Britney Spears + dairy = crazy? Okay, sure

In addition, the Royal College of Psychiatrists in the U.K. studied the relationship between mental disorders and the consumption of meat, dairy, and other animal products and concluded that "a higher national dietary intake of… dairy products predicted a worse two-year outcome of schizophrenia." They also concluded that a higher consumption of meat was linked to a worsening of schizophrenia, while consumption of beans—a vegetarian protein source—was linked to improvements. In addition, the Mental Health Sanctuary in Washington advises people with bipolar disorder to avoid dairy products.
While the medical link between mental illness and meat and dairy consumption is still evolving, there is no doubt that eating animal products is a major factor in causing other diseases, including the top killers in the U.S. According to the American Dietetic Association, vegetarians are less prone to heart disease, specific types of cancer, diabetes, and obesity than meat-eaters. While switching to a vegan diet might very well benefit Britney's mental health, it would undoubtedly benefit her physical health.