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The ABCs of B Vitamins: A Comprehensive Guide

Understanding B Vitamins

B vitamins form a group of eight water-soluble nutrients that are indispensable for a variety of physiological functions. Collectively termed the "B complex," these vitamins are individually distinguished by numbers and specific names, such as B1 (Thiamine), B2 (Riboflavin), B3 (Niacin), among others. Each member of this family contributes to an array of biochemical processes vital for cellular function[1].

The Case of the "Missing" B Vitamins

The original roster of B vitamins included a few more candidates, like B4, B8, B10, and B11. Later research clarified that these substances were either not essential or naturally synthesized within the body, thus removing them from the list of essential B vitamins. For instance:

  • B4 (Choline): Although not technically a B vitamin, choline is still an essential nutrient and often included in B complex supplements[2].
  • B8 (Inositol): Endogenously produced in the human body.
  • B10 (PABA): Synthesized by gut microbes and deemed non-essential.
  • B11 (Pteryl-hepta-glutamic acid): Classified under folates[3]. 

Functions and Deficiency Symptoms

B vitamins are commonly found in foods such as meat, fish, dairy, legumes, and leafy greens. They are instrumental in cell health, metabolism, cell proliferation, and neurotransmitter synthesis[4]. Deficiencies can lead to a range of health issues:

  • B1 (Thiamine): Deficiency can cause Wernicke-Korsakoff Syndrome or beriberi, affecting the nervous system and heart[5].
  • B2 (Riboflavin): May result in cataracts and oral health issues.
  • B3 (Niacin): Deficiency leads to pellagra, characterized by diarrhea, dermatitis, and dementia.
  • B5 (Pantothenic Acid): Causes adrenal gland issues and burning foot syndrome.
  • B6 (Pyridoxine): May result in mental health problems and neuropathies.
  • Biotin: Deficiency can lead to skin conditions and hair loss.
  • Folate: Results in anemia, poor fetal development, and elevated homocysteine levels.
  • B12 (Cobalamin): Deficiency can lead to anemia and nerve degeneration[6].

Groups with Special Considerations

Elderly: Aging presents several challenges to nutritional well-being, one of which is the decreasing efficiency in nutrient absorption. Vitamin B12 is particularly vulnerable in this respect[7]. As we age, the production of stomach acid may decline, affecting the separation of B12 from dietary proteins and making it less available for absorption. Furthermore, elderly individuals are more likely to suffer from conditions like atrophic gastritis or to be on medications like proton pump inhibitors, both of which further hinder the absorption of Vitamin B12. Deficiency symptoms can range from fatigue and weakness to more severe issues like anemia and neurodegenerative disorders. For these reasons, B12 supplementation is often recommended for older adults.

Pregnant and Lactating Women: The role of Folate (B9) in pregnancy is both profound and well-documented. It's crucial for the proper development of the baby's neural tube, which forms the basis for the nervous system[8]. Insufficient Folate levels during the critical early weeks of pregnancy can result in neural tube defects like spina bifida, which can have lifelong consequences for the child. Hence, Folate supplementation is generally advised before conception and throughout pregnancy to meet the increased needs during this critical period. 

Growing Children: During rapid growth, B vitamin deficiencies can negatively affect cognitive development and function. For instance, Thiamin (B1) is essential for energy metabolism and neural function.

Athletes: Athletes push their bodies to the limits, thereby ramping up metabolic rates and increasing the need for nutrients that support energy metabolism, like B1 (Thiamin), B2 (Riboflavin), and B3 (Niacin). Inadequate levels can compromise athletic performance, increase fatigue, and delay recovery. Athletes also lose more nutrients through sweat and urine, necessitating a higher intake to maintain optimal health and performance. 

Groups at Risk of Deficiency

Alcoholics: The relationship between alcohol consumption and B vitamin deficiencies is alarmingly strong, with Thiamin (B1) being the most affected[9]. Chronic alcohol use not only inhibits the absorption of this essential vitamin but also disrupts its storage and activation within the body. As a result, alcoholics are at high risk for developing severe conditions like Wernicke-Korsakoff syndrome, a neurodegenerative disorder that can cause memory loss, confusion, and even death. Moreover, alcohol can have a diuretic effect, leading to increased excretion of water-soluble vitamins like Folate and B12. This exacerbates the nutrient deficiency, affecting various physiological functions from metabolism to cognitive abilities. The ramifications can be so severe that addressing B vitamin deficiencies is a crucial aspect of treatment and recovery for alcohol use disorder.

Individuals with Eating Disorders: Eating disorders such as anorexia nervosa, bulimia, or binge-eating disorder pose a significant threat to nutritional health, leading to a broad spectrum of nutrient deficiencies, including B vitamins. These deficiencies can result in a host of issues, affecting everything from cellular metabolism to mental health. For instance, a lack of Niacin (B3) can result in pellagra, characterized by symptoms like dermatitis, diarrhea, and cognitive disturbances. In addition, the psychological stress and metabolic alterations associated with eating disorders can further exacerbate nutrient deficiencies, creating a vicious cycle that is challenging to break. 

Children and Teenagers: In the U.S., deficiencies in B vitamins, particularly B6 (Pyridoxine), are surprisingly common among teenagers. This nutrient is crucial for neurotransmitter function, which is fundamental to brain development and cognitive performance[10]. A deficiency in B6 can result in mood swings, irritability, and cognitive decline, symptoms often mistakenly attributed to typical teenage behavior or hormonal changes.The prevalence of fast food and processed snacks in the average American teenager's diet can contribute to these deficiencies. Foods rich in B6 include bananas, chickpeas, and certain types of fish like tuna and salmon. However, these are often overlooked in favor of convenient but nutrient-poor options. Parents should be aware of the nutritional gaps in their children's diets, as inadequate B6 levels can have long-term implications on academic performance and emotional well-being. 

Other At-Risk Groups

Celiac and Crohn’s Disease: Individuals with malabsorption syndromes like Celiac and Crohn’s Disease often experience reduced absorption of B vitamins.

Post-bariatric Surgery Patients: Alterations to the digestive tract post-surgery can result in decreased nutrient absorption, including B vitamins.

Excessive Loss Groups

Diabetics: Medications like Metformin can contribute to a B12 deficiency[11].

Diuretic Users: These medications can increase the loss of water-soluble vitamins like the B vitamins.

Individuals with Chronic Diarrhea: Loss of nutrients via stool can also result in multiple deficiencies, including B vitamins.


The B vitamins play a multifaceted role in maintaining good health, from energy metabolism and cell growth to neurotransmitter function and mental well-being. While deficiencies in these essential nutrients can lead to a host of health issues, certain populations are at a heightened risk and should consider specialized dietary intake or supplementation. Understanding the unique roles and challenges associated with each B vitamin can empower individuals to make informed choices about their nutrition. 

Whether you're young or old, an athlete or expecting mother, it's worth recognizing the immense value of the B vitamin family in your daily life. Keeping track of your B vitamin levels could be an underrated key to unlocking better health and improved quality of life.





1- Kennedy, D. O. B Vitamins and the Brain: Mechanisms, Dose and Efficacy—A Review. Nutrients, 8(2), 68, 2016

2- Zeisel, S. H., & da Costa, K. A. Choline: an essential nutrient for public health. Nutrition reviews, 67(11), 615-623, 2009

3- Fenech, M. Folate (Vitamin B9) and its impact on human health. Critical Reviews in Food Science and Nutrition, 52(7), 585-591, 2012

4- Combs Jr, G. F. The vitamins: fundamental aspects in nutrition and health, 2012

5- Lonsdale, D. A review of the biochemistry, metabolism and clinical benefits of thiamin (e) and its derivatives. Evidence-Based Complementary and Alternative Medicine, 3(1), 49-59, 2006

6- Green, R., & Datta Mitra, A. Megaloblastic Anemias: Nutritional and Other Causes. Medical Clinics of North America, 101(2), 297–317, 2017

7- Stabler, S. P. Vitamin B12 deficiency. New England Journal of Medicine, 368(21), 2041-2042, 2013

8- Czeizel, A. E., Dudás, I., Vereczkey, A., & Bánhidy, F. Folate deficiency and folic acid supplementation: the prevention of neural-tube defects and congenital heart defects. Nutrients, 5(11), 4760-4775, 2013

9- Thomson, A. D., Marshall, E. J., & Bell, D. Time to act on the inadequate management of Wernicke's encephalopathy in the UK. Alcohol and alcoholism, 48(1), 4-8, 2013

10- Morris, M. S., Sakakeeny, L., Jacques, P. F., Picciano, M. F., & Selhub, J. Vitamin B-6 intake is inversely related to, and the requirement is affected by, inflammation status. The Journal of nutrition, 140(1), 103-110, 2010

11- de Jager, J., Kooy, A., Lehert, P., Wulffelé, M. G., van der Kolk, J., Bets, D., ... & Stehouwer, C. D. Long term treatment with metformin in patients with type 2 diabetes and risk of vitamin B-12 deficiency: randomised placebo controlled trial. Bmj, 340, c2181, 2010

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