Vitamins - what is the evidence?

1. Vitamins - what is the evidence? RohanSubasinghe

2. What we know already • Billion dollar industry • One in 3 women and 4 women take vitamins • 25% older people take nutritional supplements • Folate,Vit B 6 /12 deficiency related to homocysteine levels which is an independent risk factor for CVD/CHD. • Higher concentrations have not been shown to reverse the disease process. • Folate reduces spina bifida and other neural defects by 80% • Vitamins early in life could lead to asthma and food allergies risks • Beta carotene has small adverse effect on all cause CV death

3. Folic acid • HOPE2 – 5522 with CV disease randomized to VB6+12+folate pill and placebo – lowered homocysteine by 22% but no effect on end points(MI/CVA) • NORVIT – 3749 patient - similar study - trend towards increase inn fatal/non fatal MI and CVA • Meta analysis of 12RCTS – folic acid does not reduce events or all cause mortality in patients with vascular disease. • Lowfolate levels may protect against colorectal cancer

4. Multivitamins • MAVIS – double blind RCT – • Multivitamins on morbidity from infections in older people – - no effect on self reported infections, prescriptions , QOL, primary care contact • Meta analysis of RCTs – litlle evidence to suggest multivitamins and minerals prevent infections in elderly people

5. Anti-oxidants • Meta analysis – (USA)1135000 patients in 19 trials - high dosage Vit E may increase all cause mortality. • Meta analysis of 14 trials – 170525 patients – Vit A,C,E and cancers – none were protective – 1)combination of A and beta carotene = 30 % incr. Risk of death. 2)combination of beta carotene and E=10% increase

6. Recent evidence – 2008 -Dr Goran Bjelakovic and colleagues at Copenhagen University • Systematic Reviewin examining the literature investigating the effects on mortality of antioxidant supplements. • They looked for all primary and secondary preventative randomised controlled trials conducted in adults • They looked at trials of any antioxidant supplement taken in any dose, form, combination or for any duration of time; including - vitamins A, C and E, beta-carotene and selenium compared with either an inactive placebo or no treatment.

7. Results and conclusion • 13.1% of those taking antioxidants died • 10.5% of those taking placebo or no treatment died. C • Combining the studies found there was no significant effect of antioxidant supplements on mortality • “no evidence to support antioxidant supplements for primary or secondary prevention [of mortality]” • Vitamins A, E and beta-carotene may even increase risk of mortality.

8. Contd.. • the researchers also found increased risk of death from any cause from 1)vitamin A (16%), 2)beta-carotene (7%) and 3)vitamin E (4%), • There were no significant effects on mortality from either vitamin C or selenium

9. Criticisms of review • Variable quality and inclusion criteria • Different doses and combinations • Did not examine other specific health benefits, e.g. increased energy, increased resistance to illness etc. • most trials used supplement doses that were much higher than those found in a normal diet and sometimes higher than recommended daily intake levels.  • Trials on specific antioxidants only jsut reached statistical significance

10. Link to study • http://www.mrw.interscience.wiley.com/cochrane/clsysrev/articles/CD007176/frame.html