
Fruit and vegetable intake and the risk of overall cancer in Japanese - discombobulate
http://www.sciencedirect.com/science/article/pii/S0917504016301575
======
ramblenode
Did anyone else read the statistical analysis section? There were some
"interesting"/unclear choices made, but I'm going to pick on one in particular
that could affect the outcome: the decision on how to weight the individual
cohort studies on which this study is based (pg 6).

> A random-effects model was used to obtain a single pooled estimate of the
> HRs from the individual studies for each category. The study-specific HRs
> were weighted by the inverse of the sum of their variance and the estimated
> between-studies variance component.

First note that there is no citation which motivates this weighting scheme.
There may be a valid reason for doing it this way, but that's not clear from
the paper.

Second, "the sum of their variance" I take to mean the sum of the variance
components of the regression model. That's interesting because the components
mean very different things. In the simple case of least squares, there's the
"explained variance": the "strength" of the relationship between Y and X, and
there's also the residual variance: the variance in X that isn't explained by
Y. Aside from the fact that they mean different things, their sum is not a
constant and so are not directly comparable across models/studies.

Third, weighted by the "between-studies variance component" has the effect of
down-weighting studies that show a large difference from the mean study result
and up-weighting studies which are similar. Now, what would you say if I
conducted an experiment and transformed the raw data points according to this
same procedure? "That's not fair because that's not the data we collected!"[0]
And herein lies the problem: the purpose of this meta-analysis is to assess
whether we can draw any consistent conclusions from the results of the
individual cohort studies, but by weighting studies toward the mean the
authors are taking it as a forgone conclusion that the mean study is ground
truth.

I'm by no means an expert on meta-analysis so someone please chime in if you
think I'm off base, but this all strikes me as a very peculiar and unjustified
set of steps being taken before the model is even fit.

[0] Yes, there are cases for data transformation, motivated either by theory
or meeting regression assumptions, but this is neither.

------
manmal
This is strange. Even if vegetable intake is not beneficial against cancer -
should higher veg consumption not crowd out red meat (I think you eat less
meat when eating more vegetables), leading to less cases of colon cancer?
Also, what about vegetables with high fiber that gets converted to butyrates,
and is thus anti-cancer? Is it all BS? Or is "overall cancer" a metric where
high fiber might decrease colon cancer but leads to more cancers in other
areas?

~~~
autokad
i think the most important take away with nutrition is eat what your ancestors
ate. you're probably not japanese so its less likely that the results apply to
you.

I myself switched from drinking soda to OJ. my health declined slowly for a
long time until I found out my body doesnt like oranges.

fruit can be healthy but i doubt we are supposed to eat all fruit diets. Astin
Kutcher took on Steve Job's all fruit diet and ended up in the hospital with
pancreatitis. And we all know what happened to Steve Jobs.

~~~
griffinmmahon
OJ is just sugar water though, the value of fruit is (I think) the whole
fruit.

~~~
autokad
true, but i have an even stronger alergic reaction to the fruit :)

its also worth noting that fruit is sugar water. its 98-99% water + 2% sugar
and fiber

~~~
dxhdr
> its also worth noting that fruit is sugar water. its 98-99% water + 2% sugar
> and fiber

Oranges, apples, etc are only 85% water. Grapes 80%. The rest is fiber and is
likely why your body tells you to stop eating them. Two and a half apples is a
lot less appealing than a can of soda (actual sugar water).

The whole percent water thing is completely meaningless though, human brains
are 85% water and babies are 80%.

~~~
scythe
The proportion of water is certainly _not_ meaningless when considering the
expected caloric intake of a food administered ad libitum. Satiety is
partially controlled by stretch receptors in the gut lining and common sense
will tell you it's much harder to consume the same amount of calories from a
2g/100mL sugar solution as from a 10g/100mL solution.

------
freefal67
I really liked this. I wish more negative results such as this were published
and discussed, especially when they go against general intuition and feel-good
narratives.

------
Alex3917
How are they controlling for deaths from other causes, e.g. cardiovascular
disease? If you're not dead from some other cause then you're going to be more
likely to die from cancer, even if vegetables are actually conferring a
significant anti-cancer benefit.

I see that they are using people years to track followup, but I'm not clear
from the methodology whether this is enough to fully control for this issue.

~~~
wapz
Are you stating that death from cardiovascular disease would be higher (or
lower) from people who don't eat fruits/vegetables which means they have a
"lower" chance of getting cancer?

My guess would be that they didn't take that into account and that the deaths
from cardiovascular (or other diseases) would be ignored in the assumption
they are "similar" between the two sides.

~~~
Alex3917
To rephrase, I'm suggesting that eating vegetables may lower the risk of
cardiovascular disease.

If you don't die from cardiovascular disease, then it's more likely that
cancer is the thing you do die from. So even if eating vegetables reduces your
risk of cancer, you could actually be more likely to die from cancer if you
eat vegetables.

~~~
wapz
Ahh thanks for the clarification. Your logic makes a lot of sense. I believe
there was a study that showed pesticides _may_ cause cancer (it was probably
done in mice or something) from a long time ago but this is just the top of my
head so I don't know if there's any relation to fruit/veggie consumption.

------
reefwalkcuts
Anyone, is there also a study like this where the consumption of red meat (or
meat in general) affects the risk of overall cancer?

~~~
DanBC
We know that processed red meat causes cancer.

The quality of the evidence is very very good.

The strength of the effect is weak.

Because the quality of the evidence is now very good (as good as for smoking)
the WHO information was widely misreported as "red meat as bad as smoking".

This is likely to make web searches less useful.

Here's something from the English NHS about it:
[http://www.nhs.uk/news/2015/10October/Pages/Processed-
meat-c...](http://www.nhs.uk/news/2015/10October/Pages/Processed-meat-causes-
cancer-warns-official-report.aspx)

> A key statistic provided by the infographic is that if everyone stopped
> smoking, there would be 64,500 fewer cases of cancer a year in the UK,
> compared with 8,800 fewer cases if everyone stopped eating processed or red
> meat.

~~~
cubix
Forgive my ignorance, but what exactly is the definition of _processed_ red
meat? I assume it lies somewhere between gnawing on a freshly slaughtered
animal carcass and buying beef jerky form the corner store, but I'm not sure
where, exactly.

~~~
alister
"Methods of meat processing include salting, curing, fermentation, and
smoking. Meat processing includes all the processes that change fresh meat
with the exception of simple mechanical processes such as cutting, grinding or
mixing."

[https://en.wikipedia.org/wiki/Processed_meat](https://en.wikipedia.org/wiki/Processed_meat)

------
neves
This is for Japan, doesn't they already eat a lot better than the Western
world, that is, less red meat, less processed foods, more high oily fish etc.?

~~~
mikekchar
In my experience, this is generally true, but the Japanese diet is changing
rapidly. I came to Japan almost 10 years ago and I remember seeing quite
traditional lunch boxes (called bento) in the convenience stores. Now
everything is deep fried, or comes with fairly large portions of meat. Unless
you go to a specialised bento store, it's pretty difficult to get a bento with
a piece of fish, vegetables and rice.

Also, with the reduced restrictions on imports, I've seen a veritable
explosion of steak restaurants and yaki niku places (Korean barbeque). Now
that they can get cheap pork from Canada and cheap beef from Australia, meat
has gotten very popular. The meat sections of the grocery stores in my area
are about the same size as the fish section. And even the small town I live in
has the same number of butchers as they do specialty fish stores.

Having said that, it's still not difficult to eat a traditional Japanese diet
and certainly older people tend to eat that way. Not sure what will happen in
the next generation or two, as the culture is shifting (to my eyes, anyway).
It may be for the best, though, as global fish stocks are shrinking in an
alarming way.

------
hartator
Studies that invalidate common beliefs are really interesting.

~~~
mrfusion
Keep in mind that's the only reason we're hearing about this study. If they
found what would be expected it wouldn't be as interning. Man bites dog and
all that.

There are probably lots of studies that say the opposite if you look for them.

------
minusf
Forks over knives
([https://en.wikipedia.org/wiki/Forks_Over_Knives](https://en.wikipedia.org/wiki/Forks_Over_Knives))
quite clearly argues that meat increases cancer risks manyfold.

T. Colin Campbell and Caldwell Esselstyn are no quacks either and the document
makes a solid argument for minimizing meat intake, at least for adults.

------
SwetDrems
I thought we were under the consensus that these large scale associative
studies were not accurate/effective in predicting causal effects, especially
in nutrition.

I can't find any studies right now, but I remember reading about mechanistic
explanations for plant compounds such as isothiocyanate and resveratrol in
reducing and even completely suppressing tumour growth.

------
yesbut
This study doesn't account for strict plant-based diets. There isn't a single
reference to animal product portion size. It just lumps everyone together.
Some groups had larger fruit and vegetable portions. But all had animals.

~~~
aminok
The study wasn't trying to account for strict plant-based diets. It was
attempting to find a correlation between fruit/plant intake and cancer rates.

~~~
yesbut
It would be unfortunate if someone reads the headline and thinks this means
that this study negates the meat consumption-cancer risk correlation studies.

Though, when considered in regards to the large body of plant based diet
studies, this study does add more evidence to the notion that to benifit from
plants we probably need to omit the animal products altogether.

------
thomyorkie
Perhaps pesticide consumption offsets fruit and vegetable benefits.

------
miguelrochefort
Every day, the case for eating plants gets weaker. I'm starting to believe
that plants aren't necessary for human health, and are possibly harmful.

This website has been eye-opening:
[https://zerocarbzen.com](https://zerocarbzen.com)

~~~
PerfectElement
I think you are suffering from confirmation bias.

~~~
miguelrochefort
Doesn't change the facts.

Why should I believe that plants are necessary for health?

~~~
spraak
Confirmation bias means they aren't strictly facts you're believing

