Dear Doctor: I've been taking vitamin E for years because it's an antioxidant and supposed to be good for me, but my doctor told me recently I shouldn't be taking it. Is that correct?

Dear Reader: Just before I graduated medical school in 1997, I wrote a review about vitamin E. Due to its apparent antioxidant effect, it appeared to have great benefits not just for decreasing the risk of heart disease, but also for decreasing the risk of cancer.

I was convinced by two large observational studies that were published in the New England Journal of Medicine in 1993. These studies analyzed data from both men and women who had filled out a questionnaire about diet and supplements and who were then followed for a period of four to eight years. The results were promising. Those women who took vitamin E had 34 percent fewer heart attacks compared to those women who didn't take vitamin E. Among men, those who took vitamin E had 37 percent fewer heart attacks than men who didn't take a supplement.

I was convinced and ready to preach the benefits of vitamin E.

But the biggest problem is that a questionnaire is not a good assessment of daily vitamin E intake. Thus, studies were needed that looked at intake of vitamin E supplements versus placebo.

The 2005 Women's Health Study followed almost 40,000 women over a 10-year period, giving one group of women 600 international units (IU) of vitamin E every other day and the other a placebo. Researchers found no difference in rates of heart attacks. Then there was the 2008 Physicians' Health Study, which assessed the impact of 400 IU of vitamin E every other day -- and, again, researchers found no difference in the rate of heart attacks.

Many studies have assessed supplementation of vitamin E in cancer prevention, with varying results.

Those looking at vitamin E and prostate cancer have found no benefit from supplementation. Although one study did find a decrease in prostate cancer in Finnish smokers who took 50 IU of vitamin E daily, further studies did not support this benefit in smokers.

A study in China found that people with good dietary intake of vitamin E had a lower risk of developing lung cancer, but that those who took vitamin E supplements had a higher risk of lung cancer. In addition, vitamin E supplements have been shown not to have benefit in reducing the risk of either colon cancer or the formation of colon polyps. Some experts suspect that vitamin E may even increase the rates of prostate and lung cancer, as well as increasing the virulence of melanoma.

Further, other studies have found no decrease in death rates among those who took vitamin E.

As for the other reported benefits of vitamin E, such as its potential to decrease the risk of colds, cataracts or dementia, those benefits have not panned out.

Currently, the recommended daily amount of vitamin E daily is 15 milligrams. You can get this from three ounces of almonds. Since vitamin E is a fat-soluble vitamin, if you have problems absorbing fat, you may need more of it in your diet and should consider a supplement.

But a vitamin E supplement has no benefit for a healthy individual who has a normal intake of vitamin E through the diet.

(Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.)

(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.)

Dear Doctor: I recently sent my mom an email at midnight, and ever since then she's been after me to stop using my smartphone at bedtime. She insists that the light from the screen interferes with sleep patterns. Is that really true?

Dear Reader: I'm pretty sure this isn't the answer you're looking for, but your mother is right. The ways in which the "blue light" emitted by smartphones, tablets and computer screens affects sleep patterns is quite a hot topic in scientific circles these days. And according to the scores of studies done in recent years, the answer is consistently the same: Yes, these devices do have a negative effect on your nightly rest.

This is troubling because insufficient sleep is associated with serious conditions such as high blood pressure, diabetes, coronary heart disease, depression and even obesity. About one-third of all Americans don't get the seven hours of sleep that are recommended to maintain good mental and physical health. In fact, the sleep deficit in the United States is so severe that the Centers for Disease Control and Prevention now identify it as a public health problem.

So how do the multiple screens in our lives figure into the epidemic of insufficient sleep?

Light is the cue your brain relies on to sync itself with the outside world. It regulates your circadian rhythms, which influence sleep patterns, hormone releases, body temperature and other vital functions.

Smartphones, tablets and computers all emit high-energy light in the blue spectrum. This particular wavelength, which is similar to sunlight, has been shown to suppress the release of melatonin, a hormone produced by the pineal gland in the brain that makes you feel sleepy.

When you use your smartphone at night, even up to 90 minutes before you go to sleep, you're confusing your body clock. The blue light from the screen is telling your brain it's still daytime. That suppresses the release of melatonin, which makes it difficult for you to fall asleep.

Once you do drift off, the disruption to your circadian rhythm is profound enough that it's difficult to stay asleep. What sleep that you do manage to get is often of poor quality. Instead of feeling refreshed when you wake up, you face the day tired.

Some smartphone makers have introduced an option to move the self-illuminated screen from bright blue to a warmer yellow/red spectrum, as with Apple's "Night Shift." And while this may a have modest effect on sleep, we would recommend that putting your phone away at bedtime is a better idea.

To give yourself the best chance at a good night's sleep:

-- Read from a printed book rather than an illuminated screen.

-- Make your bedroom as dark as possible. Use curtains to block exterior light, and eliminate inside light from clock dials, TV sets and, yes, smartphones.

-- Do what you can to block out sound -- earplugs or a white noise machine can help.

-- Keep your bedroom cool; 65 to 68 degrees is ideal.

-- Steer clear of large meals before bedtime.

-- Be aware that caffeine and alcohol can interfere with sleep.

Remember -- how you feel during the day has a lot to do with how well you slept the night before.

(Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.)

(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.)

Dear Doctor: I just entered my second trimester without any nausea at all. Considering a recent study linking morning sickness to a successful pregnancy, should I be worried?

Dear Reader: Nausea occurs in up to 80 percent of pregnancies. The cause appears to be related to a rapid increase of the pregnancy hormone beta hCG (BHCG) as well as the rise of estrogen. The nausea can be distressing for many women and can lead to worries about a future miscarriage.

Paradoxically, nausea may be an indication of a successful pregnancy. Preliminary studies have found this correlation, but they could not differentiate if the lack of nausea was related only to an early miscarriage or to an overall successful pregnancy.

A 2016 study in JAMA Internal Medicine looked at women between the ages of 18 and 40 who had a history of one or two miscarriages and who were trying to conceive. Of those women who were deemed to be pregnant based on a measurement of BHCG, 797 eventually became pregnant. These women kept daily diaries, recording instances of nausea and vomiting from the second week to the eighth week of their pregnancy. If a woman had nausea once, she was considered to have nausea in the pregnancy.

In week two of their pregnancy, only 20 percent of the women reported nausea, but by week eight of their pregnancy, nearly 85 percent of women had reported nausea. After the eighth week of the pregnancy, nausea was measured at monthly intervals. Also, to confirm a viable pregnancy, the women underwent an ultrasound at week six or week seven.

Investigators found that women who experienced nausea at some point during their pregnancy had a 50 percent reduction in the risk of a miscarriage. Those women who were afflicted with both nausea and vomiting at some point in their pregnancy had a 75 percent decrease in the chance of having a miscarriage. Moreover, based on the week-six and week-seven ultrasounds, the lack of nausea in the women who miscarried was not related to a lack of a viable pregnancy.

The authors proposed that nausea during pregnancy may have a protective effect by alerting a woman about her condition so as to alter her diet and avoid toxic substances, which could increase nausea or harm a pregnancy. I'm not so sure about this, but it is a possibility.

In regards to this study, I can understand the worry about your lack of nausea as you enter the second trimester of your pregnancy. But when you look further at the study, you find that nearly 94 percent of miscarriages happened in the first trimester of the pregnancy. So as you enter the second trimester, there is significantly less likelihood that you will have a miscarriage. Also, this study focused on women who had previously had a miscarriage, so its findings may be less applicable to you.

In summary, I wouldn't be concerned about your lack of nausea. But please do schedule follow-ups with your obstetrician for your regular prenatal care.

(Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.)

(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.)