Monosodium glutamate, obesity, probiotics and the gut
Previously, the taste enhancer monosodium glutamate (MSG) has been implicated in the development of obesity in rats and mice - and potentially in humans. MSG is added to snacks and in oriental foods and it is known as the source of the "umami" taste, one of the five tastes, which also include sweet, bitter, sour and salty.
Scientists initially suspected a direct effect of MSG on the brain and a consequent increase in appetite, but that theory was rejected due to the fact that MSG does not cross into the bloodstream without being metabolised.
However, the possibility that MSG boosts obesity in mice and rats - and potentially in humans - indirectly via it's effect on the gut, has also been examined. Two studies published this year have discovered that addition of probiotics (beneficial bacteria) in rats fed with monosodium glutamate have prevented and significantly reduced MSG-caused obesity.
In the most recent study referenced below, Lactobacillus and Bifidobacterium probiotics were found to reduce the level of VLDL by 32.2% and LDL by 30.6% ("bad cholesterols") and increased HDL by 25.7% ("good cholesterol"), compared to rats that were only fed with MSG but no probiotics. Secretion of adipocyte hormones (leptin and adiponectin) were also restored to normal levels.
More studies must be conducted before we fully understand the mechanism by which probiotics ameliorate the negative effect of MSG on obesity and before we understand the full implications on humans. However, avoiding MSG - which is typically found in low quality oriental food and in snacks laden with sugar, salt, fat and refined carbs - seems like a good idea...
- Journal: Fiziolohichnyi zhurnal
- Article: The effect of probiotic therapy on development of experimental obesity in rats caused by monosodium glutamate
- Link: http://www.ncbi.nlm.nih.gov/pubmed/25007523
- Excerpt: "It was shown that in rats of 4 months age, the injection of monosodium glutamate (4 mg/g) at 2, 4, 6, 8, 10 days after birth elicited abdominal obesity and metabolic syndrome. An intermittent administration of a probiotic mixture to rats treated with monosodium prevented the development of obesity."
- Journal: Journal of the European Association for Predictive, Preventive and Personalised Medicine.
- Article: The efficacy of probiotics for monosodium glutamate-induced obesity: dietology concerns and opportunities for prevention
- Link: http://www.epmajournal.com/content/5/1/2
- Excerpt: "The introduction of MSG to newborn rats caused the obesity in adulthood. Periodic administration of probiotic mixture to rat injected with MSG neonatally resulted in recovery of lipid metabolism and prevention of the obesity development."