By now, we know that a healthy diet is important for physical well-being. Researchers are studying whether probiotics — live bacteria that are safe to eat — can improve gastrointestinal health and your mood.

Probiotics are what we believe to be good organisms that are beneficial to our health. But do they work?

Possible Benefits of Probiotics

Probiotics are beneficial bacteria that exist naturally in foods like yogurt and kimchi. They're also available in pill or powder form. Probiotics are thought to improve digestive health, and they're often used to treat diarrhea or bloating.

Probiotics can have many positive effects on the body, including:

• Shaping the body's immune system
• Producing antimicrobial substances
• Fermenting fiber in the diet to generate nutrients for the cells that line our intestines

Now researchers are finding evidence that the effects of bacteria in the gastrointestinal (GI) system send signals to the central nervous system, linking the gut with the brain. This could account for some known connections between GI conditions and mental illness. For example, a higher-than-average number of people with irritable bowel syndrome also develop depression and anxiety.

Could better GI health via probiotics boost emotional health too? The link between probiotics and mood isn't clear.

But experts have observed that certain foods can seem to boost mood — just think of the comfort foods we reach for when we're low, whether it's macaroni and cheese or a bowl of ice cream. However, this might simply be a mental or behavioral association. Rather than something triggered by bacterial responses to the nutrients in that food, it's likely that our brains associate eating that item with comforting or pleasant memories.

Although it's tempting to link probiotic use with mood, more research is needed. Right now, we don't have a lot of proof that taking probiotics is going to change depression or anxiety. It's an attractive theory, but we need a lot more research to guide us.

Pick Your Probiotics Carefully

One problem with probiotics is a lack of consistency. Consumers can't always be sure of what they're getting. Probiotics are considered food supplements, not drugs, by the FDA. Therefore, we don't have a lot of regulation over how they're made or whether they even contain what they say they contain.

In the United States, Lactobacillus and Bifidobacterium are the probiotic strains most commonly used to treat GI issues, but there are many probiotic products on the market that contain different types of bacteria and in different amounts. A lack of regulation means that one batch might be different from another.

By the time you buy a probiotic off the shelf, there's no way to know if the bacteria in it are as active as they were as when the product was made. In addition, each person may have different types and numbers of bacteria in their gut. This means the probiotic that works for one person might not work for another.

How to Take a Probiotic

The good news is that it appears most probiotic strains are probably harmless. But use caution. Studies have shown that often what's on the label is not what's in the bottle, so it pays to be careful.

Will taking one a day improve your mood? The jury is still out, and it's not a good idea to use probiotics as a replacement for any prescribed mood-managing medications. But if taking one a day for a month at least helps ease your gut issues, that alone might make you feel a little bit happier.

If the probiotic you've tried doesn't have any effect at all, it may not be the right one for you. Switching to another type might be worth a try.