Title:
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Nutrition knowledge and dietary behaviour.
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There is now unequivocal evidence that dietary behaviour is related to illness and risk
of chronic diseases such as cardiovascular disease and cancer. Attempts to improve
the nation's diet are based on providing information, assuming that given more
information, the public will choose healthier diets. Many studies indicate, however,
that nutrition knowledge has little association with dietary behaviour; but a review of
the literature reveals that nutrition knowledge has been inadequately measured. In
addition, dietary behaviour has been assessed in terms of food intake and not in
relation to changes in, or readiness to change, food intake. Following the Introduction,
this research begins, in Chapter 2, by reviewing the literature measuring nutrition
knowledge. It is found that while many studies measure knowledge, typically the
measure forms only part of the study which assesses either a particular subpopulation
or a particular aspect of nutrition. In consequence, questionnaires are designed for a
one-off and specific purpose and little attention is paid to the psychometric properties
of the instrument. Dietary behaviour is measured with one of the well-established
methods of assessing intake, the problems of which are acknowledged in the literature.
Chapter 3 describes these methods with their shortcomings and use in psychological
research. In response to these reviews, a comprehensive nutrition knowledge
questionnaire was developed (in 1994) and intake was conceptualised in terms of
dietary change, in keeping with psychologists' role in nutrition. Following the
development and pilot study of this questionnaire (Chapter 4), its validity and reliability
were assessed further in Chapter 5, with positive results. Significant differences were
found between criterion groups (dietetic and computer science students), providing
evidence of construct validity. Internal consistency correlations ranged from 0.50 to
0.92 and test-retest reliability correlations ranged from 0.80 to 0.98. This measure was
then used (Chapter 6) to assess the level of nutrition knowledge among a large representative sample of British adults in a postal survey (in 1995). Nutrition
knowledge was found to be poor concerning the dietary recommendations for meat,
starchy foods, fruit and vegetables; the different types of fat (saturated, poly- and
monounsaturated); and associations between diet and diseases, such as fruit and
vegetables, heart disease and cancer. Both stages of change (using Prochaska and
DiClemente's model) and consumption of fat, fruit and vegetables (to test the stages'
validity) were also assessed as measures of dietary behaviour. Most respondents
replied that they had been limiting their fat intake for more than 6 months, but not been
thinking of increasing their fruit and vegetable intake. Multivariate analyses showed
that being female, having more educational qualifications and being in a higher socioeconomic
class were predictive of knowing more about nutrition and having a healthier
dietary behaviour. Relationships between nutrition knowledge, stages of change and
dietary intake were examined in Chapter 7 and significant associations identified. In
contrast to this cross-sectional research, the final study in Chapter 8 was longitudinal
and examined changes in nutrition knowledge and dietary behaviour over a one-year
period (from 1993 to 1994). This study aimed to provide information on the extent to
which healthier changes in dietary intake are related to increases in nutrition
knowledge. While changes occurred in dietary intake (fat and sugar intake decreased
significantly, the increases in fruit and vegetable consumption were insignificant),
knowledge scores remained unchanged. The final chapter discusses the key findings of
this research, its implications and areas worthy of future investigation. For example,
the results from this research suggest that knowledge is an important factor in food
choice and should not be discounted as a part of health promotion. It may also be
useful to integrate the construct of knowledge into the social cognition models of
dietary choice or indeed to develop a new model to include knowledge along with
motivational constructs from the social cognition models.
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