Fish oil supplements linked to prostate cancer (2013)

Fish oil supplements linked to prostate cancer (2013)(nhs.uk)

111 points by leib 7 years ago | 65 comments

rossdavidh 7 years ago |

There is, I am starting to believe (regardless of whether or not this particular finding holds up), an ongoing problem with our approach to nutrition. The anti-pattern goes like this: 1) people who eat/drink X have health benefits 2) it seems to be related to X having Y in it 3) let's sell Y as a pill 4) dang, no health benefits, how did that happen?

Now this could be for several reasons. Maybe eating/drinking X is a marker for a lifestyle that is healthy, or for coming from a background that includes beneficial genes of some sort. Maybe Y is not the only thing in X which matters, it's just the most obviously related thing, and you really need the whole package. Maybe the amount of Y you get from eating/drinking X is good, but in concentrated form at high levels there are drawbacks of some sort.

But, however you look at it, putting Y into a pill (that can often be patented and sold as medicine) is not the same as eating/drinking X, and despite the financial incentives for claiming it is, we need to recognize that.

noneeeed 7 years ago | |

It's like the whole thing with vitamin supplements. Unless you are actually deficient in one of them, taking them isn't going to do much for you, and in some cases might actually cause you harm. It's like fertiliser on a field, after a certain point the plants can't use any more and it just runs off to the rivers.

Vitamin C is a good one for that, I seem to remember reading that at best taking large doses just means your piss contains a lot of it, and at worst, if you mega-dose for long periods, it raises your chance of getting some cancers.

It reminds me of the adverts on the London Underground. Every time I travel through London to see my parents there will be adverts medicalising lack of sleep and exhaustion, flogging supplements and "remedies" for what is basically being tired, or "chronic tiredness syndrome" as one advert described it. I'm so glad I didn't choose that life.

ip26 7 years ago | | |

Also risk of kidney stones.

dpatrick86 7 years ago |

This was based on the SELECT trial data, which means that it could just as easily be measuring the effects of a very large and prolonged dose of 400 IU of alpha-tocopherol as it is omega-3. Greater than 12x RDA.

Moreover, it's been many years since this was published. If prostate cancer-promoting effects were so plainly an obvious effect of marine omega-3 supplementation, you'd expect to have seen it abundantly replicated by now.

ip26 7 years ago | |

Maybe not, it's a very slow growing cancer, so they say.

anaphor 7 years ago |

Keep in mind that this does not mean you have a 70% chance of getting prostate cancer if you take fish oil supplements.

Based on this[0], it's roughly an increase from about 0.02% chance to about 0.034% chance (given no other information to base your risk on)

[0]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2706483/

com2kid 7 years ago | |

My understanding was that basically every man will, if they live long enough, have some cancerous cells in their prostate.

The main risk seems to be going from "so slow growing you die of old age first" to "fast enough growing it becomes a problem", unless I am horribly mistaken.

papa_bear 7 years ago | | |

I worked in a lab that was studying prostate cancer for a summer internship, and most of our samples came from young men who died in motorcycle accidents. They found that a majority of the samples had some presence of benign tumors, but it only really becomes noticeable once malignant tumors develop.

I don't know how representative the samples were of the entire population - one theory was that our young motorcycle samples had significantly higher testosterone on average and were more likely to develop those tumors.

pintxo 7 years ago | | |

One pathologist I happen to know, says the chances of finding cancer cells in your prostate is about the same as your age: 50 -> 50% chance, 60 -> 60%.

jazoom 7 years ago | | |

This is how most doctors I know perceive it as well. I know quite a few doctors since I'm one myself.

nraynaud 7 years ago | | |

agreed, and the headline talks about "link" because such a refined thinking doesn't fit in a headline.

insertnickname 7 years ago | |

And this:

>This was a large, well designed study that supports previous research linking high blood levels of omega-3 fatty acids with prostate cancer risk. However, it cannot show that fish oil supplements cause prostate cancer and it is possible that other confounders affected men’s risk (although the researchers tried to take these into account).

Their conclusion contradicts their own headline.

shishy 7 years ago | | |

It does not contradict their headline.

Headline says there is some correlation between the two but they are careful to explain later that this does not necessarily imply causation and that further research is required.

dfawcus 7 years ago | |

As I understand it, the fact that 1.00 is included in the range of CI indicates that the result in question could well be down to random chance/variation. i.e. because 1.00 is included, chance has not been eliminated.

sigmaprimus 7 years ago |

Kind of an old article, here is a link to an article written around the same time that was updated last summer.

https://www.health.harvard.edu/blog/fish-oil-friend-or-foe-2...

kensai 7 years ago | |

At a certain point it says:

"Evidence linking fish oil and cancer has been all over the map. Some research suggests diets high in fatty fish or fish oil supplements might reduce the risk of certain cancers, including prostate cancer. Other research shows just the opposite, a link between eating a lot of oily fish or taking potent fish oil supplements and a 43% increased risk for prostate cancer overall, and a 71% increased risk for aggressive prostate cancer."

Go figure! I guess, inconclusive at best.

pmoriarty 7 years ago | | |

What dose of fish oil does one need to consume in order for the diet to be considered "high in fish oil"?

Also, I've read in the past that it's important to balance omega-3's with omega-6. I wonder if any of this research takes that balance in to account.

ionwake 7 years ago | | |

I wonder if anyone has compared cancer rates with those who eat euryhaline fish ( less sea toxins )

vfc1 7 years ago |

The article does not talk about alternatives. A great alternative for Omega-3s are ground flax seeds, one tablespoon a day mixed for example in your oatmeal is enough - https://nutritionfacts.org/topics/omega-3-fatty-acids

Also for the derived DHA/EPA, there are pollutant-free alternatives based on algae oil.

raverbashing 7 years ago |

> It is worth bearing in mind that this study did not assess participants’ diet and use of supplements. Researchers measured blood levels of fatty acids and analysed the association with prostate cancer risk. However, it is likely that the very high levels of fatty acids found in some participants’ blood came from supplements.

Important point

2nd point to consider: is this for all types of cancer? More, less aggressive? Benign enlargement of prostate? In the article (comparison of the lowest Om3 quartile with the highest Om3 quartile):

> 44% increased risk of low grade prostate cancer (HR (hazard ratio) = 1.44, 95% CI (confidence interval) = 1.08 to 1.93) > 71% increased risk of high grade prostate cancer (HR = 1.71, 95% CI = 1.00 to 2.94) > 43% increased risk of total prostate cancer (HR = 1.43, 95% CI = 1.09 to 1.88)

3rd point: could this be associated with something else (for example: heavy metals in fish)

As most guidance by the NHS, this is very well explained and de-sensationalized

> However, it cannot show that fish oil supplements cause prostate cancer and it is possible that other confounders affected men’s risk (although the researchers tried to take these into account)

vannevar 7 years ago |

The study in question does not link fish oil supplements to cancer. It correlates (with no clear evidence of causality) high blood levels of fatty acids with actual cases of prostate cancer. It is speculated that for at least some of the subjects, the high levels of fatty acids may have come from supplements.

FTA: "It is worth bearing in mind that this study did not assess participants’ diet and use of supplements. Researchers measured blood levels of fatty acids and analysed the association with prostate cancer risk. However, it is likely that the very high levels of fatty acids found in some participants’ blood came from supplements."

newnewpdro 7 years ago |

I prefer eating quality canned sardines regularly instead of taking these supplements which can be viewed as a heavily processed industrial food derived from sources of unknown provenance.

They have plenty of omega-3s and are very low on the food chain.

thefounder 7 years ago | |

A good meal is definitely better than a dozen of pills.

golemotron 7 years ago |

I don't like the reflexive notion that high levels of X in one's diet necessarily translate into high levels of X in one's blood chemistry.

There should be a name for that nutritional fallacy.

nickpsecurity 7 years ago |

What about the packaging or matetial of the pill itself that contains the supplements? And any additives in the process? The processed stuff usually has higher risks. I wonder if any studies have been done on what contains the drugs which they also consume.

aitchnyu 7 years ago |

NHS's Behind the Headlines is a welcome relief from pseudoscience. They apparently have a beef with The Mail Online.

https://www.nhs.uk/news/

willart4food 7 years ago |

How about some "studies" to figure out the components of a well-balanced diet?

* macros

* what's out (well, this is easy actually)

* what's in

vibrato 7 years ago |

Let me give an alternative view of this epidemiological study.

"Those more interested in their health (motivated to take supplements or eat a high omega-3 diet) more likely to be diagnosed by their doctor with common health issues"

nraynaud 7 years ago | |

Participants were selected by having a cancer. Have you read the article? it's about growth rate.

pmoriarty 7 years ago | | |

According to the article, "In this type of study, cases of people who have a particular outcome - in this case, prostate cancer - are matched against a random group of people who do not develop the condition."

That sounds to me that in fact they were looking at cancer-free people as well.

vibrato 7 years ago | | |

Right. My point is that less health conscious people would have un-diagnosed cancer. This would make it appear that more health conscious people (higher omega-3) have higher rates of cancer than baseline.

internet_user 7 years ago |

tocopherols have been shown to have negative effects, including increased mortality, in other studies too. Nothing new here.

tth3uoku 7 years ago | |

Most research has focused on α-tocopherol, which is thought to displace γ-Tocopherol. In a 2000 study of the relationship between α-tocopherol, γ-tocopherol, selenium, and prostate cancer, men in the highest fifth of the distribution for γ-tocopherol were five time less likely to develop prostate cancer than men in the lowest fifth. [1]

"Recent epidemiological and preclinical studies have indicated that γ- and δ-tocopherols may be more effective because they are more efficient traps for reactive oxygen and nitrogen species." [2]

1. https://academic.oup.com/jnci/article/92/24/2018/2633585 2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5337152/