"Does Rye Bread Protect Against Cancer?"
Previously I’ve explored the beneficial effects of flaxseeds
on prostate cancer as well as breast cancer prevention and survival,
thought to be because of the lignans in flaxseeds,
which are anticancer plant compounds
found in red wine, whole grains, greens (cruciferous vegetables),
but especially sesame seeds and flaxseeds,
the most concentrated source on Earth.
But this is per unit weight.
People eat a lot more grains than seeds.
And of the grains people eat, the highest concentration
of lignans are found in rye.
So, can rye intake decrease the risk of breast cancer?
Theoretically?
Yes, but unlike flaxseeds it’s never been put to the test.
If you measure the level of lignans in the bloodstream of women
living in a region where they eat lots of rye,
the odds of breast cancer seem to be cut in half
for women with the highest levels,
but lignans are also found in tea and berries
and so they couldn’t be sure where the protection was coming from.
So researchers decided to measure alkylresorcinol metabolites,
a class of phytonutrients relatively unique to whole grains.
They collected urine from women with breast cancer and women without,
and those with breast cancer had significantly lower levels
compared to women without breast cancer,
be they omnivores or vegetarians.
This suggests that women at risk for breast cancer
consume significantly lower amounts of whole grains like rye.
But if you follow older women in their 50s through 60s,
the intake of whole grain products
was not associated with risk of breast cancer.
A similar result was found for older men;
whole grain consumption in one’s 50s and 60s
did not seem to be linked to prostate cancer risk.
Is it just too late at that point?
Well, we know from data on dairy that diet in our early life
may be important in the development of prostate cancer,
particularly around puberty when the prostate grows and matures.
And so if you go back and look
what men were drinking in their adolescence,
daily milk consumption appeared to triple their risk
of advanced prostate cancer later in life.
And so researchers looked at daily rye bread consumption
during adolescence and indeed those who consumed rye bread
daily as kids may have cut their odds
of advanced prostate cancer in half.
This is consistent with immigrant studies
suggesting that the first two decades of life
may be most important for setting the pattern
for cancer development in later life.
Certainly important for how we should feed our kids,
but if we’re already middle-aged,
is it too late to change course?
To answer that question, researchers in Sweden put it to the test.
How about we take men who already have prostate cancer,
split them up into two groups,
half get lots of rye bread; the other half get lots of high fiber,
but low lignan wheat bread and see what happens.
There’s been some indirect evidence
that rye may be active against prostate cancer,
like lower cancer rates in regions with high rye consumption,
but it had never been directly investigated until this study.
Biopsies were taken from their tumors
before and after three weeks of bread eating,
and the number of cancer cells that were dying off were counted.
There was no change in the cancer cell clearance
in the control bread group,
but a 180% increase in the number of cancer cells
being killed off in the rye group.
A follow-up study lasting 6 weeks,
found a 14% decrease in PSA levels,
a cancer marker suggesting a shrinkage of the tumor.
Now they note since they used very high rye bread intakes,
it remains to be tested if more normal intake levels
would have effects that are of clinical importance.
As any good red blooded American, my ignorance
of the metric system did not flag 485 grams
of rye bread a day as out of the ordinary,
but that translates to 15 slices... a day!
Rather than eating a loaf of bread a day,
the same amount of lignans can be found
in a single teaspoon of ground flax seeds.