10 Jul 13
http://medicalxpress.com/news/2013-07-link-omega-fatty-acids-prostate.html
Men, don't take fish oil pills, now shown to increase the chance of prostate cancer by over 50%. That is a big number and has been confirmed.
There is a large vitamin supplement industry pushing pills and more and more of them are found to be very harmful, not beneficial as the ads say.
10 Jul 13
Originally posted by sonhouseThen why does the article you link say 43%?
Men, don't take fish oil pills, now shown to increase the chance of prostate cancer by over 50%. That is a big number and has been confirmed.
And what is the risk of prostate cancer if you don't take the supplements? ie what is it a percentage of?
I also notice later in the article:
The analysis, which combined the data from 20 studies, found no reduction in all-cause mortality, heart attacks or strokes.
You would think that if there was significant increased mortality, they would have picked it up too?
12 Jul 13
Originally posted by KewpieYes, I did read it, and yes, I agree the evidence suggests taking omega-3 as a supplement has no overall benefits. However, just throwing out a percentage without stating what it is a percentage of, is meaningless to misleading. What percentage of the population actually get either type of cancer? Without knowing this, the stats cannot be used to judge my personal risk factors.
70% for high-grade prostate cancers (the fatal ones), a much lower number for low-grade non-fatals, 43 is the overall average. The article is worth a proper read.
12 Jul 13
Originally posted by twhiteheadTry typing something like: "prostrate cancer prevalence" into google and see what comes up. The reason for giving relative risks rather than absolute ones is because that is what is being measured. They see how many people get ill in the treatment group and compare that with the number that get ill in the control group. This tells them the effect of the treatment, which is what is of interest. They don't translate that into an overall risk because it's an additional source of error. Their study hasn't measured the prevalence figures for the population as a whole (who don't spend their days taking placebo pills). The absolute numbers aren't helpful from clinical point of view and require synthesis with data not collected in that study - so if there's a problem with the prevalence data it doesn't mess up their results.
Yes, I did read it, and yes, I agree the evidence suggests taking omega-3 as a supplement has no overall benefits. However, just throwing out a percentage without stating what it is a percentage of, is meaningless to misleading. What percentage of the population actually get either type of cancer? Without knowing this, the stats cannot be used to judge my personal risk factors.
The percentage probably represents a risk ratio. A 44% increased risk means that people in the treatment group were 1.44 times more likely to get prostrate cancer than people in the control group. The real problem is that the article doesn't give the significance, or what the overall power of the study was, so it's hard to tell how seriously to take it.
12 Jul 13
Originally posted by DeepThoughtGood advice.
Try typing something like: "prostrate cancer prevalence" into google and see what comes up.
I get: 152.0 per 100,000 men
So with fish oil it becomes: 217 per 100,000 men.
Considering that the study had under 2000 men, of which about 3 would have normally had prostate cancer I wonder if the sample size was large enough. Anyone know enough statistics?
12 Jul 13
4 edits
Originally posted by twhiteheadLook up "power (statistics)" on Wikipedia. It's not simple to calculate, and depends on details of how they did their study. The effect is fairly small, but 2,000 is fairly big by the standards of studies, some phase II trials have as few as 15 people in each arm. They've probably got enough power to make the claim. I'll see if I can access the original paper or not.
Good advice.
I get: 152.0 per 100,000 men
So with fish oil it becomes: 217 per 100,000 men.
Considering that the study had under 2000 men, of which about 3 would have normally had prostate cancer I wonder if the sample size was large enough. Anyone know enough statistics?
Edit: The paper is free to download here: http://jama.jamanetwork.com/data/Journals/JAMA/5009/JRV50027.pdf
I'll tell you what I think when I've read it.
Edit 2: This is not the right paper. (But has good methods and finds no evidence that omega-3 either prevents or causes cancer).
Edit 3: Here is the correct reference: http://jnci.oxfordjournals.org/content/early/2013/07/09/jnci.djt174.abstract?sid=4283f806-047c-4f33-9646-cbaa88c24e65
It costs $32 for 1 days access to the paper. So I'm only reading the abstract.
Edit 4: This is back to front. They found 863 people with prostate cancer and looked at their blood serum. More people who had cancer had high levels of omega-3. They've shown an association, but it could be that people with prostate cancer are at high risk of having omega-3 in their blood rather than the other way round. I'd avoid reading too much into this study. A better design would be to put 10,000+ people on a long term trial where one lot take omega-3 pills and the rest take smarties, and see who does better.
12 Jul 13
1 edit
Originally posted by DeepThought
Look up "power (statistics)" on Wikipedia. It's not simple to calculate, and depends on details of how they did their study. The effect is fairly small, but 2,000 is fairly big by the standards of studies, some phase II trials have as few as 15 people in each arm. They've probably got enough power to make the claim. I'll see if I can access the origi where one lot take omega-3 pills and the rest take smarties, and see who does better.
and the rest take smarties,
Careful! Smatties contain sugar and other ingredients that might indirectly effect the chances of getting cancer!
(I remember a study sowing sugar encourage people to eat more thus leading to greater obesity. Then another study showing that obesity alone, even after filtering out other causal factors, increases the risk of many kinds of cancer)