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“In Bangladesh, China, India and elsewhere in Asia, many children subsist on a few bowls of rice a day and almost nothing else. For them, a daily supply of Golden Rice could now bring the gift of life and sight,” states Regis in his book, Golden Rice, which is published this month.

This made me think of one of the scariest papers I’ve seen: https://journals.plos.org/plosone/article?id=10.1371/journal...

> In summary, we have shown that elevated [CO2] has the potential to cause damage to human nutrition and health via leaf vegetables and feed crops, not only grain crops. The greatest threat comes from the more severe drop in N and Zn in polished rice grains, and the lower content of Ca in feed crops and leaf vegetables. In addition, a reduction in the intake of minor minerals such as Mn and S that we currently obtain in sufficient amounts might cause unanticipated health risks. Flow analysis and transcriptomics suggested that lower absorption and/or translocation of elements is a key factor underlying the lower elemental content in rice grains, and the lower expression of related transporter genes under elevated [CO2] might also play a role.

> Our results suggest that increasing [CO2] levels might have more serious consequences than previous influential predictions that were based on brown rice [1]. In particular, the drop in N in polished rice would negatively affect the nutritional status of the 153 million individuals of Bangladesh, who depend largely on rice for their protein intake and are already estimated to have an individual daily protein intake below the standard of “hungry” as defined by FAO/WHO (S1 Table).

> Our results showed that elevated [CO2] might also impair human nutrition via leaf vegetables and feed crops that we either eat directly or utilize as animal feed, not only via grain crops. As compared to the grain, elemental content declined markedly in the plant body of rice. For example, Mg and Mn content in the plant body decreased 2- and 4-fold, respectively (Fig 1C). These data, and the difference between polished (endosperm) and brown (endosperm plus bran) grains demonstrate that the elemental reduction due to elevated [CO2], is specific to each organ. The impact on leaf vegetables and feed crops should also be noted, because these are important sources of micronutrients despite being consumed in smaller amounts than staple grains.

In the analysis of feed crops, which combined our new data including rice straw with data from three previous studies (see Fig 1D, Table 1), elevated [CO2] decreased the content of five major (S, K, P, Ca, and Mg) and three minor (Zn, Fe, and Mn) essential minerals by 8.3% to 21.9%. It is especially noteworthy that the content of Ca was reduced by 12.7%. At present, much of the world’s population is facing a deficiency of Ca [21, 22]. Approximately 25.4 million adults in the United Kingdom and the United States have a high risk of Ca deficiency [21], and 54% of the population of Africa (5.7 hundred million individuals) is at risk of Ca deficiency [22]. Leaf vegetables are an important source of essential minerals; for example, in the United Kingdom and the United States, 10% of Ca and Mg intake comes from leaf vegetables [7]. The main source of Ca is milk, however, with UK adults obtaining half of their Ca intake from milk and dairy products [7]. The elemental content of the livestock's ingested feed correlates with that of the milk that they produce [23, 24]; therefore, the lower elemental content of feed crops grown under elevated [CO2] is likely to reduce the elemental content of milk and dairy products. Ultimately, elevated [CO2] might affect human nutrition and health even in high-income countries, where food supplements for micronutrients including Ca are readily available.