The most provocative finding in the cross-cultural analysis was the consistent connection between refined sugar intake and worse outcomes for schizophrenia and increased prevalence of depression. Researchers also found that consumption of pulses or whole grains and high consumption of starchy root vegetables were linked to a lower prevalence of schizophrenia and depression. The connection between dietary habits and mental illness was not seen with healthy carbohydrate consumption but strongly correlated with refined sugar consumption. Sugar consumption causes a cascade of physiological effects that may explain the increased prevalence of mental illness.
Refined sugar consumption suppresses brain-derived neurotrophic factor or BDNF, an important growth hormone in the brain. This growth hormone is extremely important for the health of neurons in the brain. BDNF triggers new connections between neurons in the brain which is crucial for memory function. Studies have shown low BDNF levels in patients with depression and schizophrenia. The consumption of refined sugar has the potential to exacerbate depression and schizophrenia by contributing to low BDNF levels.