Table 1.

A summary about beta-carotene and its effects on gastric cancer in human studies

Ref.	Region	Study type	Result
Kim et al[101]	South Korea	Case-control study	Higher dietary lycopene intake might be inversely associated with the risk of gastric cancer, especially in Helicobacter pylori-positive subjects and participants who had ever smoked
Gonzalez and Riboli[102]	European countries	Prospective investigation	Gastric cancer risk was inversely related to high plasma vitamin C levels, some carotenoids, retinol and α-tocopherol, high intake of cereal fiber and strong adhesion to a Mediterranean diet
Qiao et al[103]	Linxian, China	Follow-up study	The cumulative gastric cancer-related mortality of participants receiving “factor D” treatment, a combination of 50 µg of selenium, 30 mg of vitamin E and 15 mg of beta-carotene, decreased from 4.28% to 3.84%, which was lower than participants who did not receive factor D treatment
Persson et al[104]	Japan	Nested case-control study	The plasma level of beta-carotene was inversely associated with the risk of gastric cancer
Larsson et al[105]	Sweden	Prospective cohort study	Intake of vitamin A, retinol and the provitamin A carotenoids alpha-carotene and beta-carotene was inversely associated with the risk of gastric cancer, approximately 40% to 60% lower risk of gastric cancer than participants in the lowest quartile of intake of the nutrients
Yuan et al[106]	Shanghai, China	Cohort study	High serum levels of alpha-carotene, beta-carotene and lycopene were inversely associated with the risk of developing gastric cancer
Harvie[107]	-	Meta-analysis	Dietary intake of vitamins C and E, beta-carotene and alpha-carotene was inversely associated with the risk of stomach cancer, but blood levels of these antioxidant vitamins did not display this association
Druesne-Pecollo et al[108]	-	Systematic review and meta-analysis	Beta-carotene supplementation does not exert any beneficial effect on cancer prevention. In smokers and asbestos workers, a daily dose of 20 mg to 30 mg increased the risk of lung cancer and stomach cancer
Abnet et al[109]	Linxian, China	Prospective study	Low retinol and high lutein/zeaxanthin concentrations increased the risk of cardia cancer and non-cardia cancer, respectively
Zhou et al[110]	-	Meta-analysis	Data from the case-control study suggested that beta-carotene and alpha-carotene were inversely associated with the risk of gastric cancer, while results from the cohort study were inconsistent