Washington, June 26 (IANS): Too much vitamin B12 may promote acne, according to a study.

In the presence of vitamin B12, the skin bacteria that are commonly linked to acne start pumping out inflammatory molecules known to promote pimples.

The researchers looked at the bacteria's gene expression to find out why Propionibacterium acnes, the most common skin microbe, causes pimples in some people but not in others.

"I think there is a link between vitamin B12 and acne," co-author Huiying Li and assistant professor of pharmacology at the University of California, Los Angeles' David Geffen School of Medicine was quoted as saying by Live Science.

In humans, vitamin B12 plays a key role in metabolism, red blood cell formation and the maintenance of the central nervous system and is found in multivitamins.

By looking at the gene expression patterns, Li's team first found that the pathway that produces vitamin B12 was significantly altered in the skin bacteria of people with acne, compared with the skin bacteria of people without acne.

The researchers confirmed that the B12 supplement repressed the expression of genes in P. acnes involved in synthesizing the vitamin.

A week after receiving the vitamin B12 injection, one of the 10 participants broke out in pimples.

That person's P. acnes gene-expression pattern also changed, the researchers found.

Together, the new results suggest that when too much B12 is present, the bacteria have changes in their gene expression that suppress further synthesis of the vitamin.

These bacteria switch to producing porphyrins and in some people this uptick in inflammatory compounds may contribute to acne.

"We think the pathway we studied could potentially explain part of acne's pathogenesis," Li said.

The study was published in the journal Science Translational Medicine.