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 firstname.lastname@example.org. Due to the volume of mail, personal replies cannot be provided.