2.2. Other questionnaires and supplements taken
All participants completed questionnaires which gave information about smoking habits, self-rated health, alcohol consumption, physical activity, education and the kind of salt used. With
regard to salt used, both the kind and the amount of salt were
examined at follow-up. Participants were asked open questions on
what salt brands they had in their kitchen. Afterwards, the answers
were divided into 3 groups: always use iodized salt, never use
iodized salt, and sometimes use iodized salt. The amount of
household salt used was asked about in two questions: low, moderate or high addition when cooking, and no, low, moderate or high
addition at the table. These answers were combined, with equal
weight, andfinally the participants were divided into 5 groups
according to the amount of household salt used.
Participants were asked to bring with them all dietary supplements taken. In C1a, brand names, doses and frequency of usage
were recorded. In C1b, the daily intake of iodine from supplements
was recorded.