Dear Doctor: I have just been diagnosed with a herniated disc and pressure on the sciatic nerve in my lower spine. Currently, I participate in yoga, weights and machines at the gym, and I walk for most of my errands. Am I helping or hurting my recovery with these activities?

Dear Reader: First, let's take a look at your spine. The bones of the spine are called vertebrae; in between those are intervertebral discs. The discs help hold the vertebrae together, but also act like shock absorbers when you jump, run, walk or lift.

The outside portion of a disc is essentially a ring of strong, cartilagelike material. Within this ring is a gel-like material called the nucleus pulposus, which also helps absorb shock. When a disc herniates, the gel-like nucleus pulposus bulges through the cartilage-like layer of the disc. The problem with disc herniation is that the bulge pushes upon the nerves coming out of the spine. In the lumbar spine, this can lead to nerve pain that radiates down the leg. This is termed radiculopathy, which is what you seem to be describing.

The pain of lumbar radiculopathy can be debilitating, leading to time off work, inability to exercise and poor sleep. The encouraging fact is that the majority of people with lumbar radiculopathy recover fully.

As for exercise, the amount should depend on the activity and whether the activity increases the pain.

A 1999 study in the New England Journal of Medicine looked at 183 patients with symptoms of lumbar radiculopathy, separating the groups into those with bed rest and those who maintained their daily activities. The authors found that there was no difference in symptoms between the groups at either two or 12 weeks.

Similarly, a 2002 Journal of Neurosurgery study of 250 patients with symptoms of radiculopathy failed to find any difference at one, two or six months between those who underwent bed rest versus those who maintained their daily activities. Nor did a 2004 combined review of 11 studies find any benefit to bed rest in those with lumbar radiculopathy. In fact, among people with lower back pain, maintaining activity showed greater benefit than bedrest.

As for yoga, I would consider a class that focuses on breathing and gentle stretching rather than intense stretching. If done properly, yoga can help improve posture, decrease muscle tightness and reduce pain. However, the more aggressive flow-type of yoga can have negative effects if positions are performed improperly. Take similar care with weights. Avoid any such exercises that place strain on the back -- especially dead-lifting -- and be sure to decrease the number of pounds you're lifting.

Walking is somewhat different. It shouldn't worsen your symptoms -- and may in fact be helpful. That said, while you recover from your disc herniation, I would recommend avoiding stairs because going up or down them may be jarring to your back.

My advice? Be prudent about the types of exercise and activities you do with a herniated disc, because activities that place stress upon the lower back may make the herniation worse. As your symptoms get better, you can start back-strengthening exercises that will reduce your risk of future low back pain.

(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 just read that stress can cancel out the health effects of eating "good" oils, like olive oil. If that's true, why should I even bother trying to eat better?

Dear Reader: We knew when this study began making news last year that health care providers were in for some challenging conversations about diet. And while your reasoning does follow a kind of logic, we hope that a deeper dive into the facts can help add some perspective.

The study in question looked at the physical effects of two different types of fat on 58 women. Both groups ate a breakfast of eggs, biscuits with gravy, and turkey sausage. The food for one group was prepared with palm oil, which is high in saturated fats. The food for the second group was prepared with high oleic sunflower oil, which is considered to be one of the "good" fats. Each breakfast clocked in at a hefty 930 calories, with 60 grams of fat.

Researchers then measured the levels of inflammation markers in the blood of both groups of women. Inflammation is an immune response by the body to repair damage, and to protect it from infection and unfriendly organisms. However, when there is nothing to neutralize, the over-vigilant immune system can wind up doing harm to the body's own tissues. For example, chronic inflammation is a common denominator in conditions as diverse as diabetes, rheumatoid arthritis and heart disease.

The unexpected result of this particular study wasn't that the "bad fats" group had measurably higher blood levels of inflammation markers than the "good fats" group. That was pretty much expected. What surprised the researchers was that women in the "good fats" group who experienced significant stress in the previous 24 hours had blood test results similar to those in the "bad fats" group.

The study results are certainly interesting and add an intriguing new wrinkle to our understanding of the interplay of stress and diet. But it's important to note certain limitations. First, the sample size is quite small and the scope of the study covers a single meal. Also, that meal is high in both fat and calories. It would be instructive to see the results of a similar study that includes a group eating a healthful meal of lean proteins and a variety of vegetables. Take it a step further and see how vegetarians and vegans fare.

But back to your question, which we suspect is more exasperated than serious. Our answer is yes, please do stick to a healthful way of eating. Although the metrics of diet -- calorie counts, serving size, grams and types of fat and carbs -- play out on a daily basis, the truth is we're looking at years and decades. The long haul.

When it comes to eating habits that stretch over a lifetime, you're quite likely to reap benefits from choosing the fresh peach more often than the peach cobbler. And a deliberate timeout every day for a few moments of calm and quiet, along with a bit of deep breathing (how about right now?), can also do a world of good.

(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 smoked cigarettes for years, but I always used the filtered kind. (I've since stopped.) Now I'm hearing that people who smoke filtered cigarettes have increased rates of lung cancer compared to those who smoke unfiltered cigarettes. How can this be?

Dear Reader: First of all, let me congratulate you for kicking the habit. No doubt it was hard, but giving up smoking was the best thing you could have done for your health. By doing so, you decreased not only your risk of lung cancer and emphysema, but also your risk of a heart attack and vascular disease.

That said, I agree; at first glance, it doesn't make sense that filtering the tar from cigarette smoke can increase the risk of lung cancer. The cigarette industry, knowing the health risks of smoking tobacco, invented the filtration system in the 1950s specifically to reduce smoking-related injury to the lungs. In the late 1960s, only 7 percent of cigarettes had a filtering system, but by 1982, nearly 100 percent of cigarettes had a filtering device.

Prior to unfiltered cigarettes, the majority of lung cancers were squamous cell cancers. Because smokers at the time were predominantly male, these cancers were largely found in men. As filtered cigarettes became the predominant cigarette on the market, the rates of another type of lung cancer, adenocarcinoma, began to increase. During this same time period, women began smoking at greater rates, and these cancers were often the predominant type among female smokers.

In fact, rates of lung cancer in women have consistently been increasing since the 1970s, and the majority of these cancers have been adenocarcinomas. Further, while the overall rate of lung cancer in men has decreased over the last 40 years, the percentage of men with adenocarcinoma has increased.

Those facts establish a correlation between filtered cigarettes and adenocarcinoma of the lung. But a direct connection is less clear. After all, filtered cigarettes do substantially reduce the amount of inhaled tar. In 1954, a cigarette delivered 38 milligrams of tar; in 1997, it delivered 12 milligrams of tar. Cigarette companies even advertised the fact that filtered cigarettes delivered less tar, calling them "light" or "ultralight" cigarettes. That sounds good, doesn't it?

Note, however, that the filters themselves can lead smokers to take bigger inhalations to overcome the filters. Thus, they inhale more of the toxic substances and cancer-causing materials in the cigarettes. Additionally, filtered cigarettes burn more slowly, leading to more puffs per cigarette and the inhalation of more toxic substances. Also, without the high heat of unfiltered cigarettes, toxic substances are less likely to burn off. And finally, a cigarette filter -- based on where it sits upon a person's lips -- leads to increased water content within the filter, which enables toxic particles to move more easily into the lungs.

All these factors mean that toxic chemicals, such as nitrosamines and NNK, which have been linked to lung adenocarcinomas, are more likely to travel deeper within the lungs of people smoking filtered cigarettes than those smoking unfiltered cigarettes. Research has not yet proved that filtered cigarettes lead to higher rates of adenocarcinoma, but the Surgeon General's 2014 report suggested that cigarette design changes in the 1950s may indeed have led to the rise in adenocarcinomas of the lung.

Ultimately, the fact remains that cigarettes are extremely addictive -- and filters don't change that fact. With or without filters, cigarettes cause lung cancer. So the best course of action is to stop smoking (or to never start) and to not believe that a filter will decrease your risk of lung cancer.

(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.)