Dear Doctor: I recently read that fast food interferes with a woman's chances of conceiving. What's the connection?

Dear Reader: Fast food would seem to be an easy fall guy for our current health status: The United States ranks first in the amount of money we spend on healthcare, but 31st in overall longevity. But as much as we'd like to blame a specific industry for our unhealthy habits, the situation is much more complex than that. Further, we as individuals are the ones who, of our own free will, order the burgers, french fries, onion rings, sodas and milkshakes.

The study you mentioned looks at different foods and the role they play in pregnancy and fertility. In it, 5,628 pregnant women from New Zealand, Australia, Ireland and the United Kingdom were given dietary questionnaires 15 weeks into their pregnancy. The questions had to do with the consumption of fruits, green leafy vegetables, fish and fast food in the month preceding conception. A midwife researcher also asked questions about the time it took for the women to become pregnant. A timespan greater than 12 months was defined as infertility.

The study did not find an association between green leafy vegetables or fish and time to pregnancy (TTP). But it did find an association between fruit intake and TTP. Compared to women who ate fruit three times per day, those who ate fruit only one to three times per month had a 19 percent longer TTP and a 29 percent increased rate of infertility.

Fast food, which included burgers, french fries, pizza and fried chicken, had an even greater association with TTP delay and infertility. Compared to women who ate fast food four times or more per week, those who ate fast food two to four times per week had an 11 percent shorter TTP and an 18 percent lower infertility rate; and those who ate it less than twice a week had a 21 percent quicker TTP and a 34 percent lower infertility rate. Women who reported no fast food intake had a 24 percent quicker TTP and a 41 percent lower infertility rate, compared to the women who ate it four times or more per week.

Among the study's problems: It was based on dietary recall and thus subject to recall bias. For example, a woman who had difficulty conceiving may have overestimated a factor she believed could have caused a delay in her conception. Further, 90 percent of study participants identified themselves as Caucasian, so the results may not be applicable in a multi-racial society. And lastly, fast food and lack of fruit in the diet may simply be markers of an unhealthy lifestyle. The authors did appear to adjust for this in their study, however.

That said, the results are concerning and point to the importance of diet in fertility. Many fast food restaurants have healthier options, and while these are intermixed with unhealthy food, they at least give women a choice. Of course, a better option is going to the market, selecting healthy food and taking the time to prepare it well. Even if there's no time for the latter steps, major markets now have readymade food that is both healthy and fast.

(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 old enough to remember when eggs were good, then bad, and then so bad they were probably going to give you a heart attack. Now I'm hearing we've come full circle and eggs are good for you again. What gives?

Dear Reader: We're right there with you on the confusing -- and seemingly endless -- back-and-forth about whether eggs are friend or foe. Now, the continuing line of inquiry that ushered the egg white omelet into our lives has produced new research that comes out in favor of the beleaguered egg. According to findings from a study published in the journal Heart, eating an egg each day may reduce the risk of stroke by as much as 25 percent. This is a departure from previous studies, which had either identified eggs as problematic for cardiovascular health or at best were inconclusive on the subject.

At the root of the egg's bad rep is one particular stat in its nutritional profile. At just about 70 calories each, eggs provide varying amounts of vitamins A, B2, B12 and folate, trace minerals like selenium, iodine, iron and zinc, and about 6 grams of protein. They also contain a hefty dose of cholesterol -- about 210 milligrams each -- which is what landed them on the nutritional blacklist. But as of 2016, the federal government's Dietary Guidelines for Americans dropped its recommendation to limit dietary cholesterol to 300 mg per day, which in turn eased restrictions on eggs.

Meanwhile, because cardiovascular disease and stroke have become a leading cause of death in China, as in the rest of the developed world, researchers there looked into the role of eggs in the diet. They mined data gathered from more than 500,000 participants in an ongoing health initiative known as the China Kadoorie Biobank study, which uses questionnaires, a range of physical measurements, and regular blood samples to track health outcomes. They focused on data from individuals who ranged in age from 30 to 79, came from a wide geographic area, and were free of cancer, cardiovascular disease and diabetes at the time they joined the study.

In sorting the data for the effects of eggs in the diet, researchers discovered that people who ate an egg each day had a lower incidence of cardiovascular disease overall than those who ate no eggs. They had a 25 percent lower incidence of hemorrhagic stroke, which is the rupture of a blood vessel in the brain, and a 12 percent reduction in risk of ischemic heart disease, in which narrowing of the arteries results in less blood and oxygen reaching the heart.

As the study's authors themselves point out, it's important to remember that this is an observational study. While results can be extrapolated, the specific conditions that contributed to the outcomes are not known. What's encouraging for egg lovers is that the results appear to bolster the new(ish) understanding that cholesterol levels in food don't automatically translate to a corresponding rise in blood levels of cholesterol. So while the conversation about eggs is likely to continue for some time, for now, eggs in moderation for people without heart disease or the risk for heart disease have gotten a green light.

(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: Do "eye vitamins" have any benefit at all? I know a lot of seniors who believe in them, but I'm skeptical.

Dear Reader: Skepticism should be a marker for overall health, especially with the flood of vitamins sold in vitamin shops, grocery stores and pharmacies. Vitamin supplements have been touted for nearly every condition with scant evidence of their efficacy when compared with a healthy diet.

Lutein and zeaxanthin generally top the list of "eye vitamins." That's because these dietary carotenoids -- related to beta carotene and vitamin A -- help form retinal macular pigment. This pigment absorbs damaging light rays and thus protects the macula, the part of the retina responsible for detailed vision. Additionally, these carotenoids are antioxidants, protecting the eye from cellular damage.

Now let's examine the evidence. Diets high in lutein and zeaxanthin have been associated with a lower risk of the late changes of macular degeneration. And, in a review of eight studies, higher blood levels of lutein and zeaxanthin were linked to a decreased cataract risk. Leafy green vegetables such as lettuce, spinach, kale and parsley are high in these carotenoids, as are eggs, so a diet containing these foods may help protect your vision.

But taking a vitamin? In people who already have macular degeneration, antioxidants such as vitamin C, vitamin E, lutein and zeaxanthin do seem to slow the progression of macular degeneration. In fact, these antioxidants -- when taken with zinc -- are linked to a 28 percent reduction in late macular degeneration. People who substituted beta carotene for lutein and zeaxanthin reported similar benefits. Note, however, that beta carotene has been associated with increased lung cancer rates in people who smoke.

That's not to say that antioxidants lower the chances of developing the disease in the first place. A 2017 review of five studies assessed the impact on 55,614 people without macular degeneration who took antioxidants from four to 10 years. The authors found that neither vitamin E, vitamin C nor beta carotene decreased the rate of macular degeneration compared with a placebo. In fact, vitamin E was associated with a slight increase in the rate of late macular degeneration.

As for multivitamins, one of the studies assessed the potential effects of the multivitamin Centrum Silver and found a 22 percent relative increased rate of macular degeneration compared with a placebo.

As for non-antioxidant vitamins, a 2009 study did show a decreased rate of AMD with higher doses of B vitamins (specifically B12, B6 and folic acid). The study included 5,442 female health care professionals who had either risk factors for coronary artery disease or actual cardiovascular disease and who took B vitamins. After an average follow-up time of 7.3 years, women who took the B vitamins had a 34 percent decreased risk of macular degeneration. Increased dietary intake of B12, B2 and B3 also has been associated with a decreased rate of cataracts.

My recommendation is to get most of these so-called "eye vitamins" from your diet. If you have risk factors for heart disease, you may find benefit with B vitamins, or if you have macular degeneration, you may benefit from antioxidant vitamins. But that's as far as the science on "eye vitamins" goes.

(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.)