The main paper, which is just a rehash of other previously published and biased meta-analyses, concludes that “Limited evidence supports any benefit from vitamin and mineral supplementation for the prevention of cancer or cardiovascular disease. Two trials found a small, borderline-significant benefit from multivitamin supplements on cancer in men only and no effect on cardiovascular disease.”
I have written before about how meta-analyses, if wrongly used, can basically reduce any effect to zero, which is effectively what this bit of twisted statistics does. I learnt nothing new from it.
Given numerous well designed trials showing clear benefits for, for example:
• Vitamin C in relation to blood pressure, blood sugar and even cholesterol
• Vitamin D, for bone health, osteoporosis risk, as well as reducing cancer and heart disease risk
• Vitamin B6, B12 and folic acid, for reducing rate of brain shrinkage, and correlating with much lower risk for dementia/Alzheimer’s
Any intelligent person realises that meta-analyses that reduce all positive effects to zero are just not reflecting reality, which is the purpose of good scientific research.
The second study was actually a new trial giving a multivitamin or placebo to 1708 people with cardiovascular disease to see if it reduced their risk of dying or having a further cardiovascular event. But the study ran into big trouble. The patients were meant to take the multivitamin for at least 3 years. Half failed to do so and 17% dropped out of the study. In the tiny number of people left (390) there was no statistically significant difference between them and the placebo group – no benefit or harm. The authors point out, ‘However, this conclusion is tempered by the non adherence rate.’
That’s not all that’s wrong with this study. It is well known that people who have had a cardiovascular event are almost always put on a cocktail of drugs that can easily mask any potential benefit of supplements. This factor wasn’t properly taken into account but the authors did analyse a small sub-group of patients who either refused to take statins or were intolerant to them (eg had adverse effects from them), concluding: “We found a significant interaction of vitamin therapy with statin use, reflecting a greater effect of high-dose vitamins in patients not receiving a statin.”
Overall, this is a meaningless study due to its poor compliance, low numbers and lack of taking into account the masking effect that medication has on supplementation, although the authors do acknowledge that those not on statins, but taking vitamins, did better.
The third study gave multivitamins to six thousand doctors aged 65 and older, then followed them up with telephone cognitive assessments over an average of 8.5 years. There was no effect and the authors themselves conclude that ‘Doses of vitamins may be too low or the population may be too well-nourished to benefit from a multivitamin.’
These are major flaws. However, there is a more serious flaw that means this study may be meaningless. Even in the placebo group, there was no significant decline in the memory scores over the 12 years measured on the TICS test (Telephone Interview for Cognitive Status). Any score above 27 means a person does not have cognitive decline. Both the placebo group and the B vitamin group started with an average score of 34.3 and ended up with a score of 33.1 in the placebo group and 33.2 in the supplement group, confirming that this was not an ‘at risk’ group of people. So, the B vitamins had nothing to protect them from.
In previous studies of people ‘at risk’ with blood homocysteine levels above 10mcmol/l (which quadruples a person’s risk of developing dementia) with an initial TICS score of 19, there was a substantial reduction in risk of developing dementia, and in rate of memory decline and brain shrinkage when given high dose B6 (20mg), folic acid (800mcg) and B12 (500mcg). In this study the level of B12, for example, was twenty times lower than the level that has been shown to protect ‘at risk’ older people from brain shrinkage and memory loss.
In essence this is a study of a well-educated, reasonably well nourished group of doctors, not ‘at risk’, given relatively low levels of vitamins. Nothing changed. The only real conclusion that can be drawn is that giving a multivitamin based on RDAs does not enhance cognition in people without cognitive impairment.
It is a real shame that national newspapers don’t bother to think beyond the headlines of biased press releases and look at the actual studies.
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