Dear Doctors: It seems like every new health discovery is connected to the gut microbiome these days. I’m 68 years old, and this is new to me. I understand about probiotics, and I even take one, but now I’m seeing ads for prebiotics and postbiotics. What are they? Do I need to take them?

Dear Reader: When it comes to the gut microbiome, we’re all on a learning curve, no matter our age.

Targeted study of our microbial companions dates back to the 17th century, but it’s the recent leaps forward in genomic sequencing technology that have made present-day discoveries possible. Emerging research continues to show that the composition, diversity and behaviors of the trillions of bacteria, fungi, yeasts, viruses and other microbes that colonize our bodies play a pivotal role in human health and well-being.

We agree with you that we’re hearing about new breakthroughs at what feels like a dizzying pace. In the last few years alone, reputable studies have linked the gut microbiome to blood sugar control, Type 1 diabetes, a variety of neurodegenerative diseases, some chronic gastrointestinal disorders, immunity and immune disorders, mood, depression and mental health. These findings have ignited intense interest in the gut and its microscopic residents.

They have also spurred the emergence of a vast and somewhat chaotic marketplace of products -- and a new vocabulary to go with them. This includes terms like “probiotics,” as well as the “prebiotics” and “postbiotics” that you’re asking about. At the root of these new terms is the word “biotics,” which refers to the living components of an ecosystem. In this instance, the living components are the colonies of intestinal microflora, and their ecosystem is the gut.

The word probiotic was coined in 1965. At that time, it described a substance that is produced by one organism and benefits another organism. Today, probiotics refers to the intestinal flora themselves. Someone takes probiotics in an effort to introduce certain species of beneficial microbes into their gut. This can be via supplements or by eating certain foods in which bacteria and other microflora naturally occur.

The trillions of microorganisms in the gut need something to eat, and that’s where prebiotics come into play. The word prebiotics refers to those components of food that, because they are not digestible, reach the large intestine intact. There, they act as food for the microflora of the gut.

Most recently, the word postbiotics has entered the gut microbiome conversation. This refers to the waste products that result from the digestion of prebiotics and probiotics. They include nutrients such as vitamin K and certain B vitamins, and also short chains of proteins that can help control the growth of potentially harmful bacteria.

Retail shelves are stocked with supplements in each of these categories. But whether or not they’re helpful remains unclear. What we do know is that our gut microbiomes are primarily shaped by what we eat. The best way to maintain yours is with a diet that includes naturally fermented foods, a wide range of fresh fruit and vegetables, grains and legumes, and limits added sugars and processed foods.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: I’m having hand surgery next year to help with carpal tunnel, and I’m not thrilled about having anesthesia. I’ve been reading about surgeons whose patients use virtual reality headsets to need less anesthesia. Does that really work?

Dear Reader: The use of anesthesia during surgical procedures dates back to antiquity. The historical record shows that the Incas used extracts of plants like datura and coca to reduce pain and induce unconsciousness, and early Chinese physicians offered patients opium-laced potions. Centuries later, efforts to refine and improve the process continue. And small wonder.

Anesthesia is a complex practice with multiple, and sometimes conflicting, objectives. The treatment must sedate the patient and suppress their pain response but not interfere with the body’s critical physiological functions, including heartbeat, breathing and maintaining steady blood pressure. While modern anesthesia is safer than ever before, it still carries an element of risk. That’s why research into novel drugs and new techniques continues.

For the past several years, that research has included inquiries into the use of virtual reality, or VR, as an add-on therapy. This approach is being explored in conjunction with what is known as regional anesthesia. Unlike general anesthesia, where the patient is completely unconscious, someone undergoing regional anesthesia is sedated, but remains conscious. Nerve blocks are used to inhibit sensation from a specific and limited part of the body. The technique is often used in surgery on an extremity, such as an arm, hand, leg or foot.

Because the patient remains awake during regional anesthesia, managing their stress and anxiety is crucial. Many patients receive sedation so they can relax or even doze off during the procedure. With the advent of computer-generated virtual reality, which uses special headsets to plunge the user into an immersive 3D world, researchers began to wonder if it might lessen a surgical patient’s need for sedation.

The most recent study into this idea yielded intriguing results. Over the course of eight months, researchers at a medical center in Boston evaluated the anesthesia needs of 34 patients who were undergoing hand surgery. The patients were divided into two groups. All received drugs to completely block pain response, and all received intravenous sedation. But one group was also given VR headsets with a selection of programs specially designed to promote relaxation and a sense of calm. These included nature scenes, such as a secluded meadow or mountaintop, guided meditations or immersive visuals, such as a starry night sky.

At the end of the study, the data showed that the patients who used VR headsets during their surgery needed markedly less sedation than did the VR-free control group. Additionally, the post-surgical recovery period for the VR group, during which patients wait for the effects of sedation to wear off, was significantly shorter.

While the research is promising, it’s important to note that the surgical teams and the patients understood that VR might lessen the need for sedation, and this could have influenced the outcomes. In your own case, it’s crucial that you discuss your concerns about anesthesia with your surgeon. Understanding the process, the risks and the benefits can help allay your concerns.

(Send your questions to askthedoctors@mednet.ucla.edu. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: When our grandson first learned his colors, he sang them along with music. We thought he was copying that song for learning the ABCs. But when he got older, he started saying that he “hears” the colors. We have been told this is called synesthesia. How and why does it happen?

Dear Reader: Synesthesia is a somewhat rare and quite fascinating phenomenon. It’s a neurological condition in which sensory input gets cross-wired in the brain. The result is that incoming information that would ordinarily be interpreted by a single sense spills over and stimulates another unrelated sense. While this blending of the senses has been described and referenced throughout the centuries, the emergence of the word “synesthesia” dates back to the late 1800s.

For some people with the condition, sounds will also activate the vision centers of the brain. For others, colors can also have flavor, flavors can evoke a physical shape, numerals can have colors and reading printed words can elicit distinct aromas. Depending on how the senses combine, there may be as many as 60 different forms of synesthesia. Estimates of the number of people who experience some form of synesthesia range from as low as 1-in-20,000 individuals to as high as 1-in-23.

Another ongoing discussion, which has not been conclusively resolved, concerns whether the condition appears in women more often than in men. The audiovisual variety that your grandson has described is considered to be one of the more common forms. The rarest is known as lexical-gustatory synesthesia, which causes speakers to “taste” the words they are saying.

Someone is either born with synesthesia or develops the condition at an early age. The condition does not affect an individual’s general health, nor is it linked to any diseases or physical disorders. It’s important to note that, despite the very different way that someone with synesthesia experiences and processes the world, it is not a form of, or a sign of, mental illness. In fact, studies and anecdotal data suggest that people with synesthesia are often highly intelligent and perform better on memory tests than those who don’t have the condition. Interestingly, there is also some evidence that people with the condition may often have a poor sense of direction.

As for the cause, that remains unknown. From the time synesthesia was first named and described, researchers have been looking into its origins. Some suspect the sensory crossover occurs due to the presence of additional neurons, which may link the affected senses. Another theory involves changes to how the brain receives information, as well as how that information gets processed.

The condition has also been found to run in families. Up to 40% of people with synesthesia turn out to have a close relative who also has a form of the condition. This makes it likely that heredity and genetics play a role. Meanwhile, advances in imaging technologies continue to aid in synesthesia research. It’s quite likely that we’ll have more answers in the not-too-distant future.

(Send your questions to askthedoctors@mednet.ucla.edu. Owing to the volume of mail, personal replies cannot be provided.)