DEAR DR. BLONZ: I am hoping you can provide a logical explanation of acidity and alkalinity in food and the body. My interest relates to information I’ve read that the body can maintain itself better with a more alkaline diet. Is this so? Also, can a pH test of saliva be an accurate determination of the body’s acid/alkaline level? -- S.F., Janesville, Wisconsin

DEAR S.F.: The degree of acidity or alkalinity is expressed in terms of pH, which is a mathematical calculation based on the hydrogen ions present. Each hydrogen ion has a single positive charge. Substances considered “acidic” have high concentrations of hydrogen ions, while those considered “basic” have a low concentration.

A pH of 7 is considered “neutral.” Distilled water has a pH of 7.0. The greater the distance from 7.0 in either direction, the stronger the acid or base. For example, coffee is considered weakly acid with its pH of 5.0, but battery acid, a strong acid, has a pH of 0.8.

As a general rule, the human body is slightly alkaline, with its pH kept within a very narrow range: between 7.35 and 7.45. (There are exceptions, such as there being an acid environment in the stomach to facilitate digestion.) There are overlapping systems designed to keep our pH within those limits, since essential chemical reactions in our bodies can be impacted if the pH gets out of whack.

The pH of foods varies widely; check bit.ly/2VnHpPO for a table of the pH values of common foods and ingredients compiled by Clemson University. A healthy body is quite adept at dealing with these pH variances, making adjustments while foods are in the digestive system, and then after they are absorbed, as needed. The kidneys play a key role: The pH of urine changes according to our state of health and any disease processes that might be underway, and also based on what we eat, drink or do. Aside from urine, our perspiration and breath also help to keep body pH in its optimal range.

You mention doing a pH test of saliva, but this is of questionable value as a general diagnostic, or as an indicator of your body’s pH. Aside from the fact that salivary pH varies normally, it can be affected by ongoing dental issues and by the flora that live in the mouth.

Certain disease states, anxieties, stress and medications can all exert short-term effects on the body’s pH, but the systems are designed to compensate and keep things on track. There is no proven benefit to “eating alkaline” as an end in itself. A healthful, whole-foods, plant-based -- but not necessarily plant-exclusive -- diet, along with an active lifestyle, remains the best strategy.

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: My wife asks me to use low-fat milk and cottage cheese, but I prefer whole-milk dairy products. I'm 71, in good health with stable weight. I drink about a half cup of whole milk daily and eat about a quarter cup of whole-fat cottage cheese every other day. I read about a study of adult women that indicated a benefit from whole-milk products. My belief is that the fat keeps me satiated and that I would be consuming more of the low-fat variety. And the full-fat tastes better. What are your thoughts? -- S.S., Oakland, California

DEAR S.S.: I have no issues with full-fat dairy. We need to enjoy what we eat, so feel free to exercise choice in deciding where the naturally occurring fats in your diet come from; variety is an important element. Fat is one player in what will (ideally) be an overall plant-based, whole-foods diet, an essential add-on being an active lifestyle. You state that you are in good health and have a stable weight, and this speaks well to your approach (assuming, of course, that your weight is in line for your age and height). Routine wellness checks help complete the picture, verifying that your blood values and other measures are in line. Research does not raise red flags here. One study in the February 2018 issue of the European Journal of Clinical Nutrition compared the effects of whole versus skim milk on blood lipids, insulin and glucose in healthy subjects. Using separate 3-week treatment periods, where each subject received both treatments (crossover design), the study found that the daily addition of 0.5 liters (16.9 ounces) of whole milk daily did not adversely affect any of the measures, and that full-fat resulted in an increase in HDL cholesterol (the good one) when compared with skim.

DEAR DR. BLONZ: My coconut yogurt does not show that it contains any added sugar, but on the nutrition facts label, it states there are 12 grams of carbohydrate composed of “Dietary fiber 6g” and “Sugars 6g” per serving. The ingredients only state coconut cream (no sugar in that), tapioca starch and probiotic cultures. I am trying to reduce my sugar intake and find this information confusing. Is this sugar natural occurring in yogurt, and not harmful? Thank you. -- S.M., Orinda, California

DEAR S.M.: The coconut and tapioca starch provide the carbohydrate in your yogurt. The 12 grams per serving are listed as being 6 grams of dietary fiber, plus 6 grams of sugars. Note that it shows sugars, with an “s,” which is a general term used to describe any of a number of non-starch, non-fiber carbohydrates in the yogurt. While sucrose, the granular crystals also known as table sugar, is indeed one of the “sugars,” this term does not mean that it is entirely sucrose. You can see all the carbs in the “sugars” category at b.link/pdf57. There is no indication of any added sugar/sucrose in this food, just those naturally found in coconut and tapioca. Also, my thoughts are that the 6 grams, which provides 24 calories, are not a significant amount in the scheme of things.

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 have been diagnosed with macular degeneration. Upon searching for help, I found that eating pistachio nuts and Brazil nuts is recommended to stave off the expected decline of my sight. Although I don't care for either of those, my question is: How much and how often should I eat these two nuts? I read that three Brazil nuts daily are recommended but have no information on the quantity of pistachios. Any information from you will be appreciated. My ophthalmologist hasn't talked to me about what to eat. -- J.G., via email

DEAR J.G.: While they can provide healthful benefits to any diet, there are no exceptional powers in pistachios or Brazil nuts per se as regards macular degeneration. However, I do have a couple of resources for you. First is an article on age-related blindness (b.link/bay43); next is a link to the American Macular Degeneration Foundation that provides material about macular degeneration, but also has information about a cookbook focused on this issue (macular.org/good-food).

DEAR DR. BLONZ: About a year ago I was introduced to Hawaiian black salt. While I am not a heavy salt user, I like the taste and texture. One of the ingredients is activated charcoal. Is it OK to eat activated charcoal? -- R.L., San Ramon, California

DEAR R.L.: Activated charcoal is specially processed to increase the size of the pores on its surface, which effectively increases the total surface area. This type of charcoal has a greater ability to bond with and hold on to certain substances on its surface. It is used commercially in water filters because it attracts and holds heavy metals and unwanted minerals and odors. The activated charcoal itself is not absorbed; it travels down the gastrointestinal tract and is eliminated. Taking in significant amounts of activated charcoal can make certain substances consumed at the same time unavailable for absorption. However, given the small amount that would be consumed in a salt, plus the issue of whether the charcoal in the salt is, indeed, “activated,” makes this less of an issue. On the cautious side, it would be prudent to not use this salt in or around the time you are taking medications. I must admit that I am skeptical that your salt has actual “activated” charcoal. One reason is that activated charcoal does not taste that great, and can affect the flavors of other items you are eating. Hawaii has amazing black-sand beaches, and I would predict that this is plain charcoal present in the regions where the salt was harvested.

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.