Would You Like Extra Viruses With Your Yogurt?

Editor's Note: This item was originally published as a blog post in the Amplifier.

A recent study published in the Proceedings of the National Academy of Sciences analyzed the viral content of the human gut (Manrique et al., PNAS, 2016). The research focused on a particular kind of virus called bacteriophage, which only infect bacterial cells and do not infect human cells. Manrique and colleagues found that healthy individuals had a “core” group of bacteriophage. In addition, they found that these core bacteriophage were less frequently found in individuals with gastrointestinal disease. This novel finding reveals a potential link between the viruses in our gut and our health.

Joshua Weitz, a professor in the School of Biological Sciences explains the findings:

Yogurt is a breakfast staple. In my family, we pack single-serve yogurt containers with our kids’ lunches and eat “stinky” cheese. In doing so we are also serving our children bacteria. Intentionally. Yogurt and cheese are examples of “living” food. The living component are cultures of bacteria.

As any shopper knows, the marketing of yogurt is tied not just to its taste but to its health benefits. The active bacteria in yogurt differ among company and brands. Irrespective of the brand-name, the active bacteria are nearly all close relatives of “lactic acid bacteria”. Lactic acid bacteria take the sugars in milk, break them down, and release lactic acid. That lactic acid and other byproducts give yogurt its distinctly sour taste.

The idea that eating more bacteria could be good for you reflects a paradigm shift in the scientific attitude towards microbes and health. Bacteria can make us sick. But, many bacteria keep us healthy. We could not go about our daily routine without them. These bacteria constitute part of our “microbiome” – that is the world of bacteria that lives in and on us. Yet, despite the changing attitudes towards bacteria, there has not been a similar paradigm shift with respect to viruses. I have yet to see a yogurt offered with extra viruses. I would imagine it would not be a sales hit… Or would it?

The study of Manrique and colleagues identified a core “virome” correlated to human health. But we still do not know if there is a causative link between the two, e.g., do bacteriophage in the human virome infect components of the healthy human microbiome and/or do they infect otherwise harmful pathogens? Future research will be needed to tease apart these relationships. But one thing is clear: consumers may eventually need to consider the health benefits of viruses and bacteria when thinking about maintaining or improving their health.