Does eating fermented foods help you lose weight?

Kimchi is a Korean food that traditionally consists of fermented cabbage and spices.  It is a staple in the South Korean diet, and is one of the most frequently consumed fermented foods.  The presence of bacteria in the kimchi has led many to speculate that it can exert a positive influence on the microbiome, and kimchi is believed to have anti-obesity effects.  In order to test this hypothesis researchers from South Korea conducted a clinical trial in which they put obese women on a kimchi diet.  The women were split into two groups, one of which consumed fermented kimchi, while the other consumed non-fermented kimchi.  A summary of the study was recently published by Molecular Nutrition and Food Research.

Surprisingly, fermentated kimchi did not appear to affect the women’s body measurements or specific health indicators when compared to the non-fermented version.  For example, women on both diets had similar decreases in weight, waist circumference, body fat, blood pressure, and cholesterol. There were some important differences though, fermented kimchi increased fasting insulin levels and fasting blood glucose.

The scientists also measured the two groups’ gut microbiomes and blood gene-expression in the study.  The group that ate fermented kimchi had higher abundances of Bacteroides and Prevotella in their microbiomes, and an increased Bacteroides/Firmicute ratio, which has been linked to weight loss.  Bifidobacterium longum, a major lactic acid bacterium that ferments kimchi, has also been linked to weight loss, and to this end, a significant correlation between an increase of this bacterium in the microbiome and decrease in waist circumference was observed.    In addition, a gene known as Acyl-CoA synthetase long-chain family member 1 was found to be significantly upregulated in subjects consuming fermented kimchi compared to those consuming fresh kimchi. This gene plays an important role in metabolism, and it is important in breaking down fatty acids. A second gene, aminopeptidase N (ANPEP) was also expressed more in subjects consuming fermented kimchi.  ANPEP is important for regulating inflammation, and has been associated with a healthy blood pressure.

Overall, this study showed fermented kimchi possibly has beneficial effects on metabolism and immunity when compared to the non-fermented variety. While this study is limited by its small sample size, among other factors, it still shows that the bacteria involved in the fermentation process could benefit us in more ways than we currently know.  These bacteria not only make kimchi taste good, but they may make us healthy too!

Hand washing dishes may decrease risk of allergies

A study published on Monday by the journal Pediatrics has gotten a lot of press this week because it shows a connection between allergies in children and the method by which parents wash their dishes. Parents, especially new parents, often consider good hygiene as one of the most important factors in raising their new child, but according to the hygiene hypothesis it may be true that too much cleanliness actually negatively affects a young child.  Asthma, eczema, and other autoimmune diseases are becoming more common conditions in children, and each has been linked to the hygiene hypothesis.  Researchers in Sweden reinforced this link when they discovered a possible connection between allergies in children and whether dishes were washed by hand (less clean) or by machine (more clean) in their homes.

 The researchers sent a questionnaire to parents of children aged 7-8 which was filled out by 717 families in Molndal, Sweden and 312 families in Kiruna, Sweden. The questionnaire asked many questions pertaining to the children, including previous symptoms of asthma or eczema, method of washing dishes, and if their food was farm grown or fermented.  When examining the results it is important to remember that all forms of bias cannot be eliminated when doing surveys, because, among other reasons, it is difficult to get a perfectly random sample.

Results of the study showed that there were lower instances of allergies in children whose families washed their dishes mainly by hand rather than by machine. In addition, this effect was amplified if the children ate food that was either fermented or purchased from a farm (both of which should introduce diverse bacteria to the children).  Of course, there were other variables that were not inquired in the questionnaire that are also known to decrease rates of allergies in children, and which may be related to washing dishes by hand, for example a lower socioeconomic status.  Then again, the authors suggest that hand washing dishes may reasonably be responsible for these lower rates of allergies in children of lower socioeconomic status.

So, you may be wondering how exactly this pertains to the microbiome. Hand washing dishes cleans less thoroughly than highly efficient machines, which sounds gross, but the exposure to more microbes when you are young may help develop the microbiome and immune system.  While this study is not perfect, it still shows us that exposure to bacteria is potentially a good thing for the new and developing microbiome.