September 2011

Trends in Vitamin D Intake from Food Sources among Adults in the Minneapolis-St Paul, MN, Metropolitan Area, 1980-1982 through 2007-2009. Lisa J. Harnack, DrPH, RD; Lyn Steffen, PhD; Xia Zhou, MS; Russell V. Luepker, MD, MS

The purpose of this study was to examine the trend in vitamin D intake over a 25 year period. To the authors’ knowledge, no previous research has been implemented to observe vitamin D dietary intake trends. Data was collected from six different survey periods. The researchers used cluster sampling and randomly selected 40 household clusters to represent the Minneapolis-St Paul metropolitan area. In order to continue to properly represent the population, in the last two survey periods, 2000-2002 and 2007-2009, the researchers included 4 more random clusters to account for the population increase. In the 1980-1981, 1995-1997, 2000-2002, and 2007-2009 survey periods, all age-eligible adults in the households were asked to be a participant. During the 1981-1982, 1985-1987, and 1990-1992 survey periods, only one participant from each household was randomly chosen for the study.

Data was collected on the participants through both an in-home interview and a clinic visit. A 24-hour recall was used to obtain the dietary intake data through food and beverages from participants. Dietary supplement use was not observed in this study. Trained interviewers performed the dietary assessments using the multiple pass approach, which included the following four specific steps: 1) Collect the food and beverage intake from the participant 2) Check the list for accuracy and completion 3) Obtain details on portion sizes and extra items (such as condiments) 4) Recheck the accuracy of this detailed list. The measurement of vitamin D intake was calculated by using the most current version of NCC Food and Nutrient Database. Only the complete dietary recalls from participants 25 to 74 years of age was then analyzed through SAS software. Variables observed in the study included: BMI, sex, education level, and ethnicity. The researchers chose to structure the analyses by separating men and women’s vitamin D intake due to the differences in nutrient intake and daily nutrient requirements between the genders.

The results of this study revealed an overall decrease of vitamin D intake in both men and women. Men’s vitamin D intake decreased from 7.24 µg/day to 6.15 µg/day (-1.09 µg/day), and women’s intake decreased from 4.77 µg/day to 4.53 µg/day (-0.24 µg/day). These results remained generally the same over all ages, education levels, and BMI’s. Although the trend in vitamin D intake decreased over the time period of this study, there was an increase in intake over the 1990-1992 and the 1995-1997 survey periods.

The researchers recognized that a drawback of the 24-hour recall is the possibility of participants underreporting intakes. Although this could mean the vitamin D intake of the participants in this study could have been under calculated, the authors point out that if underreporting holds consistent, the decreasing trend would still remain. It was also acknowledged that the majority of the participants were white men and women who lived in the metropolitan area of Minneapolis-St Paul and therefore the study cannot be generalized to other populations. The authors also mentioned that increase in vitamin D intake over the 1990-1992 and the 1995-1997 survey periods could be due to a change in survey method from paper and pencil to the computer at that time.

Harnack, L. J., Steffen, L., Zhou, X., Luepker, R. V. (2011). Trends in Vitamin D Intake from Food Sources among Adults in the Minneapolis-St Paul, MN, Metropolitan Area, 1980-1982 through 2007-2009. Journal of the American Dietetic Association, 111 (9), 1329-1334.