biologically plausibility, specificity, time frame, and doseresponse effects [23].
9. The advice of a statistical expert (preferably in the nutrition
area) is recommended when selecting a design and also calculating sample size.
10. The term “apparently healthy volunteers” is frequently found
in studies which aim to modify risk factors. However, these
subjects cannot be considered suitable as a representative sample because some risk factors of the disease being studied can
modify metabolism. Therefore a certain number of them (the
number depending on the study) should be a prerequisite.
Studies with subjects with differing vitamin A nutritional status
(deficient and within the normal range) are not comparable
when studying the effects of provitamin A carotenoids.
11. Sample size is typically calculated with data from the main
dependent variable (outcome) and therefore the following
data are needed: mean value and standard deviation, the percentage of variation pursued with the intervention (ideally, to
obtain not only statistical significance but also biological/clinical relevance) and the percentage of statistical power assumed.
If sample size is not calculated, it would happen that the results
(observed effects) obtained do not have enough statistical
power to be extrapolated to similar populations.
12. Habitual intake (i.e., accurate individual weight, estimation of
foods consumed); past or habitual ingestion (i.e., 24-h recall,
dietary history, food frequency consumption). The most frequently used methods are the 24 h dietary recall (3 days) and
the food frequency questionnaire.
Acknowledgments
Spanish Carotenoid Network (CaRed) funded by the Spanish
MINECO (Ministry of Economy, Industry and Competitiveness)
grants BIO2015-71703-REDT and BIO2017-90877-REDT, the
European Carotenoid Network (EuroCaroten) funded by the
European Commission COST Action CA15136 and Instituto de
Salud Carlos III-ERDF grant PI16/01991.
References
1. Reglament EU 1924/2006 Of the European
Parliament and of the council of 20 December
2006 on nutrition and health claims made on
foods.
https://eur-lex.europa.eu/legal-con
tent/en/ALL/?uri¼CELEX%
3A32006R1924.
2. Commission regulation (EC). No 353/2008
of 18 April 2008 establishing implementing
rules for applications for authorisation of
health claims as provided for in Article 15 of
Regulation (EC) No 1924/2006 of the
European Parliament and of the Council
Intervention Studies
371
9. The advice of a statistical expert (preferably in the nutrition
area) is recommended when selecting a design and also calculating sample size.
10. The term “apparently healthy volunteers” is frequently found
in studies which aim to modify risk factors. However, these
subjects cannot be considered suitable as a representative sample because some risk factors of the disease being studied can
modify metabolism. Therefore a certain number of them (the
number depending on the study) should be a prerequisite.
Studies with subjects with differing vitamin A nutritional status
(deficient and within the normal range) are not comparable
when studying the effects of provitamin A carotenoids.
11. Sample size is typically calculated with data from the main
dependent variable (outcome) and therefore the following
data are needed: mean value and standard deviation, the percentage of variation pursued with the intervention (ideally, to
obtain not only statistical significance but also biological/clinical relevance) and the percentage of statistical power assumed.
If sample size is not calculated, it would happen that the results
(observed effects) obtained do not have enough statistical
power to be extrapolated to similar populations.
12. Habitual intake (i.e., accurate individual weight, estimation of
foods consumed); past or habitual ingestion (i.e., 24-h recall,
dietary history, food frequency consumption). The most frequently used methods are the 24 h dietary recall (3 days) and
the food frequency questionnaire.
Acknowledgments
Spanish Carotenoid Network (CaRed) funded by the Spanish
MINECO (Ministry of Economy, Industry and Competitiveness)
grants BIO2015-71703-REDT and BIO2017-90877-REDT, the
European Carotenoid Network (EuroCaroten) funded by the
European Commission COST Action CA15136 and Instituto de
Salud Carlos III-ERDF grant PI16/01991.
References
1. Reglament EU 1924/2006 Of the European
Parliament and of the council of 20 December
2006 on nutrition and health claims made on
foods.
https://eur-lex.europa.eu/legal-con
tent/en/ALL/?uri¼CELEX%
3A32006R1924.
2. Commission regulation (EC). No 353/2008
of 18 April 2008 establishing implementing
rules for applications for authorisation of
health claims as provided for in Article 15 of
Regulation (EC) No 1924/2006 of the
European Parliament and of the Council
Intervention Studies
371