Dear Doctor: Can white button mushrooms help control my blood glucose? I saw some headlines about this a while back, but it sounds like a correlation to me -- not a clear cause and effect. Maybe it's just that people who eat more mushrooms also eat less junk food?

Dear Reader: Spoken in the true scientific spirit. You are indeed correct that how we view the results of a study depends, in part, on how it is structured. In this case, we're talking about a mouse study in which researchers from Penn State's College of Agricultural Sciences looked at whether a diet that included daily servings of white button mushrooms would affect the gut microbiomes of laboratory mice.

What edges the results of this particular study into the realm of cause and effect is the use of two different groups of mice. One group included typical laboratory mice with a normal gut microbiome. The second group, however, was made up of germ-free mice who did not have a gut microbiome. That allowed the scientists to observe exactly how the microbiota of the "normal" mice changed as compared to the control group.

What they found was that eating a daily serving of white button mushrooms caused subtle changes to the makeup of the gut microbiome in the normal mice. Specifically, adding the mushrooms to their diets resulted in a rise in the overall numbers of a specific bacterium. Known as Prevotella, it produces certain short-chain fatty acids that have a positive effect on genes that improve glucose management.

What's interesting is that the function of the mushrooms in this case was as a prebiotic. That is, they served as food for the community of tens of millions of bacteria that make up the microbiome. For reasons that are not yet fully understood, the mushrooms allowed the Prevotella to flourish, which translated to a measurable effect on blood glucose management in the liver.

The results of the study invite future research into strategies to prevent and manage diabetes, a chronic and progressive disease in which the body cannot properly metabolize glucose. That's important, considering that more than 30 million Americans -- close to 10 percent of the population -- are now living with diabetes, and an estimated 1.5 million new cases are diagnosed each year. Diabetes, which increases the risk of heart attack and stroke, was the seventh-leading cause of death in the United States in 2015.

Another intriguing aspect of this study is the new light it sheds on the effect our diet can have on the populations within the gut microbiome, and how those microbial communities affect the workings of our bodies.

As for whether eating white button mushrooms can help you with your own blood glucose management, it's too soon to say. This study was conducted in mice and for a definitive answer, a human study is needed. According to the researchers in this study, the portion size fed to the mice translates to about 3 ounces of mushrooms per day for us humans. There's no reason not to add a portion of white button mushrooms to your daily diet, barring an allergy, of course. Just don't saute them in a lot of butter.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: My husband and I have two teenagers, and we also take care of my 80-year-old mother. The kids and my husband and I all got our regular flu shots, but I just read about a new flu shot that's for people who are over 65. Why do older people need a different flu vaccine? Does it really work?

Dear Reader: You're referring to Fluzone High-Dose, which, as you say, is licensed specifically for individuals who are 65 and older. Like all flu shots, it works by priming the immune system to defend itself against the specific flu strain that the vaccine is targeting. This happens because a flu shot contains antigens, which are the uniquely shaped proteins found on the surface of a flu virus. When you get a flu shot, your immune system responds to the presence of those antigens by generating antibodies, which are your body's first line of defense against infection. It takes about two weeks after you get your flu shot for the antibodies to develop. Once that happens, you have an additional layer of protection against the virus in the vaccine.

The Fluzone High-Dose vaccine contains about four times more of the flu antigen than does the standard dose vaccine that you, your husband and your children got. That means the high-dose vaccine will generate a more powerful immune response. The reason this is important for older individuals is the fact that as someone reaches his or her mid- to late 60s, their immune system becomes weaker. The immune system becomes less effective at protecting the body from infection, and it no longer responds in a robust way to vaccines. That means that not only are people in their mid-60s and older more susceptible to becoming infected by the flu virus, they are also less able to build up the needed antibodies in response to a flu shot.

In a study mandated by the Food and Drug Administration to assess the safety of the new high-dose vaccine and to gauge how well it works, it was found to be 24 percent more effective than the standard-dose vaccine at preventing the flu among people 65 and older. In addition, there appeared to be a measurable reduction in serious complications among those individuals who did contract the flu. Those complications, which are often life-threatening, include pneumonia, inflammation of the heart, a worsening of existing heart disease and COPD, or chronic obstructive pulmonary disease.

At this time, the high-dose flu vaccine is specifically approved for older patients. In our practices, we are giving the high-dose flu shot to all of our patients who are 65 and older. However, if a high-dose vaccine is not available, it's important not to delay getting a flu shot. An advisory from the Centers for Disease Control and Prevention states: "No preference is expressed for any one vaccine type. Vaccination should not be delayed if a specific product is not readily available."

Bottom line: Everyone 6 months of age and older should get a flu vaccine, this season and every season.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I'm 35 years old and a regular exerciser. Sometimes, though, when I'm on vacation or just want to veg out, I need a break. Now I'm hearing that this is really bad for your metabolism, especially as you get older. Seriously? Taking a couple of weeks off really makes that much difference?

Dear Reader: We're sorry to rain on your hammock time, but the newest research suggests that yes, taking as little as a two-week break from your regular exercise routine has negative health effects for older adults that can be long-lasting. This new insight comes from two recent studies that looked at what happened when physically active adults stopped exercising, even for a short time. Among the ill effects was a rise in blood sugar levels, a drop in insulin sensitivity and weight gain. As though that wasn't enough bad news, it turned out that even after the study participants returned to their regular exercise regimens, the metabolic changes were slow to fully reverse.

A study conducted by researchers from the University of Liverpool in England looked at a group of 45 men and women between the ages of 24 and 50 who were quite active. They each walked more than 10,000 steps per day, did not have diabetes and were metabolically fit. When the study participants were asked to suddenly cut down on their exercise and begin sitting for at least 3 1/2 hours per day, their metabolisms changed. Over the course of the two weeks that the participants slowed down -- their activity monitors logged under 2,000 steps per day -- their blood sugar spiked, they showed signs of insulin resistance, and their blood lipid results started to become distinctly less healthy. Not only did they lose muscle mass in their legs, they gained fat around their middles. Although most of them recovered their lost ground when they began to exercise again, several of the participants showed ongoing signs of insulin resistance.

A second study from Canada's McMaster University focused on adults aged 65 and older. In that study, the participants were also active, walking between 7,000 and 8,000 steps per day. However, in this case, they all had elevated blood sugar levels, which put them at risk of developing Type 2 diabetes. As with the Liverpool study, these adults were asked to drastically reduce their activity levels to below 1,000 steps per day, and to spend several hours sitting.

They suffered the same ill-effects as their younger peers, but more quickly and more severely. In fact, the sudden lack of exercise pushed some participants dangerously close to developing Type 2 diabetes, and they had to stop their participation in the study. Another difference between this group and the younger participants is that even after resuming normal activity for two weeks, most had not made up the metabolic ground lost to their enforced inactivity.

Yes, these are small studies, and more research is needed. But based on conclusions thus far, it appears that when we stop being active for weeks at a time, we pay a significant price.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)