From the Guidelines
B vitamins typically don't make you feel tired; in fact, they often help combat fatigue. B vitamins play essential roles in energy production, with B12, B6, and folate being particularly important for converting food into energy 1. However, in some cases, people might experience temporary tiredness when starting high-dose B vitamin supplements as their body adjusts. This is usually mild and short-lived. Certain individuals may also have paradoxical reactions to specific B vitamins due to genetic factors or underlying health conditions.
If you're experiencing fatigue after taking B vitamins, consider taking them earlier in the day, reducing the dosage, or consulting with a healthcare provider. Most people find that adequate B vitamin intake through diet or supplements actually improves energy levels rather than causing tiredness, as these vitamins are crucial for proper cellular metabolism and red blood cell formation. Some studies suggest that vitamin B12 replacement can improve fatigue in patients with deficiency, and oral treatment may be a cost-effective option 1. Additionally, other vitamins like vitamin D may also play a role in fatigue, particularly in patients with inflammatory bowel disease or cancer 1.
Key points to consider:
- B vitamins are essential for energy production and can help combat fatigue
- Temporary tiredness may occur when starting high-dose B vitamin supplements
- Paradoxical reactions to specific B vitamins can occur due to genetic factors or underlying health conditions
- Consult a healthcare provider if experiencing fatigue after taking B vitamins
- Vitamin B12 replacement may improve fatigue in patients with deficiency, and oral treatment may be a cost-effective option 1
From the Research
B Vitamins and Fatigue
- B vitamins play a crucial role in maintaining fundamental cellular functions and various essential metabolic pathways in the body, including energy metabolism processes 2.
- A study found that 28 consecutive days of vitamin B complex supplementation significantly improved exercise endurance performance and reduced exercise fatigue biochemical metabolites in non-athletes 2.
- However, another study found that vitamin B12 supplementation is likely ineffective for improving cognitive function and depressive symptoms in patients without advanced neurological disorders, and there was no overall effect on measures of depression or idiopathic fatigue 3.
Effects of B Vitamin Supplementation
- A systematic review and meta-analysis found no evidence for an effect of vitamin B12 alone or B complex supplementation on cognitive function outcomes, and no significant associations of treatment effects with potential predictors 3.
- A narrative review summarized the biochemical bases and actions of B vitamins, vitamin C, iron, magnesium, and zinc, and connected them with cognitive and psychological symptoms, as well as manifestations of fatigue that may occur when status or supplies of these micronutrients are not adequate 4.
- A systematic literature review found that high-dose, B-complex multivitamin/mineral supplementation showed improvements in perceived stress, physical stamina, concentration, and general mental health, and significant reductions in anxiety and improvements in self-reported vigour in healthy populations 5.
Relationship between B Vitamins and Brain Metabolism
- A randomized control trial found that 6-month high-dose B-group vitamin supplementation increased vitamin B6 and vitamin B12 levels, reduced homocysteine, and had significant relationships between vitamin B6 and N-acetylaspartate (NAA), choline, and creatine, as well as between vitamin B12 and creatine 6.
- The study also found that high-dose B-group supplementation may reduce oxidative stress and inflammation through increasing oxidative metabolism, and promote myelination, cellular metabolism, and energy storage 6.