Elevated atmospheric carbon dioxide concentrations decrease protein content by 6-14% and reduce essential minerals like zinc, iron, and B vitamins in major food crops including wheat, rice, and soybeans. Temperature increases and altered precipitation patterns further compound these nutritional deficits while reducing overall crop yields. This research synthesizes multiple field studies demonstrating that climate-driven changes in plant physiology fundamentally alter the nutritional composition of foods that billions depend upon. The implications extend far beyond simple caloric availability, potentially exacerbating micronutrient deficiencies in populations already vulnerable to malnutrition. Countries heavily reliant on plant-based diets face the greatest risk, as compensating for reduced nutrient density through increased consumption may not be economically or practically feasible. While agricultural adaptation strategies like selective breeding for nutrient retention show promise, the timeline for widespread implementation remains uncertain. This represents a largely overlooked dimension of climate health impacts that could undermine nutrition security even in regions maintaining adequate food production volumes. The findings suggest urgent need for integrated approaches addressing both environmental sustainability and nutritional adequacy in food systems planning.