT, Wilson LD, de Heer HD, Foster RL, Carnot MJ. C-reactive protein response to a vegan lifestyle intervention. Complementary Therapies in Medicine [Internet]. 2015 [cited 8 January 2024];23(1):32–7. Available from:
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  6. The Vegetarian Society UK [Internet]. 2023 [cited 12 January 2024]. Available from:
  7. Sajeev E.P.M., Martin R., Waite C., Norman M. Is the UK ready for plant-based diets? [internet]. 2020 [cited 14 January 2024]. Available from:
  8. Bakaloudi DR, Halloran A, Rippin HL, Oikonomidou AC, Dardavesis TI, Williams J, et al. Intake and adequacy of the vegan diet. A systematic review of the evidence. Clinical Nutrition [Internet]. 2020 [cited 19 January 2024];40(5):3503–21. Available from:
  9. British Nutrition Foundation. Nutrition Requirements [Internet]. 2023 [cited 19 January 2024]. Available from:
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