Diet and nutrition research

A work-site nutrition intervention: its effects on the consumption of cancer-related nutrients

OBJECTIVES

In a work-site nutrition intervention targeting fat and fiber, we examined the intervention's effect on specific nutrients implicated in carcinogenesis, including trace metals, vitamins, and categories of fatty acids. The rationale was based on the association observed in a variety of epidemiologic studies between these nutrients and epithelial cancers.

METHODS

Data were taken from eight control companies and five intervention companies that fully implemented the Treatwell intervention. Analyses of variance were used preserving the study's nested design.

RESULTS

Significant intervention-related associations were observed for increased total vitamin A and carotene. Marginal intervention effects were observed for relative decreases in the percentage of calories from both saturated and monounsaturated fatty acids, a relatively smaller increase in the percentage of calories from polyunsaturated fatty acids, and an increase in the consumption of vitamin B6.

CONCLUSIONS

Results indicate a broader effect of the intervention than on fat and fiber only. Increased intake of carotene, the single most important of these other nutrients, is plausibly related to a variety of epithelial cancers.

Natural killer cell activity in a longitudinal dietary fat intervention trial

It has been hypothesized that dietary fat may affect natural killer (NK) cell activity, a factor of potential importance in early tumor surveillance. Fourteen men successfully completed an intervention trial designed to test the effect of dietary fat on NK activity in humans. Study subjects lowered their fat intake to an average of 22% of calories as fat and consumed two dietary supplements (of coconut and safflower oils), in a cross-over design. These supplements resulted in large changes in the ratio of polyunsaturated to saturated fatty acids (1.73 to 0.34, on average). Results of a general linear model in which we fitted covariates on exercise, body mass, intervention sequence, and various dietary predictors revealed a significant effect of decreased total dietary fat intake on increased NK activity at an E/T ratio of 100:1 (about 0.79% increase for each absolute percent of calories as fat, P = 0.04). Similar results were obtained at E/T ratios of 50:1 and 25:1. No other nutritional predictor was significantly associated with NK activity at any E/T ratio.