A new study suggests that high amounts of zinc might lower the risk of lung cancer by 42%, and iron from specific sources might also lower the risk.
The Rotterdam Study, a prospective population-based cohort study, sought to examine if dietary calcium, copper, iron, magnesium, selenium and zinc intake were linked with lung cancer risk among 5435 participants aged 55 years and older. Subjects underwent detailed clinical examinations and assessment of diet, and follow-up visits were held every 3-5 years. The mean follow-up time was 15.2 years, although some patients were followed for up to 22 years.
During the follow-up period of 22 years, 211 incident cases of lung cancer were identified. A higher zinc intake was linked with a 42% reduction in risk of lung cancer (highest intake vs lowest intake), and higher iron intake was also linked to a lower risk of lung cancer. The results didn't change if subjects who used mineral supplements were excluded. After stratification by gender, the inverse link between dietary iron intake and lung cancer was only observed in men. There was no link between dietary intake of calcium, copper, magnesium and selenium and lung cancer risk.
The links are not causal, meaning we can't state that zinc or iron prevent lung cancer based on this study, merely that there's a correlation. However, zinc and iron do have specific effects which can help explain how they might fight lung cancer.
Oxidative stress is implicated in lung cancer, and zinc protects cells against oxidative damage. Also, zinc has an important role in DNA repair, and immune functioning.
Too much or insufficient iron can cause oxidative DNA damage. Low dietary intake of iron, together with low DNA repair capacity can lead to a higher risk of lung cancer, as can low dietary intake of zinc and low DNA repair capacity.
The important findings and implications of the study are that zinc and iron from food sources other than red meat may help prevent lung cancer, and heme iron (iron from animal dietary sources) intake was inversely linked with lung cancer risk. There was no link between non-heme iron (from plant sources) and lung cancer risk.
Sources of heme iron from poultry or fish have been linked with a decreased lung cancer risk, whereas red meat is linked with an increased risk. The authors of this study remark,
In the current investigation, we adjusted for red meat; therefore, it can be speculated that the observed beneficial role of heme iron may be due to other animal dietary sources.
Take-home message
Zinc and iron at optimal levels, not too high or too low, might help prevent lung cancer, but red meat should be avoided as it can increase lung cancer risk. Zinc from sources other than red meat might protect you against lung cancer.
Women need about 18 mg of iron per day, and men need 8 mg. The recommended amount of zinc for women is 8 mg/day, and for men it's 11mg. These amounts will change according to age and pregnancy status. Do not use iron supplements unless you're anemic.
We all need plant-based foods for best health, and try to include some servings of fish, or poultry to obtain enough zinc and heme iron.
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