Friday, September 23, 2011

In Which You are What You Eat

I love food. Always have – both the process of making food (which may be why I’m a synthetic chemist) and the joy of consuming one’s labors (which lab work definitely doesn’t allow!). Recently, however, modern science blurs the line between the stomach and brain. “You are what you eat” no longer just refers to body weight or proper nutrient intake. We humans are superorganisms, meaning that our intestinal microbiology plays a huge role in our everyday lives. Turns out, where you were born, where you live, what you eat, and where you’ve travelled can all influence the metabolic phenotype (appearance) of the bacteria that inhabit your intestinal tract.
Hey baby, what's your gut microbiome?
Credit: Healthy Perceptions blog
Some microbiologists posit that humans can be grouped, not by race, creed, height, or sex, but by “gut profile.”  A recent multi-institution Nature paper, led by Bork and Ehrlich, disclosed three major enterotypes (gut profiles), based on DNA sequencing (of, well, poop) of 22 people from 4 different countries. The scientists try not to paint too broad a picture with this initial result, but note that gut bacteria influence key genes that regulate aging and body mass index, which may suggest microbial management of a wide variety of diseases.
Your gut bacteria also impact your emotions. WSJ’s Jonah Lehrer reports that yogurt – specifically the kind filled with “good” (probiotic) bacteria – can actually cause marked behavioral effects, at least in mice. Probiotic-fed mice showed fewer symptoms of stress and anxiety, even when placed in new situations. An ideal cure for modern social anxiety, right? Unfortunately, no: other scientists interviewed quickly point out neurological patients’ inability to feel fear or stress causes them to make even worse future decisions in similar situations, since they lack the negative feedback from the prior event.
Mmm, gene regulation!
Yogurt aside, your salad may also be helping to regulate your genes. Earlier this week, researchers in China disclosed new methods that can detect short strands of plant-derived RNA present in human bodily fluids. The researchers were especially surprised to find certain microRNAs actually inhibited the removal of LDL (low-density lipoprotein, the so-called “bad cholesterol”) from the bloodstream. Overall, the team found about 40 different microRNAs, from at least five different crops, and expects to find many more. Just more news to chew on, while you ruminate over your afternoon snack.


  1. I find it remarkable that microRNAs can survive the gut. Less prone to hydrolysis than I thought?

  2. Doing a little digging on PubMed, I hit upon a possible idea (Disclaimer: I am not a professional biologist) - it seems exosomes, small membrane-enclosed vesicles with microRNA payloads, are used to pass RNA information between cells, and can survive outside the cell for some time.

    Perhaps the microRNAs survive the gut by wearing a "raincoat" and then being absorbed in the lumen.