DEAR DR. BLONZ: Can you please explain a bit about the controversy with taking vitamin A as beta carotene, namely that it might contribute to lung cancer in smokers? -- R.T., Phoenix

DEAR R.T.: Cancer can be thought of as stemming from a “mistake” in a cell’s DNA, the inherited genetic blueprint that tells a cell what to do. Substances that alter genes fall into two categories: Mutagens cause genetic changes that may or may not lead to cancer; carcinogens alter genes in ways known to cause cancer.

Tobacco is a very powerful carcinogen, and inhaled smoke comes in direct contact with sensitive lung tissues. Normally the lungs secrete mucus to entrap dust and other inhaled particles. The healthy lung then works to shuttle the mucus out of the lungs through a series of cilia, or hairs. Tobacco smoke introduces that carcinogen while at the same time causing a breakdown in the self-cleaning system. The mucus then tends to collect in the lungs, resulting in a hacking “smokers’ cough,” since coughing is another way the lungs attempt to eject unwanted substances.

Lung cancers are often present years, or even decades, before the signs emerge. Early symptoms of lung cancer include coughing, weight loss and decreased appetite, but these get disregarded as expected effects of smoking. The fact that fewer than 1 out of 10 lung cancer patients survive for five years once diagnosed is a testimony to the virulence of the disease once it develops.

Now, about beta carotene. It is an antioxidant, but it’s not all-powerful. It works as a member of the team of nutrients in our diet, and that “team” concept is critical. Many studies have found that the risk of lung cancer is lower in those who have higher levels of beta carotene naturally present from the foods they eat.

Concerns about the connection between beta carotene and lung cancer came initially from a 1994 study in The New England Journal of Medicine. That study was conducted in Finland, using males between 50 and 69 years of age. All were smokers, having an average of 20.4 cigarettes a day. These individuals smoked for an average of 35.9 years before the start of the study, so many of them may have already had the disease brewing before the study began. The paper reported a higher incidence of lung cancer in those who took beta carotene supplements for six years.

It should be noted that beta carotene taken as a supplement has never shown any ability to remove cancer once it’s already set up shop -- especially a cancer as virulent as lung cancer.

A well-nourished body needs a daily supply of all nutrients, ideally from foods, as opposed to supplements. Antioxidants should be included in the mix, as well as the beneficial substances found in plants. While nutrients do different things, they work together to produce the powerful synergy we need. You cannot rely on supplements and feel you’ve got the bases covered.

Good nutrition helps protect us, but it cannot make us invincible. Long-term exposures to cancer risk factors, such as tobacco, are going to take their toll, regardless of what foods we eat or supplements we take.

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’ve been taking 1 to 3 grams of RNA/DNA nucleic acid supplements per day for the last 30 years. I’m almost 70, but most people think I’m 50. -- H.W.

DEAR H.W.: It has been 40 years since the publication of “Dr. Frank’s No-Aging Diet” by Benjamin Frank. This book is considered to be the popular starting point of the dubious concept that dietary nucleic acids can slow aging and assist with degenerative diseases. I used the word “dubious” because there has been no reliable evidence in the scientific literature to support such a notion.

Stepping back a bit, the principle nucleic acids in our genetic material are DNA (deoxyribonucleic acid), which is found mainly in the nucleus of our cells, and RNA (ribonucleic acid), which can be found throughout the cells. Both DNA and RNA are large, complex biochemical compounds that contain particular sequences of substances known as purine and pyrimidine bases. Similar to how sentences in Morse code are made up of dots and dashes, the arrangement of the bases in the nucleic acids contain a message, which, in this case, is the genetic blueprint of how we are made.

Frank promoted in his book that increasing one’s dietary intake of nucleic acids, from either foods or supplements, could “de-age” the body and slow ailments connected with getting older.

It would be great, if it were that simple.

At the time, the concept was characterized by promoters as a “revolution in the making,” but there are problems with the logic. First, everyone’s nucleic acids are unique. Most nucleic acid supplements come from yeast, and it is a bit of a stretch to think that they would have the claimed effects for us. Another problem is that when consumed, the nucleic acids will be broken down by the digestive system. Finally, individuals at risk for gout should be aware that taking nucleic acids will increase their dietary intake of uric acid. All this said, these dietary supplements are still available in stores.

The most telling fact is that in the 40 years since the book was published, there has been no evidence in the scientific literature to support claims of youth promotion from nucleic acid supplements.

One reliable benefit from RNA and DNA supplements? Profits for their marketers.

DEAR DR. BLONZ: I eat the whole apple -- seeds, stem and all. Is this bad? -- J.G.

DEAR J.G.: How many entire apples are we talking about? The skin and flesh are good food, and no problem. There would be no problem with eating a washed stem, although I don’t see the attraction.

One thing to be aware of are the seeds, which for any plant are the keys to the next generation and, in essence, the survival of the species. Plants have evolved to produce chemical defenses in seeds to help them survive and develop. The seeds of apples contain amygdalin, a compound that degrades into hydrogen cyanide: a deadly toxin in high doses.

Swallowing apple seeds intact should not represent a problem, as their tough seed coats will allow them to pass through your system. Nor should crunching a few seeds by accident send you to the ER; as with most toxic substances, it’s the dose that makes the poison. A danger zone for a 150-pound individual, for example, would take the contents of over 200 apple seeds. Check out the article at b.link/seeds35 for more details.

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’m taking vitamin and mineral supplements in an isotonic form, because it is a more efficient delivery system. They go through the stomach and right to the small intestine, thereby allowing close to 95% absorption, due to not being diluted by stomach acids. This also speeds up entry into the circulatory system, occurring within five to 15 minutes, as opposed to the average four hours or more than a pill or capsule form does. What are your thoughts on this? -- C.G. San Diego, California

DEAR C.G.: Those statements read like they were taken directly from the product promotion. Ninety-five percent absorption for all the nutrients? Ridiculous, unless the product is only water. What the body absorbs of the different nutrients varies greatly, and will also be influenced by whether there is a deficiency or a sufficiency at the time. With many nutrients, only a small fraction is absorbed even under the best of conditions. Dietary allowance takes into account each nutrient’s typical efficiency of absorption.

You say “a more efficient delivery system,” but as a consumer, I would demand evidence to support this and their “95%” claim. Unclear if you will get any meaningful response. Pills and capsules (assuming they dissolve), or powders, work just fine.

Remember that food must be the first priority, but if you are going to take a vitamin and mineral supplement, it’s best, as a general rule, to take it at mealtime. Post-meal digestion and absorption processes are designed to get the good stuff out of our foods by keeping the mass of food churning and in contact with the absorptive surfaces for extended periods.

DEAR DR. BLONZ: What makes peanut butter dangerous? I was confused when I saw it on a list of items that could add to the risk of death. -- S.Q. Berkeley, California

DEAR S.Q.: The idea that peanut butter is a risk factor stems from the possible presence of a cancer-causing substance called aflatoxin that can attack the liver.

Aflatoxin is produced by a mold that can grow on peanuts and other grains. There are specific controls and inspections designed to prevent such contamination, keeping contaminated peanuts from getting into peanut butter. On rare occasions, contaminated peanuts have gotten past checkpoints. This can happen, but it tends to be more of a problem in developing countries than the U.S. The major brands of peanut butter have an excellent record for keeping aflatoxin out of their products. Conceivably, there might be a greater risk in warm, moist climates with in-store peanut grinding where nuts sit for a while. Following this logic, one might consider opting to make such purchases in stores that sell a lot of fresh-ground butter and keep their machinery clean.

Peanuts are a healthful food with a variety of nutrients. Whether packaged or sold in bulk, they represent a better choice than french fries, chips, candy, cookies, pastries and the like. The group that needs to be on guard are those allergic to peanuts. While many childhood food allergies tend to abate as one enters adulthood, peanut allergies tend to persist, although science is working on strategies to change this. At present, those who suffer from a peanut allergy must be ever vigilant.

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.