In postmenopausal Iranian women, higher adherence to an unhealthy plant-based diet, characterized by increased intake of refined grains, potatoes, sugar-sweetened beverages, and sweets/desserts, is associated with a 2.6- to 4.2-fold higher odds of low bone mineral density in the femoral neck and lumbar spine, independent of age, BMI, physical activity, education, and calcium supplement use.

Eating too many refined grains, sugary drinks, and sweets causes the body to become more acidic and removes essential nutrients needed to build strong bones. This acidity makes the kidneys flush out more calcium, leaving less available to harden bone tissue. At the same time, the lack of magnesium, potassium, and vitamin K from whole plant foods weakens the cells that build bone, so bones become porous and weak.