Follow-up of Linxian Nutrition Intervention Trial

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godsilove

Follow-up of Linxian Nutrition Intervention Trial

Post Number:#1  Post by godsilove » Sun Mar 29, 2009 11:56 am

Abstract wrote:Background
The General Population Nutrition Intervention Trial was a randomized primary esophageal and gastric cancer prevention trial conducted from 1985 to 1991, in which 29 584 adult participants in Linxian, China, were given daily vitamin and mineral supplements. Treatment with "factor D," a combination of 50 mug selenium, 30 mg vitamin E, and 15 mg beta-carotene, led to decreased mortality from all causes, cancer overall, and gastric cancer. Here, we present 10-year follow-up after the end of active intervention.

Methods
Participants were assessed by periodic data collection, monthly visits by village health workers, and quarterly review of the Linxian Cancer Registry. Hazard ratios (HRs) and 95% confidence intervals (CIs) for the cumulative effects of four vitamin and mineral supplementation regimens were calculated using adjusted proportional hazards models.

Results
Through May 31, 2001, 276 participants were lost to follow-up; 9727 died, including 3242 from cancer (1515 from esophageal cancer and 1199 from gastric cancer). Participants who received factor D had lower overall mortality (HR = 0.95, 95% CI = 0.91 to 0.99; P = .009; reduction in cumulative mortality from 33.62% to 32.19%) and gastric cancer mortality (HR = 0.89, 95% CI = 0.79 to 1.00; P = .043; reduction in cumulative gastric cancer mortality from 4.28% to 3.84%) than subjects who did not receive factor D. Reductions were mostly attributable to benefits to subjects younger than 55 years. Esophageal cancer deaths between those who did and did not receive factor D were not different overall; however, decreased 17% among participants younger than 55 (HR = 0.83, 95% CI = 0.71 to 0.98; P = .025) but increased 14% among those aged 55 years or older (HR = 1.14, 95% CI = 1.00 to 1.30; P = .47). Vitamin A and zinc supplementation was associated with increased total and stroke mortality; vitamin C and molybdenum supplementation, with decreased stroke mortality.

Conclusion
The beneficial effects of selenium, vitamin E, and beta-carotene on mortality were still evident up to 10 years after the cessation of supplementation and were consistently greater in younger participants. Late effects of other supplementation regimens were also observed.


Editors' note wrote:CONTEXT AND CAVEATS
Prior knowledge

The undernourished population of Linxian, China, has high rates of cancer of the esophagus and gastric cardia. In the General Population Nutrition Intervention Trial of 1985–1991, 29 584 Linxian villagers aged 40–69 years were given daily supplements of one or more of four vitamin and mineral combinations. "Factor D," which contained selenium, vitamin E, and beta-carotene, was associated with reduced mortality overall, from cancer, and from gastric cancer.

Study design

For 15-year follow-up, villagers were interviewed monthly concerning their health and registered cancer deaths were reviewed to look for sustained and delayed effects of the vitamin supplements. Hazard ratios for death by cancer, stroke and other causes were calculated for the four supplement combinations.

Contribution

Ten years after the end of the trial, participants who took factor D still had a 5% reduction in total mortality and 11% reduction in gastric cancer; these effects were concentrated among participants younger than 55 years. Esophageal cancer decreased 17% in participants younger than 55 years, but increased 14% in those older than 55 years.

Implications

Sustained benefits were associated with a combination of selenium, vitamin E, and beta-carotene supplementation. More subtle long-term effects were also observed for other vitamin supplements.

Limitations

It is not known which items in the supplement combination are responsible for the combined effect. Because the study was preformed in a nutritionally deprived population with high rates of esophageal and gastric cancer, the findings might not be applicable to other populations. It is possible that the findings could be biased by a general improvement in nutrition among the participants over the postintervention period.


http://jnci.oxfordjournals.org/cgi/cont ... t/djp037v1

Just for reference, these were the dosages used:
Vitamin C: 120 mg
Retinol: 5000 IU
Zinc: 22.5 mg
Riboflavin: 3.2 mg
Niacin: 40 mg
Molybdenum: 30 µg
Selenium: 50 µg
Alpha-tocopherol: 30 mg
Beta-carotene: 15 mg

I'm not sure what kinds of conclusions can be drawn from this follow-up study, since there are many uncontrolled factors at play. Nonetheless, the finding that supplementation has higher benefits in those under the age of 55 is interesting, as the benefits in those over 55 were either small or non-existent.

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Re: Follow-up of Linxian Nutrition Intervention Trial

Post Number:#2  Post by ofonorow » Mon Mar 30, 2009 4:29 am

Thank you for posting this, the dosage amounts to a multivitamin. 120 mg of vitamin C is double the RDA, but still a small amount. And the dosage of vitamin E is also quite small (30 International Units of Vitamin E is about 20 mg alpha-tocopherol). We can argue that most in the western world would obtain these amounts from their diet. Can ew infer that a multi-vitamin, in the malnourished, can have significant health benefits? And with the prevalence of junk food in the western diet, it probably applies to a significant population in the west as well.

I also wonder what the life expectancy is of the study population. Maybe 55 is exceptionally old age in this part of China?
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