DEAR DR. BLONZ: As people in our mid-60s, my spouse and I are aware that we are getting on in years. General stiffness in the mornings and occasional body aches have limited our activities to a degree, but aside from that, we are in good shape. We have not been very physically active, though, and are interested in some general coaching to help limit the chances that one of the serious ailments will come knocking on our door. -- T.C., Sun City, Arizona

DEAR T.C.: I recall when thoughts of retirement began in one’s 50s. At present, productivity and vitality often continue well beyond that -- with people living longer, doing more and enjoying better health than ever before. A good deal of the credit can be attributed to research on how various short- and long-term behaviors affect our health. There is also better health care that can focus on potentially life-altering conditions before they become disruptive. Unfortunately, such advances have yet to become accessible to all levels of society. That’s certainly something to work on.

That said, our lifestyle and the foods we eat remain vital components to help us hold back obesity, heart disease, diabetes, cancer, arthritis and cognitive decline, at least to the extent that we can. Good nutrition helps the body’s disease-fighting immune system to work at its best, but the years will always take a toll. What occurs is a product of our genes, mixed with how we have led our lives.

A widely held theory on aging pins some of the blame on compounds called free radicals, which gum up the works and facilitate the path toward disease. Research evidence continues to reveal how whole grains and nutrient-rich whole foods can combat free-radical damage. Phytochemicals, the beneficial compounds that plants evolved to help them survive, can help our bodies, as well. But it takes a plant-based, whole foods diet to facilitate that payoff. Eating well can help keep you off the sick list -- though nothing can be guaranteed in this regard, of course -- and, if you do become ill, can aid in faster wound healing, fewer surgical complications and shorter hospital stays. This is of critical importance in today’s debates about health care.

Energy is the most basic commodity of life, and the body saves all it gets its mitts on. We are designed to cut back on systems that are not routinely used, saving extra energy whenever possible. Dietary excesses get converted to energy and stored whenever possible, but being “wealthy” in this regard can set us up for chronic disease.

A healthful lifestyle keeps the body on notice that we want to keep all our parts in working order. Even the best-built engine will become sluggish if not used regularly. The “use it or lose it” proposition comes into even greater play as we age. It is easier to maintain fitness than to become fit, but patience, persistence and guidance from knowledgeable professionals can chart a course that is appropriate for each situation.

We can’t undo years of inactivity with last-minute changes, but the body can be very forgiving. It’s better to make positive changes at any age than give up without trying. There is no antidote for aging, nor is there a magic product or formula that can assure good health. A wellness visit with your health professional can assess things as they are, and you can discuss options moving forward; perhaps you would benefit from a personal coach, or you can enroll in a class at your local Y. (Many facilities now offer online classes that can be done from home, if that better fits your needs.) Keeping your focus on the big picture and maintaining the right attitude will help you enjoy all the healthy years your body can give.

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 will be having a routine colonoscopy next month and just received the preparation instructions. It says that in the week before the test, I should avoid seeds and even corn (one of my favorite foods). What defines a seed? What about fruits and nuts? -- F.S., Des Moines, Iowa

DEAR F.S.: A colonoscopy is a test in which a specialist, usually a gastroenterologist, uses a device that provides a view of the lining of the large intestine. It is a method used both for routine screening and for patients with symptoms that require a closer look. The preparation during the days before the test is no fun, but this is a very important procedure that can be a lifesaver. For your practitioner to get the needed view, it is essential that the surface inside your colon be as clean as possible. Once the procedure is over, you can begin to resume your regular menu, comforted that you have taken an important step to assess this aspect of your health.

Medical practices can have different methods of preparation before the test. Our doctor’s office had us on a very low-fiber diet for three days, and then on the day before the colonoscopy, nothing but clear liquids, such as flavored gelatin (any color but red), clear juices and soups. There were no fruits, vegetables or fiber-rich foods during any of the four days. My menu during the three days consisted of cream of wheat, eggs, cheese, meat, juices (no pulp), white rice, and English muffins with butter. I read labels to make sure nothing contained more than 1 gram of fiber per serving.

A key period of the preparation is the day before the test, and the use of medications that empty out your digestive tract. I used magnesium citrate, which I found to be a bit more palatable than the sodium phosphate product that was also an option. Some physicians rely on a PEG (polyethylene glycol) solution to be consumed throughout the day. There is no real culinary joy with any of these; it is something we have to endure, with the knowledge that in a short time, it will be over. Most instructions say that you should drink lots of water that last day. Please rely on your doctor’s office and the specific instructions they provide.

As for the specifics of your question: Fruits, nuts and seeds are higher in fiber, so they might be a problem, especially on the three “modified diet” days before the test. The day before, of course, they are out of the question.

Again, good preparation is the key to a good reading, so toe that line as best you can. An inadequate preparation might make it impossible for your doctor to see what needs to be seen and draw medical conclusions. Your preparation can affect how long you are allowed to wait before your next test, so there is a benefit to doing it right! Best wishes for a clean test.

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 do not eat much fish, and my doctor suggested taking fish oil capsules. My question is whether flaxseed oil is an effective alternative source of omega-3 fatty acids. This would be preferable to me, as it does not come with the risk of containing mercury or other contaminants, and there is no fishy smell. -- S.M., Phoenix

DEAR S.M.: Our body requires certain specially built fatty acids in the same way it requires vitamins, minerals and protein. Fatty acids are long chains of carbon atoms bound together. In chemistry, the term “omega” refers to the location of the first double bond along the chain. If it begins on the third carbon, it is called an omega-3 fatty acid. If it starts on the sixth, it’s an omega-6, and beginning at the ninth carbon, it’s an omega-9 fat. The precise point of that first double bond and the length of the chain affect what the substance can do in the body. We can make double bonds in some locations along a chain (such as at the omega-9 position), but not at carbon 3 or 6. We need fats built this way for various functions, and this is what makes omega-3 and omega-6 fatty acids dietary essentials.

Omega-6 fats are found in many vegetables, such as corn, soy, sunflower and safflower. The richest dietary source of omega-3 fatty acids is coldwater fish, such as salmon. There are also plant sources, and flaxseed is among the highest. Omega-3s can be found in lesser amounts in walnut, canola, soy and other plants, but these are shorter cousins to the ones found in fish oil, and it’s that longer version that the body requires for certain functions.

That means that while fish oil omega-3s are ready for the job, our bodies need to elongate plant omega-3s before using them. This can be done, but it is not an efficient process. Eating fish rich in omega-3 is definitely the best and most efficient way of getting these essential fats; the highest levels are found in salmon, tuna, mackerel, sardines and herring.

I consider fish oil capsules to be a lesser alternative. Concerns about contaminants are legitimate, so be sure to find a provider that goes the extra distance to assure the purity of the supplement before you buy.

Regardless of the source, omega-3 fatty acids must be stored properly as they are quite reactive. If they react with oxygen -- become oxidized -- they turn rancid and develop the odor characteristic of rotten fish. At that point, they change from an asset to a health liability. Refrigeration is ideal protection for these fats.

One final note: The intake of omega-3 fatty acids can affect how blood clots. Anyone using anticoagulant medications, such as Coumadin, or those at risk for issues involving blood clotting should get clearance from their health professional before starting or increasing their intake of omega-3 fatty acids.

For more information on omega-3 fatty acids from the National Institutes of Health, see b.link/EFAs.

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.