DEAR DR. BLONZ: I have been active most of my life and have always eaten well. As time has passed, my abilities have decreased (as expected), and now that I have just turned 70, I am wondering whether there need to be changes in what I eat and drink. My partner and I take a fitness class that is promoted to improve flexibility, balance and strength. -- O.M., Chicago

DEAR O.M.: Nutritional requirements for active older people are not much different from those who are sedentary, with two exceptions: water and calories. Both require a varied diet that focuses on nutrient-dense fruits, vegetables, grains, nuts, seeds and dairy products, along with high-protein foods such as fish, poultry and meats. As an active person, you will simply require more total calories than a sedentary peer.

Our metabolisms go through changes as we progress through midlife to our senior years. Most of us become less active, and muscle mass shrinks following the dictates of the body's "use it or lose it" mandate. Smaller, less active muscles require fewer calories; think of the analogy of the gas used by an eight-cylinder versus a four-cylinder engine.

Over time, some aspects of the digestive system become less efficient, and our ability to sense thirst diminishes, which can result in dehydration. Mineral loss in our bones can begin to become apparent at about age 40. We tend to get a bit shorter (although most tend to think their height is the same as it was in their youth), and this means an increased risk of osteoporosis. There is less range of motion in the joints due, in part, to fewer demands on the way we move. This is the script for a sedentary lifestyle, but more active types, especially those who include flexibility and movement exercises, will experience fewer of these negatives.

Though you say you have long been active, I would like to spend some time addressing any readers who want to start becoming more active in their later years.

First of all, start slowly. Touching base with your health professional makes sense if there are any health issues. While muscles don't respond as they did in your youth, you will slowly adapt to your new routines. I encourage all to consult with credentialed trainers who can map out a reasonable course. An important benefit is that muscular work helps you hold on to your bone strength, and as long as you go slowly and don't overdo it, the joints will regain and retain more flexibility to help support the physical activity. This will also help improve your balance. The circulatory system also improves, providing fuel and removing waste materials from the working muscles. You may also find improvements in your sleep habits.

A word on water: Drink some before, during and after exercise because it helps keep the body cool through perspiration. In addition, water facilitates the shuttling of waste products from energy production out of the body through the urine. Dehydration, even when mild, impairs performance and can cause the body to overheat and malfunction. This can be especially dangerous in the older athlete, because the kidneys do not operate as efficiently. Because one's awareness of thirst can be lost during exercise, it's best to make drinking water a part of any exercise routine.

You might want to take a complete set of body measurements before you start. Finding that your clothes begin to fit differently is great feedback. Hunger may increase, but try to focus on fruits, vegetables and other nutrient-dense foods, all eaten slowly. Keep track of your weight weekly, but be less concerned with the numbers than with the knowledge that you are doing things for yourself that nobody else can do.

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, Please forgive the indelicacy of this question, but what is a good approach to the problem of intestinal gas? B.I., San Jose, Calif.

Dear B.I.: After we swallow, the foods we have eaten get exposed to a series of enzymes and churning actions designed to break down large, complex nutrients into sizes small enough to be absorbed through the tiny portals along the walls of the digestive system. That which is not absorbed travels on to the large intestine and waits in queue for elimination. This bulk includes such non-digestible items as bran and other fibers, bits of food and phytochemicals the body does not handle well, and any other components the body might have had trouble digesting. Our intestinal flora, composed of microorganisms that inhabit our large intestine, now have a chance to devour these compounds -- in fact, that's what they live on. Gases are produced as a byproduct of their action. Some gas can be absorbed back into the body, but if the rate of production exceeds that ability, the passing of gas will result.

A normal, healthy individual will pass gas an average of 10 times per day, and most of the gas produced does not present an assault to the senses. Some gaseous compounds are on the other end of the spectrum, and when you add ten grams of a nonabsorbable carbohydrate, the type that flora feast upon, the incident of gas passing can rise substantially. With any increase comes the awareness of the bloating and the need to let it out.

The gassy nature of foods, however, can vary from meal to meal, and depend on portion size, timing and other factors such as how often we eat a particular food, whether we're relaxed or anxious, the speed at which we eat, or even how completely we chew. The best bet is to keep track, as best you can, of the foods and any coincident factors to find out which combinations give rise to the undesired effects.

A large bowl of beans on an empty stomach, eaten by someone who doesn't eat them very often, will produce more gas than the same serving eaten slowly as a part of a full meal by a regular bean-eater. Having a combination of protein, fat and carbohydrate tends to slow the rate at which food travels through the digestive system. In this case, gas absorption into the body can keep up with production. By contrast, when a single gassy food is eaten, the flora are able to go one-on-one with the problem-causing material and the results will be more obvious.

Key foods include legumes, as they contain a type of carbohydrate that the body has trouble digesting. Lactose in dairy products can also be a problem. Note that there are over-the-counter products that can help with these two types of foods. Sorbitol and other sugar alcohols, and certain soluble fibers in grains or laxatives can also be a problem.

Although foods are the first thing people think of with intestinal gas, other factors also need to be considered. These include medications, especially antibiotics, laxatives and the inadvertent swallowing of air, often occurring when eating too quickly or talking while chewing and swallowing. Health problems with the digestive system itself can also be an issue. Stress, anxiety and smoking can also affect efficient digestion. Any persistent digestive problem should be brought to the attention of your health professional.

I recommend a read of the page from the National Digestive Diseases Information Clearinghouse at http://tinyurl.com/3og8t.

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 purchased sugar-free ice cream and noticed that the carton stated "sugar alcohol: 7 grams per half cup." What is sugar alcohol, and is this anything I should be concerned about? -- D.D., Lafayette, Calif.

DEAR D.D.: Most think of alcohol in relation to beverages and the ethyl alcohol they contain, but in chemistry, the term "alcohol" can refer to any compound containing a particular chemical structure. A sugar alcohol belongs to the family of carbohydrates having the "alcohol" structure and also a sweet taste. The sugar alcohols include sorbitol, mannitol, maltitol and xylitol. Each has a slightly different take on "sweet," but one thing they share is that you don't need to show an ID to buy products containing them (unless, of course, they also contain ethyl alcohol).

When compared to regular sugars such as sucrose, glucose or fructose, sugar alcohols contain about half the calories, they are not as rapidly absorbed and they have an insignificant impact on blood sugar level. This makes them useful as a sugar substitute for diabetics and others looking to limit their sugar intake.

Sugar alcohols are metabolized differently than other carbohydrates; one beneficial aspect of this is that they do not feed the acid-producing bacteria that live in our mouths. As such, sugar alcohols do not contribute to tooth decay.

They are not considered "sugars" for food-labeling purposes, and don't have to be declared on the label, but they can be. The FDA allows food sweetened only with sugar alcohols to be labeled "sugar free." While they have their benefits, be careful not to overdo it. Part of the sugar alcohol is not efficiently absorbed, and passes through and ends up being fermented by flora that live in the lower part of the digestive system. This can contribute to abdominal gas and cramping, especially when consumed on an empty stomach.

DEAR DR. BLONZ: I would like to find out more about hearts of palm. I eat them in a salad quite frequently, and it just occurred to me that it was part of the palm and I don't want to be adding palm oil to my diet. I belong to an eating club, and we are all senior citizens interested in living a long life. We debated the benefits and potential dangers of this at our last meeting, and are all anxious to know your answer. -- G.G., Tucson, Ariz.

DEAR G.G.: Hearts of palm come from the palm plant, but not from the oil-containing portion. A one-third cup serving of hearts of palm contains less than a half-gram of fat, 14 calories, 207 mg of sodium, 1.5 mg of iron, and 1 gram of dietary fiber, together with manganese and smaller amounts of vitamin C, folate and other nutrients.

Finally, why do you classify palm oil as a no-no? This undeserved reputation originated from the misplaced branding of palm oil -- and all other tropical oils -- as foods to avoid at all cost. These foods, especially when present as a part of a whole food, can play a role in any well-balanced diet.

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.