By Kristina Fiore, Staff Writer, MedPage Today
High vitamin E intake seemed to have a protective effect against liver cancer, Chinese researchers found.
Among people ages 40-70, higher dietary intakes of the vitamin were associated with a significantly lower cancer risk (P=0.01 for trend), and taking vitamin E supplements almost cut the risk in half (HR 0.52, 95% CI 0.30 to 0.90), Xiao-Ou Shu, MD, PhD, of the Vanderbilt Epidemiology Center in Nashville, and colleagues reported online in the Journal of the National Cancer Institute.
If confirmed, the findings “could open a new venue for prevention of liver cancer,” the researchers wrote.
The link between dietary factors, vitamin supplementation, and liver cancer hasn’t been clear, so Shu and colleagues assessed data on 132,837 Chinese patients from the Shanghai Women’s Health Study and the Shanghai Men’s Health Study.
They evaluated vitamin intake from diet and supplements via food frequency questionnaires.
During follow-up, 267 patients developed liver cancer over an average of 10.9 years for women and 5.5 years for men.
Shu and colleagues found that greater levels of dietary vitamin E intake were associated with lower risk of liver cancer. Patients in the two highest quartiles of intake had significantly lower risk (HR 0.66, 95% CI 0.46 to 0.94 and HR 0.60, 95% CI 0.40 to 0.89, respectively, P=0.01 for trend).
Using vitamin E supplements nearly halved the risk of liver cancer compared with not taking these supplements (HR 0.52, 95% CI 0.30 to 0.90).
In further analyses, however, the association appeared to be stronger among women, but the researchers noted that it was consistent among patients with and without liver disease, or a family history of liver cancer.
Some explanations for the vitamin’s potential protective effects could be its ability to prevent DNA damage, enhance DNA repair, prevent lipid peroxidation, inhibit the activation of carcinogens, or boost the immune system.
When looking at other vitamins, the researchers found that vitamin C appeared to increase the risk of liver cancer (HR 1.96, 95% CI 1.29 to 2.98), as did multivitamins among men (HR 1.84, 95% CI 1.13 to 2.98).
Yet use of both of these supplements was associated with an increased risk among patients with liver disease and a family history of liver cancer (P=0.01 and P=0.06, respectively).
That could lead to a case of reverse causality, the researchers noted, as patients with liver disease or a history of liver cancer may be more likely to take supplements in an attempt to lessen disease risk.
Shu and colleagues also noted that intake of vitamin C and other vitamins from dietary sources wasn’t related to liver cancer risk. Nor was there any association between the use of vitamin B or calcium supplements and risk of liver cancer.
The study was limited by a relatively short follow-up time, its reliance on a food frequency questionnaire to assess dietary intake, lack of information on specific doses of vitamins, and an inability to rule out unmeasured confounders such as hepatitis B and C and other risk factors.
Still, the researchers said vitamin E may play an important role in liver cancer prevention for Chinese patients.
The study was supported by the National Institutes of Health and the Key State Project Specialized for Infectious Diseases of China.
The researchers reported no conflicts of interest.
Primary source: Journal of the National Cancer Institute
Source reference:
Zhang W, et al “Vitamin intake and liver cancer risk: A report from two cohort studies in China” J Natl Cancer Inst 2012; DOI: 10.1093/jnci/djs277.
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Kristina Fiore
Staff Writer
Kristina Fiore joined MedPage Today after earning a degree in science, health, and environmental reporting from NYU. She's had bylines in newspapers and trade and consumer magazines including Newsday, ABC News, New Jersey Monthly, and Earth Magazine. At MedPage Today, she reports with a focus on diabetes, nutrition, and addiction medicine.
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