Dear Doctor: A friend who was working on his old Victorian home in New Orleans started getting bad headaches. He tested high for heavy metals, and now he’s supposed to do something called “chelation therapy.” What is that?

Dear Reader: Chelation therapy is a treatment that rids the body of heavy metals such as lead, copper, mercury, zinc, arsenic, cadmium and iron.

Although these metals are naturally present in the environment, concentrated amounts become toxic. Since your friend was working on an older home, he may have been exposed to high levels of lead in the original paint. According to the Environmental Protection Agency, there’s a high likelihood of finding lead-based paint in homes built prior to 1978, when a federal ban on lead paint went into effect. When someone is renovating a house that contains lead paint, the sanding and scraping that typically take place create toxic dust, which is easily inhaled or may be accidentally ingested.

Signs of lead poisoning in adults include headaches and abdominal pain. Other symptoms can include tingling and numbness in the hands and feet, confusion or trouble concentrating, exhaustion, high blood pressure, nausea and diarrhea.

If one of a group of blood tests reveals that someone has heavy metal poisoning, a chemical process known as chelation therapy is the preferred method of treatment. It works by introducing certain chemicals into the blood, which have the ability to bind to the toxic metal ions. One such chelating agent is ethylene diamine tetra-acetic acid, a synthetic amino acid commonly referred to as EDTA.

With chelation therapy, a medication binds with the lead so that it is then excreted in urine. A possible side effect of the therapy is a burning sensation at the site of the injection. Less common are headache, nausea, high blood pressure, rash or vomiting. Years ago, when chelation therapy was delivered in high doses, it was linked to more dangerous side effects, like irregular heartbeat or kidney damage.

It’s important to note that chelation therapy is approved by the FDA only for heavy metal poisoning. We mention this because of its use as an alternative therapy for other conditions, including heart disease, autism and Alzheimer’s disease. Studies on using chelation therapy to treat heart disease show minimal benefit, and only in certain cases. It has not been shown to be successful in treating Alzheimer’s. And the American Academy of Pediatrics warns against chelation therapy, saying there's no evidence it’s is effective for autism, and that it can be dangerous.

(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’ve always heard that it’s the saturated fat in red meat that leads to a heart attack. But now I’m reading that it has something to do with the gut? Does that mean probiotics will make it OK to eat steak, which my wife and I just love?

Dear Reader: You’re referring to a study published earlier this year that found a connection between a diet heavy in red meat and a marked increase in a certain compound produced by gut bacteria, which has been linked to an increased risk of heart attack and stroke. That byproduct is trimethylamine N-oxide, also referred to as TMAO. In earlier studies, researchers uncovered a link between elevated levels of TMAO in the blood and the development of arterial plaque, which can block blood vessels and lead to heart disease.

The study you’ve been reading about, which was published in the European Heart Journal last February, analyzed how each of 113 volunteers responded to three different diets. The diets, which the volunteers followed for four weeks, used either red meat, white meat from poultry, or non-meat products such as legumes, nuts and grains as a source of protein. Every aspect of the meals, from portion size to ingredients to preparation methods, was uniform and highly controlled. The volunteers followed the three different diets in random order.

Only the red meat diet resulted in increased levels of TMAO, both in the blood and in the urine. The majority of volunteers following the red meat diet had levels of TMAO that measured two to three times higher than volunteers who were getting their protein from white meat poultry or vegetal sources. In some cases, the levels of TMAO in blood and urine were as much as 10 times higher in the red meat group than in the white meat and vegetal groups.

Researchers also discovered that the red meat diet interfered with the kidneys’ ability to excrete TMAO. That kept the circulating levels of the potentially damaging bacterial byproduct high. The good news is that a month after they stopped eating a diet rich in red meat, both blood and urine levels of TMAO had fallen significantly. The researchers speculated that the metabolic pathways suggested by this study might account for why the Mediterranean diet, which is low in red meat, is associated with lower risk of heart attack and heart disease.

Since the study shows that red meat causes the gut bacteria to produce potentially harmful compounds, your idea about taking probiotics as protection won’t actually work. However, if it’s only as an occasional splurge, it’s probably fine for you to have that juicy steak.

(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: West Nile virus is active again in southern California. What happens when you are infected? Is there a vaccine?

Dear Reader: There’s been a surge of West Nile virus in people this summer, with southern California, Nevada and central Arizona recording the highest number of cases of the mosquito-borne illness. According to statistics released by the Centers for Disease Control and Prevention at the beginning of September, 326 confirmed cases of West Nile virus disease in humans have been reported in 35 states. Of those, close to two-thirds resulted in neuro-invasive diseases such as meningitis or encephalitis.

West Nile virus has been identified as the leading cause of mosquito-borne disease in the continental United States. It’s caused by the bite of an infected mosquito and is seen in birds, humans, horses and other mammals. Mosquitoes acquire the virus when they feed on an infected bird. Since many species of birds migrate great distances, and since mosquitoes inhabit virtually every corner of the world, West Nile virus has spread rapidly. The virus isn’t transmitted between humans or other mammals. Although it can be acquired via a blood transfusion or an organ transplant from an infected donor, the U.S. blood supply is tested for the virus and is thus considered safe.

West Nile cases typically spike during late spring to late autumn. That’s when warm temperatures and wet weather create ideal conditions for mosquitoes to breed and spread. Scientists say that our rapidly warming world is also playing a role in the global spread of the disease. First identified in Africa in 1937, the disease made its first appearance in the U.S. in New York City in 1999. The virus now is seen across a majority of the continental U.S. As rising temperatures extend the breeding season of mosquitoes, scientists warn that cases of West Nile will continue to rise.

The good news is that about 80% of people who become infected with the virus will have no symptoms at all. About 20% will have symptoms that are mild and not life-threatening. These include flu-like symptoms such as fever accompanied by headache, body aches and nausea. Additional symptoms of mild illness may include rash, joint pain and stiffness, as well as fatigue, which can persist for weeks. A fraction of the population -- about one in every 150 people infected with the virus -- will develop potentially serious illnesses, including neurological conditions such as encephalitis, which is inflammation of the brain, or meningitis, in which the membranes surrounding the brain and spinal cord become inflamed.

Symptoms of severe illness include high fever, headache, muscle weakness, stiffness in the neck, changes to cognition, tremors, numbness and paralysis. If infection with West Nile virus is suspected, seek medical help. Although vaccines are available for horses, there is not yet a vaccine for humans.

(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.)