Dear Doctor: Stem cell therapies are being heavily marketed here in Florida as promising treatments for a variety of illnesses, but I have my doubts. As a retired doctor, I hate to see people go into debt to pay for something fraudulent or unsafe. Am I being too critical?

Dear Reader: Stem cell therapies are making headlines right now in two very different ways. One is the news that a patient infected with HIV has been in remission for 18 months following a stem cell transplant. The other stem cell news arises from the subject of your letter. That is, unproven and unapproved stem cell treatments. These are being widely marketed as miracle cures for everything from Parkinson’s disease, autism, arthritis and dementia to depression, multiple sclerosis, macular degeneration and traumatic brain injury.

Although the use of embryonic stem cells is federally monitored, adult stem cells can be extracted from a patient’s own body. That makes regulation and oversight challenging.

Despite extravagant claims of success by stem cell clinics, outcomes are largely unproven. However, the potential dangers are clear. In the past year, at least 17 people in five states have become gravely ill following stem cell treatments that used injections of umbilical cord blood and required hospitalization. In one such case, a man who received an injection of umbilical cord blood to address joint pain developed sepsis, a life-threatening infection. He spent 58 days in the hospital.

Last December, the Centers for Disease Control and Prevention published a report warning about unapproved stem cell treatments. The Food and Drug Administration has issued numerous warnings on the issue as well.

The allure of stem cells is that they are a kind of blank canvas. These "unprogrammed" cells divide rapidly and have the ability to change into other types of cells, such as bone, brain or muscle cells. As a result, stem cells are the centerpiece of regenerative medicine, in which disease and injury are treated by growing new cells, or by replacing or repairing those that are dead and damaged.

Thanks to their unique properties, stem cells are seen as important tools in potential new therapies for diabetes, Parkinson’s and heart disease, among others. But because stem cells are undifferentiated, they must first go through a special process, somewhat like programming, in which they are prepared to become specific types of cells. It is during this process, as well as during the act of transplantation, that potential risks to patients can arise.

According to the CDC, a number of vials of stem cell products made from umbilical cord blood were found to be contaminated with E. coli. Even before this latest spate of bad news, various unapproved stem cell treatments were found to cause harm to patients that included severe respiratory illness, blindness and even death.

With few consumer protections in place at this time, the FDA recommends that patients avoid stem cell therapies that are not part of an approved clinical trial. To find ongoing and upcoming clinical trials that use stem cells, visit clinicaltrials.gov. The home page contains a form that you can use to focus your search.

(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 read with interest your column about how sugar likely affects the gut, and I now have questions concerning antibiotic treatment. Are all gut bacteria eliminated? Can they be restored? Do probiotic supplements help the gut return to normal? I thought the body produces its own.

Dear Reader: In the same way that the discovery of penicillin launched a medical revolution in the late 1920s, the near-daily discoveries about the power and potential of the gut microbiome are now transforming our understanding of both health and disease.

The 10 trillion to 100 trillion microorganisms that each of us harbors in our digestive tract consist of more than a thousand species with more than 3 million genes. Not only do they play significant roles in digestion, synthesize vitamins and other nutrients, and coordinate with the immune system, research shows that our gut flora has a hand in regulating mood, weight, inflammation and certain disease processes.

So what happens to the gut microbiome after antibiotic treatment? Two well-regarded studies into the question, one performed in mice and one in healthy men, had similar answers. An outcome common to both studies was that, following antibiotic therapy, the numbers and diversity of the microbial communities were vastly reduced. The other was that once antibiotic therapy concluded, the gut microbiome began to quickly repopulate. However, in both the mouse and human studies, a comparison of pre- and post-therapy fecal samples revealed that the landscape of the new gut microbiomes had changed significantly.

The mouse study found that in addition to nearly eradicating the native microbes, antibiotic therapy reduced the metabolic rate of those that managed to survive. The antibiotics also caused certain changes to the environment of the gut itself. These two factors opened the door to repopulation of the mouse guts by new species, some of them potentially harmful.

The human study found that although the gut had repopulated the majority of its original species six months after antibiotic therapy, nine common beneficial bacteria failed to return. At the same time, several potentially harmful bacteria made an appearance. The takeaway is that while the gut microbiome in most healthy adults is resilient in the face of antibiotics, the breadth and diversity of our microscopic partners do take a hit.

One new area of research is the use of fecal transplants to both restore the original ecosystem of the gut and protect against colonization by undesirable species. This was done in a recent study in patients undergoing intense cancer treatment. Using fecal samples that were frozen and stored prior to their procedures, patients recovered a significant portion of their pre-treatment gut flora.

When it comes to countering the effects of antibiotics with probiotic supplements, though, the jury is still out. One study found that while probiotic supplements successfully colonized the gut, they also delayed the return of native flora. Until we have definitive answers, time and diet look like best approach for gut recovery. That means eating from a wide range of fermented, cultured and fiber-rich foods, and limiting sugar and red meat, all of which have been shown to contribute to gut health.

(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: What do you know about the new cancer treatment called MuTaTo? It is being reported as a cure for all cancers. Is it available here yet? Does it work?

Dear Reader: You’re referring to claims made by Israeli scientists in January, stating that they are about a year away from releasing what they describe as a complete cure for cancer. The treatment is advertised as taking just a few weeks to complete, mostly free of serious side effects, and costing less than treatments currently available. At this time, the researchers have completed a mouse study, but have not yet published supporting research materials in a peer-reviewed journal. The new therapy has also not yet undergone any clinical trials.

The name MuTaTo derives from the phrase "multi-target toxin." Unlike existing precision therapies, which mostly focus on a single target in a cancer cell, the Israeli scientists say they have developed a multi-pronged approach. The idea is that the new therapy will disrupt the growth of cancer cells at several sites and at multiple stages of their development, which will interfere with their ability to mutate. It’s this ability for cancer cells to quickly adapt that allows them to become immune to a specific treatment and thus resume their growth and spread. The Israeli researchers also said that in time, the new therapy would be customizable. That is, each patient’s cancer would be biopsied and analyzed at the molecular level, and a personalized form of the new drug would be created.

In the big picture, the researchers have likened their new therapy to an antibiotic that will target cancer cells. They also compared the concept behind the new therapy to the multiple-drug cocktails that proved to be game-changers in the fight against HIV.

The proposed new therapy reportedly will also include a toxin that, because it will be precisely targeted, kills cancer cells but spares healthy cells. This would lessen or even eliminate the often-debilitating side effects of existing cancer treatments. Researchers said they will embark on clinical trials soon, with the hope of making their cancer drug available in a few years.

The announcement of MuTaTo by the chairman of the board of Accelerated Evolution Biotechnologies, the company that is developing the treatment, has been met with a hefty dose of skepticism in the medical community in the United States and worldwide. While agreeing that it would be a remarkable step forward in cancer treatment if the promised drug regimen proved successful, doctors and researchers expressed concern that the announcement could give cancer patients false hope.

According to American Cancer Society’s chief medical officer, who published his thoughts on the ACS website, it’s important to keep in mind that the research remains in an early stage. The mechanism of this proposed new drug reflects a new and exciting treatment pathway that many scientists are now exploring. However, MuTaTo is still at the start of the long and exacting process required to move a potential new therapy from the laboratory bench to a patient’s bedside.

(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.)