Yesterday, salt was bad for you, but today it’s just fine. Multiply these  findings by a hundred and you have the confounding noise that passes for research in most nutritional studies. What the heck is going on?

The problem is, human dietary studies are hard. Most of them depend on people recalling what they ate over the last few weeks, and the combination of forgetfulness and the desire to look good makes the data suspicious. A truly randomized, controlled trial needs to take place in some kind of uber-regimented locked-down facility that even college volunteers wouldn’t appreciate. This is why many of these studies are done with mice and rats.

There’s another way, and it’s called a meta-analysis: a mathematical technique that combines multiple studies to wring the most out of all of them. Meta-analyses have their own issues, mainly because studies need to be well-matched to combine them. But they provide a way to create data sets with larger populations and potentially greater power.

So it has been reassuring to see studies like this recent Chinese meta-analysis of over 700 people demonstrating that probiotic consumption is indeed associated with reduced measures of anxiety. The researchers point out that there were conflicting data, but overall, the results were significant. With over 350 million people in the world afflicted with anxiety and depression, studies like this provide some hope.

Big fleas have little fleas,
Upon their backs to bite ’em,
And little fleas have lesser fleas,
and so, ad infinitum

Bacteria are everywhere, but it’s not always an easy life. Just as all creatures have tormentors, out gut bacteria have viruses that can kill them in a most gruesome way: they sneak into the bacteria and force the poor microbe to produce hundreds of copies of themselves. Finally the viruses are too numerous to fit. They explode out of the bacteria’s body and spread out to infect more bacteria. These special viruses are called phages, which means “eaters”.

Each phage is very particular about which kinds of bacteria they will attack. Unlike broad-brush antibiotics, they home in on a single species and leave other bacteria alone. They are pretty easy to target: you just smear the bacteria you want to kill on a petri dish and let them grow to form a film. Then you place spots of various phages on top. When a clear spot shows up in the dish, that means a phage has obliterated the target bacteria. Just cut out that spot and you have a few million phages, ready to go. Unlike antibiotics that may require multiple rounds to do the job, phages keep multiplying as long as their target exists.

Surprisingly, phages have been known and used for decades — in Eastern Europe. Only recently has the FDA shown an interest. But there are some great anecdotes that are making the FDA sit up and take notice. With antibiotic resistance and all the other problems that come with antibiotics, it’s about time. Phages could represent the medicine of the future.

The connection between the brain and the gut goes both ways. Psychobiotics in the gut can soothe your brain, but the brain can also affect your microbes. In a new study from the University of Nottingham, rats raised in isolation showed differences in their gut bacteria as well as changes in anxiety and brain development. The study suggests that life in solitary is no picnic. Early stress can produce lasting changes in gut microbes, leading to abnormal brain and immune function. This in turn can produce abnormal behavior and may play a key role in the development of psychiatric illness.