Eating meat provides healthy saturated fats, which enhance the function of the immune and nervous systems. Saturated fats contain the fat-soluble vitamins A, D, E and K, [49] and the cholesterol from saturated animal fat is needed for the proper function of serotonin receptors in the brain. According to a Feb. 7, 2014 study by researchers at the Institute of Social Medicine and Epidemiology, vegetarians "suffer significantly more often from anxiety disorder and/or depression." [133] Low cholesterol levels have been linked to depression. Saturated fats are also essential for building and maintaining cell health, and help the body absorb calcium. [101]