Transcript Vitamins - what is the evidence?

Vitamins - what is the evidence?
Rohan Subasinghe
What we know already
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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
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.
• Low folate levels may protect against colorectal cancer
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
Anti-oxidants
• Meta analysis – (USA)1135000 patients in 19 trials high dosage Vit E may increase all cause mortality.
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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
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, betacarotene and selenium compared with either an
inactive placebo or no treatment.
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.
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
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
Link to study
• http://www.mrw.interscience.wiley.com/cochr
ane/clsysrev/articles/CD007176/frame.html