Many fruits and vegetables require planting / harvesting / maintenance by humans because no mechanized system has yet been created. The people working these jobs are usually the poorest people which can be found and often work in squalor.
60% of child laborers age 5-7 are "employed" in agriculture.
If you have a grain-heavy diet with well sourced meat (avoiding confinement-raised animals) you can be assured that the people who worked to produce your food made a decent living.
If you only eat from the produce aisle you have to ask yourself how well the people picking your food were treated and how good their lives were, the answers generally aren't very positive.