Here we are again with a few letters from you, the readers. The ongoing dialogue you create is fascinating, informative and often inspiring. Your thank-you notes, in which you let us know that something we explained or suggested has helped you in some way, are especially gratifying. And quite often, the information you share about your own health care journeys is valuable enough to pass along.

After reading our column about hip replacement, a reader was kind enough to share her own story. Taking the time to get ready for surgery made all the difference to the success of the procedure.

"The best advice I got for my hip replacement was from my internist and surgeon –- prepare beforehand for the surgery," she wrote.

The reader was in her 40s when she learned that a hip replacement was in her future. Fast-forward a few decades and, at age 70, tired of the ongoing pain, she decided it was time to get a new hip. Two new hips, as it turned out. Although her surgeon was skeptical because no one her age had ever had a double hip replacement at that hospital, she was determined.

"The only way (my surgeon) would do it was if I lost weight and got in shape," she wrote. At 5 feet 6 inches tall and 182 pounds, this was definitely a challenge. Following the advice of her internist, our intrepid reader joined an exercise class in the warm water therapy pool at her local YMCA.

"I gave myself a year," she wrote. "Went to class six days a week for an hour a day. I became a vegetarian, except I do eat fish."

Following a successful surgery to replace both of her hips, she spent 3 1/2 days in the hospital. Four weeks later, she gave up her walker. Eleven weeks post-surgery, she returned to her exercise classes in the YMCA pool.

"Tell your patients to prepare, prepare, prepare," she wrote. "It makes all the difference in the world for ease of any pain and for mobility. If you lose the weight, it is easier getting up and down. I'm down to 144 pounds, and it has made a world of difference."

To which we would like to add a hearty congratulations! 

A reader (and retired journalist) from Clovis, California, was interested in the list of gut-friendly foods in our column about boosting the bacterial microbiome. She is allergic to walnuts and wonders whether any other nuts are considered to be prebiotics. The answer is that yes, almonds are also a gut-friendly food. A handful per day will make your intestinal flora quite happy.

(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.)

Finally, in our column about how to gain weight, we heard from a registered dietitian. She wishes that we had included the suggestion that the reader consult with a registered dietitian to learn the complexities of the body mass index, or BMI, as well as a broader array of strategies to add calories to the diet.

As ever, thank you for reading our columns and for the ongoing conversation. It's both a pleasure and an honor.

Dear Doctor: Colorectal cancer is rising among young people, as I recently read in a news report. But why? I thought colorectal cancer required a lifespan of unhealthy behavior.

Dear Reader: When I went through medical school, my professors had the same notions about colon cancer. The prevailing belief was that colon cancer was predominantly a disease of those over 50. Yes, colorectal cancers did occasionally occur in younger people, but these cases were attributed to familial diseases such as Lynch syndrome or familial adenomatous polyposis, or to a significant family history of colon cancer. Ulcerative colitis or extensive Crohn's disease could also put younger people at risk of colon cancer.

However, data have been warning for several years now of a rise in colon cancers diagnosed prior to the age 50. A 2015 study in JAMA Surgery looked at colorectal cancer data from nine states between 1975 and 2010. During that time, the overall rate of colon cancer decreased -- but only because the rate of colon cancer after the age of 50 decreased. In that study, 92 percent of colorectal cancer cases occurred after age 50; 8 percent occurred before age 50; and only 1 percent occurred between the ages of 20 and 34. In that same study, the 35-to-49 age group experienced little change in the colon cancer rate, but among those ages 20 to 34, the rate of colorectal cancer cases increased by 2 percent per year.

When the researchers looked specifically at localized (meaning they hadn't spread) rectal cancers and sigmoid colon cancers in this younger age group, they found that the rate of these cancers had increased by 4 percent. Because the total numbers of colorectal cancers in this age group was small, the increased rate of cancer in that age group was also small. But the authors noted that over the next 20 years, the rates may continue to increase at the current rate, and a substantial number of cancers, especially in the rectal and sigmoid areas, may be diagnosed among people ages 20 to 34.

A 2017 study looked at similar data from the same nine states between the years 1974 and 2013 -- and had similar findings. As expected, the rates of colorectal cancers decreased in those over 55 and decreased even further in those over 70. Among people ages 20 to 40, the cancer rates decreased between 1974 and 1985, but then substantially increased between 1985 and 2013. Between 1985 and 2013, people ages 30 to 39 had a rate increase of about 1 percent, and those 20 to 29 had a rate increase of 2.4 percent. Again, the absolute rate of colorectal cancers in this age range is low, such that the incidence increased from 1 in 200,000 people per year to 1 in 100,000 per year.

But why the increase? Consider that the increased rates of colorectal cancers in this younger age group coincide with increased rates of obesity among young Americans, with multiple studies confirming the correlation. Further, colorectal cancer has been linked to decreased consumption of fruits, vegetables and fiber and an increased consumption of processed meats -- characteristics of a modern American diet reliant upon processed food.

Although the rates of colorectal cancer in younger Americans are still relatively low, the increased incidence in this age range is emblematic of unhealthy habits among younger Americans. If those habits don't change, we can expect the colorectal cancer rates to keep rising.

(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: A neurologist diagnosed me with vestibular neuritis after an "event" a year ago that put me in the hospital for a week. My MRI was unrevealing, but I am still unbalanced and find it hard to get around. Besides physical therapy, can anything else be done?

Dear Reader: Vestibular neuritis is a condition that occurs when either the inner ear, or the nerves that connect the inner ear and the brain, become inflamed due to infection. This results in dizziness (vertigo) that can range from mild to severe. In the most severe cases, vertigo can cause a constant spinning sensation that makes it difficult to stand or walk, and can cause headache, nausea and vomiting.

What exactly is vestibular neuritis?

The word "vestibular" refers to the vestibular system. This is the portion of the inner ear and the brain that interprets the sensory information the body uses to regulate balance and control eye movements. Neuritis is a general term for diseases in which a nerve or a group of nerves becomes inflamed.

When the vestibular system is healthy, the signals to the brain from the left and right sides of the body match up. When the nerves on one side become swollen due to inflammation, the information sent to the brain gets scrambled. This results in the brain being unable to match up what the left and right sides of the body are saying, and the result is varying degrees of vertigo.

Balance is affected, and vision or hearing may also be involved. Some people find it difficult to concentrate, and some experience tinnitus, which is the presence of a ringing sound with no outside source.

Most inner ear infections are viral in nature. Unfortunately, not a lot is known about how these infections are transmitted. In many cases, the viral infection runs its course over a period of weeks and symptoms go away. In some cases, if the vestibular nerves have been damaged, the dizziness can persist.

As you probably learned, there is no definitive test for vestibular neuritis. The MRI that you had was not to diagnose vestibular neuritis, but rather to rule out conditions with similar symptoms such as head injury or stroke. Other conditions with similar symptoms include allergic reactions, the side effects of certain prescription or nonprescription medications, a neurological disorder or anxiety.

In cases where dizziness persists, further testing may be appropriate. This is done to confirm that the diagnosis is correct, and to pinpoint the location of the problem within the vestibular system. In addition to a hearing test, a physician or audiologist may recommend electronystagmography or videonystagmography tests used to evaluate the vestibular system. A short course of steroids may be recommended to decrease the inflammation in the vestibular system. The hopeful news is that, over time and with the help of rehabilitation exercises, the brain adjusts to the altered signals and the dizziness can abate.

(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.)