Dr. Rae Osborn 23 Dec 2022

B vitamins are vital to your health as essential cofactors for cellular reactions and to ensure the normal functioning of the nerves, muscles, and blood cells. Hence, vitamin B deficiency can lead to multiple health hazards.

How much of each B vitamin does a healthy adult need every day?

B vitamins are water-soluble, so your body does not store enough long-term. This means that you need to follow a diet rich in B vitamins to maintain good health.

Below is a list of the B vitamins and the daily recommended intake.

  • B1: for women 1.1 mg and men 1.2 mg
  • B2: for women 1.1 mg and men 1.3 mg
  • B3: for women 14 mg and men 16 mg
  • B5: 5 mg for both men and women
  • B6: 1.5 mg for women and 1.7 mg for men
  • B7: 30 µg for both men and women
  • B9: 400 µg for both men and women
  • B12: 2.4 µg for both men and women

Pregnancy and the importance of B vitamins

B vitamins are important for the health of a pregnant woman and her baby. A lack of vitamin B9 (folate) in the diet can cause the infant to be born with birth defects like spina bifida. Vitamin B12 also needs to be taken in and absorbed in sufficient quantities to prevent birth defects.

The recommended amounts of B vitamins for a pregnant woman per day are as follows:

  • B1: 1.5 mg
  • B2: 1.5 mg
  • B3: 18 mg
  • B5: 6 mg
  • B6: up to 25 mg three times a day if you have morning sickness
  • B7: 30 µg
  • B9: 600 µg
  • B12: 2.6 µg

Note: If you are considering taking a vitamin supplement, you must always check with your doctor first to find out the supplement that is safest and best suited for you.

What causes vitamin B deficiencies?

There are many reasons you can become deficient in B vitamins. These are listed and discussed below:

  • Diet: Eating food that does not contain enough B vitamins can cause deficiencies.
  • Malabsorption: Even though your diet may include all the B vitamins, they may not be absorbed in the digestive system for some reason.
  • Genetic factors: Several genes impact the transport and uptake of B vitamins in the intestine.
    • Mutations of the TCN2 gene could play a role in B12 deficiency because this influences the uptake of B12.
    • In the case of B1, thiamine-responsive megaloblastic anemia results from a mutation in a thiamine transporter gene.
  • Medication: Certain medications impact the uptake of vitamin B12; for instance, metformin - taken by people with diabetes - interferes with B12 uptake

Who is at risk of Vitamin B deficiency?

The following factors make a person more susceptible to vitamin B deficiency.

  • Ethnicity: Certain ethnic groups are vulnerable to B deficiencies. For instance, studies reveal that vitamin B12 deficiency is prevalent among populations in the Indian subcontinent, Central and South America, and regions in Africa.
  • Autoimmune conditions: Certain autoimmune illnesses, such as Crohn’s disease and celiac disease, can lead to poor absorption of B vitamins.
  • Veganism: Vitamin B12 is mainly found in animal-based foods like meat and eggs. Vegans avoid these foods, placing them at risk of B12 deficiency.
  • Vegetarianism: A lack of B12 can also occur among vegetarians if they are not cautious about what they eat. Including acceptable sources of vitamin B12, such as dairy products, certain types of mushrooms, and fortified foods in the diet, can be helpful.
  • Pregnant women: The need for B vitamins increases during pregnancy because they are needed for proper fetal development.
  • The elderly: Conditions such as atrophic gastritis (an inflammation and thinning of the stomach lining) and pernicious anemia that impede vitamin B12 absorption are more common in older people. The stomach also produces less acid as we age. Thus, less B12 is absorbed.
  • Alcoholism: Individuals who consume alcohol excessively are at a high risk of B vitamin deficiency because the alcohol irritates the lining of the digestive system, making it difficult for the body to absorb vitamins properly.

The link between ethnicity and vitamin B deficiency

South Asians, particularly those of Indian ethnicity, often have low levels of vitamin B12. This could be due to cultural and religious factors , leading to a lack of animal products (especially B12-rich meats) in the diet.

Pernicious anemia is a condition where there is not enough intrinsic factor in the stomach, which is needed to properly absorb vitamin B12. While this is more common in older people, it is also prevalent in certain ethnic groups, mainly people of Northern European and African descent.

Treatment of vitamin B deficiencies

Vitamin B supplements may help treat vitamin deficiencies. However, it is best to check with your doctor before starting any new diet or taking any vitamin supplement.

If the problem is in absorbing the vitamins, an injection may be needed instead. This is often the case with B12 deficiency in people who have problems absorbing it through the gut.

For many people, B vitamin deficiencies can be corrected by consuming food rich in B vitamins. This is more of a challenge for vegans and vegetarians who do not eat animal products. Following a diet that includes all the vitamins you need is crucial.

Types of vitamin B deficiency and food sources

People can be deficient in any one of the B vitamins. Listed below are the types of deficiencies and associated symptoms of each, and the best food sources for each vitamin.

Vitamin B1 (Thiamin) deficiency and best food sources

Vitamin B1 deficiency results in a condition known as beriberi and is most common in alcoholics. It is also prevalent in people who consume excessive amounts of white flour and other processed carbohydrates.

Symptoms of beriberi include:

Best food sources for vitamin B1:

  • Fortified whole grain cereals
  • Soy and nuts
  • Pork
  • Peas

Vitamin B2 (Riboflavin) deficiency and best food sources

This deficiency is more common in Africa and Asia and in women who take birth control pills. Signs of this deficiency include :

  • Fatigue
  • Blurry vision
  • Skin itching and cracking, including around the mouth
  • Swollen throat
  • Hair loss

Best food sources for vitamin B2:

  • Eggs
  • Fish and red meat
  • Soybean and almonds

Vitamin B3 (Niacin) deficiency and best food sources

Vitamin B3 (Niacin) deficiency leads to pellagra, and the symptoms include:

Best food sources for vitamin B2:

  • Liver and red meat
  • Chicken
  • Tuna fish
  • Quinoa
  • Muesli

Vitamin B5 (Pantothenic acid) deficiency and best food sources

This is a very rare deficiency, mainly found in people with severe malnutrition. Symptoms include:

  • Fatigue
  • Depression
  • Upset stomach
  • Irritability
  • Insomnia
  • Muscle cramps
  • Burning feeling in the extremities

Best food sources for vitamin B5:

  • Nuts and seeds
  • Liver and red meat
  • Milk
  • Avocado
  • Fortified cereal

Vitamin B6 (Pyridoxine) deficiency and best food sources

Pyridoxine may be deficient in those with autoimmune illnesses, pregnant women, and alcoholics.

Signs of B6 deficiency include the following:

  • Cracked lip corners
  • Skin rashes
  • Mood changes
  • Glossy tongue
  • Weakened immune system

Best food sources for vitamin B6:

  • Chickpeas
  • Liver
  • Fish and poultry
  • Dark green leafy vegetables
  • Papaya and bananas

Vitamin B7 (Biotin) deficiency and best food sources

An uncommon vitamin B deficiency, it can occur in people with biotinidase deficiency (a rare hereditary disorder), health conditions that affect nutrient absorption, or due to certain medications. Biotin deficiency symptoms include:

  • Skin irritation around the mouth and on the face
  • A rash around the mouth, eyes, and nose
  • Hair loss

Best food sources for vitamin B7:

  • Seeds and nuts
  • Sweet potato
  • Eggs
  • Fish
  • Liver

Vitamin B9 (Folate) deficiency and best food sources

Vitamin B9 deficiency is common in alcoholics, people aged 65 and older, and pregnant women. The signs of folate deficiency are as follows:

  • Lack of appetite
  • Pale skin
  • Irritability
  • Fatigue
  • Diarrhea
  • Megaloblastic anemia (where the bone marrow produces abnormally large cells)

Best food sources for vitamin B9:

  • Seafood
  • Liver
  • Leafy green vegetables and beans
  • Sunflower seeds and peanuts

Vitamin B12 (Cobalamin) deficiency and best food sources

Vitamin B12 deficiency is quite common in people who don’t eat meat and who avoid dairy products. It is also a problem with certain autoimmune conditions. There are also genetic factors at play in the absorption of B12. The signs of B12 deficiency include:

  • Mouth ulcers
  • Red tongue
  • Yellowish skin color
  • Paresthesia: pins-and-needles feeling
  • Irritability and depression
  • Problems with vision
  • Macrocytic anemia: abnormally big blood cells are produced

Best food sources for vitamin B12:

  • Red meat
  • Cheese and milk
  • Eggs
  • Fortified cereals
  • Fish

What happens if you take excess vitamin B?

It is possible to consume excess vitamin B if you use supplements. This can be harmful and lead to nerve damage even though B vitamins are water-soluble. Your safest bet is to stick to the recommended daily allowances and always check with your doctor before using supplements or changing your diet.


Most vitamin B deficiencies are uncommon in people with good nutrition. However, you may be susceptible to vitamin deficiency due to certain medical conditions, aging, genetics, and special diets that cut out certain food categories. Pregnant women need to be especially careful to ensure they take in the correct amounts of B vitamins to prevent birth defects. Remember to always check with your doctor before changing your diet or taking vitamin supplements.

To search for the best Dietitian/Nutritionists in Croatia, Germany, India, Malaysia, Slovakia, Spain, Thailand, Turkey, the UAE, the UK and The USA, please use the Mya Care search engine.

To search for the best doctors and healthcare providers worldwide, please use the Mya Care search engine.

About the Author:

Dr. Rae Osborn has a Ph.D. in Biology from the University of Texas at Arlington. She was a tenured Associate Professor of Biology at Northwestern State University where she taught many courses for Pre-nursing and Pre-medical students. She has written extensively on medical conditions and healthy lifestyle topics, including nutrition. She is from South Africa but lived and taught in the United States for 18 years.


  • Carmel, R., & Johnson, C. S. (1978). Racial patterns in pernicious anemia: early age at onset and increased frequency of intrinsic-factor antibody in black women. New England Journal of Medicine, 298(12), 647-650.
  • Mahabadi, N., Bhusal, A., & Banks, S. W. (2022). Riboflavin Deficiency. In StatPearls [Internet]. StatPearls Publishing.
  • Mearns, G. J., & Rush, E. C. (2017). Screening for inadequate dietary vitamin B-12 intake in South Asian women using a nutrient-specific, semi-quantitative food frequency questionnaire. Asia Pacific journal of clinical nutrition, 26(6), 1119-1124.
  • Surendran, S., Adaikalakoteswari, A., Saravanan, P., Shatwaan, I. A., Lovegrove, J. A., & Vimaleswaran, K. S. (2018). An update on vitamin B12-related gene polymorphisms and B12 status. Genes & nutrition, 13(1), 1-35.
  • Wong, C. W. (2015). Vitamin B12 deficiency in the elderly: is it worth screening. Hong Kong Med J, 21(2), 155-64.

Disclaimer: Please note that Mya Care does not provide medical advice, diagnosis, or treatment. The information provided is not intended to replace the care or advice of a qualified health care professional. The views expressed are personal views of the author and do not necessarily reflect the opinion of Mya Care. Always consult your doctor for all diagnoses, treatments, and cures for any diseases or conditions, as well as before changing your health care regimen. Do not reproduce, copy, reformat, publish, distribute, upload, post, transmit, transfer in any manner or sell any of the materials in this blog without prior written permission from