B vitamins: Why they only work as a team – and what is dangerous when taken in isolation

Norman Reffke
Jul 22
3 min read

Introduction

Do you often feel tired, irritable, or nervous? Or have you ever reached for a single B vitamin because you read somewhere that it helps with exhaustion or hair loss? Then you should read this article very carefully. Because B vitamins don't act alone. They're a finely tuned team that only functions optimally when all players are on the field. In this article, you'll learn how B vitamins interact biochemically, why taking them in isolation carries risks, and which combinations actually make sense.

Biochemical basics: The B vitamin team
Symptoms of functional imbalance
Risks of single doses: When the balance tips
Target groups with increased needs
Optimization: Bioactive forms and combination strategies
Study situation and research
Conclusion with coaching integration
Sources

Biochemical basics: The B vitamin team

B vitamins are water-soluble and act as coenzymes in numerous metabolic processes. Many of these processes require several B vitamins simultaneously:

B vitamin	function	Required co-factors
B1 (thiamine)	Pyruvate dehydrogenase, nerve signal transmission	B2, B6, magnesium
B2 (riboflavin)	FAD, antioxidant enzymes, thyroid	B6, B3, selenium
B3 (niacin)	NAD/NADP, cellular respiration, DNA repair	B2, B6
B5 (pantothenic acid)	Coenzyme A, fatty acid synthesis	B1, B2
B6 (pyridoxine)	Amino acid metabolism, neurotransmitters	B2, B12, folate
B7 (biotin)	Carboxylases, fat and sugar metabolism	B5, B12
B9 (folate)	DNA synthesis, methylation	B12, B2, B6
B12 (cobalamin)	Cell division, myelin synthesis	B9, B6

Particularly important: Homocysteine is only detoxified through the interaction of vitamin B6, vitamin B9 (folate), and vitamin B12. A lack of one of these can increase the risk of cardiovascular disease.

Symptoms of functional imbalance

Even with "normal" blood values, functional deficiencies can occur. Typical symptoms of B vitamin imbalances include:

Exhaustion, irritability, difficulty concentrating (B1, B6, B12)
Skin problems, hair loss, chapped lips (B2, B3, B7)
Neuropathies, numbness (B6, B12)
Elevated homocysteine (B6, B9, B12)
Depressive mood, anxiety (B3, B6, B9)

Risks of single doses: When the balance tips

Taking a B vitamin in isolation can have a paradoxical effect:

B6 in high doses (>100 mg/day) : May cause nerve irritation if B2 or B12 is deficient
Folic acid without B12 : Can mask neurological symptoms
B3 (niacin) high dose : Can strain the liver and disrupt methylation processes
B1 high doses in chronic stress : Can deplete other cofactors (e.g. magnesium)

Conclusion: B vitamins should never be taken individually and in high doses over a long period of time.

Target groups with increased needs

Vegans & vegetarians : risk of B12 deficiency, often also B2 & B6
Seniors : Poor absorption due to low stomach acid
Stressed people : Higher consumption of B1, B2, B5, B6
Alcohol consumers : Increased loss of B1, B6
Athletes : Increased energy expenditure requires more B vitamins
Medication users (e.g., metformin, PPI): Increased risk of B12 and folate deficiency

Optimization: Bioactive forms and combination strategies

A good B complex contains:

B1 as benfotiamine (better bioavailable)
B2 as riboflavin-5-phosphate
B6 as pyridoxal-5-phosphate (P5P)
B9 as methylfolate instead of synthetic folic acid
B12 as methylcobalamin or hydroxocobalamin

Recommendation : B complexes with moderate dosages (e.g. 50–100% NRV per B vitamin) are safer for everyday use than high-dose monoproducts.

Study situation and research

“Clinical and metabolic effects of B-vitamin supplementation” (Smith et al., 2020, BMJ )
“The interplay between B vitamins and methylation” (Hoffman et al., 2018, Nutrients )
“Functional biomarkers for B-vitamin deficiencies” (O'Leary et al., 2019, American Journal of Clinical Nutrition )
“High-dose vitamin B6 toxicity” (Kang et al., 2021, Neurology )

All show: A balanced B-complex preparation is more useful than individual vitamins, except in clearly diagnosed exceptional cases.

Conclusion with coaching integration

B vitamins act like cogs in the body's biochemical machinery. If one of them isn't working properly, energy, nerves, and detoxification suffer. Taking them in isolation can help in the short term but be harmful in the long term. In VMC Coaching, we focus on balanced combinations tailored to your daily routine, your diet, and your stress levels. B2, B6, folate, and B12 are especially crucial during the reset phase (detoxification and cell regeneration).

Sources

Smith AD et al. "Clinical and metabolic effects of B vitamin supplementation." BMJ. 2020. https://www.bmj.com/content/370/bmj.m2562
Hoffman RM et al. "The interplay between B vitamins and methylation." Nutrients. 2018. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6163315
O'Leary F et al. "Functional biomarkers for B vitamin deficiencies." AJCN. 2019.https://academic.oup.com/ajcn/article/110/5/1125/5560598
Kang JH et al. "High-dose vitamin B6 toxicity." Neurology. 2021. https://n.neurology.org/content/96/12/e1696