Smoking and Lung Damage and Emphysema - The Vitamin A Link

Vitamin A is required to protect the cells that line the airways (and other cells) from infection and the harmful effects of carcinogens (cancer causing substances). It is these cells first line of defence and functions as a barrier against infection and maintains their integrity and function.

Please note I do not advocate or support smoking. However, as many people find it very difficult to quit, any information that may help prevent damage caused by smoking should be presented.

In 1991 researchers T.E. Edes and colleagues reporting in the journal Nutrition and Cancer hypothesized that depletion of vitamin A can be induced by exposure to carcinogens (cancer causing substances) such as benzopyrene found in cigarette smoke.

The study was designed to determine if benzopyrene exposure depletes tissue vitamin A and whether beta-carotene might prevent the depletion. Rats were fed a diet containing benzopyrene supplemented with or without beta-carotene.

The authors noted there was a decline in tissue retinol (vitamin A) in the liver and small intestine by two weeks, with a 30% decline by four weeks. But, in the case of the rats fed beta-carotene, there was no effect of benzopyrene on tissue vitamin A levels. A note of interest is that the benzopyrene had no effect on serum (blood) vitamin A levels in both groups of rats during four weeks.

The authors concluded that a high intake of beta-carotene prevented the vitamin A depletion effect of benzopyrene exposure. They went on to say, “Further studies appear warranted to determine whether some of the adverse effects of environmental carcinogens, as found in cigarette smoke, charcoal-broiled meats, and industrial wastes, might be alleviated by dietary intervention.” (Nutrition and Cancer. 1991;15(2):159-66.).

In 1993 Edes and a colleague at the Harry S. Truman Memorial Veterans Affairs Hospital, Columbia, Missouri, reported in a review that exposure to benzopyrene, a carcinogen (cancer causing substance) promotes vitamin A depletion in exposed tissues.

They noted that the effect is apparent while on a vitamin A sufficient diet but significantly, without a decline in serum (blood) Vitamin A. In other words, benzopyrene depleted vitamin A even when the diet was adequate in the vitamin, and this depletion is not apparent in blood tests.

Reviewing the studies to date they observed that although these studies involved dietary intake of benzopyrene, it would be realistic to surmise cigarette smoke exposure “would have a similar effect in the lungs and perhaps stomach and bladder.”

ScienceDaily reported on July 28, 2004 that while studying the relationship between vitamin A, lung inflammation, and emphysema, Richard Baybutt, associate professor of human nutrition at Kansas State University, made a surprising discovery: a link between vitamin A and emphysema in smokers. He found that a common carcinogen in cigarette smoke, benzo(a)pyrene, induces vitamin A deficiency.

In his initial research, Baybutt took just weaned male rats and divided them into two groups, one of which was exposed to cigarette smoke, and the other to air. In the rats exposed to cigarette smoke, levels of vitamin A dropped significantly in direct correlation with their development of emphysema.

The ScienceDaily article quoted Baybutt: “When the lung content of vitamin A was low, the score of emphysema was high,” he said. “So, the hypothesis is that smokers develop emphysema because of a vitamin A deficiency.”

In the second study, both groups of rats were exposed to cigarette smoke, but one group was given a diet rich in vitamin A. Among those rats receiving the vitamin A-rich foods, emphysema was effectively reduced.

Baybutt believes vitamin A’s protective effects may help explain why some smokers do not develop emphysema.

The ScienceDaily report further quoted Baybutt: “There are a lot of people who live to be 90 years old and are smokers,” he said. “Why? Probably because of their diet…The implications are that those who start smoking at an early age are more likely to become vitamin A deficient and develop complications associated with cancer and emphysema. And if they have a poor diet, forget it.”

In this study published in The Journal of Nutrition, Ting Li, Richard Baybutt and colleagues stated: “We showed previously that vitamin A deficiency per se causes emphysema. Benzo(a)pyrene, a constituent in cigarette smoke, induces vitamin A depletion when administered to rats; therefore, we tested the hypothesis that cigarette smoke induces vitamin A depletion, which is associated with the development of emphysema.”

They noted that Vitamin A levels decreased significantly in serum, lung and liver of smoke-treated rats. The researchers’ conclusion: Exposure to cigarette smoke induces vitamin A depletion in rats, which is associated with the development of emphysema. (The Journal of Nutrition August 1, 2003; 133(8): 2629 - 2634.)

It is worth noting that marijuana smoke contains more of the cancer causing substance (and vitamin A depleting) chemical benzopyrene than tobacco smoke. An average marijuana cigarette contains 30 nanograms of this carcinogen, compared to 21 nanograms in an average tobacco cigarette. (Marijuana and Health, National Academy of Sciences, Institute of Medicine report, 1982.)

Once again, let me reiterate that I am in no way promoting smoking! If any damage can be prevented in those who cannot quit and those around them, then the information may help save lives and government costs – not to mention the trauma suffered by families of people with emphysema. Also note that benzopyrene is not exclusive to cigarettes.

Smoking is not the only source of benzopyrene

Benzopyrene is found in coal tar (coal tar may be found in shampoos and hair dyes), in automobile exhaust fumes (especially from diesel engines), tobacco smoke, and in charbroiled food. Recent studies have revealed that levels of benzopyrene in burnt toast are significantly higher than once thought, although it is unproven whether burnt toast is itself carcinogenic.

A 2001 National Cancer Institute study found levels of benzopyrene to be significantly higher in foods that were cooked well-done on the barbecue, particularly steaks, chicken with skin, and hamburgers. Japanese scientists showed that cooked beef contains mutagens, chemicals that are capable of altering the chemical structure of DNA.

References

Journal of Nutrition (Vols. 130 and 133).

McCullough, F. et al. The effect of vitamin A on epithelial integrity. Proceedings of the Nutrition Society. 1999; volume 58: pages 289-293.

Edes TE, Gysbers DG, Buckley CS, Thornton WH Jr. Exposure to the carcinogen benzopyrene depletes tissue vitamin A: beta-carotene prevents depletion. Nutr Cancer. 1991;15(2):159-66.

Edes TE, Gysbers DS. Carcinogen-induced tissue vitamin A depletion. Potential protective advantages of beta-carotene. Ann N Y Acad Sci. 1993 May 28;686:203-11; discussion 211-2. Review.