B vitamins play an extremely important role in brain health. That's emphasized in a 2016 review of the scientific literature by Dr. David O. Kennedy of Northumbria University. And the importance applies not just to one or a few of them, but rather to all eight B vitamins:
- thiamine (B1)
- riboflavin (B2)
- niacin (B3)
- pantothenic acid (B5)
- vitamin B6
- biotin (B7)
- folate (B9)
- vitamin B12
According to Dr. Kennedy, many clinical studies of vitamin B supplements have focused on just three of the B vitamins. Those are folate, B12, and B6. But they've ignored the other five.
That's problematic. As we’re now just beginning to understand, the B vitamins’ effects on the body are all connected.
For instance, thiamine, riboflavin, niacin, pantothenic acid, and B12 are all essential to the generation of cellular energy. And a deficiency in just one of these vitamins could interrupt the whole process.
Similarly, folate, B6, B12, riboflavin, and niacin all play necessary roles in the folate and methionine cycles. And these cycles are critical to proper cellular function. Deficiency in any one of these vitamins is “rate-limiting” for the whole process.
B vitamins also play connected roles in metabolizing and synthesizing proteins. B6 is essential to 140 enzymes involved in these processes, and pantothenic acid is essential to 4% of all mammalian enzymes.
B vitamins are especially important for brain function. They exist in the brain in much higher concentrations than in the rest of the body. B vitamin deficiencies or dysfunctions have been implicated in many brain disorders, including schizophrenia, Parkinson’s, and neural tube birth defects. And here are some examples of how they function in the brain:
- Thiamine and B6 are precursors to many neurotransmitters and also play a role in regulating them.
- Riboflavin and pantothenic acid are involved in the metabolism of fatty acids in brain lipids.
- Niacin and B6 modulate brain inflammation and play roles in DNA repair and gene transcription.
- Folate and B12 are also involved in DNA repair and gene transcription, as well as in synthesizing neurotransmitters.
- Biotin regulates brain glucose.
B Vitamins May Improve Mood and Heart Health
Because of the B vitamins’ role in brain health, a number of human trials have looked at the effect of supplements. However, most of these studies have supplemented with only one B vitamin at a time. And they’ve focused almost exclusively on folate, B12, and B6, to the exclusion of the other B vitamins. They’ve also focused almost exclusively on using vitamin B pills to reduce high blood levels of homocysteine.
It’s well established in the scientific literature that homocysteine increases the risk of dementia. And B vitamin supplements reduce levels of homocysteine. Studies have also established that deficiencies of folate and B12 in the elderly are somewhat predictive of dementia.
The logical conclusion is that, in order to stave off dementia, you should supplement with B vitamins. But surprisingly, studies of B vitamin supplements have found little evidence that they reduce dementia symptoms. These studies have been widely criticized on methodological grounds, so there’s more work to be done. But currently the evidence doesn’t favor B vitamin supplements for dementia prevention or treatment.
There's at least one possible reason for the equivocal results. Studies of just one B vitamin don’t take into account its interactions with the other B vitamins. For instance, a 2007 study found that folate acts as a neuroprotector in patients with adequate levels of B12. But the study also found that folate harms cognition in patients that are B12 deficient.
Likewise, a 2003 study found that folate supplements increase rates of riboflavin deficiency. In other words, folate may be limiting the uptake of other B vitamins. And that may be harmful unless you’re also getting plenty of those other vitamins.
One area where B vitamin supplements have shown more promise is in improving mood. Several studies have shown that B vitamin deficiencies predict elderly depression.
A different set of studies has experimented with B vitamin supplements for the elderly. They found it to have a protective effect on mood. And the best results came from studies in which folate, B12, and B6 were administered in combination rather than in isolation.
B6, in particular, has been shown to increase the brain’s production of serotonin and to increase the vividness of dreams. Only a single study has extended the mood research to thiamine (vitamin B1). It found that 50 mg/day of thiamine improved both mood and reaction time in young women.
B vitamin supplements may also help regulate cardiovascular health and glucose metabolism. In several studies, 1.6 mg/day of riboflavin increased the blood levels of hemoglobin and the concentration of red blood cells.
Mega-doses of biotin have been shown to increase glycemic control and insulin sensitivity in diabetics. They have also been shown to regulate lipid concentrations in blood plasma.
Niacin supplements have exhibited cardioprotective effects. And they appear to have reduced risk of heart disease in a number of human trials.
Unfortunately, no study has ever examined the effects of a B multivitamin. But of course many human trials have looked at broad-spectrum multivitamins that include the B Vitamin Complex.
For instance, some studies used spectroscopy and electroencephalography to measure brain activity during supplementation. And they found that a single dose of a multivitamin can increase attention, cerebral blood flow, and metabolism during cognitive tasks.
In studies of children, most studies have found a positive effect of multivitamins on IQ. In adults, multivitamin supplements appear to improve mood and performance on memory tasks.
Optimal Vitamin B Complex Dosage May Be Higher Than RDA
The human body does not synthesize the B vitamins, so they have to be obtained from food. They’re primarily made by plants. But they can also be obtained from higher up the food chain, in vitamin B foods like meat and eggs.
The exception is B12, which is synthesized by animals’ gut bacteria and is abundant in red meat. This makes supplements particularly important for persons on a vegetarian or vegan diet.
Our hunter-gatherer ancestors may have consumed a lot of B vitamins in their diet. That diet probably included many different kinds of plants. But we get fewer B vitamins from modern diets that are heavy on sugars and processed grains.
So what is the optimal B vitamin dosage?
The US government sets a “minimum daily intake” or “recommended dietary allowance” (RDA). But there’s not much science behind the recommendation. It’s just a rough estimate of the average daily intake of the US population.
The RDA also has changed little over the last 40 years. And it takes insufficient account of changes in scientific understanding or of individual differences between people.
Based on the RDA, US deficiency rates for the various B vitamins range from 10% to 30%. Deficiency rates are especially high among the obese and diabetic. In fact, deficiencies of thiamine and biotin, which help metabolize glucose, may be causal factors in obesity and diabetes.
Some scientific studies have looked for symptoms of vitamin deficiency. They found that the US government’s recommended allowances for B12 and riboflavin are too low.
They found that between 18% and 38% of the US population shows symptoms of vitamin B-12 deficiency. And they found that riboflavin deficiency may affect over 50% of the adult population. The US government itself has issued statements acknowledging that the RDAs may be “less than optimal.”
Studies from the early 2000s showed that vitamin B6 and folate improved endothelial function when taken at 12 times their RDAs. Studies from early 2010s showed that large doses of vitamin B6 reduce inflammation. And they showed that patients with high levels of inflammation need several times the RDA of B6 just to avoid deficiency.
Studies of riboflavin supplements have recommended a dose of at least 4 mg/day, or 3 times the RDA. That’s unless you’re among the 10-15% of people with a genetic restriction on vitamin B2 absorption. Then a dosage of 26 mg/day has been recommended.
Studies have also found benefit from megadoses of biotin and niacin ranging from 30 to 500 times the RDA. But see the cautionary note on niacin below.
Increasing vitamin B dosage may be especially important for the elderly. They often suffer from vitamin malabsorption and thus higher levels of deficiency. One study suggests a daily B12 dose of 500 µg (200 times the RDA) to reduce deficiency in older people. And another recommends 1 mg/day of folic acid (2.5 times the RDA) to normalize older adults’ folate levels.
Because the B vitamins are water soluble, excess is generally excreted as urine. This makes most of them safe even at very high doses.
However, folic acid may not be safe at dosages above 1 mg/day. Higher doses may promote cancer.
Niacin can cause skin flushing at doses above 100 mg/day and vomiting and diarrhea at doses above 1 g/day. So it’s recommended you keep your daily Niacin dose under 35 mg.
And vitamin B6 can cause nerve damage at doses above 1 g/day. So the recommended daily upper limit is 100 mg.
Conclusion on B Vitamin Complex Dosage
There’s lots of research still to be done on B vitamins, especially to assess how they interact with each other. However, the current literature appears to support B vitamin doses well above the Recommended Dietary Allowances (RDAs).
For most of the B vitamins, large doses should be safe. But, to avoid side effects, take care with three of them. Don't exceed 1 mg/day of folic acid, 35 mg/day of niacin, or 100 mg/day of vitamin B6. And always remember to seek competent medical advice for your personal situation.
Among the likely vitamin B benefits are improved mood and improved cardiovascular health. There may also be benefits from vitamin B for energy, cognition, and metabolism.
Thrivous Clarity provides safe high doses of all 8 B Vitamins in high quality bioavailable forms. Clarity also includes clinical doses of Synapsa Bacopa Monnieri, Rhodiola Rosea, and Zinc Picolinate. These complement the brain health benefits of Vitamin B Complex.