Serum vitamin A, E forms tied to prostate cancer risk

Several forms of serum vitamin A and E were associated with prostate cancer risk, with significant effect modification by smoking and alcohol consumption status, according to an analysis that used data from the Singapore Prostate Cancer Study.

Participants were 508 male Singaporean patients (240 cases and 268 controls) recruited from the Singapore General Hospital (SGH) between 2007 and 2009. Cases were men diagnosed with incident prostate cancer who have not undergone treatment. Controls had no history of malignant disease at the time of recruitment. This analysis included participants who had complete data on potential confounders and available sera samples. [Nutrients 2023;15:2677]

“[Using data from this retrospective,] hospital-based, case-control study, we measured serum concentrations of 15 different forms of vitamins A and E in 156 prostate cancer patients and 118 control subjects,” said the researchers. “These forms included retinol, lutein, zeaxanthin, α-cryptoxanthin, β-cryptoxanthin, α-carotene, β-carotene, lycopene, ubiquinone, δ-tocopherol, γ-tocopherol, α-tocopherol, δ-tocotrienol, γ-tocotrienol, and α-tocotrienol.”

Compared with the lowest category, the highest category of serum concentrations of vitamin A and E forms was positively associated with prostate cancer risk. These forms include retinol (adjusted odds ratio [aOR], 6.08), lutein (aOR, 2.07), α-carotene (aOR, 3.27), β-carotene (aOR, 3.04), ubiquinone (aOR, 2.44), α-tocopherol (aOR, 2.40), δ-tocotrienol (aOR, 3.70), γ-tocotrienol (aOR, 3.02), and α-tocotrienol (aOR, 2.76).

The associations remained significant even after adjusting for various comparisons. There was a significant increasing trend in prostate cancer risk according to tertiles of ubiquinone (p_trend=0.020), α-tocopherol (p_trend=0.034), δ-tocotrienol (p_trend=0.00079), γ-tocotrienol (p_trend=0.0049), and α-tocotrienol (p_trend=0.0066).

Of note, for the association between serum ubiquinone concentrations and prostate cancer risk, ORs were more pronounced for high-grade and advanced prostate cancer, the researchers noted. However, more observational data are needed before further conclusions can be drawn.

Smoking, alcohol as effect modifiers

Associations were stronger among ever- vs never-smokers for the highest concentrations of lutein (ORs, 6.43 vs 2.75; p_interaction=0.011), β-cryptoxanthin (ORs, 7.50 vs 1.08; p_interaction=0.0054), and β-carotene (ORs, 5.61 vs 1.88; p_interaction=0.011).

Associations were also stronger among regular vs non-regular alcohol drinkers for the highest concentrations of lutein (ORs, 2.71 vs 1.81; p_interaction=0.036), β-cryptoxanthin (ORs, 2.96 vs 1.28; p_interaction=0.044), ubiquinone (ORs, 3.35 vs 1.99; p_interaction=0.030), γ-tocotrienol (ORs, 3.39 vs 2.71; p_interaction=0.026), and α-tocotrienol (ORs, 3.06 vs 1.46; p_interaction=0.021).

These findings suggest that these lifestyle factors may act as effect modifiers, said the researchers. “Cigarette smoke and alcohol consumption have been reported to accelerate degradation of micronutrients such as carotenoids. The harmful breakdown products generated may represent one possible way through which interactions contribute to increased prostate cancer risk.” [Ann Nutr Metab 2010;56:113-118; FASEB J 2002;16:1289-1291]

Larger studies warranted

“Our findings support existing evidence regarding the involvement of vitamin A and E in prostate cancer risk,” said the researchers.

Owing to limitations such as study design, small sample size, and missing data, a prospective large-scale study is warranted to better establish a temporal link between serum vitamin A and E levels and prostate cancer risk. “A thorough collection of data on lifestyle factors such as smoking and alcohol consumption can help reduce residual confounding,” they said.

Mechanistic studies may also be valuable in shedding light on the precise biological pathways that connect these serum vitamin levels to prostate cancer risk, while multicentre studies may enhance generalizability of the findings.

The researchers also called for larger and more extensive studies spanning various populations to determine if the findings can be replicated.