Background: Knowledge on proper nutrition favours the creation of pro-healthy nutritional behaviours of people. Studies related to the nutritional knowledge of adults, diet quality and incidence of breast or lung cancers are limited.
Objective: Analysis of the relationship between the level of nutritional knowledge, diet quality and risk of breast cancer in women or lung cancer in men from the Warmia and Mazury region in Poland.
Material and methods: The study was carried out in 202 subjects aged 23-80 years, including 107 women (17 cases of breast cancer) and 95 men (54 cases of lung cancer) from the Warmia and Mazury region in Poland. Nutritional knowledge was evaluated with the Questionnaire of Eating Behaviours (QEB), including 25 statements. Based on the frequency of the consumption of 16 food items, two diet quality indices were created: the pro-Healthy-Diet-Index-8 (pHDI-8) and the non-Healthy-Diet-Index-8 (nHDI-8). The values of pHDI-8 and nHDI-8 were calculated on the basis of the sum of the daily frequency of consumption of the selected food items and expressed as times/day. The Odds Ratio (OR) of both breast cancer or lung cancer in relation to the level of nutritional knowledge was calculated based on a logistic regression analysis.
Results: The incidence of breast or lung cancer in the bottom, middle and upper tertile of nutritional knowledge was 57.6%, 32.6% and 15.8%, respectively. As nutritional knowledge grew in the subsequent tertiles, pHDI-8 was on the increase (2.63 vs. 3.78 vs. 4.22 times/day) and n-HDI-8 was on the decrease (1.32 vs. 1.21 vs. 0.94 times/day). In the upper tertile of nutritional knowledge, the Odds Ratio for the incidence of breast or lung cancers varied from 0.06 (95% CI: 0.02; 0.17; p<0.05, with adjustment for cancer type and age) to 0.17 (95% CI: 0.04; 0.69; p<0.05, with adjustment for age and sex) when compared to the bottom tertile (OR=1.00). In the middle tertile of nutritional knowledge, the Odds Ratio of both cancers varied from 0.27 (95% CI: 0.12; 0.62, p<0.05, with adjustment for cancer type and age) to 0.35 (95% CI: 0.18; 0.71, p<0.05, variables without adjustment) when compared to the bottom tertile.
Conclusions: A higher level of nutritional knowledge was associated with the higher quality of a pro-healthy diet and lower risk of breast cancer in women or lung cancer in men. In contrast, a lower level of nutritional knowledge was associated with a lower diet quality and a higher risk of both types of cancers.