Beta-carotene supplementation for patients with low baseline levels and decreased risks of total and prostate cancer

Article · November 1999with13 Reads
DOI: 10.1002/(SICI)1097-0142(19991101)86:93.0.CO;2-N
Abstract
The Physicians' Health Study was a randomized, double-blind, placebo-controlled trial using a 2x2 factorial design including supplementation with beta-carotene (50 mg every other day) in the primary prevention of cancer among 22,071 U.S. male physicians ages 40-84 years at randomization. Before randomization, the authors collected baseline blood specimens to determine whether any benefit was greater among or confined to those with low baseline levels of beta-carotene. Baseline blood samples were collected from 14,916 participants. These samples were assayed, according to a nested case-control design, from 1439 men subsequently diagnosed with cancer over 12 years of follow-up (631 with prostate carcinoma) and 2204 controls matched by age and smoking habits. Men in the lowest quartile for plasma beta-carotene at baseline had a marginally significant (P = 0.07) increased risk of cancer compared with those in the highest quartile (relative risk [RR] = 1.30, 95% confidence interval [CI], 0.98-1.74). Men in the lowest quartile assigned at random to beta-carotene supplementation had a possible but nonsignificant decrease in overall cancer risk (RR = 0.83, 95% CI, 0.63-1.09) compared with those assigned to placebo. This was primarily due to a significant reduction in the risk of prostate carcinoma (RR = 0.68, 95% CI, 0. 46-0.99) in this group. After the first 2 years of follow-up were excluded, the results were virtually unchanged. These prespecified subgroup analyses appeared to support the idea that beta-carotene supplementation may reduce risk of prostate carcinoma among those with low baseline levels. Further follow-up of this population will help determine whether these findings are valid.
    • β-Carotene has been extracted mainly from orange and yellow fruits and vegetables. There are many studies that correlate between the high dietary consumption of carotenoids and low risk of prostate cancer[68,69]. The inhibitory effect of β-carotene in the proliferation of human cancer cell lines (PC-3, DU 145, and LNCaP) has been determined by Williams et al.[70].
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    • Studies suggest that antioxidants may lower a smokersÊ risk of lung cancer. [35, 36] Studies also suggest that carotenoids may help to prevent prostate, breast [36][37][38][39][40][41][42][43][44][45][46]and skin [47, 48] cancer as well as endometrial cancer. [46] Astaxanthin is another carotenoid, found in salmon, red fish, shrimp and crab, which shows anticarcinogenic effects in mouse lung and liver cancer models.
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    Full-text · Article · Mar 2014 · BJU International
    • However, a subgroup analysis showed that men in the lowest quartile for plasma b-carotene had a decrease, although not statistically significant, in overall cancer risk (RR, 0.83; 95% CI, 0.63–1.09) compared with those assigned to placebo (Cook et al., 1999). No protective effect was found for b-carotene on skin cancer (RR, 0.98; 95% CI, 0.92–1.05)
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    Article · Jun 2011
    • Studies suggest that antioxidants may lower a smokers' risk of lung cancer [26, 27]. Studies also suggest that carotenoids may help to prevent prostate, breast2728293031323334353637, and skin [38, 39] cancer as well as endometrial cancer [37]. Astaxanthin (Figure 1D) is another carotenoid, found in salmon, red fish, shrimp and crab, which shows anti-carcinogenic effects in mouse lung and liver cancer models.
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    Full-text · Article · Jan 2011
    • These studies have found no relationship between supplementation and prostate cancer among generally nonsmoking study populations [18]. In addition, the PhysicianU s Health Study reported a 32 percent reduction in prostate cancer incidence for those men receiving S -carotene supplementation who were in the lowest quartile of plasma betacarotene when the study began [12]. This fact lends support to the hypothesis that S -carotene may be protective at the doses available from dietary intake alone rather than from megadoses in supplement form [19].
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    Full-text · Article · Jun 2008
    • association (Shibata et al. 1992, Giovannucci et al. 1995). In one intervention study β-carotene supplementation seemed to reduce prostate cancer incidence in subjects with low baseline plasma β-carotene levels (RR = 0.68, 95% CI 0.46-0.99), but to increase prostate cancer incidence in subjects with high baseline levels (RR=1.33, 95% CI 0.91-1.96; Cook et al. 1999). Other vitamins investigated include C, D and E. Vitamin C is a scavenger of reactive oxygen species and free radicals (Yu et al. 1994). Maramag et al. (1997) showed that vitamin C inhibits cell proliferation in prostate cancer cell lines. However, data from prospective cohort studies show no consistent effect (Shibata et al. 1992, Gio
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