Estimation of the use of dietary supplements in the National Diet and Nutrition Survey: People Aged 65 Years and Over. An observed paradox and a recommendation

Abstract

Objective: To compare the evidence derived from blood biochemical status indices with the evidence from a questionnaire and from a 4-day weighed dietary record of micronutrient supplement use in the British National Diet and Nutrition Survey (NDNS) of People Aged 65 Years and Over; to resolve some apparent incompatibility between nutrient intake and status estimates, and to recommend an approach towards supplement recording that should improve accuracy. Design: The survey procedures described in the National Diet and Nutrition Survey Report (1998) included a health-and-lifestyle questionnaire, a 4-day weighed diet record, and fasting blood and urine sample for biochemical indices, including a wide range of micronutrients. Setting: Eighty randomly selected postcode sectors from mainland Britain during 1994±1995. Subjects: Of 2060 people interviewed, 1467 provided a blood sample and 1217 provided both a blood sample, and a complete 4-day diet record. About 20% were living in institutions such as nursing homes, and the remainder were living in private households. Results: After assigning the subjects to four categories by the use of dietary supplements (A, those not taking supplements (by questionnaire or by the 4-day record); B, those taking supplements (excluding prescribed ones) by questionnaire only; C, those taking supplements by 4-day record only; and D, those taking supplements by both questionnaire and 4-day record), these categories were then compared with respect to estimated total nutrient intakes and blood biochemical indices. Those in category B had estimated (4-day) nutrient intakes (from foods and supplements) that were indistinguishable from those in category A, but had biochemical indices that indicated signi®cantly higher dietary intakes of several vitamins. Conclusions and recommendation: The 4-day weighed intake record may not have identi®ed all of the subjects who were regularly taking micronutrient supplements in amounts suf®cient to improve their biochemical status. Because survey respondents may use supplements irregularly or change their usual patterns of supplement use during a period of intensive diet-recording, it is important to design a dietary instrument that will minimise this potential source of inaccuracy. We therefore recommend that population surveys in which an accurate estimate of micronutrient intakes is required, from supplements as well as from food, should record supplement use for a period longer than 4-days. It is likely that a better estimate of long-term intakes can be achieved by combining a 4-day weighed diet record with a structured recall or several weeks of diary records, which focus speci®cally on the use of supplements.

Serum vitamin B12 concentrations and atrophic gastritis in older New Zealanders

“…Around one-third of older Americans use vitamin B 12 containing supplements (Kaufman et al, 2002) compared with 15% in our study and somewhat less in the United Kingdom (Bates et al, 1998). Food fortification with vitamin B 12 is uncommon in New Zealand.…”

Micronutrients: highlights and research challenges from the 1994–5 National Diet and Nutrition Survey of people aged 65 years and over

“…Therefore, the differences cannot be ascribed to supplement use alone but insufficient information on supplements was collected in the survey to resolve this question. Further analyses of the complex questions surrounding supplement use are addressed elsewhere (Bates et al 1998a). Table 6 presents the mean biochemical index values from several earlier British population surveys Social Security, 1972, 1979;Gregory et al 1990Gregory et al , 1995 and those of the present survey (free-living sample only).…”

Association of Dietary Supplement Use with Specific Micronutrient Intakes among Middle-Aged American Men and Women: The INTERMAP Study

“…From 1994 to 2000, sales of supplements grew by 80% to an estimated $15.7 billion (3). Most studies on dietary supplements have focused on populations from specific geographic areas or used instruments with predetermined lists of supplements, thereby limiting scope of supplement intake assessment (4)(5)(6)(7)(8). National nutrition monitoring surveys, like the Continuing Survey of Food Intakes by Individuals have been criticized for placing little emphasis on consumer use of dietary supplements (9).…”