Dear Doctor: My doctor wants me to take amiodarone for my heart. But the potential side effects scare the heck out of me: possible death, permanent blindness, liver problems, thyroid problems. Should I do catheter ablation instead? My doctor says my fears are unwarranted.

Dear Reader: I can understand your concerns regarding amiodarone; the potential side effects do sound alarming. But keep in mind that the drug has been used for many years to help control the heart from going into abnormal rhythms and, unlike other medications used to maintain normal heart rhythm, amiodarone is less likely to cause abnormal heart rhythms, meaning that it is less likely to lead to sudden cardiac death. Because of this, amiodarone is the most commonly prescribed anti-arrhythmic medication.

That doesn't mean one should discount the possible side effects. First, amiodarone can be toxic to the lungs, causing an inflammatory reaction that leads to cough, shortness of breath, weight loss and chest pain. Lung toxicity occurs 5 to 15 percent of the time at doses higher than 400 milligrams per day, but only 1.9 percent of the time at doses of 150 to 330 milligrams per day. Because amiodarone is stored in fat cells, it may take months for the symptoms to begin to reverse, so afflicted patients will need to take prolonged courses of oral steroids to decrease inflammation.

Amiodarone can also affect the thyroid, causing low or high thyroid levels in the blood. Low thyroid levels are most likely, occurring in up to 20 percent of patients on high doses of the medication, but in only 3 to 4 percent of patients taking lower doses. High thyroid levels can result up to 3 percent of the time. Because of these effects, you should have your thyroid levels checked before starting amiodarone and every six months after starting the medication.

As you mentioned, the drug can also cause nerve dysfunction in the eye, leading to blindness, though this is rare. Amiodarone can also affect other nerves of the body, leading to tremors, loss of sensation and loss of bodily control. This happens much less frequently at lower doses, but still occurs about 4 percent of the time. Further, the drug can elevate blood tests for liver enzymes, with some people developing significant liver inflammation. As with the thyroid, you should monitor your liver function every six months while taking amiodarone.

A host of minor side effects include nausea, skin reactions and urinary difficulties.

You mentioned considering catheter ablation, which is sometimes performed for abnormal heart rhythms. In this procedure, an energy source is used to destroy the portion of the heart causing the abnormal rhythm. However, with some heart rhythm problems, such as atrial fibrillation, catheter ablation may initially convert the rhythm, but after one year the atrial fibrillation returns in up to 60 percent of patients. Using amiodarone before and after the catheter ablation can significantly increase the rate of success for the ablation. So, if you have atrial fibrillation, you may benefit from both amiodarone and catheter ablation.

I'm not certain what type of heart condition you have or why your doctor recommends amiodarone specifically. But it is indeed a good medication for preventing abnormal heart rhythms. Just be sure you're monitored closely for lung toxicity, thyroid abnormalities and liver inflammation.

(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 reading a lot about a fasting-mimicking diet, which is supposed to help you live longer. What is it? I've been planning to lose some weight and wonder whether this diet might be worth trying.

Dear Reader: The approach you're referring to falls into an ever-expanding category of dieting known as intermittent fasting. It has its roots in research that has found a correlation between periodic fasting and increased longevity, as well as positive health outcomes. We live in a culture obsessed with the notion that we're just one ingredient or rule or combination of foods away from a perfect diet, one that will keep us (no pressure) lean and fit and healthy and happy, so it's not too surprising that the fasting-mimicking diet would have its moment.

Let's start with the background. A number of studies have found that intermittent fasting can bestow a range of metabolic benefits. These include a reduction in body fat and overall body weight, lower blood pressure, improved blood lipid levels and improved regulation of blood sugar. Several methodologies fall under the intermittent fasting umbrella, including 24-hour fasts, alternate-day fasting, restricted calorie diets and time-restricted diets, which allow eating only during certain hours of the day. The downside of this approach to eating is that it is quite restrictive and can be difficult to adhere to. In addition, there is concern that intermittent fasting, which entails a certain amount of deprivation, can lead to bingeing and other extreme eating behavior.

When it comes to the fasting-mimicking diet, the food restrictions kick in for just five days out of the month. That is, the diet mimics a fast without requiring daily deprivation. During those five days, calories are limited to about 800 per day. The nutrient profile of the diet is typically high in fat, low in protein, with carbohydrates falling somewhere in the middle. Some versions of this approach, which are more extreme, allocate nutrients in accordance with the high-fat ketogenic diet. In this approach, 80 percent of daily calories come from fat, with the rest divided equally between carbohydrates and protein.

A study published in the journal Science Translational Medicine last year followed 71 individuals who either followed a fasting-mimicking diet for five days each month for three months, or else switched to the fasting-mimicking diet after first following their normal diet for three months. Among both groups, researchers saw a drop in both body weight and body fat, as well as beneficial effects to blood pressure, fasting blood glucose and markers of inflammation. Interestingly, these benefits were more pronounced among individuals at greatest risk for disease than in those who were not at risk. And while the authors of this study concluded that the five-day fasting-mimicking diet is both safe and feasible for healthy adults, they also point out that larger studies are needed to see whether these results can be replicated.

As for whether this particular approach is one you should try, we believe that's a discussion you should have with either a dietician or your family physician. While the benefits of this approach to diet are appealing, it requires both discipline and consistency for optimal results.

(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: Being physically fit in middle age can decrease the risk of dementia, according to my sister-in-law. She walks four miles a day and runs on the weekends, so I imagine she's covered. But I work full-time and am a single mom to three busy kids, so I'm short on free time. Just how much exercise is enough?

Dear Reader: Your sister-in-law appears to be referring to a study conducted in Sweden, which has yielded some rather dramatic findings. According to the researchers, middle-aged women who had a very high degree of physical fitness were almost 90 percent less likely to develop dementia when they reached old age compared to women with medium or poor physical fitness. When women from the "very fit" group did develop dementia, it was at about age 90 rather than 79, a full 11 years later than the average age at which cognitive decline appeared in members of the less-fit groups.

The study, published online in the medical journal Neurology in March, began in 1968. That's when researchers tested the level of physical fitness of a group of 191 women between the ages of 38 and 60. The women's peak cardiovascular capacity was gauged via a test on a stationary bicycle, which they were asked to ride in several stages until they reached a point of exhaustion. They were then sorted into sub-groups based on their levels of cardiovascular fitness. Over the course of the next 44 years, the women who remained in the study underwent periodic cognitive screening.

During that time, 44 study participants went on to develop dementia. Of those, just 5 percent came from the group deemed "very fit." In the group of women who tested as moderately fit, 25 percent developed dementia. Among the women with the lowest degree of physical fitness, almost one-third of them went on to develop dementia.

When it comes to translating those results into daily life, it's important to note that the most pronounced reduction of dementia risk was observed among the women with the very highest levels of cardiovascular fitness. The women who were unable to complete the bicycle test without taking a break went on to have the highest rates of dementia. And lest the findings seem like a fluke, the authors refer to a number of other studies, both in the United States and in Europe, that associate increasing levels of physical fitness with lowered risk of cognitive decline.

As mothers ourselves, we understand the challenge of finding time for exercise. But a mounting body of research suggests that every minute you put into physical fitness now will pay off for years to come. For general health, current guidelines suggest at least 30 minutes of physical activity per day. When it comes to improved fitness and cardiovascular health, which was linked to lowered dementia rates in the study, the goal becomes up to 60 or 90 minutes per day. This can be broken up into 10- or 15-minute segments. It sounds daunting, but we know from personal experience that, with planning and determination, it's possible and worth the effort.

(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.)