Why balanced meals are so important.

If you were to switch from vegetarianism to meat-eating, or vice-versa, chances are the composition of your gut bacteria would also undergo a big, swift change.

The research, published Dec. 11 in the journal Nature, showed that the number and kinds of bacteria -- and even the way the bacteria behaved -- changed within a day of switching from a normal diet to eating either animal- or plant-based foods exclusively.

Not only were there changes in the abundance of different bacteria, but there were changes in the kinds of genes that they were expressing and their activity.

The study suggests that this bacterial community and its genes -- called the microbiome -- are extraordinarily flexible and capable of responding swiftly to whatever is coming its way.

In the study, participants who switched from their normal diet to eating only animal products, including meat, cheese and eggs, saw their gut bacteria change rapidly within one day.

While the participants were on the animal-based diet, there was an increase within their guts in the types of bacteria that can tolerate bile (a fluid produced by the liver that helps break down fat), and a decrease in bacteria called Firmicutes, which break down plant carbohydrates.

Gut bacteria also tended to express (or "turn on") different genes during the animal-based diet, ones that would allow them to break down protein. In contrast, the gut bacteria of another group of participants who ate a plant-based diet expressed genes that would allow them to ferment carbohydrates.

The differences between the gut bacteria of the people on the plant-only and animal-only diets "mirrored the differences between herbivorous and carnivorous mammals.

Bonnie: Having all the bacteria at our disposal to break down fats, carbohydrates, and proteins is crucial. This is why going vegan or going strictly paleo is too extreme! Balance is everything. This study also shows us how devastating antibitoics can be because they wipe out ALL bacteria and completely obliterate our microbiome.