How Toxic are Synthetic B-Vitamins vs Natural B-Vitamins?

The Potential Toxicity of Synthetic B-Vitamins: The Hidden Danger

B-vitamins play an essential role in maintaining good health, particularly in energy production, brain function, and red blood cell formation. However, while these nutrients are widely available in foods and supplements, synthetic B-vitamins—those artificially produced and found in many fortified foods and supplements—can carry risks if consumed in excess. Though B-vitamins are water-soluble and generally flushed out of the body when taken in excess, prolonged use of high doses or incorrect supplementation can lead to toxicity, causing a range of harmful side effects.

The Most Dangerous Synthetic B-Vitamins

While all B-vitamins are crucial for health, synthetic forms of certain B-vitamins pose more significant risks when overconsumed. One of the most dangerous is Vitamin B6 (pyridoxine), which, in excessive amounts, can lead to nerve damage, resulting in symptoms like numbness and difficulty coordinating muscle movements.

Vitamin B3 (niacin), in its synthetic form, can cause severe flushing, liver damage, and gastrointestinal issues at high doses.

Folic acid (synthetic folate), often found in fortified foods and supplements, can mask a vitamin B12 deficiency, delaying diagnosis and treatment, potentially leading to irreversible nerve damage. Consuming these synthetic B-vitamins in excessive amounts, especially through supplementation rather than food, can lead to adverse effects. It is important to stay within the recommended daily intake, which can usually be achieved through a balanced diet.

Reducing the Risk

To reduce the risk of synthetic B-vitamin toxicity, individuals should focus on obtaining their B-vitamin intake primarily from natural food sources, such as leafy greens, whole grains, eggs, and meat, which provide a balanced range of B-vitamins. Supplements should only be taken when recommended by a healthcare provider and under appropriate dosages. Avoiding high-dose B-vitamin supplements unless specifically advised is also important. Individuals should monitor their intake of fortified foods and be cautious with multivitamin use. For those who need supplements, consulting with a healthcare professional for personalized recommendations is crucial in preventing the risk of toxicity.

One study found that: 

"Synthetic forms of vitamins, administered in this experiment, might have been treated by animal bodies as xenobiotics. Vitamins B₁ and B₆ cannot be found in the form of hydrochlorides in natural food products, and vitamins B₂ (E 101) and niacin (E 375) are also synthetic food additives, and recognized by the body as xenobiotics they could have contributed to changes in the antioxidant status" (Goluch-Koniuszy & Drozd). 

References

Berg, J. M., Tymoczko, J. L., & Gatto, G. J. (2015). Stryer Biochemistry (8th ed.). W.H. Freeman and Company.

Haug, W., & Lührs, F. (2001). Toxicity of synthetic B-vitamins. Food and Chemical Toxicology, 39(3), 237-246. https://doi.org/10.1016/S0278-6915(00)00172-5

Shahidi, F., & Ambigaipalan, P. (2015). Synthetic vitamins and their potential risks. Journal of Food Science, 80(4), R743-R750.

Z. Goluch-Koniuszy and R. Drozd, “Modified Diet Supplementation With
Group B Vitamins Changes Antioxidant Defense Activity Of Brain,”
International Journal for Vitamin and Nutrition Research, vol. 87,
no. 3–4, pp. 159–168, May 2017.