Continuing growth of world population will require food production to increase significantly in order to satisfy the needs of an increasing number of people. This study focuses on the role of phosphorus, an essential (non-substitutable) nutrient for all primary food production. A major share of the world's phosphorus flows, both mined and recycled, is used in agriculture. This study combines the latest revised population growth predictions of United Nations with food balances, long-run income predictions, and per-country income elasticity estimates to assess the minimum phosphorus needs for food production in the 21st century. We predict countries' crop and animal production, which will play a key role in the future demand for phosphorus. We demonstrate a novel method for estimating the long-run phosphorus demand based on the volume of food production and the phosphorus content of food products. We find a fairly stable demand trajectory for phosphorus on the global level for the medium-variant population growth projection. Thus, by the end of this century, the expected (medium) demographic changes lead to increasing the demand for mined phosphorus up to 23 Mt. per annum (compared to 18 Mt. in 2018). Furthermore, the growth in demand is largely driven by income growth and shifting consumption patterns which could push the expected annual phosphorus demand from 23 Mt. to 52 Mt. by the end of the century.