What if just one lifestyle change
could help you avoid getting cancer,
or diabetes, or heart disease,
or high blood pressure?
This one change could cut your risk of chronic disease
and add years to your life.
Well, the simple solution to so many of these problems
is to eat a healthy diet.
In other words, one centered around whole plant foods.
Welcome to the Nutrition Facts Podcast,
I'm your host, Dr. Michael Greger.
Today, we discover the some of the health benefits of eating onions.
Onions are potentially a good source of antioxidants,
though interestingly, the antioxidants are concentrated
in the outer layers immediately under the papery peel.
Unfortunately, most consumers discard these most nutrient-rich
outermost layers, thus losing a valuable part.
Here are some numbers. Look at that!
More than 10 times more antioxidants in the
outer layer of white onions, compared to the core.
You’ll also note that yellow onions in general
have more antioxidants than white.
And red onions beat them both, based on three
different antioxidant testing methods.
That’s why I always try to buy red.
Though red onions are indeed slightly better, yellow
or white onions are no slouches, containing
considerable levels of antioxidant activity.
So, nutritious, sure, but are there any particular
clinical benefits to onion consumption?
Evidently, older white women who consumed onions at least
once a day had an overall bone density that was 5% greater than
individuals who consumed onions no more than once a month (P < 0.03).
Now 5% might not sound like a lot, but that improvement in
bone density could potentially translate into decreasing
their risk of hip fracture by more than 20%
if indeed, it was cause and effect.
Daily administration of onion did cause a big bump in bone density.
This opens the possibility for a low-cost, safe, and effective
nutritional approach to osteoporosis and—
you guessed it...in the rat. Another rodent study.
Rats!
But finally, here we go.
Tremendous strides have been made
in treating osteoporosis with drugs, but they have the potential
for serious adverse side effects, so scientists have drawn
their attention to natural remedies.
So, let’s randomize people to drink... onion juice
or placebo onion juice.
I don’t know what sounds worse: sugary onion juice
or fake sugary onion juice.
And as if drinking onion juice wasn’t bad enough,
it was all for nothing. It didn’t even work.
What about the antiallergy activities of shallots
and any therapeutic effects on helping allergic runny noses?
Sixteen such patients were randomized equally into
an antihistamine group or a group that got antihistamines
plus some capsules containing dried shallot powder.
And it looked like the shallot group did better,
but there was actually no statistically significant difference
in total symptoms between the two groups;
so, another #OnionFail.
There has to be something onions can do.
What about testing the effects of fresh yellow onion consumption
on breast cancer patients to try to decrease the toxic effects
of a chemotherapy drug called doxorubicin?
Unfortunately, no significant benefit was found on decreasing
damage to the liver or heart.
But here we go . . . finally, a clinical benefit to onions.
The consumption of fresh yellow onion ameliorates
the high blood sugars and insulin resistance in breast cancer
patients during doxorubicin- based chemotherapy.
Doxorubicin isn’t just toxic to the liver and heart,
but it may also contribute to insulin resistance.
So, let’s do a randomized, triple-blind, controlled clinical trial
randomizing patients to like a whole onion a day
or a third of an onion a day. What happened?
The high onion group experienced a significant decrease
in blood sugars and insulin resistance
compared to the low onion group.
They went up in the low onion group but down in the high onion group.
So, make onions your friend.
What’s the worst that can happen— a little onion breath and BO?
Probably the least of your worries if you have cancer on chemotherapy.
In our next story,
we learn what an eighth of a teaspoon a day of onion powder
can do for body fat,
and what can raw red onion do for cholesterol.
Enter "The Effect of Steamed Onion
Consumption on Body Fat in Overweight Subjects."
The researchers used steamed onions so they could better disguise it
against placebo, and dried it into an onion powder, and gave people
just a minuscule amount, about an eighth of a teaspoon a day.
Surely, a little daily dusting of onion powder isn't going to affect the course
of people's weight, but check out these results reported in the abstract:
a significant reduction in body fat mass on both DEXA scan
and measured by CT scan — a significant decrease in the areas
of whole fat, visceral fat, and subcutaneous fat.
Hold on. If a little onion powder is so effective for weight loss,
why wasn't it featured in my book "How Not to Diet?"
Because, as so often happens in studies, the spin in the abstract
doesn't accurately represent the actual data.
Here are the DEXA scan results.
No significant change of fat in the group that got the placebo capsules;
they only appeared to lose about a spoonful of fat.
Whereas the group unknowingly taking an eighth of a teaspoon of onion powder
stuffed into capsules lost nearly one and a half pounds of body fat,
a significant drop from baseline, but not a statistically significant drop
compared to the placebo group,
meaning the loss could very well have been due to chance.
Same thing with the CT scan results: five times more loss of overall fat,
and 30 times more loss of the dangerous visceral fat,
but did not reach statistical significance compared to placebo.
A more recent study tried four teaspoons of onion powder a day
and similarly failed to accelerate the loss of body fat
compared to placebo, but the placebo was also
four teaspoons of onion powder a day.
They used yellow onions versus white onions, and it seems they both may
have caused a loss of body fat, without a significant difference between them.
Either way, you can look at these two studies and say, yeah,
but what are the downsides?
I mean just an eighth teaspoon of onion powder a day. Why not give it a try?
Can't hurt, but we just don't have confidence
that it's actually going to help.
Turning now to polycystic ovary syndrome, also known as P.C.O.S., or PCOS.
It's one of the most common hormone disorders, affecting 5% to 10%
of reproductive-aged women. In addition to symptoms like irregular periods,
PCOS is also a pre-diabetic state with decreased insulin sensitivity.
PCOS treatment is a big challenge due to medication side effects.
So what about using dietary options?
How about a randomized controlled clinical trial of raw red onion intake?
Why onions? Well, onion extracts evidently help in diabetic rats,
and more importantly in diabetic humans,
but evidently not in non-diabetic humans.
PCOS sufferers are kind of pre-diabetic, so would it work for them?
First, let's look at those other two studies.
Here's the diabetic one on the "Metabolic Effects of Onion and Green Beans."
Diabetics spent a week eating either a small onion a day,
or the same diet with about five cups of green beans instead,
and they both worked.
The onion group dropped people's blood sugars by about 10%,
and the green beans more like 15%.
Here's the study that supposedly shows no blood sugar benefits for non-diabetics.
It's true, onions don't lower normal blood sugars, which is a good thing,
but check out what happens when you feed people sugar.
Have people down about two tablespoons of corn syrup, and their blood sugars
shoot up over the next two hours before their body's able to tamp it back down.
But give people the exact same amount of sugar, but with more and more onion,
and the blood sugar spike is significantly dampened,
almost as much as if you had instead given them an antidiabetic drug.
And we see the same when you give people a shot of adrenaline —
with or without onions.
So, are there blood sugar benefits for diabetics and non-diabetics alike?
No difference was found between the higher and lower onion groups
of PCOS patients, nor were there any differences
in a marker of inflammation between the two groups.
But women with PCOS aren't just at higher risk for diabetes
and inflammation, but also high cholesterol.
Women with PCOS are seven times more likely
to have a heart attack, the number one killer of women,
but raw red onion consumption appears to be effective
as a cholesterol-lowering food,
though the high onion group only dropped their LDL cholesterol
about five points, not significantly different than the low onion group.
I did find this study from nearly 50 years ago where researchers fed
people nearly an entire stick of butter, and their cholesterol shot up
about 30 points within hours of consumption,
but only nine points or three points
when combined with about a third cup of raw or boiled onion,
the moral of the story being don't eat a stick of butter.
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To see any graphs, charts, graphics, images, or studies mentioned here,
please go to the Nutrition Facts Podcast landing page.
There you’ll find all the detailed information you need –
plus, links to all of the sources we cite to each of these topics.
My latest two books are “How to Survive a Pandemic”,
available on e-book, audiobook, or actual book.
And the “How Not to Diet Cookbook”, with more than 100 recipes for
delicious and nutritious meals.
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