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Vitamin B complex: functions, sources, deficiency and supplements
Written byMedico Digital
Reviewed byCaroline Hill
Known for energising and balancing both brain and body, these unsung heroes are vital. Unlock the secrets of the vitamin B complex, their roles, sources and why they're essential to your health
Summary
1What’s vitamin B complex?
Vitamin B complex is the collective name for all eight B vitamins essential for the healthy functioning of the body…
2Potential vitamin B complex benefits
Each B vitamin is responsible for maintaining homeostasis. In short, this means they help keep all the processes in your body working…
3How much of each B vitamin do I need?
The amount of vitamin B you need depends on your age, sex and other factors, like whether you’re pregnant…
Feeling a little ‘B-wildered’ by all the different B vitamins? You're not alone!
Whether you're familiar with some of the Bs or just know they're important, the vitamin B complex has a lot more going on than meets the eye. From boosting energy to keeping your brain and body in balance, these vitamins are thought to be the unsung heroes of your health.
Curious about what each one does, how to get enough from your diet and what happens if you’re running low? Let’s break it down and discover why the B complex is a big deal for your wellbeing.
What’s vitamin B complex?
Vitamin B complex is the collective name for all eight B vitamins that are essential for the healthy functioning of the body.1-3 The eight B vitamins that make up vitamin B complex are:1-3
- vitamin B1 (thiamin)
- vitamin B2 (riboflavin)
- vitamin B3 (niacin)
- vitamin B5 (pantothenic acid)
- vitamin B6 (pyridoxine)
- vitamin B7 (biotin)
- vitamin B9 (folate)
- vitamin B12 (cobalamin)
The B vitamins are water-soluble, which means that their main properties are partly lost when food is washed or boiled.4 In addition, with the exception of biotin, B vitamins aren’t naturally produced by the body.1,3 This means that the primary source of B vitamins is the food you eat.1
If you follow a vegan diet, you’re at a higher risk of a vitamin B12 deficiency.2,3 This is because vitamin B12 isn’t naturally found in foods such as fruit, vegetables and grains.3 So, people who follow a vegan or plant-based diet are advised to take a vitamin B12 supplement.5
Potential vitamin B complex benefits
Each B vitamin is responsible for maintaining homeostasis.2,6 In short, this means that B vitamins help to keep all the processes in your body working properly to maintain your health and keep you alive.6
With this in mind, each B vitamin plays a specific role in your body:1-3
- vitamin B1 – Contributes to the normal function of your heart and nervous system and supports your body in breaking down and releasing energy from food
- vitamin B2 – Contributes to the maintenance of normal red blood cells, mucous membranes, skin and vision. It also contributes to the reduction of tiredness and fatigue, protection of cells from oxidative stress, the normal functioning of the nervous system and supports your body in breaking down and releasing energy from food
- vitamin B3 – helps to keep your nervous system functioning normally and supports your body in breaking down and releasing energy from food
- vitamin B5 – contributes to the reduction of fatigue, and normal mental performance as well as being involved in the normal synthesis and metabolism of steroid hormones, vitamin D and some neurotransmitters
- vitamin B6 – Contributes to the normal function of the immune system and could help to reduce inflammation in the body. It also contributes to the regulation of hormonal activity, the reduction of fatigue and the normal functioning of the brain and nervous system7,8
- vitamin B7 – helps your body metabolise fats, carbohydrates and protein, and maintain normal hair and skin9,10
- vitamin B9 – Contributes to the normal function of the immune system and helps with normal blood formation, cell division and the growth of maternal tissue during pregnancy – which is often why it is found in many prenatal supplements. There is evidence to suggest that supplementing folate during pregnancy could also reduce the risk of birth defects11
- vitamin B12 – helps your body release energy from food, reduce fatigue, make red blood cells and keep the nervous and immune systems functioning normally12
How much of each B vitamin do I need?
The amount of vitamin B you need depends on your age, sex and other factors, like whether you’re pregnant.1,3 As a result, the amount of each B vitamin that you need changes throughout your life.1
Below are the reference nutrient intakes for adults aged 19–64:3
| Vitamin | Female | Male |
|---|---|---|
| B1 | 0.8mg | 1mg |
| B2 | 1.1mg | 1.3mg |
| B3 | 13.2mg | 16.5mg |
| B5 | up to 200mg* | up to 200mg* |
| B6 | 1.2mg | 1.4mg |
| B7 | up to 0.9mg* | up to 0.9mg* |
| B9 | 200μg | 200μg |
| B12 | 1.5μg | 1.5μg |
*No reference nutrient intake. This is the amount that you should not exceed in supplement form
However, people who are trying to conceive or are currently pregnant should take 400μg of folate (vitamin B9) until they’re 12 weeks pregnant.3
Sources of vitamin B complex
All the B vitamins you need are present in both plant and animal-based food products.2 As a result, eating a varied, balanced diet should ensure you get enough B vitamins day-to-day.3,10
Here are some excellent vitamin B food sources:3,9,12,13,14
- vitamin B1 – peas, fresh fruits (such as bananas and oranges), nuts, wholegrain breads, some fortified breakfast cereals, liver (should be avoided if you’re pregnant)
- vitamin B2 – milk, eggs, fortified breakfast cereals, mushrooms, plain yoghurt
- vitamin B3 – meat, fish, wheat flour, eggs
- vitamin B5 – chicken, beef, liver (should be avoided if you’re pregnant), kidneys, eggs, mushrooms, avocado
- vitamin B6 – pork, poultry (such as chicken or turkey), some fish, peanuts, soya beans, wheatgerm, oats, bananas, milk, some fortified breakfast cereals
- vitamin B7 – organ meats, eggs, fish, seeds, soybeans, nuts
- vitamin B9 – broccoli, brussels sprouts, leafy green vegetables (such as cabbage, kale, spring greens and spinach), peas, chickpeas and kidney beans, liver (should be avoided if you’re pregnant), breakfast cereals fortified with folic acid
- vitamin B12 – meat, fish, milk, cheese, eggs, some fortified breakfast cereals
For more information about the best dietary sources of vitamin B, take a look at our dedicated guide.
You can also explore our range of recipes, including our super bean chilli or our high protein chickpea pasta with red lentil pesto, to see how tasty getting B vitamins can be…
Vitamin B deficiency: are there any signs or symptoms?
As each B vitamin plays a different role in the body, a deficiency in any one of the B complex vitamins can result in different symptoms.10 These can range from fatigue to confusion, anaemia, skin rashes and a compromised immune system.10 Below is a list of more specific symptoms associated with a deficiency in each B vitamin:10
- vitamin B1 and vitamin B2 – confusion and cracks along the side of the mouth
- vitamin B3 – digestive issues (nausea and abdominal cramps), mental confusion and a condition called pellagra, which causes diarrhoea, dermatitis and dementia
- vitamin B5 – personality changes, fatigue, headache, irritability, nausea, stomach pains, malaise, numbness, muscle cramps, sleep disorders, upper respiratory infections, burning feet and an increased sensitivity to insulin
- vitamin B6 – anaemia, skin disorders (such as cracks and a rash around the mouth), confusion, depression, nausea, dermatitis and a susceptibility to infections
- vitamin B7 – red rash (around the eyes, nose, mouth and genitals), hair loss, numbness and tingling in the hands and feet, lethargy, depression, hallucinations, seizures and impaired immune function
- vitamin B9 – fatigue, poor growth, diarrhoea, irritability, a tender or smooth tongue and birth defects in newborn babies
- vitamin B12 – mood changes, numbness or tingling (in hands, legs or feet), anaemia, loss of breath, pale skin, dizziness, difficulty walking, hallucinations, weight loss, poor memory, fatigue
The final say
Vitamin B complex is made up of eight B vitamins that are essential for many processes in your body, keeping you healthy and alive.2,3,6 As a result, deficiency in each of the B vitamins comes with a range of different symptoms.10
You should be able to get all the B vitamins you need from eating a varied and balanced diet.2,3,10 Still, if you follow a vegan or plant-based diet, the NHS advises taking a vitamin B12 supplement.5 You can find our full range of vitamin B12 supplements and vitamin B supplements on our website.
For personalised advice, you should always speak to a healthcare professional, such as your GP or dietitian.
The advice in this article is for information only and should not replace medical care. Please check with your GP or healthcare professional before trying any supplements, treatments or remedies. Food supplements must not be used as a substitute for a varied and balanced diet and a healthy lifestyle.
While we strive for accuracy and balance, please be aware that this article may discuss products available for purchase through Holland & Barrett. Consult a healthcare professional before making any health-related decisions.
- Ali MA, et al. Dietary vitamin B complex: Orchestration in human nutrition throughout life with sex differences. Nutrients. 2022;14(19):3940. https://doi.org/10.3390/nu14193940
- Peterson CT, et al. B vitamins and their role in immune regulation and cancer. Nutrients. 2020;12(11):3380. Available from: https://doi.org/10.3390/nu12113380
- NHS. B vitamins and folic acid - Vitamins and minerals [Internet]. [cited 2024 Jul 18]. Available from: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-b/
- Hrubša M, et al. Biological properties of vitamins of the B-complex, part 1: Vitamins B1, B2, B3, and B5. Nutrients. 2022;14(3):484. https://doi.org/10.3390/nu14030484
- NHS. The vegan diet [Internet]. [cited 2024 Jul 18]. Available from: https://www.nhs.uk/live-well/eat-well/how-to-eat-a-balanced-diet/the-vegan-diet/
- Billman GE. Homeostasis: The underappreciated and far too often ignored central organizing principle of physiology. Front Physiol. 2020;11:200. https://doi.org/10.3389/fphys.2020.00200
- Stach K, et al. Vitamin B6 in health and disease. Nutrients. 2021;13(9):3229. https://doi.org/10.3390/nu13093229
- Mikkelsen K, Apostolopoulos V. Vitamin B1, B2, B3, B5, and B6 and the immune system. In: Mahmoudi M, Rezaei N. (eds) Nutrition and Immunity. Springer, Cham; 2019. Available from: https://doi.org/10.1007/978-3-030-16073-9_7
- Hanna M, et al. B vitamins: Functions and uses in medicine. Perm J. 2022;26(2):89–97. https://doi.org/10.7812/tpp/21.204
- LeBlanc JG. B-complex vitamins. IntechOpen; 2022. Available from: https://www.intechopen.com/books/11021
- Moges N, Ermias Sisay Chanie, Rahel Mulatie Anteneh, Melkamu Aderajew Zemene, Asaye Alamneh Gebeyehu, Belete MA, et al. The effect of folic acid intake on congenital anomalies. A systematic review and meta-analysis. Frontiers in Pediatrics. 2024 Jul 19;12. https://pmc.ncbi.nlm.nih.gov/articles/PMC11294162/
- European Commission. Food and Feed Information Portal Database: Health Claims [Internet]. [cited 2025 Feb 19]. Available from: https://ec.europa.eu/food/food-feed-portal/screen/health-claims/eu-register
- Butola LK, et al. Vitamin B12 - Do you know everything? J Evol Med Dent Sci. 2020;9(42):3139–46. https://www.researchgate.net/publication/344804062_Vitamin_B12_-Do_You_Know_Everything
- Gille D, Schmid A. Vitamin B12 in meat and dairy products. Nutr Rev. 2015;73(2):106–15. https://doi.org/10.1093/nutrit/nuu011
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