Assessing the potential of milk iodine intake to mitigate iodine deficiency in pregnant women of the United States via supplementation of Ascophyllum nodosum meal to dairy cows: A sensitivity analysis

The brown seaweed Ascophyllum nodosum is known to bioaccumulate iodine (I). Previous research showed a linear relationship between A. nodosum meal (ASCO) intake and milk I concentration in dairy cows. Thus, improving milk I concentration by supplementation of ASCO to dairy cows may be a compelling strategy to naturally boost I intake in humans. A sensitivity analysis was conducted to gain insights regarding how different milk I intakes affect the I status of pregnant women relative to the United States Institute of Medicine (US IOM) recommended dietary allowance (RDA; 220 µg/d) and the World Health Organization (WHO) recommended nutrient intake (RNI; 250 µg/d) for I. Four studies in which dairy cows received various amounts of ASCO generated the milk I data set used in the sensitivity analysis. The annual per capita consumption of 2% reduced-fat milk in the United States, converted to daily intake (i.e., 0.26 cup; 1 cup = 236.6 mL), was used as the actual milk intake in the simulations. Five additional milk intake scenarios (2, 3, 4, and 5 times the actual per capita milk consumption and the 3 cups-equivalent recommended by the 2015-2020 Dietary Guidelines for American were also included in the sensitivity analysis with varying milk I concentrations (180, 765, and 483 µg/L). The 180, 765, and 483 µg/L values are milk I concentrations derived from cows not receiving ASCO or fed various amounts of ASCO in the diet or a single level (113 g/d) during the grazing season, respectively. With the actual United States milk per capita consumption of 0.26 cup/d and milk I concentrations of 180, 765, and 483 µg/L, 5.09, 21.7, and 13.6% of the RDA for I for pregnant women were met based on the US IOM, respectively. Similarly, 4.48, 19, and 12% of the RNI for I advised by the WHO was achieved with intake of 0.26 cup/d of milk containing I concentrations of 180, 765, and 483 µg/L, respectively. When 3 cups/d was included in the simulations, 58.2, 247, and 156% (US IOM), and 51.2, 217, and 137% (WHO) of the RDA or RNI for I required by gestating women was satisfied with milk I concentrations of 180, 765, and 483 µg/L, respectively. A regression analysis between I intake and milk I concentration revealed that 103 g/d of ASCO in the diet of dairy cows reached the maximum 500 µg/L threshold of I in milk recommended by the European Food Society Authority. Overall, milk from dairy cows fed ASCO can prevent I deficiency in pregnant women, but the amount of ASCO fed to cows needs to be fine-tuned to avoid excess I in milk. Further research is required to better understand the interactions between goitrogenic compounds from forages and concentrates and milk I concentration in cows fed ASCO. Research to evaluate the concentration of I in retail organic milk should be also conducted because of the high prevalence of ASCO fed in organic dairies in the United States.