Considerable Variation in Intake of Live Food Microbes in Dutch Adults

Background: Diet is an important source of microbial exposure, potentially protecting against allergic disease. However, changes in dietary habits may have altered the intake of live food microbes. Aim: We quantitatively assessed the intake of live food microbes in Dutch adults and compared these estimates with those obtained from duplicate portions. Methods: In 34 Dutch adults (20–70 years), we estimated the food-microbial content of their diet for three dominant groups: total contaminating bacteria (TCB), lactic acid bacteria (LAB), and yeasts/moulds (YM). A food-microbial load database was compiled with minimum, best, and maximum estimated levels of these food microbes (in colony forming units (CFU)/g food). To estimate microbial intake, the amounts of food consumed (in grams) based on three 24 h dietary recalls were multiplied by the corresponding microbial content/gram of food. For validation, one 24 h duplicate portion per person was analysed for microbial content by conventional plate counting. We applied a one-way ANOVA to assess interindividual variation in microbial exposure, a two-way ANOVA to assess intraindividual variation in microbial intake, the so-called MOM2 analysis and regression analysis to identify foods contributing most to the level and variation of microbial intake, and Bland–Altman plots to assess the agreement between microbial intake estimated from 24-HDR and microbial counts determined in duplicate food samples. Results: The estimated total microbial exposure varied considerably across individuals (p < 0.05), ranging from 5.7 to 11.6 log (5.4 × 105–4.4 × 1011) CFU/day. The exposure to TCB ranged from 2.5 to 11.4 log (3.0 × 102–2.5 × 1011) CFU/day, LAB from 3.4 to 11.5 log (2.3 × 103–3.0 × 1011), and YM from 2.6 to 9.6 log (3.6 × 102–4.3 × 109) CFU/day. Also, intraindividual exposure differed significantly (p < 0.05). Estimates were confirmed by microbial analysis of 24 h duplicate foods, revealing total microbial levels of 6.4–11.0 log (2.8 × 106–9.4 × 1010) CFU/day. On average, the best estimated total microbial exposure was 0.6 log CFU higher than values determined by plate counting of the duplicate foods. Foods responsible for the observed variation were identified. Conclusions: The intake of live food microbes among Dutch adults varied considerably, ranging from nearly a million to more than 100 billion cells per day. Further validation of the food-microbial database is required.