Dear Doctor: I always thought fiber was fiber, but it seems that the FDA is about to crack down on food manufacturers who add weird ingredients to bulk up processed foods. Does it really matter whether the fiber we're eating is added or is a natural part of our food?

Dear Reader: For anyone not familiar with this topic, 26 ingredients that food manufacturers add to their products in order to bump up the dietary fiber numbers on food labels are currently under review by the Food and Drug Administration. These include fibers that have been extracted from plant-based sources, as well as synthetic fibers cooked up in a lab.

For example, inulin, frequently seen on processed food labels, is a naturally occurring carbohydrate that resists digestion. (It's the "resists digestion" that makes it, or any carbohydrate, qualify as dietary fiber.) Found in more than 36,000 plant species, inulin is most often sourced from chicory when it is used in food production. Polydextrose, on the other hand, another common entry on food labels, is a synthetic fiber. It may sound familiar if you've read the food labels on products ranging from breakfast cereals and baked goods to ice cream, salad dressing and even certain beverages.

All of which leads to the point behind the FDA's move to reconsider what, specifically, can count as a dietary fiber on food labels. The argument isn't whether or not these substances qualify as fiber. They are carbohydrates that can't be fully digested -- so in the broadest sense, they do. However, their presence in foods that are otherwise nutritional black holes can, in truth, allow manufacturers to use language like "high in fiber." And that, according to those behind the push to bump certain types of fiber from food labels, can mislead consumers as to the nutritional value of certain foods.

The FDA's goal, as stated in a rule published in 2016, is that "only certain naturally occurring dietary fibers such as those found in fruits, vegetables and whole grains, and added isolated or synthetic fibers that FDA has determined have a physiological effect that is beneficial to human health, could be declared on the label under 'Dietary Fiber.'"

And the truth is, whether or not those oddball added fibers meet the "beneficial to human health" criteria is not yet known.

Research has proven the beneficial effects of naturally occurring dietary fiber for decades now. Soluble fiber, which dissolves in water, forms a gel-like substance during digestion and can help slow the absorption of simple sugars. Insoluble fiber, which does not dissolve, adds bulk to the materials passing through the digestive system and helps with elimination. Diets high in fiber are associated with improved bowel health, lower blood cholesterol levels and regulation of blood sugar levels. In the bigger picture, studies associate high-fiber diets with lower rates of cardiovascular disease and certain cancers.

At this time, the FDA has hit the "pause" button on the food label decision when it comes to fiber. Meanwhile, if that sugary carton of yogurt is claiming to be high in fiber, we think a glance at the small print on the food label could be educational.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: As a fan of the TV show "Homeland," I was skeptical (and also creeped out) when a character was assassinated by someone hacking his pacemaker. But I just read that this might actually be possible. My dad has a pacemaker, and now I'm worried. Is this really a serious risk?

Dear Reader: We remember when that scene aired and the resulting stir that it caused, and we admit that we share your discomfort. The idea that an unseen individual can take control of a medical device in someone else's body is profoundly disturbing. And while it would be great to be able to brush it all off as the product of a TV writer's overheated imagination, the possibility of such hacking, while remote, does exist.

A paper recently published in the Journal of the American College of Cardiology tackled this very subject, which is perhaps how it came to your attention. The authors point out that, in a world increasingly dependent on (and connected by) online technology, it's not only pacemakers that are vulnerable. Defibrillators, neurostimulators and implantable drug pumps, like insulin pumps, rely on the same embedded computers and software radios for their two-way communication. Their findings are that weak security features have left these devices potentially vulnerable to outside manipulation.

The possibility of this type of interference first arose about a decade ago. That's when technological advances made it possible to program and communicate with a pacemaker wirelessly. Up until that time, a patient had to visit the cardiologist's office for the doctor to collect data from the device, and to deliver any updates. As soon as things went wireless, that meant there was software involved. And the nature of software, as we see every day, is that it can be hacked. In addition to concerns about attacks on the functioning of various implanted medical devices, experts warn that the highly sensitive data those devices collect from patients and send out to health care providers can be compromised as well.

The Food and Drug Administration and the Department of Homeland Security have both become involved in the issue. The FDA has published a cybersecurity update on its website and outlined the steps it is taking to protect the public. Earlier this year, DHS put out an advisory regarding potential vulnerabilities in a certain cardiac device, which caused the company to evaluate and address the issue.

Unfortunately, the only foolproof fix to reduce the risk of hacking is to ditch the wireless technology. But considering the many benefits of remote access, which facilitates software updates, allows real-time monitoring and can deliver updates to treatment protocols without the physician physically present, it's realistic to expect that wireless tech is here to stay.

In addition to addressing the vulnerabilities in wireless medical technologies, the lead author has been careful to state, both in the paper and in subsequent media interviews, that the risk of such hacking remains theoretical. Here in the real world, at this point in time, there have been no documented cases of implantable cardiac devices being hacked.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Hello again, dear readers -- and happy spring!

We closed a past column with a question about how any health-related New Year's resolutions were going, whether there was success or stagnation, and what plans people had in place to move forward. And because of the focus on diet, weight loss and general health in the responses we received, we've put several columns about these topics into the pipeline, with more to come. We hope you'll find them useful.

And now, from the mailbox:

-- We always learn from your letters, and this time it's food scientist Bob Hutkins from the University of Nebraska-Lincoln who helped out. Writing about the finer points of kefir production, he explained that it's actually an added enzyme, lactase, that works the magic of making kefir lactose-free. The enzyme turns lactose into a different type of sugar, and thus allows those who are lactose-intolerant to enjoy the benefits of kefir without gastrointestinal discomfort.

-- In response to the column about ocular migraines, we heard from Kurt in nearby Thousand Oaks, California. Although Kurt experienced the visual disturbances of an ocular migraine, a brain scan led to a different diagnosis:

"The cause of the vision loss was TIAs from microemboli," he wrote. A TIA, or transient ischemic attack, is a temporary blockage of blood flow to the brain. In Kurt's case, tiny particles, which can often be blood clots, caused the blockage.

"Upon initiation of low-dose aspirin therapy, the visual symptoms immediately resolved," he wrote. "Although migraine is a serious condition, it is not life-threatening in contrast to the possible outcome of TIAs. I would encourage you to inform readers of other possible causes of transient vision loss and the need to have a thorough workup to diagnose."

-- The recent changes to blood pressure guidelines prompted more than a few of you to write, both in confusion and frustration. We agree that it can be unnerving when the same blood pressure reading that was considered normal one day is classified as elevated the next.

At this time, a reading of less than 120/80 is the new normal. A top (systolic pressure) number between 120 and 129 is now considered 'elevated' blood pressure. When the bottom (diastolic pressure) number exceeds 80, and the top number is 130 or greater, the results are considered high blood pressure.

If it's any consolation, the updated blood pressure guidelines have caused quite a bit of conversation in the medical world, and no small amount of controversy. The reason given for the changes is to promote increased vigilance by physicians and patients in dealing with high blood pressure before it causes harm.

-- To the reader who is worried that his newly diagnosed prostate cancer might be contagious, please be reassured that it is not. We quote no lesser authority than the American Cancer Society when we say there is no evidence that close contact of any type can result in the spread of cancer from one person to another.

As ever, thank you for your letters. We are grateful for your interest in this column and realize how fortunate we are to have readers like you.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)