Dear Doctor: I developed acute prostate problems at the early age of 29. My doctor's prescriptions didn't work, so when a neighbor recommended 50 milligrams of zinc a day for at least 30 days, I gave it a shot. I haven't had any problems since -- and that was more than 30 years ago. Why don't more people use this miracle mineral for an enlarged prostate?

Dear Reader: Before you posed this question, I had never heard of any relationship between zinc and the prostate. Like most people, I thought of zinc simply as an important element in the body -- necessary for multiple enzymatic processes involved in human metabolism. I also knew that zinc concentrates in the liver, kidney, muscle and retina and is found at very high levels in the prostate.

After some research, I also found that the content of zinc in the prostate is about 100 times that found in the bloodstream. At high tissue concentrations, zinc can inhibit the formation of dihydrotestosterone, the main hormone that leads to prostate enlargement. It has also been shown to help preserve the normal tissue structure of the prostate and to help maintain prostate function. Zinc may also increase the ability to kill bacteria that lead to infections of the prostate.

A 2016 analysis of 10 studies assessed blood levels of zinc in men with prostate cancer. Seven of the studies found low concentrations. This is notable because multiple lab studies have shown that zinc can inhibit prostate cancer growth by hindering the function of prostate cancer cells and by turning on mechanisms that lead to the death of prostate cancer cells. In Japan and China, where zinc intake is high, the rates of prostate cancer are low. But after one generation in the United States, ethnic Japanese, for example, have the same rates of prostate cancer as Caucasians in the U.S.

As for prostate enlargement, this same analysis evaluated five studies assessing a potential link between blood levels of zinc and decreased risk of prostate enlargement -- and found none. In fact, three of the five studies showed a link between higher zinc concentrations and prostate enlargement, countering the notion that zinc could decrease the enlargement of the prostate.

So, although low zinc may be linked to an increased risk of prostate cancer, the same does not hold true for a decreased risk of prostate enlargement. A laboratory study of prostate tissue did show that zinc at high doses decreases smooth muscle proliferation in the prostate and thus possibly could decrease prostate size. Further, in a 2017 Italian study, 62 patients with symptoms related to prostate enlargement were given 10 milligrams of zinc in addition to herbal extracts. After six months, a majority of men reported decreased urinary frequency, increased flow rates and less urine retained in the bladder. Note that because zinc was administered with other therapies, it is difficult to know what effect the mineral alone had.

Because you had prostate problems early in life, I suspect your prostate issues may have been related to infection, rather than the more typical prostate problems of older men. It's possible that zinc may have had an antibacterial effect of preventing further infections of the prostate. Because of decreased infections, your prostate didn't enlarge and cause future problems. Perhaps this is why zinc helped you -- and why it may be helpful to others who have early prostate infection or inflammation.

Thanks for your question. Clearly, zinc therapy for the prostate should be studied further.

(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: I'm a 63-year-old female, and for the last four months, I've had tingling sensations in my arms, legs, eyes and other parts of the body. These are followed by muscle spasms. Two doctors have told me they don't know the cause. What do you think is happening?

Dear Reader: As we've mentioned in the past, our column is not designed to offer specific diagnoses. What we can do, though, is look at the big picture and try to shed light on the symptoms you're experiencing. We also think it's important, despite the two doctors who were unable to help, that you seek out another medical opinion. To that end, we have some thoughts on specific information you can provide that can be useful to the next doctor you see.

When patients report a collection of symptoms that include tingling or prickling sensations in the extremities, as well as muscle spasms, one of the things to consider is a condition known as peripheral neuropathy. This occurs as a result of injury or damage to the peripheral nervous system. That's the complex network of nerves and other structures that allow the brain and the spinal cord to communicate with the rest of the body.

About 20 million Americans have some form of peripheral neuropathy, according to statistics kept by the National Institutes of Health. Additional symptoms can include numbness, sensitivity to touch, phantom pain, burning sensations, muscle weakness and muscle wasting. These can develop over the course of a few days, or take months and even years to become apparent.

With more than 100 different types of peripheral neuropathy identified thus far, each with its own distinct set of symptoms, it's a fairly broad diagnosis. The causes are as wide-ranging as disease, trauma, repetitive stress injuries, endocrine disorders, infections, cancers, overuse of alcohol, side effects of certain medications and environmental factors.

If your doctor suspects peripheral neuropathy, then the next step is a neurological examination. Also relevant is a detailed medical history, information about work and home environments as well as family medical history.

The neurological exam will include testing muscle strength as well as assessing the ability to detect changes in temperature, vibration, light touch and body position. These simple tests can indicate what types of nerve fibers are affected. Metabolic conditions like diabetes, kidney or liver dysfunction, or vitamin deficiencies can be detected through blood and urine tests. Additional tests, like an MRI, may be called for.

During any type of medical exam, you are your own best advocate. Be prepared to tell your doctor where, exactly, the tingling and spasms occur. Describe them in detail. Are they associated with a time of day or night, with an activity or a specific movement? When it comes to your medical history, give complete details, even if they seem unimportant to you. Infections like shingles, Epstein-Barr or West Nile virus can cause neuropathy. So can Lyme disease and other tick-borne infections.

By observing and accurately recording the details of your symptoms, you can give your doctor the vital information she or he needs. And by understanding the nuts and bolts of the diagnostic process, you can become an advocate for your own behalf.

(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: How about a warning about the effect of too many vitamins? One example: B6. I recently checked my daily vitamin formula and found that it had more than twice the recommended B6. This is on top of what I get from my daily "health drink" and my healthy diet. My B6 level recently tested five times above the suggested level.

Dear Reader: Thank you for the opportunity to explore this topic. As you might imagine, I encounter many people who are dubious of the medications, treatments and advice that doctors have to give, but who also take remedies that haven't been studied or who take vitamins at excessive dosages with a blind disregard to potential side effects.

Let's begin with vitamin B6. This crucial vitamin is involved in metabolic processes that help the formation of glucose, heme, niacin and neurotransmitters in the body. Many foods contain B6, including pork, turkey, beef, eggs and potatoes, breakfast cereals, bananas, nuts, beans and peas. Deficiency of B6 is rare, but when it happens it can lead to inflammatory conditions of the mouth, irritability, confusion, depression and, rarely, nerve dysfunction in the legs and arms. People with severe deficiency can develop seizures. Some medications (Sinemet for Parkinson's disease, hydralazine for high blood pressure and isoniazid for tuberculosis, for example) can lead to B6 deficiencies, as can alcoholism, diabetes, asthma and lymphoma.

Requirements for B6 vary for different age groups, from 1 milligram per day in children to 1.7 milligrams per day in men over the age of 50. If you have a balanced diet, you should be able to get this daily intake of B6 from the foods you eat. B complex supplements can contain 2 to 10 milligrams of B6, with some people taking formulas containing ridiculously high levels. That may not seem like a big deal, but too much B6 can cause nausea, dizziness and nerve dysfunction in the legs and arms, leading to burning, tingling and numbness.

Another B vitamin, niacin, can cause liver and muscle inflammation when taken at doses greater than 3,000 milligrams.

Keep in mind that the list of potentially problematic everyday vitamins neither starts nor stops with the B vitamins.

Vitamin C: In those predisposed to kidney stones, vitamin C at high doses increases the risk of them.

Vitamin D: The recommended intake for vitamin D, which is important for bone mineral density and overall health, is about 600 to 800 units per day. However, manufacturers make -- and some practitioners recommend -- doses up to 10,000 units daily. Unfortunately, chronic intake of high doses of vitamin D can lead to a loss of bone density, calcium deposition in the kidneys and muscle pain. Those who take even higher doses of vitamin D can have severe elevation of calcium in the blood, which can lead to confusion, vomiting, poor appetite and muscle weakness.

Vitamin A: This vitamin is necessary for visual health, and deficiency (rare in the United States) leads to night blindness and even complete blindness. Recommended daily intake of vitamin A is 2,300 to 3,000 units. However, some people take more than 30,000 units per day, which can lead to liver toxicity, muscle and bone pain, vision problems, and coordination and balance difficulties.

This is just a starter list of examples of toxicity linked to high vitamin doses. If you have an illness that can lead to vitamin deficiencies, checking your blood vitamin levels -- and potentially adding supplements -- is appropriate. But most people need a reminder that blindly taking high doses of vitamins can lead to unnecessary side effects; you're to be commended for looking for information on labels. When it comes to vitamins, more is not always better.

(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.)