August 1 -- A study led by researchers at the San Francisco VA Medical Center (SFVAMC) has found that the lower the level of vitamin C in the blood the more likely a person will become infected by Helicobacter pylori, the bacteria that can cause peptic ulcers and stomach cancer.
"This is the largest study to look at the relationship between vitamin C levels and infection by H. pylori," said Joel A. Simon, MD, MPH, SFVAMC staff physician and UCSF associate professor of medicine and epidemiology and biostatistics.
The study was published in the August 1 issue of the Journal of the American College of Nutrition. Simon and his collaborators utilized data and blood samples collected from a random sample of nearly 7,000 American adults by the National Center for Health Statistics and the U.S. Centers for Disease Control and Prevention during NHANES III, the Third National Health and Nutrition Examination Survey, conducted between 1988 and 1994.
From the available data, researchers cannot determine whether or not vitamin C might prevent initial infection by H. pylori, which often happens during childhood, Simon said. Neither do the data shed light on the mechanism for the association between vitamin C and bacterial infection they observe. "We cannot be certain if the infection lowers blood levels of vitamin C or if higher blood levels protect against infection. However, some studies using animal models suggest that adequate vitamin C intake may reduce infection with these bacteria," Simon said.
Even if it is infection itself that lowers blood levels of vitamin C, Simon said, it would still be prudent for people who test positive for H. pylori infection to increase their intake of vitamin C. "The bottom line is that higher levels of vitamin C may have the potential to prevent peptic ulcers and stomach cancer," he said.
In 1982, scientists discovered that H. pylori was responsible for causing peptic ulcers--painful sores in the lining of the stomach or the duodenum, the upper portion of the small intestine. (One in 10 Americans develops an ulcer at some time in their lives.)
More recently, researchers discovered that H. pylori is also associated with stomach cancer, a particularly deadly form of cancer.
For the current analysis, researchers used data collected during the first phase of NHANES III, which was conducted from October 1988 through October of 1991. The survey included participants between 2 months and 90 years of age. Researchers tested stored blood samples for H. pylori infection.
Samples of nearly one-third (32 percent) of the 6,746 participants tested positive for antibodies to H. pylori, indicating that their immune systems had previously mounted an attack against the bacteria. More than half of those who tested positive showed evidence of infection by the particularly toxic strain of the bacteria.
In addition to testing for H. pylori infection, the researchers analyzed vitamin C, or ascorbic acid, levels in the blood of these participants. After accounting for age, ethnicity, weight and other factors, they found that white participants with the highest blood levels of vitamin C had a 25 percent lower prevalence of infection.
Testing is now widely available for H. pylori infection and is often performed when stomach or duodenal ulcers are suspected or have been diagnosed. Simon encourages those who test positive--as well as all Americans--to increase their consumption of vitamin C-rich foods because they may help prevent infection with H. pylori or mitigate the effects of infection with the bacteria. "Current public health recommendations for Americans are to eat five or more servings of fresh fruits and vegetables a day to help prevent heart disease, cancer and other chronic diseases and recent data suggest that we're not doing very well in achieving that goal."
Additional authors include statistician Esther S. Hudes, PhD, MPH, of the UCSF Department of Epidemiology and Biostatistics and Guillermo I. Perez-Perez, DSc, of the New York University School of Medicine.
This research was supported by a donation from Roche Vitamins, Inc. and a grant from the National Heart, Lung, and Blood Institute.
None of the researchers involved in this study have financial interests in Roche Vitamins, Inc. or in Roche pharmaceuticals.