Nutrient interventions against lung cancer have a ways to go before public health application

That was the key finding from a review by China's Qingdao University, which sought to explore the potential of nutrients for preserving lung function and preventing lung cancer, as well as to suggest several hypothetical intervention patterns.

As lung cancer and COPD have shared aetiology — including lung function impairment, and key aetiological changes such as DNA damage and changes in epigenetics — targeting this may help to prevent both.

Micronutrients and phytochemicals

Due to their potent antioxidant or methyl-donating properties, certain micronutrients (vitamins and minerals) and phytochemicals (carotenoids and phenols) have received considerable attention.

The researchers reviewed observational studies and supplementation trials, and reported that the consumption of vitamins A, B12, C, D and E — among others — carotenoids, flavonoids, curcumin, resveratrol, magnesium, and omega-3 had all shown protective effects against the loss of lung function.

Some of these components were said to have done so mainly be enhancing average lung function, while others reportedly did so by lowering the lungs' rate of decline.

Timing also played a part in the effectiveness of dietary interventions; those who receive interventions early in life may experience better lung function reserve over their lifespan.

For smokers, protective nutrient interventions were said to be likely to "mitigate the effects of cigarettes on lung health"​.

• Carotenoids and vitamin A​

Carotenoids, known for their anti-oxidative properties, were found to aid lung function. Higher baseline levels of carotenoids and an increase in pro-vitamin A carotenoid concentrations were reported as indicators of 15-year slower decline in lung function in young adults.

However, smokers may need to be cautious when it comes to their carotenoid intake.

On the other hand, studies on vitamin A's role in lung function produced conflicting results, with inconsistencies found in the relationship between lung function and both vitamin A consumption and circulating vitamin A levels.

The review noted that while both retinols and carotenoids can be considered vitamin A, many studies did not distinguish between the two.

Retinol is relatively unstable, and its levels in lung tissue do not reflect vitamin A intake, meaning serum retinol levels may be an unreliable indicator for assessing dietary interventions.

• Phytochemicals​

Anthoycanin was shown to protect significantly against age-related lung function decline in elderly men, while in a few cross-sectional studies, flavonoids, catechins and pro-anthocyanidins had a similar effect on participants.

Curcumin-rich curry had a dose-dependent impact on forced expiratory volume in Chinese seniors, and improve pulmonary function in smokers such that it was almost on par with that of non-smokers.

Additionally, wine-drinking was found to possibly help improve lung function, with resveratrol repeatedly associated with lower COPD risk.

However, when it came to omega-3, there was insufficient evidence that it could lower lung cancer risk or improve lung function.

Previous research had found beneficial effects of dietary vitamin E​ and carotenoid​ intake on reducing lung cancer risk. At the same time, consuming fruit high in polyphenols​ has been said to improve lung function.

Considerations for transition

The researchers behind the current study stated that supplementation trials could produce direct evidence of the benefits of certain micronutrients and phytochemicals, though any temporal relationship does not necessarily constitute causation.

However, most studies in this area are limited to large observational or cohort studies, which help to identify potential protective nutrients or phytochemicals, providing evidence for further confirmation in clinical trials.

The researchers added that mechanistic studies were important for providing experimental evidence to determine causation, and that this review offered new perspectives for the design of future clinical trials.

They concluded: "More prospective cohorts and well-designed clinical trials are needed to promote the transition of individualised nutrient interventions into health policy."​

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Source: Nutrients​

https://doi.org/10.3390/nu10070813​

"Potential Micronutrients and Phytochemicals against the Pathogenesis of Chronic Obstructive Pulmonary Disease and Lung Cancer"​

Authors: Ting Zhai, et al.​