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In this paper, we reviewed the role of dairy products in dietary zinc absorption. Dairy products can have a reasonable contribution for dietary zinc intake in Western diets, where dairy consumption is high. However, the co-ingestion of dairy products can also improve zinc absorption from other food products. Such improvements have been observed when dairy products (e.g., milk or yoghurt) were ingested together with food such as rice, tortillas or bread products, all of which are considered to be high-phytate foods with low inherent zinc absorption. For foods low in phytate, the co-ingestion of dairy products did not improve zinc absorption. Improved zinc absorption of zinc from high-phytate foods following co-ingestion with dairy products may be related to the beneficial effects of the citrate and phosphopeptides present in dairy products. Considering that the main dietary zinc sources in areas in the world where zinc deficiency is most prevalent are typically high in phytate, the inclusion of dairy products in meals may be a viable dietary strategy to improve zinc absorption.

Different metabolic pathways of supplemental and fortification Fe, or inhibition of Zn absorption by Fe, may explain adverse effects of supplemental Fe in Fe-sufficient infants. We determined whether the mode of oral Fe administration or the amount habitually consumed affects Fe absorption and systemic Fe utilisation in infants, and assessed the effects of these interventions on Zn absorption, Fe and Zn status, and growth. Fe-sufficient 6-month-old infants (n 72) were randomly assigned to receive 6·6 mg Fe/d from a high-Fe formula, 1·3 mg Fe/d from a low-Fe formula or 6·6 mg Fe/d from Fe drops and a formula with no added Fe for 45 d. Fractional Fe absorption, Fe utilisation and fractional Zn absorption were measured with oral (57Fe and 67Zn) and intravenous (58Fe and 70Zn) isotopes. Fe and Zn status, infection and growth were measured. At 45 d, Hb was 6·3 g/l higher in the high-Fe formula group compared with the Fe drops group, whereas serum ferritin was 34 and 35 % higher, respectively, and serum transferrin 0·1 g/l lower in the high-Fe formula and Fe drops groups compared with the low-Fe formula group (all P<0·05). No intervention effects were observed on Fe absorption, Fe utilisation, Zn absorption, other Fe status indices, plasma Zn or growth. We concluded that neither supplemental or fortification Fe nor the amount of Fe habitually consumed altered Fe absorption, Fe utilisation, Zn absorption, Zn status or growth in Fe-sufficient infants. Consumption of low-Fe formula as the only source of Fe was insufficient to maintain Fe stores.

Background: Biofortification of staple food crops is a promising strategy to combat zinc deficiency, and it is of particular interest for rice and crops that are not consumed as flours and therefore not suitable for postharvest fortification. Because zinc absorption is decreased by phytic acid (PA) and perhaps other dietary components, it is important to measure the absorption of zinc from a biofortified crop before determining its efficacy. Objective: In this study, we compared the zinc absorption from zinc-biofortified rice (hydroponically enriched with 70Zn) with that from a control rice of the same variety fortified with 70ZnSO4 at point of use to reach the same total zinc content of 1.1 mg/meal. Both rice meals had a PA:Zn molar ratio of 12. Methods: Fractional absorption of zinc (FAZ) was measured with the use of the double-isotope tracer ratio method in 16 apparently healthy adults [18-45 y old; BMI (in kg/m2) 19-25] who consumed 2 single meals at 4-wk intervals in random order in a crossover design. Results: The FAZ from the biofortified rice (mean ± SD: 25.1 ± 8.7%) did not differ significantly from that of the point-of-use fortified rice (mean ± SD: 20.8 ± 7.1%) (P = 0.08). Conclusions: These results suggest that the native zinc accumulated in the biofortified rice was readily released from the rice matrix and that its absorption by adults was influenced by PA and other food components in a similar way to the inorganic zinc compound added to the rice at point of use. Moreover, rice biofortification is likely to be as good as postharvest zinc fortification as an intervention strategy to combat zinc deficiency. This trial was registered at clinicaltrials. gov as NCT01633450.

We examined the effects of feeding several types of insoluble dietary fiber (100 g/kg diet), including cellulose (control), wheat bran (demineralized), sugar-beet fiber and corn husk fiber, on zinc absorption in rats. Zinc absorption was higher after intake of a zinc-deficient diet (0.229 mmol/kg diet) containing corn husk fiber than that after intake of a cellulose-containing diet for 3 wk. Ingestion of wheat bran or sugar-beet fiber did not influence zinc absorption. We compared the effects of cellulose and demineralized- and washed-corn husk fiber at graded levels in the diets (1, 2 and 3 parts to 10 basal diet). Zinc absorption in rats fed the diet with the lowest level of corn fiber was higher than that in rats fed a diet with the same level of cellulose or a fiber-free diet (control). In rats fed the diets with higher levels of corn fiber, the zinc absorption was lower than that in rats fed either the diet with the lowest level of cellulose or the fiber-free diet in the period day 9–12, however, reduced absorption that occurred upon intake of the high-fiber diet recovered in the period day 18–21. Cecal fermentation and the bulking action of corn husk fiber may not be responsible for the zinc absorption-promoting effect of the dietary fiber. In conclusion, corn husk fiber is effective in increasing zinc absorption when ingested at low levels, but absorption is inhibited upon intake at higher levels in rats.