D-Vitaal Amendment 1.0, version: 1.0, date: 2013-12-17: This amendment contained changes to the study protocol that do not affect the safety of the participants or the investigational product. Main changes: 1. Addition of alternative recruitment strategies, due to disappointing inclusion results; 2. Two blood draws instead of three, to reduce the burden on respondents. This has no scientific consequences. 3. We moved questions from the interviews (baseline, 6 and 12 months) to a pre-fillable questionnaire to reduce interview time. 4. Addition of a short questionnaire on physical functioning to the screening, as the original questionnaire performs less well as a screening tool in this study population. 5. As an additional safeguard for respondent safety, we added a sentence to the informed consent form that the respondent gives permission for his/her primary care physician to be informed if any health problems come to light during the study.