Vanderbilt Study Raises Concerns about Multivitamin Supplements

Too much dietary zinc increases susceptibility to infection by Clostridium difficile - "C. diff" - the most common cause of hospital-acquired infections.

The findings, reported at the end of September in Nature Medicine, call into question the consumption of dietary supplements and cold therapies containing high concentrations of zinc.

"It is important to know what you are putting into your body," said Eric Skaar, PhD, MPH, professor of Pathology, Microbiology and Immunology at Vanderbilt University. "Multivitamins and other supplements are really only needed by those with a particular nutritional deficit in their diet."

Skaar and his colleagues including Joseph Zackular, PhD, discovered that high levels of zinc change the gut's microbiome in a way that mimics antibiotic treatment, the primary risk factor for C. diff infection. In addition to raising concerns about multivitamin consumption, the findings have particular importance for patients who are hospitalized or taking antibiotics and who are also receiving zinc-supplemented nutrition, which may put them at even greater risk for C. diff infection.

The findings may also partially explain the increasing rates of C. diff infection in people who haven't been hospitalized or treated with antibiotics, Skaar said. In the United States, C. diff infects about 500,000 people each year, causing disease ranging from diarrhea to life-threatening inflammation of the colon, according to the Centers for Disease Control and Prevention.

Skaar and his colleagues used mouse models to explore the impact of dietary metals on susceptibility to infectious diseases. They demonstrated that mice consuming a high-zinc diet had altered gut microbiota and were susceptible to C. diff infection at lower antibiotic doses compared to mice on a normal zinc diet. Moreover, C. diff caused more severe disease and lethality in mice on a high-zinc diet. The investigators also showed that the zinc-binding protein calprotectin is important for combating C. diff by limiting zinc availability during infection.

The findings add to growing evidence that the microbiome is dramatically affected by diet, and suggest that efforts to treat C. diff infections with an "ideal" mix of microbes will be difficult. Fecal transplants - transfer of stool from a healthy donor to the gastrointestinal tract of a patient with C. diff - have been effective for treating recurrent C. diff colitis, prompting attempts to treat C. diff with a small number of microbes. But the first clinical trial of a "reduced microbial transplant" for C. diff recently failed.