Podání vit. E bez prokázaného benefitu
Age-related maculopathy
- Meta-analysis of two RCTs providing more than 50 mg/day of supplemental alpha-tocopherol
- Did not show a significant effect of supplementation on the risk of age-related maculopathy compared with placebo (I2 = 19 %) (Evans, 2008). [2]
Alzheimer’s disease
- Systematic review with meta-analysis of seven observational studies (Li et al., 2012)
- Significant inverse association between dietary intake of ‘vitamin E’ from food and the risk (pooled RR (95 % CI): 0.76 (0.67–0.84), I2 = 43.2 %, p = 0.103).
- No quantitative data can be derived from these meta-analyses in order to set DRVs for alpha-tocopherol [2]
- No convincing evidence that doses of up to 2000 units/day slow the progression of Alzheimer disease [9]
- No decrease the risk of prostate cancer [9]
Mild cognitive impairment (MCI) and those with AD
- Level of markers of oxidative damage to DNA, proteins, and lipids is increased
- Expression and activities of glutathione and antioxidant enzymes are reduced [10]
- Meta-analysis
- Other studies
- Low concentrations of vitamin E in cerebrospinal fluid of cognitively impaired patients [10]
- Reduction in oxidative stress may help maintain cognitive status
- And/or prevent deterioration
- Multicenter, randomized, placebo-controlled study in individuals with AD of moderate severity
- Supplementation with 2,000 IU/day of all-rac-alpha-tocopherol (equivalent to 900 mg/day of RRR-alpha-tocopherol) for 2 years
- Significantly delayed cognitive decline
- Slowed disease progression
- Increased median survival
- Placebo-controlled trial in 769 patients with MCI
- Same dosage of vitamin E
- Did not affect the probability of progression from MCI to AD over a 3-year period
- Double-blind, placebo-controlled trial
- Randomized to receive 800 IU/day of all-rac-alpha-tocopherol (360 mg/day of RRR-alpha-tocopherol) for 6 months
- Mini Mental State Examination (MMSE) scoring system improved
- Only when the treatment effectively reduced oxidative stress
- Assessed by the measure of total glutathione
- Markers of lipid peroxidation in the blood
- Failure to reduce oxidative stress resulted in supplemental vitamin E being more detrimental to the cognitive function of AD patients than placebo !!!
- Multicenter, randomized, double-blind, placebo-controlled study
- Supplemental vitamin E (2,000 IU/day; form of vitamin E not mentioned in the publication) for over 2 years
- Significantly delayed functional decline
- Determined by the (in)ability to perform basic activities of daily living
- Reduced the annual mortality rate
- In mild and moderate AD patients
- vitamin E failed to affect cognitive performance measured with MMSE scores and other cognitive ability tests [10]
- Little evidence to suggest that long-term supplementation of vitamin E provides any cognitive benefits in healthy older adults [10]
Katarakta
- Cross-sectional study
- vitamin E concentrations were found to be significantly lower in the lens and blood of subjects with
- Age-related nuclear, but not cortical, cataracts
- When compared with an age-matched control group [10]
- Earlier studies reported higher vitamin E concentrations in the lenses and blood of patients with cataracts [10]
- Results of several observational studies
- Meta-analysis of eight studies
- Including 15,021 participants
- Found a 17% reduction in the risk of age-related cataract in subjects
- In the highest versus lowest quantile of dietary vitamin E intake [10]
- Prospective cohort study of 31,120 Swedish men
- Followed for a mean of 8.4 years
- Observed a greater risk of developing cataract in occasional and regular users of high-dose (about 100 mg/day) vitamin E supplements only
- When compared with non-supplement users
- Use of supplemental high-dose vitamin E with additional supplements or the use of low-dose vitamin E-containing multivitamin supplements was not found to be associated with an elevated cataract risk [10]
- A meta-analysis based on data from over 350,000 participants in 10 studies
- Including the above-cited study by Zheng Selin et al.
- Found no association between supplemental vitamin E and risk of cataract [10]
- Supplementation of high-dose vitamin E — alone or in addition to other supplements
- Was found to be safe
- Benefits regarding cataract risk or progression were limited [10]
- Early intervention trial
- Daily supplement of 50 mg of synthetic alpha-tocopherol (equivalent to 25 mg of RRR-alpha-tocopherol)
- Did not alter the incidence of cataract surgery in male smokers [10]
- A randomized, placebo-controlled intervention trial in 4,629 men and women
- Daily supplement
- 500 mg of vitamin C
- 400 IU of all-rac-alpha-tocopheryl acetate (equivalent to 180 mg of RRR-alpha-tocopherol)
- 15 mg of beta-carotene [10]
- Did not affect development and progression of age-related cataracts over a seven-year period
- Did not limit the progression of cataract in a five-year intervention trial [10]
- Four-armed, randomized, placebo-controlled study of 11,267 men
- From the Selenium and Vitamin E Cancer prevention trial (SELECT)
- Failed to observe a reduction in cataract incidence
- With 400 IU/day of supplemental all-rac-alpha-tocopheryl acetate (180 mg/day of RRR-alpha-tocopherol)
- Alone or in combination with selenium (200 µg/day)
- During a mean 5.6 years of follow-up [10]
- Four-year randomized, placebo-controlled trial
- 500 IU/day (335 mg/day) of RRR-alpha-tocopherol
- Did not reduce the incidence or progression of cataract in older adults [10]
Age-related macular degeneration
- Pooled analysis of four randomized controlled trials in 62,520 subjects
- Found that supplemental vitamin E or beta-carotene
- Did not reduce the risk of developing age-related macular degeneration (AMD) [10]
- Review of currently available data
- Supplements of antioxidants plus zinc
- May reduce the progression of AMD and vision loss in affected individuals [10]
- Age-Related Eye Disease Study (AREDS)
- Participants with borderline to advanced age-related macular degeneration (AMD)
- Randomized to receive
- (1) placebo;
- (2) 15 mg/day of beta-carotene, 500 mg/day of ascorbic acid, and 400 IU/day of all-rac-alpha-tocopheryl acetate
- (3) zinc (80 mg/day) and copper (2 mg/day)
- (4) both antioxidant vitamins and zinc and copper
- Five-year results indicated that the risk of developing advanced AMD was
- Significantly reduced in those taking zinc with or without antioxidant vitamins [10]
- Antioxidant vitamins alone failed to prevent the progression to advanced AMD
- Even in individuals at higher risk
- Combination of antioxidant vitamins and minerals may benefit people with intermediate AMD or advanced AMD in one eye [10]
Ca obecně
- Most clinical trials have failed to find any beneficial effects of vitamin E supplementation on the risk of various cancers
- Randomized, placebo-controlled trial (RCT) in 39,876 women
- Women's Health Study
- Supplementation with 600 IU (400 mg) of RRR-alpha-tocopherol every other day for 10 years
- Had no effect on overall cancer incidence or cancer-related deaths [10]
Cardiovascular disease-related outcomes
- ‘vitamin E’ or alpha-tocopherol through diet or supplementation (alone or in combination)
- Number of systematic reviews, RCTs, prospective cohort studies and case–control studies (Heinonen et al., 2012).
- Effect of aspirin or 300 mg/day of ‘synthetic alpha-tocopherol’ supplementation compared with a placebo = no conclusion [2]
- Alpha-tocopherol supplementation of at least 50 mg/day
- Did not have an effect on
- Intermittent claudication (Tornwall et al., 1997; Tornwall et al., 1999),
- Abdominal aortic aneurysm (Tornwall et al., 2001),
- Intima–media thickness (Hodis et al., 2002)
- Cardiovascular events (fatal and non-fatal) (Tornwall et al., 2004b) [2]
- Alpha-Tocopherol supplementation (50 mg/day, background alpha-tocopherol intake not reported)
- Did not have any significant effect on
- Primary stroke incidence [2]
- Mortality in normotensive male smokers (50–69 years at inclusion) during an RCT (median duration: six years) or post trial (Leppala et al., 2000b; Leppala et al., 2000a; Tornwall et al., 2004a). [2]
- Prospective cohort study in 34 492 post-menopausal women followed for 11 years
- No relationship between risk of death from stroke and quintiles of intake of ‘vitamin E’ from food and supplements, food only or supplements only [2]
- Prospective cohort study in 559 men (mean age: 72 years) free of chronic diseases in 1985
- Mean alpha-tocopherol intake (± SD), without dietary supplements, was 9.1 ± 4.6 mg/day at baseline (Buijsse et al., 2008) [2]
- After 15 years alpha-Tocopherol dietary intake at baseline was not associated with
- 15-year cardiovascular disease mortality after adjustments, in all the models tested. [2]
Cancer
- No relationship was observed between ‘vitamin E’ or alpha-tocopherol intake and
- Breast cancer (Yuan et al., 1995; Freudenheim et al., 1996; Do et al., 2003; Nissen et al., 2003; Frazier et al., 2004; Nagel et al., 2010),
- Bladder cancer (Riboli et al., 1991; Albanes et al., 1995; Jacobs et al., 2002; Brinkman et al., 2010),
- Cervical, endometrial and ovarian cancers (Fairfield et al., 2001; Xu et al., 2007; Ghosh et al., 2008; Kim et al., 2010),
- Renal cancer (Hu et al., 2009),
- Pancreatic cancer (Rautalahti et al., 1999),
- Stomach cancer (Alkhenizan and Hafez, 2007),
- Testicular cancer (Bonner et al., 2002),
- Skin carcinomas (Kirkpatrick et al., 1994; Fung et al., 2002)
- Lung cancer (1994; Albanes et al., 1995; Ocke et al., 1997; Alkhenizan and Hafez, 2007). [2]
- Inconsistent results
- Risk of colorectal carcinoma (Bostick et al., 1993; Ferraroni et al., 1994; Albanes et al., 1995; Slattery et al., 1998; Malila et al., 1999; Jacobs et al., 2001; Wu et al., 2002; Chiu et al., 2003; Satia-Abouta et al., 2003; Murtaugh et al., 2004; Kune and Watson, 2006; Arain and Abdul Qadeer, 2010).
- Risk of prostate cancer (Albanes et al., 1995; Rautalahti et al., 1999; Alkhenizan and Hafez, 2007; Wright et al., 2007; Bidoli et al., 2009; Gaziano et al., 2009; Lippman et al., 2009; Klein et al., 2011; Kristal et al., 2014; Wang et al., 2014). [2]
All-cause mortality
- Three meta-analyses of RCTs (Miller et al., 2005; Bjelakovic et al., 2007; Abner et al., 2011)
- ‘vitamin E’ supplementation, alone or in combination with other micronutrients, and all-cause mortality.
- Often performed in patients with chronic diseases, form of ‘vitamin E’ was often unknown, trials often used doses of the vitamin exceeding the UL [2]
Primary open-angle glaucoma
- Two large prospective cohort studies (one in men and the other in women)
- No significant association between ‘vitamin E’ intake (Kang et al., 2003). [2]
Tarditive diskinesia
- Whether supplements can protect against tardive dyskinesia is controversial [9]