Increasing intake of vitamin C may be able to help prevent stomach cancer, suggest researchers in the US.
The team from the San Francisco VA Medical Center (SFVAMC) 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.
The study, the largest to look at the relationship between vitamin C levels and infection by H. pylori, used random blood samples from nearly 7,000 American adults collected for the Third National Health and Nutrition Examination Survey (NHANES 3).
Writing in the 1 August issue of the Journal of the American College of Nutrition, Dr Joel Simon and colleagues said they could not be sure whether or not vitamin C might prevent initial infection by H. pylori, which often happens during childhood. And the data did not help explain the association between vitamin C and bacterial infection.
"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, people who test positive for H. pylori infection would still do well to increase their intake of vitamin C, he added.
"The bottom line is that higher levels of vitamin C may have the potential to prevent peptic ulcers and stomach cancer," said Simon.
In 1982, scientists discovered that H. pylori was responsible for causing peptic ulcers found in the lining of the stomach or the duodenum and more recently, the bacteria has also been associated with stomach cancer, a particularly deadly form of cancer.
The researchers tested the blood samples, from people aged between 2 months and 90 years old, for H. pylori infection. Nearly one-third (32 per cent) 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.
The team also analysed 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 per cent lower prevalence of infection.
The findings give further weight to the importance of the five-a-day message. Fruit and vegetable intake has been linked in several studies to reduced risk of cancer and mortality, with vitamin C thought to have heart-protective effects too. It appears that the vitamin could also help prevent infection with H. pylori or reduce the effects of infection with the bacteria.