DEAR DR. BLONZ: What controls the amount of cholesterol the body manufactures? Can it make more cholesterol than it gets from food? -- D.D., Sun City, Arizona

DEAR D.D.: Cholesterol is an essential structural element in every cell of the body. In addition, it serves as a base material for the body's manufacture of a number of hormones, including estrogen and testosterone. Most of the cholesterol in the body is manufactured in the liver. If there wasn't any cholesterol in your diet, your body would have to make some. When cholesterol is present in the foods we eat, the liver is programmed to make less.

There are a number of rare genetic conditions in which the body makes more cholesterol than it needs. More common, however, is an unbalanced diet that's heavy on fats and carbohydrates and light on whole foods like greens, grains and fruits. Add to this a stress-filled, unhealthy lifestyle, and you end up with blood cholesterol levels that are not ideal.

DEAR DR. BLONZ: Is it true that the body can maintain itself better with a more alkaline diet? Can a pH test of saliva be an accurate determination of the body's acid/alkaline levels? -- G.W., San Francisco

DEAR G.W.: Degrees of acidity or alkalinity are expressed in terms of their pH. Distilled water has a pH of 7.0 and is considered neutral. When the pH is higher than 7.0, the substance is a base (i.e., alkaline), and when the value is lower, the substance is an acid. The greater the numerical distance from 7.0, the stronger the acid or base. Coffee is considered weakly acidic with its pH of 5.0, but battery acid, a strong acid, has a pH of 0.8.

The pH of the human body is slightly alkaline and it is kept within a very narrow range: between 7.35 and 7.45. There are overlapping systems set up to maintain the correct pH because essential chemical reactions won't take place if the pH is out of whack.

The pH of food varies (for examples, see tinyurl.com/lfdmusr). The human body is adept at dealing with variances; it makes its adjustments while foods are in the digestive system, and also after they are absorbed. The kidneys play a key role: The pH of urine will change according to our state of health and/or disease, and it reacts to what we eat, drink or do. In addition to urine, our perspiration and breath also help to keep the body's pH in its optimal range.

Relying on a saliva pH test is of questionable value as a general diagnostic, or as an indicator of your body's pH. Our salivary pH varies, being affected by ongoing dental issues as well as by the flora that live in the mouth. Certain disease states, anxieties and medications can also influence pH. The systems in our body are designed to compensate to keep things on track. Healthful, whole foods from plants tend to be more alkaline, but we don't need these foods just for their alkaline nature: They are assets to health because they provide nutrients and naturally occurring phytochemicals honed by nature over the millennia to support the vitality of the plant. We do best with an assortment of healthful foods coupled with an active and limited-stress lifestyle.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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: How much does the grade of olive oil (extra-virgin, virgin, etc.) have to do with the fatty-acid proportions and other health values? -- F.M., Walnut Creek, California

DEAR F.M.: The most prevalent component in olive oil is oleic acid, which is an 18 carbon-long monounsaturated fatty acid. Most of the oleic acid will be present as part of a triglyceride, where there are three separate fatty acids attached to the compound glycerol. (This is where the word "triglyceride" comes from.)

Higher grades of olive oil have only a small amount of free fatty acids -- those not attached to a triglyceride -- which is referred to as "acidity" on the product label. The lower the acidity, the better. The International Olive Oil Council states that extra-virgin olive oil must have no more than 0.8 percent acidity, and virgin olive oil can have no more than 2 percent acidity.

In the big scheme of things, though, this type of grading has little to do with the proportion of monounsaturated, saturated and polyunsaturated fatty acids. The health value of olive oil goes beyond its high percentage of monounsaturates. The olive contains active phytochemical substances, which are nature's way of protecting the olive's fats from attack. These substances, which include polyphenols and tocopherols, are present primarily in extra-virgin oil, which is the first oil to come out during pressing.

DEAR DR. BLONZ: Why is alcohol present in so many cough and cold medicines? Does it have any role in the effect of the medicine? -- D.S., San Diego

DEAR D.S.: I have written in the past that there is evidence of a beneficial health effect from a moderate consumption of alcohol. A moderate intake is considered to be one to two drinks per day, with a drink defined as a 4-ounce glass of wine, 12-ounce glass of beer or 1-ounce shot of hard liquor. But the presence of alcohol in some medications has nothing to do with health. The alcohol is there because it's an excellent solvent, and it serves as a vehicle to keep certain types of medications in solution.

DEAR DR. BLONZ: Are less expensive domestic wines as good for the heart as fine French red wines? -- S.C., Lafayette, Louisiana

DEAR S.C.: Research studies on the benefits of wine have come from both sides of the Atlantic, and I am not aware of any study performing a head-to-head comparison. I'd think it safe to assume that the wine made from similar grapes in both areas would have comparable effects. An important point not to lose sight of is that a person's overall diet and lifestyle carry more weight in determining one's state of health than any possible contribution alcohol might make.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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 recently had a blackout when I stood up after dinner. It is doubtful that it could be from dehydration, as I was drinking at the meal. Perhaps not enough salt?

I was working in the garden before dinner, and had been getting dizzy when I got up from sitting earlier in the day. Then after the meal, I stood for a minute and next thing I knew, I was on the floor. I think I was only out for a few seconds. I am active, often biking and running, and have had problems with heat exhaustion in the past. Any help/thoughts? -- S.T., Waukesha, Wisconsin

DEAR S.T.: There can be many explanations for an unexpected loss of consciousness; you have mentioned a few. It could have been a freak intersection of factors that ended up leading to a rapid drop in blood pressure (vasovagal episode). Staying hydrated is important, and if you tend to perspire heavily, it is reasonable to replenish lost electrolytes along with fluids when exercising or doing physical work. Anemia is also a possibility.

But -- and this is key -- I am not a physician and I have no real handle on other health issues in your life. You asked for my advice, so here it is: Make note of all the circumstances and share them with your health provider at your next opportunity. If anything like this has happened in the past, make the appointment now. If this type of weakness, dizziness or lightheadedness occurs again, make an immediate phone call to be seen and checked out by your physician. This may be nothing, but why take a chance?

DEAR DR. BLONZ: I buy special milk in bulk, usually a six-carton case at a time. The cartons usually have an expiration date two to three weeks in the future. If I freeze a couple of cartons as soon as I bring them home, then open them after the date on the carton, are they safe to use, and for how long? I'm not concerned about the taste because I blend the milk with protein powder and fresh fruit. I usually finish a carton within five to six days. -- B.S., Sun City, Arizona

DEAR B.S.: Assuming that the packages are appropriate for freezing, and there is sufficient air space to allow for normal expansion during the freezing process, I see no problem here from a food-safety standpoint. The clock stops during freezing. Any days left before the expiration date at the time of freezing transfer over to the time after the milk returns to its liquid state.

Also, blending the milk after it thaws, as you do, helps counter the fact that freezing tends to undo homogenization, meaning that milk fat tends to float on the surface in containers of defrosted milk. Even so, be sure to give the carton a good shake before pouring.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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.