Epidemiology studies regarding to monosodium glutamate and health are limited, since three studies surveyed by questionnaires the relation between monosodium glutamate and Chinese restaurant syndrome; five studies analyzed the association of monosodium glutamate and overweight or obesity; one study related the monosodium glutamate and hypertension; one study investigated the improvement of hemoglobin in Chinese; and another study the association of sleep-disordered breathing. The results of this studies showed that in one of the Chinese restaurant syndrome study conducted by a questionnaire on dietary frequency of monosodium glutamate in Hawaiian men, neurological symptom occurred significantly less often among men who used monosodium glutamate than among non-users. What is more, in another survey conducted in the US found that those people who believed they had experienced Chinese restaurant syndrome reported non-specific symptoms. On the other hand, overweight and monosodium glutamate has been also a concern. Results of these studies have been controversial since from five surveys, two found no associations while three found associations. One of the group of investigators to whom it was reported that monosodium glutamate was not associated with prevalence of weight gain in 2010, the following year published that monosodium glutamate could raise blood pressure in people who took hypertension medication. In 2012 they reported that monosodium glutamate improved the hemoglobin, having an inverse relationship between monosodium glutamate intake and the risk of anemia, and in the last publish, they reported that monosodium glutamate was associated with sleep-disordered breathing. This review covers these epidemiological studies. However, since then they reported controversial results as well as limit number of surveys conducted, it is difficult to make a conclusion. We need further studies to understand and analyze better the relation between monosodium glutamate and health in free-living subjects.