DEAR DR. BLONZ: I am a borderline diabetic. I like beer, so I drink a 12-ounce bottle about three times a week. Am I doing a disservice to my health by drinking beer? What about drinking it before a meal, as opposed to after? -- L.K., San Diego

DEAR L.K.: It would be a disservice to consume your beer, or any alcoholic substance, before driving or engaging in other tasks where alertness and concentration are essential. Having alcohol before you eat amplifies the danger.

Alcohol is treated by the body as a toxin, and as soon as it's absorbed, it goes to the liver for priority processing. One of the liver's many functions is to help maintain our blood glucose level between meals when there's no energy coming in. The liver provides the glucose by breaking down its glycogen, which is the stored form of glucose it is directed to always have at the ready.

A healthy liver has about 100 grams of glycogen for this use, the equivalent of about 1/2 cup of sugar. When alcohol enters the body, the liver turns its focus to metabolizing the toxin, which causes it to stop releasing glucose. The net effect is that the body's blood glucose can drop, which is even more problematic for those with diabetes and on medications designed to regulate blood glucose. Alcohol in these situations can contribute to a variety of symptoms that include dizziness, shakiness, hunger, slurred speech and general confusion. These symptoms might be thought of as a direct effect of the alcohol, but they can be caused by alcohol-induced hypoglycemia. As a general rule, if you are going to have alcohol, it should be with food. (For more on alcohol and diabetes, see b.link/6f2f2bd.)

Be sure to check the label of any beer brand you are considering. There are various beers with a range of ingredients. A light beer will have about 6 grams of carbohydrates, while a regular beer will have about 14 grams. (By comparison, a can of regular soda contains 38 grams of carbohydrates.)

DEAR DR. BLONZ: Is there a nutritional difference between cane sugar and regular sugar? -- B.V.

DEAR B.V.: There is no nutritional difference -- they are both sucrose, the double sugar (disaccharide) composed of a glucose linked to fructose. Cane sugar comes from sugarcane, and while "regular" sugar can come from cane, it can also come from sugar beets. An interesting side note: Sugars tend to be hygroscopic, which means they can pull moisture out of the air. Sugar's tendency to absorb or react with moisture from the environment can be bothersome, which explains why food products often include tiny moisture-absorbing packets. Such food products often include directions to keep them well sealed, especially if they are stored in the refrigerator, which is a typically moist environment.

You won't find those moisture-absorbing packets in bags of sugar, but salt-free oyster crackers can be helpful for long-term sugar storage. Interestingly, the fine-powder confectioner's sugar, which would be more vulnerable to clumping due to moisture, often includes a tiny bit of cornstarch, arrowroot or tapioca starches to keep it free from moisture.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: There is a history of macular degeneration in my family, and I understand that lutein and zeaxanthin are nutrients needed to slow its progression. What is your view on supplements as a preventive? My father and both of his siblings were diagnosed with this condition by age 75. -- M.F., Charlotte, North Carolina

DEAR M.F.: The macula is the part of the eye where the images are focused. At the center of the macula is the "fovea centralis," the point of the eye where our vision is at its best. It is the macula where the electrical impulses that correspond to what we are looking at are initiated. Milliseconds later, after the signals have made their way to the brain via the optic nerve and have been interpreted, we understand what we are seeing.

An unfortunate condition associated with aging is a breakdown of these tissues. Macular degeneration is the leading cause of blindness in older Americans. The precise cause of macular degeneration is not yet known, but the retina -- and the lens -- are thought to be susceptible to oxidative damage.

Antioxidants, including zinc, vitamins C, E and A and selenium, all have reactions that prevent unwanted oxidation. However, the key is to have antioxidants that distribute to all vulnerable tissues, which points to the need to maintain a diet that includes a variety of healthful, whole foods that provide a range of compounds to protect all tissues.

The carotenoids, particularly the antioxidant compounds lutein and zeaxanthin, are known to concentrate in the macula. In fact, they are the only carotenoids known to be in the retina's macular region, and are referred to as macular pigments.

Spinach and corn are good sources of lutein and zeaxanthin. A study in the journal Investigative Ophthalmology and Visual Science from August 1997 reported how increased intake of these foods effectively increased blood levels of the key macular pigment compounds. A study in the same journal in October 2000 reported increased macular pigment levels after 12 weeks of supplemental lutein, or 10 mg per day. In the June 2000 issue of the American Journal of Clinical Nutrition, another study reported how servings of corn and spinach effectively raised blood levels of these macular pigments.

Other good food sources of lutein and zeaxanthin include kale, collard greens, cress leaf, Swiss chard, chicory leaf, mustard greens, beet greens, red pepper, okra, endive, celery, romaine lettuce, leek, broccoli, leaf lettuce, green peas, pumpkin, iceberg lettuce, Brussels sprouts, yellow pepper and green beans. Fruits contain lesser amounts, but some of the best include avocado, plums, kiwis, pears and grapes.

Supplements are a reasonable option, but they do not replace the need to eat healthful foods. When taken as a supplement, lutein is best absorbed when taken with meals that contain fat. Be aware that while many multipurpose supplements claim to contain lutein (or zeaxanthin), the amounts can vary. Always check the label and compare it with the 10 mg per day used in the study cited above.

Read more about macular degeneration at b.link/xu9pj8j, which includes a section on treatments and therapies.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: I would like your help to settle an argument at a recent dinner. There seems to be such a push to restrict salt consumption in general, but the only hazard I am aware of is that salt can raise blood pressure in some people. Is there any other risk associated with salt? -- H.T., via email

DEAR H.T.: The main issue with excess salt intake is, as you mention, its association with high blood pressure (hypertension). But this is nothing to be dismissive about. High blood pressure currently affects roughly half of adults. It's called "the silent killer" because there are no warning signs until problems such as heart disease, stroke or kidney disease have already developed. The only reliable way to determine whether you have hypertension is to check your blood pressure regularly.

Salt and sodium are not automatically antagonistic for everyone, even those with high blood pressure. But there is no health benefit from excessive salt -- only liability. For those at high or uncertain risk about their blood pressure, it is best to keep salt to a minimum. Another point to consider is that one's sensitivity to salt, and ability to consume it safely, can change over time.

Finally, saltiness is one of our basic tastes. Salt helps to bring out the flavors in food. But the point should be to enjoy the natural flavor of foods, rather than that which comes from the salt shaker. Consider it a warning sign if you routinely reach for the shaker before you taste the food. (See b.link/2qkdb4 for more on high blood pressure.)

DEAR DR. BLONZ: I work with second- and third-graders as a student teacher. We would like to know: How do scientists determine the levels of protein and other nutrients in fruits, vegetables, meats or processed foods that contain them all? And where can I take my students to show them scientists analyzing foods? -- T.T., Chicago

DEAR T.T.: To analyze foods, representative samples are put through a series of laboratory tests that measure the amounts of macronutrients -- such as protein, fat and carbohydrate -- and micronutrients in the item. ("Macro" means larger amounts of the nutrient, whereas "micro" means smaller amounts. Read more at b.link/33chvc.) Each nutrient has its own test. Independent laboratories around the country perform these analyses, although food companies often have their own labs, as well.

You should check in your area for food manufacturers with in-house labs that offer tours. Consider creating a list of options and allowing the students to vote for their selection. I grew up in the Chicago area, and a trip like that was one of my most memorable class outings. I predict you will find companies willing to open their doors to your students.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.