DEAR DR. BLONZ: Much of the advice I have received about managing my digestive issues has mentioned the need to avoid certain food combinations. This advice is based on the logic that “bad” combinations overwhelm the digestive system, preventing the foods’ nutrients from being properly absorbed and contributing to digestive upsets. Is this based in fact? -- O.C., New York City

DEAR O.C.: Foods are a complex combination of different types and sizes of nutrients and non-nutrient components. Our digestive system, by contrast, likes things simple. For our bodies to absorb foods’ components, foods must be taken apart piece by piece. Think of our digestive system as a “disassembly” line.

The digestive tract workers are enzymes: chemicals with specific abilities to pull apart the proteins, carbohydrates or fats in food. Enzymes are the epitome of specialization, in that each performs one action on one type of nutrient. For example, one enzyme splits big proteins into smaller pieces, while others break the small pieces into their amino acid parts. Similar-staged disassembly occurs with complex carbohydrates and fats.

We rely on over a dozen different enzymes to digest a typical meal. The beauty of the human digestive system is that it’s designed explicitly for that mixed diet. That means the advice you were given was off the mark. Since different food components get handled in different areas and by different enzymes, we don’t have to eat our foods one at a time.

Digestion begins even before the first bite: The cephalic phase starts when we see, smell or even think about food. We have all experienced our stomachs rumbling in anticipation of a meal. This is also connected to our tendency to eat meals at the same time most days, and becomes especially noticeable when a meal is delayed. In the cephalic phase, acid gets released in the stomach in preparation for the food about to arrive. In the mouth, chewing increases a food’s surface area and mixes it with our enzyme-containing saliva to facilitate the actions ahead.

The stomach is our high-acid, muscular churning compartment that denatures proteins. The acid environment activates certain enzymes involved in protein digestion, and it can also help destroy unwanted microorganisms hitchhiking on the food. The stomach is spared from self-digestion by a protective layer of mucus. Those with the misfortune of having gastroesophageal reflux disease, or GERD, have experienced the discomfort of the stomach acid splashing up into the esophagus, where that protection is not present. (More on GERD at b.link/7kae7.)

As the stomach completes its work, the partially digested mass of food, referred to as chyme, leaves through the pyloric sphincter. As the chyme departs, it is immediately doused with the body’s own antacid solution. Your meal is now in the small intestine, a veritable enzyme factory where the central part of digestion and absorption occurs.

Returning to your question, many of us may have found that certain foods or food combinations work best for us. Consider that we are creatures of habit, and our bodies do acclimate to the way we eat.

When making major changes in what we eat, it makes sense to do things slowly, but this advice is based more on our bodies’ habit-bred efficiency than a defect of human digestion. There appears to be no physiological reason to refrain from including a variety of foods at every meal.

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: What are your thoughts about personal qualities that might determine who will be successful at losing weight? -- S.O., Los Angeles

DEAR S.O.: An instructive paper in the American Journal of Clinical Nutrition (November 1990) comes to mind, which examined three different types of women. The first group lost weight, but then regained it; they were called the relapsers. The second group lost weight and kept it off; these were the maintainers. The third group was the control group, who remained at the same “non-obese” weight.

The researchers looked at the subjects’ weight histories -- including prior attempts at dieting -- and their childhood food experiences, meal and snacking patterns, emotion-related eating, and how they typically handled troubling situations. The paper revealed some interesting differences that address your question.

The relapsers were more likely to take appetite suppressants and participate in formal weight-loss programs. More relapsers skipped breakfast, and they often went on restrictive diets that denied them many of the foods they enjoyed. In comparison, most maintainers did not seek help from support groups, diet partners or health professionals. If using the same approach to weight loss, relapsers adapted their lifestyle to the program, while maintainers usually tailored the program to fit their lifestyle.

During the weight-loss period, both maintainers and relapsers reported stressful events involving family or careers. Maintainers tended to confront and solve problems, while relapsers often resorted to avoidance behaviors such as eating, sleeping and/or drinking more, or merely wishing that the problem would go away.

Another significant finding was that 90% of the maintainers, versus 34% of the relapsers, engaged in exercise at least three times a week. Studies often report that the body decreases its baseline metabolic rate (the rate at which calories are burned at rest) when weight is lost. This unfortunate decrease can slow the rate of weight loss and help explain why it is hard to keep pounds off. Regular exercise helps counter this decrease, in addition to burning more calories.

These findings suggest that personality can be an essential determinant for long-term success with weight reduction. It also tells us there’s no such thing as a one-size-fits-all diet plan. Most commercial programs suggest their methods and products work for anyone, but their main accomplishment may only be a short-term loss of pounds. People seeking treatment for a weight problem should be screened and guided into a program that suits their personality.

One hopeful message here is that a relapser can become a maintainer. Some maintainers in this study had been relapsers at one time. New habits and behaviors had to become established for that switch to occur. For example, no longer would working out be a chore only done to lose weight; rather, it was understood and internalized as a fundamental element of a new, more healthful lifestyle.

While reflecting on this, it’s essential to appreciate that realistic goals are a part of the process; you may never drop you as low as you want to go. Healthy people often carry some extra weight. Likewise, simply because someone happens to be thin is no guarantee that they are better off.

Health is as health does, and this holds true at any weight. Society-imposed pressures to achieve a particular body type do little to promote our physical and mental health and well-being.

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 question is about blueberries -- dried blueberries, in particular. I spent a pretty penny for dried blueberries to put on my cereal every morning until a friend told me that dried berries have no antioxidant value. Can you comment on this? And what about the antioxidant value of frozen berries? -- R.L., Berkeley, California

DEAR R.L.: Dried blueberries -- and other dried berries, such as cranberries, currants and cherries -- are great, and they have considerable nutritional and antioxidant value. I don’t know where your friend got their information, but I would consider carefully any other recommendations you get from that source.

FYI, I rotate among different types of berries to add to my cereal every morning. In season, I use fresh fruit, but off-season, I use frozen or dried. It’s a great way to start the day.

DEAR DR. BLONZ: I have read that shark cartilage can be effective against cancer, but my doctor had never heard of this and was cynical. I see it for sale at many vitamin stores, so I wonder why it is being offered. Are you aware of any evidence that shows that this works? If so, how much is needed? -- S.G., Phoenix

DEAR S.G.: I share the skepticism of your doctor. Please do not consider the presence of a health product at a store as evidence of its efficacy.

Shark cartilage gained fad fame as an anti-cancer compound because it was advertised to contain something unique that could prevent the development and spread of any cancer. The hypothetical mechanism was a substance in the cartilage that inhibited new blood vessels’ creation -- a process integral to cancer cells’ growth and spread. The evidence for all this is severely lacking. As support, shark cartilage proponents cite the fact that sharks do not develop cancer, but this has also been refuted.

While there is no evidence that it is harmful to take, please consider the insidious harm wrought by delay. Many early-stage cancers can be treated, but opting for a bogus remedy can give cancer a chance to grow -- and even to spread to the point where more aggressive treatments are required. At that point, the odds for success can suffer.

DEAR DR. BLONZ: What is the difference between pasteurization and ultra-pasteurization of dairy products? -- D.C., Lombard, Illinois

DEAR D.C.: Pasteurization and ultra-pasteurization are heat treatments designed to reduce the presence of potentially harmful microorganisms. The two differ in the amount and duration of heat used. Pasteurization heats a dairy product to 161 degrees (all temperatures Fahrenheit) for 15 seconds, while ultra-pasteurization heats the product to 280 degrees for up to 3 seconds. Immediately after either heat treatment, the milk gets rapidly chilled to 39 degrees.

The higher heat used in ultra-pasteurization results in a more shelf-stable product, which means it will have a longer shelf life. The product label will indicate which method was used. Neither process sterilizes the product, so once opened, both require refrigeration and will last about seven to 10 days.

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.