The research team from Montreal University also found that smokers, particularly males, who consume high quantities of fruit and vegetables, also reduce their risk.
“In our study, high dietary intakes of β-carotene, α-carotene, β-cryptoxanthin, lycopene, and vitamin C were associated with a decreased risk of lung cancer,” wrote Martine Shareck, lead author.
The risk reductions of 25-35% were irrespective of age, gender or smoking status.
Gender effect in smokers
When results were analysed by different levels of smoking history, the protective effects were more gender specific.
“Odds ratios (OR) suggestive of a protective effect were found for elevated intakes of β-carotene, α-carotene, β-cryptoxanthin, and lycopene in male heavy smokers,” noted the team.
By contrast, only vitamin C provided a significant benefit in female heavy smokers.
Nevertheless, β-carotene, β-cryptoxanthin and lycopene indicated protection in female moderate smokers.
For the two latter carotenoids, statistical significance was only reached for the middle tertile of carotenoid intake, rather than the highest.
Study details
Using data from a case control study of lung cancer, scientists examined the relationship between intakes of dietary carotenoids and vitamin C with lung cancer risk.
They calculated carotenoid intakes using food frequency questionnaires of participants’ fruit and vegetable consumption during the previous two years.
Intakes were divided into tertiles, and the risk reductions of 25%-35% compare upper versus lower tertile intakes.
The study also found a link between higher carotenoid intake and decreased cell development in different subtypes of cancer.
Beta-carotene, α-carotene, ß-cryptoxanthin, lycopene and vitamin C were inversely related to progression of squamous cell carcinoma.
Alpha-carotene and ß-carotene slowed adenocarcinoma cell growth, while ß-cryptoxanthin and lycopene show inverse associations with small cell carcinoma development.
Contrasting findings
The findings contrasted with two previous large randomised controlled trials, the Beta-Carotene and Retinol Efficacy Trial (CARET), and the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study.
Both concluded that β-carotene supplementation increased lung cancer risk in smokers, particularly females, with the latter recommending, “Smokers should avoid β-carotene supplementation.”
The researchers suggested that contrasting results could be because carotenoids in this study were from dietary fruit and vegetable consumption whereas in the CARET and ATBC trials they were supplement based.
“Fruits and vegetables containing carotenoids and vitamin C are also rich in other nutrients and phytochemicals which could be responsible for their observed protective role against lung cancer.”
In conclusion, they added, “even though smoking remains the strongest predictor of lung cancer risk, it appears desirable, in light of these findings, to further promote consumption of fruits and vegetables rich in carotenoids and vitamin C to reduce the lung cancer burden among both smokers and non-smokers.”
Source: Frontiers in Oncology
Published online ahead of print. doi: 10.3389/fonc.2017.00023
“Inverse Association between Dietary Intake of Selected Carotenoids and Vitamin C and Risk of Lung Cancer.”
Authors: Martine Shareck, Marie-Claude Rousseau, Anita Koushik, Jack Siemiatycki, and Marie-Elise Parent