More questions from readers in honor of National Nutrition Month "Nutrition from the ground up":

"Dear Barbara, I just read your wonderful article on the benefits of chocolate in today's Florida Times-Union and I wonder about the caffeine content in chocolate. I have always heard that chocolate contains caffeine, and I know one of the benefits you cite is the relaxation of blood vessels in the head. Would you please comment? --Julie M, Jacksonville, Fla.

Dear Julie,

I wrote that "natural substances contained in cocoa powder help arteries relax and thus lower blood pressure." These substances appear to be the antioxidant "polyphenols" in cocoa, not the caffeine.

According to the National Institutes of Health, caffeine does not relax blood vessels; it causes them to constrict. That is why caffeine sometimes helps control pounding migraine headaches.

Chocolate is actually fairly low in caffeine content. One ounce of dark chocolate contains about 20 milligrams of caffeine; 1 ounce of milk chocolate contains about 6 milligrams. By comparison, an 8-ounce cup of coffee has 100-200 milligrams of caffeine, depending on how strong you like it.

So, it's not the caffeine, but the polyphenols in cocoa beans that have been shown to relax arteries (and maybe contribute to headaches in folks who are sensitive.) Coffee beans contain these substances, too, which may explain a new study that found coffee drinking lowered the risk for stroke...even if people drank decaffeinated coffee.

"Dear Barbara, I hope you have time to give some details about the correct amount of calcium, vitamin D, and magnesium for women over 70 years of age.

There are so many choices on the pharmacy shelves: Citracal, calcium carbonate, those with vitamin D, magnesium, big ones that choke you and small ones that mean you need a handful. I stand there and read labels, and then wonder if I have made the right choice. My doctor just says be sure and take calcium, but not too much vitamin D. Thanking you in advance. --Carolyn S.

Dear Carolyn,

Confused? Join the club... For adults over 70, the current dietary reference intake for vitamin D is 400 IU (International Units) but that amount is expected to be increased soon based on new vitamin D research. Up to 2000 IU of vitamin D daily is now considered the safe "upper tolerable limit" without a doctor's recommendation.

Calcium needs for those over 70 is 1200 to 1500 milligrams per day...no more than 2500 milligrams (from food and supplements combined). For magnesium, the requirement is 350 milligrams a day.

Remember that these recommendations are called DIETARY reference intakes for good reason. Our DIET is the first place to look for these nutrients. Supplements are meant to supplement what we don't get in food. (Three cups of milk provide more than 900 milligrams of calcium, 300 IU vitamin D and 80 milligrams magnesium, for example.)

That said, many experts recommend calcium citrate as the supplement of choice for those over the age of 70. (Citracal is the common brand.) This "citrate" form contains less calcium per pill, which is why you have to take more (or bigger) pills. You can pop calcium citrate anytime and it appears to be well absorbed.

Calcium "carbonate" is the least expensive and most condensed form of calcium. But to best absorb it, you need to take it with or right after meals while your digestive enzymes are active. Most important adjunct to a calcium supplement is vitamin D, which is difficult to get in even the best diet. Added magnesium also helps, especially if you are prone to constipation...

Keep those nutrition questions coming in March...National Nutrition Month!