Q. Some people say that a diet extremely low in carbs and high in protein and fat can prevent Alzheimer's disease. What is your opinion of this type of diet for brain health, and for general health, too?

Terry Z., Boston

A. That's an important question, and we'll help you get a clear picture of the healthiest diet choices to make.

First, most North Americans eat lots of processed carbs that are stripped bare of their nutrients, and that fuels obesity and unhealthy glucose levels; high levels are linked to Alzheimer's. Also, these foods often are fried or combined with trans fats and added sugars, guaranteeing they'll damage your brain and overall health. So, low-carb? For THOSE carbs, we'd say low isn't good enough. Banish them completely!

On the other hand, 100 percent whole grains and fiber-rich carbohydrates (fruits and vegetables) deliver nutrients that are essential for heart and immune health, digestive function and brain strength, not to mention a good sex life.

Now, about high protein: Most low-carb diets say red meat is OK. Not only do red meat and the saturated fat it contains increase your risk for cancer and stroke, eating processed red meat (bacon and sausage are big culprits) lowers sperm quality and count by 30 percent. In addition to clogging up your arteries and causing erectile problems, red meat makes whatever does happen less fertile.

However, good fats, like omega-3 fatty acids from nuts and salmon, and monounsaturated fats like extra-virgin olive oil, are beneficial for your heart, brain, skin and sex life.

But wait! You can't just eat your way to lifelong good health. You also need to walk 10,000 steps (or the equivalent) daily, and get 30 minutes of strength training two to three days a week. Then you'll have a healthy life, good brain power and a younger RealAge.

Q. I'm 40 and am trying to get pregnant for the first time. I hear there's a new screening test for fetal abnormalities that's less risky than amniocentesis. Is it reliable?

Jeanette J., Clarksville, Tenn.

A. There are several noninvasive screening methods and tests that can detect chromosomal abnormalities and the risk of problems such as inherited disorders, cardiac defects, Down syndrome or neural tube defects. But before you become pregnant, you and your partner may want to have blood tests to ID any genetic risks you carry for conditions such as Tay-Sachs or sickle cell anemia.

Once you're pregnant, noninvasive screening methods can identify fetal chromosomal abnormalities (most women 35 and older opt to have them done) and also may eliminate the need for the more risky invasive tests.

There's a triple test that combines ultrasound evaluation of fetal nuchal translucency thickness (that's fluid at the back of the fetus's neck), blood tests for maternal serum free beta-human chorionic gonadotropin and pregnancy-associated plasma protein A. Together they detect about 85 percent to 90 percent of existing problems, with a false-positive rate of 5 percent.

A new noninvasive maternal blood test, cf-DNA, detects Down syndrome and several other chromosomal defects 98 percent to 99 percent of the time, with a false-positive rate of less than 0.5 percent. But it identifies fewer chromosomal abnormalities than combination screening or the more invasive chorionic villus sampling and amniocentesis. If cf-DNA comes back positive, you generally have the finding confirmed by an invasive test. CVS (at around 11 weeks) has a 1 percent chance of causing a miscarriage, and amniocentesis (at around 15 weeks) has a less than 1 percent chance.

Deciding what screening or tests you want — and what you want to do with the information — is a highly personal decision. At your age, the risk of carrying a child with Down syndrome is about 10 times greater than a 30-year-old's, and doctors can do fetal surgery these days to correct heart problems and other conditions before birth! Knowing ahead of time that your child will have health issues can help you be prepared. Remember, knowledge is power!
