Does Beta-Carotene Cause Lung Cancer?

If smokers take high doses of beta-carotene supplements, it could increase their risk of lung cancer. But is beta-carotene from food, e.g. B. from carrots just as dangerous?

What is beta carotene?

Beta carotene is a phytochemical from the carotenoid family. Carotenoids, on the other hand, are fat-soluble plant substances with a yellow to red color. One speaks of a carotenoid-rich diet when the diet contains a high proportion of yellow and orange or red vegetables.

Beta carotene is the best-known carotenoid. Hardly any other food contains it as richly as carrots and kale. Although kale is green and not yellow or orange, the green of the chlorophyll masks the orange tones of the beta-carotene.

What carotenoids are there?

Examples of other carotenoids are

  • alpha-carotene (e.g. in pumpkin and carrots),
  • the lycopene (especially in tomatoes),
  • the beta-cryptoxanthin (e.g. in pumpkin and red pepper),
  • the lutein (e.g. in savoy cabbage, parsley, and kale),
  • the astaxanthin (produced by algae) and
  • the zeaxanthin (e.g. in red peppers).

They are all considered powerful antioxidants that fight free radicals and oxidative stress and can thus prevent numerous diseases such as cardiovascular diseases, rheumatic diseases, eye diseases, but also Alzheimer’s and Parkinson’s, and cancer.

Does beta-carotene protect against lung cancer?

As recently as the 1980s, beta-carotene was considered very healthy for everyone, whether they smoked or not. In 1986 there was even a study on the subject. It found that smokers who didn’t eat carrots had a three times higher risk of lung cancer than smokers who ate carrots at least once a week. There was also a significantly increased risk of lung cancer for those who only ate a few green leafy vegetables. Liver and cheese (vitamin A) apparently had no protective effect, because those who did not eat either had no increased risk of developing lung cancer.

Another study (1,663 participants) in the same year found similarly that a carotenoid-rich diet protected smokers in particular from lung cancer.

But who wants to bother with all those vegetables? At least that’s the thought of many smokers who, on the whole, rarely eat health-consciously. However, since lung cancer is not a desirable goal for them either, and quitting smoking is rarely an option, the solution was obvious: Why not just take a beta-carotene pill every day? Because it was known that a high level of beta-carotene in the blood reduced the risk of lung cancer. So you could certainly take the beta-carotene in pill form.

Beta-carotene in pill form increases the risk of lung cancer

In 1996, a rapid study of beta-carotene pills was published in the Journal of the National Cancer Institute: Over 29,000 men between the ages of 50 and 69 who smoked more than 5 cigarettes a day took 50 mg of vitamin E (alpha-tocopherol ), 20 mg beta-carotene or both, or a placebo for an average of 6 years.

In terms of vitamin E, there was no effect on the risk of lung cancer. However, beta-carotene appeared to increase the risk of lung cancer (albeit only slightly), particularly in heavy smokers (more than 20 cigarettes a day) compared to smokers who smoked less. Even in men who also indulged in higher alcohol consumption, there was an increased risk of lung cancer due to the intake of beta-carotene.

The study stopped due to frequent cases of lung cancer

The so-called CARET study, which was published in the same year, brought similar results. Here, over 18,000 participants were given 30 mg of beta-carotene and 25,000 IU of vitamin A or a placebo daily. The study had to be stopped after just 21 months since 28 percent more lung cancer cases and 17 percent more deaths were recorded in the beta-carotene group. The participants in the study were smokers, ex-smokers, or asbestos workers, i.e. all people with an inherently high risk of lung cancer.

At the same time, there were also studies that did not find any disadvantages after taking beta-carotene, such as the study also published in 1996 (in the New England Journal of Medicine) which found the following:

Beta-carotene in pill form is not always harmful

Over 22,000 healthy men between the ages of 40 and 84 took 50 mg of beta-carotene or a placebo every other day for 12 years. Among them were both smokers and former smokers as well as non-smokers. However, after 12 years, there were no significant differences in cancer risk, cardiovascular risk, or mortality risk. Even fewer men developed lung cancer in the beta-carotene group than in the placebo group (82 versus 88), although this was not statistically significant.

Three years later (1999) a study of almost 40,000 healthy women – whether smokers or non-smokers – showed that a dietary supplement with 50 mg of beta-carotene every other day for an average of 2.1 years had no effect on cancer or cardiovascular risk or even mortality.

Problematic: The long-term intake of carotenoids in pill form

But then another study appeared in 2009 with a negative outcome: Researchers at the University of North Carolina at Chapel Hill found, based on data from over 77,000 participants, that long-term use (up to 10 years) of beta-carotene supplements and other carotenoid or vitamin -A-containing supplements (retinol and lutein) can increase the risk of lung cancer, especially in smokers. The study appeared in the American Journal of Epidemiology.

The scientists were able to observe that the risk of lung cancer in smokers was higher the longer they took the supplements. The dose of the supplements was of secondary importance, even moderate doses increased the risk if the supplements were taken long-term.

It was not possible to determine whether taking these supplements also increases the risk of lung cancer in non-smokers, since hardly any of the non-smokers developed lung cancer.

dr Jessie Satia, Professor of Epidemiology and Nutrition at the UNC Gillings School of Global Public Health said:

“We believe that the antioxidant beta-carotene has oxidative effects in excessive doses, which then increases the risk of cancer.”

Carotenoids from a diet rich in vegetables reduce the risk of lung cancer

Recently, it makes sense to focus more on the effects of a diet rich in carotenoids, i.e. a diet rich in vegetables. For example, in 2014, Cancer Science reported that a study involving over 10,000 participants found that high levels of carotenoids in the blood (alpha-carotene and beta-cryptoxanthin) were significantly associated with a lower risk of dying from lung cancer.

The lung cancer risk of smokers also decreased significantly by 46 percent with high levels of alpha-carotene and by 61 percent with high levels of beta-cryptoxanthin.

The study by the research center of the University of Montreal/Canada from 2017 is even more recent. Here, too, it was shown that increased consumption of vegetables rich in carotenoids protects against lung cancer (squamous cell carcinoma and adenocarcinoma) – including among heavy smokers.

Conclusion: Vegetables protect against lung cancer, carotenoid pills do not
Isolated beta-carotene and vitamin A preparations should not be taken by smokers over a longer period of time. However, they have no harmful effects on non-smokers.

A carotenoid-rich diet, which consists of plenty of carrots, pumpkin, peppers, tomatoes, sweet potatoes, herbs (parsley, dill, etc.), kale, spinach, and other green leafy vegetables, should be practiced by everyone because it has been shown to reduce the risk of lung cancer – and both for non-smokers and smokers (including heavy smokers).

Note: For the sake of completeness, we would like to point out that with a carotenoid-rich diet there is no need to worry about a vitamin A overdose, no matter how many carrots you may eat. Some carotenoids can be converted into vitamin A in the body, but only in the amount required by the organism.

The situation is very different if you take cod liver oil or like to eat liver, both of which are very rich in vitamin A. A vitamin A overdose is possible here, but it should be avoided at all costs – especially during pregnancy, as it can lead to malformations and brain damage in the embryo.

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Written by Micah Stanley

Hi, I'm Micah. I am a creative Expert Freelance Dietitian Nutritionist with years of experience in counseling, recipe creation, nutrition, and content writing, product development.

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