MSG

May Cause Liver Inflammation and NAFLD

In 2008 the Journal of Autoimmunity published an animal study which examined mice injected with MSG. The researchers found that at 6 and 12 months all mice treated with MSG developed NAFLD (non-alcaholic-fatty liver diease). [Source]
In 2002 the Indian Journal of Clinical Biochemistry published an animal study in which mice injected with 4 and 8 mg/g body weight MSG for 6 consecutive days had increases in free radical activity and a reduction in antioxidant activity in hepatic (liver) tissue. [Source]

In 2010 Cephalalgia conducted a double-blind, placebo-controlled trial in which 14 men drank soda that contained either MSG or a placebo. There was a significant increase in reports of headaches and muscle tenderness after MSG and systolic blood pressure increased after MSG when compared to a placebo. [Source]
In 2013 the Journal of Headache and Pain published a double-blind, placebo-controlled trial in which 14 subjects were given 5 daily doses of MSG or a placebo for one week. Headaches occurred in 8 of 14 subjects in the MSG group and 2 of 14 subjects in the placebo group. Blood pressure was also significantly elevated in the MSG group [Source]

In 2011 the Journal of Hypertension published a study based on data from a nutrition study involving 1227 Chinese adults. The data showed an association between MSG intake and increased blood pressure. [Source]