Nature assessment counts 5 billion people's annual B12 and selenium in aquatic invertebrate production

Of the numbers in the study, the aquaculture split is the one a reader can check with division. Invertebrates are about a third of farmed aquatic production by weight and supply more than half of nutrients such as iodine, vitamin B12, vitamin C and iron ^[6]. That puts their nutrient content per kilogram at least 1.5 times the average for farmed aquatic food, and at least twice that of the other two thirds of the tonnage ^[13]. The gap holds for those nutrients, in aquaculture, on those two shares. The phys.org account of the work does not set invertebrates against finfish nutrient by nutrient ^[18].

The 5-billion figure is built differently. It is the nutrient content of current global invertebrate production divided by what one person needs in a year ^[2]. It counts what is in the animals farmed and landed, not what reaches a plate, and it says nothing about whether that B12 lands in a diet short of it. The same arithmetic clears the annual needs of more than a billion people for iodine, zinc, copper and omega-3 fatty acids ^[3].

Model coverage is the second thing worth holding onto. Measurements came from hundreds of species, and the models then estimated nutrient content for more than 50,000 potentially edible ones ^[4]. Read "hundreds" as anywhere from 200 to 999 and the measured base is roughly 0.4 to 2 percent of the species that now carry a number ^[14]. The write-up reports no out-of-sample accuracy for those predictions ^[19].

What the study argues against is tonnage as the yardstick. Aquatic food systems are usually assessed on how much food they produce, not on the nutrients in it ^[11]. "For far too long, we have measured success of aquatic food systems in tons of production, rather than in the nutrients they deliver to people," said Jessica Zamborain-Mason, the lead author and an assistant professor of marine science at KAUST ^[9][12].

The processing finding needs care. A hundred grams of dried invertebrate tissue often has higher mineral concentrations than 100 grams of raw tissue ^[7]. Some of that difference is water that left during drying, so the same kilogram of live animal has not gained minerals ^[17].