Do beliefs, knowledge, and perceived norms about diet and cancer predict dietary change?

Objectives: We hypothesized that belief in an association between diet and cancer, knowledge of dietary recommendations and food composition, and perceived norms would predict healthful dietary changes.

Methods: Data are from a population-based sample of Washington State residents (n = 607). Psychosocial constructs measured at baseline (1989/90) were used to predict changes in dietary practices, fat intake, fiber intake, and weight over 3 years.

Results: Adults who strongly believed in a diet-cancer connection decreased the percentage of energy consumed from fat by 1.20 percentage points and increased fiber intake by 0.69 g, compared with decreases of 0.21 percentage points and 0.57 g among those with no belief (P < .05). Adults with knowledge of the National Cancer Institute fat and fiber goals decreased their percentage of energy from fat by 1.70 points compared with an increase of 0.27 points among those with little knowledge (P < .05). Food composition knowledge and perceived pressure to eat a healthful diet were not significant predictors of changes in fat intake, fiber intake, or weight.

Conclusions: Interventions that increase the public's beliefs in diet and health associations and communicate diet recommendations can encourage healthful dietary change.