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.)

Dear Doctor: I recently heard a radio report that said Tylenol could ease the pain of hurt feelings. That seems hard to believe. If it's true, how does it work?

Dear Reader: When you consider the language we use to express how it feels when someone is unkind, it's filled with pain. Their words sting, you ache, you're wounded, your heart is broken, you're torn up inside. Now, new research is shining an unexpected light on how accurate that imagery turns out to be.

Here at UCLA, Naomi Eisenberger, Ph.D., the director of the Social and Affective Neuroscience Laboratory, has been at the leading edge of research into the physical and emotional effects of loneliness and social isolation. Part of that is looking at how emotional distress affects the body. In an experiment conducted by Eisenberger and some colleagues, the group was surprised to find that the same neural circuitry that gets activated by physical pain also lights up in brain scans of individuals undergoing emotional pain.

This particular study centered on an online game of catch. Several players seated at computers in different locations "tossed" a ball to each other. One of those players was the test subject, whose brain activity was being scanned.

At first the ball is thrown equally between all of the players in the game. But at a certain point, the other players begin to exclude the test subject. As the test subjects begin to realize that they are being ostracized, their brain activity changes. It mirrors what you would see when someone is experiencing physical pain.

A further twist to the findings involved how each test subject responded to being excluded. Those who became visibly angry or upset showed a marked increase in activity in two regions of the brain associated with physical pain. The players who shrugged off the change in the game -- Who cares? this isn't important -- showed significantly less activity in the physical pain centers.

Then the researchers reverse-engineered the experiment. They gave over-the-counter pain medications to some of the subjects for a period of three weeks, and again measured their brain activity during the online game. This time, the subjects who received the medication and not a placebo had significantly less activity in the physical pain centers of their brains.

It turned out that the same pain meds that eased physical aches also provided relief for emotional pain. This strongly suggests that the brain processes both types of pain in the same way. As a result, the meds work on both types of pain.

As for why this would be, researchers suspect it's because living in interconnected groups was crucial to the survival of our earliest ancestors. Physical pain alerts us to injury. Emotional pain warns us that we may be drifting too far from our fellow humans. Both put us at grave risk. So, over time, the two types of warning signs -- physical pain and emotional pain -- began to share the same neural pathways.

The bottom line? We need to take emotional pain just as seriously as we do physical 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 know that colonoscopies are more thorough than the at-home DNA stool test for colon cancer. But how much better? I have such a terrible time with anesthesia and gas. Both make me nauseated for several days. No one in my family has ever had any colon problems or polyps. I'd really like to pass, if possible.

Dear Reader: As we discussed in a previous article, although colonoscopy remains the gold standard in colon cancer screening, it does indeed pose the risk of complications, leading some people to skip the procedure. If you have problems with anesthesia -- which isn't required but makes the procedure more tolerable -- I can understand your additional worry. As for the DNA stool test, known as Cologuard, it's relatively new (approved by the FDA in 2014), but can provide an option in some cases.

Let's take a look at how the test works. It helps to understand that colon cancer arises from a series of genetic changes and alterations in how genes transmit their information. An effective way to detect these genetic markers in stool tests had been unsuccessful until the advent of Cologuard. The test looks at four molecular DNA markers in addition to a highly specific test for hemoglobin in the stool.

A 2014 study published in the New England Journal of Medicine compared the Cologuard test with FIT screening (a test that simply looks for hemoglobin in the stool); 9,989 people had both of the tests and then had a colonoscopy 90 days later. Of the 9,989, 65 people were found to have colon cancer. FIT detected about 73.8 percent of these cancers, while Cologuard detected 92.3 percent. That sounds good, doesn't it? But when it comes to advanced precancerous polyps, Cologuard detected 42.4 percent, while FIT detected only 23.8 percent. For non-cancerous polyps, Cologuard detected only 17.2 percent, while FIT detected 7.6 percent.

The problem in not being able to accurately detect non-cancerous polyps is that such polyps can develop into cancer that goes undetected until the next time you screen for colon cancer, by which point it may be advanced. Currently, the recommendation for Cologuard is to test every three years. Although you could conceivably test more frequently to detect precancerous lesions as they become cancerous, Cologuard has a high false-positive rate of 16.1 percent.

Here's why that matters in practical terms: Each positive result with Cologuard means a patient then must undergo a colonoscopy. So high rates of false positives ultimately lead to more colonoscopies.

Cologuard is a good test for colon cancer, but its inability to find non-cancerous colon polyps, its high false-positive rate and its cost ($599) prevent it from being a great test. It would be a good choice for people who simply cannot undergo a colonoscopy. That includes people with illnesses that increase the complication rate of colonoscopy, such as severe diverticulitis, diabetes, heart failure and cancer, and people over the age of 75.

Remember, you don't have to use anesthesia to undergo a colonoscopy. If you can tolerate the procedure, I would still recommend colonoscopy. It's the best colon cancer screening test for a healthy person.

(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.)