Written by Susan Sweeny Johnson, PhD. Participants that consumed selenium, alpha-tocopherol, and beta carotene showed a 5% reduction in total mortality and an 11% reduction in gastric cancer mortality.
Linxian, China is known for its unusually high incidence of esophageal cancer (1). The community, when first identified in the 1980’s, also showed nutritional deficiencies, suggesting a possible link between cancer and nutrition (2). The initial Linxian General Population Nutrition Intervention Trial (NIT), a large-scale, randomized, double-blind trial, took place between March 1, 1986, and May 31, 1991. It tested the efficacy of four combinations of vitamins and minerals in reducing esophageal and gastric cardia cancer (cancer located at the opening of the esophagus into the stomach) (3-5). The results of the initial study showed that supplementation with the “antioxidant” combination of selenium, vitamin E, and beta carotene significantly reduced total mortality, total cancer mortality, and gastric cancer mortality (4).
In a new study, researchers followed up the participants in the NIT study for 10 more years to determine if the five years of vitamin supplementation had any lasting long-term effects. The initial study included 29,584 adults, aged 40-69, of which 9727 died over the course of the 15 years, 3242 from cancer of which 2388 were esophageal type. No vitamin intervention was provided during the 10 year follow-up, however, nutrition in this community in general improved over the follow-up period (6).
In the initial study, participants were placed into four random groups, each receiving a mixture of daily supplements:
- Group A: retinol (5000 IU, as retinol palmitate), zinc (22.5 mg, as zinc oxide)
- Group B: riboflavin (3.2 mg), niacin (40 mg)
- Group C: ascorbic acid (120 mg), molybdenum (30 μg, as molybdenum yeast complex)
- Group D: selenium (50 μ g, as selenium yeast), alpha-tocopherol (30 mg), and beta carotene (15 mg)
The preventative effect of Group D supplementation over the initial 5 years lasted for an additional 10 years such that 10 years after completion of the initial trial, those from Group D still showed a 5% reduction in total mortality* and an 11% reduction in gastric cancer mortality. Over the course of the entire 15 years, one in 70 people from Group D was spared death from all causes, and one in 227 was spared death from gastric cancer over the entire 15-year period. Further statistical analysis of the follow up study showed that the protective effect of Group D supplements was age-dependent, particularly for cancer and esophageal cancer.**
In addition, Vitamin A and zinc supplementation was associated with increased total and stroke mortality; vitamin C and molybdenum supplementation, with decreased stroke mortality.
The results of this follow up study were compared to other published supplementation studies by the authors. In particular, the Linxian study was conducted in a nutritionally deficient population compared to the other well-nourished populations, which may yield different results. Also, supplementation in already diseased populations may have adverse effects on mortality compared to pre-disease populations, evidenced by the decreased cancer mortality in the younger Linxian population.
More large, long-term studies of vitamin supplementation should be conducted in clearly defined populations to clarify the potential benefits.
*The results of the follow-up study showed that participants from Group D still had a statistically significant reduction in total mortality from 33.6% to 32.3% (HR = 0.95, 95% CI = 0.91 to 0.99; P = .009).
**There was no overall association between Group D and esophageal cancer mortality for all subjects (HR = 1.01, 95% CI = .91 to 1.11; P = .905); however, in subjects younger than 55 years, Group D esophageal cancer mortality decreased (HR = 0.83, 95% CI = 0.71 to 0.98; P = .025), whereas in individuals aged 55 years or older, it increased (HR = 1.14, 95% CI = 1.00 to 1.30; P = .047).
Source: Qiao, You-Lin, et al. “Total and cancer mortality after supplementation with vitamins and minerals: follow-up of the Linxian General Population Nutrition Intervention Trial.” Journal of the National Cancer Institute (2009).
© 2017 Oxford University Press
Posted May 11, 2009.
References:
- Li JY , Liu BQ , Li GY , Chen ZJ , Sun XI , Rong SD . Atlas of cancer mortality in the People’s Republic of China. An aid for cancer control and research . Int J Epidemiol . 1981 ; 10 ( 2 ): 127 – 133.
- Yang CS , Sun Y , Yang QU , et al . Vitamin A and other deficiencies in Linxian, a high esophageal cancer incidence area in northern China . J Natl Cancer Inst . 1984 ; 73 ( 6 ): 1449 – 1153.
- Li B , Taylor PR , Li JY , et al . Linxian nutrition intervention trials. Design, methods, participant characteristics, and compliance . Ann Epidemiol . 1993;3 ( 6 ): 577 – 585.
- Blot WJ , Li JY , Taylor PR , et al . Nutrition intervention trials in Linxian, China: supplementation with specifi c vitamin/mineral combinations, cancer incidence, and disease-specific mortality in the general population . J Natl Cancer Inst . 1993;85 (18): 1483 – 1492.
- Tran GD , Sun XD , Abnet CC , et al . Prospective study of risk factors for esophageal and gastric cancers in the Linxian general population trial cohort in China . Int J Cancer. 2005 ; 113 ( 3 ): 456 – 463.
- Zou XN , Taylor PR , Mark SD , et al . Seasonal variation of food consumption and selected nutrient intake in Linxian, a high risk area for esophageal cancer in China . Int J Vitam Nutr Res. 2002 ; 72 ( 6 ): 375 – 382.
