Apples are poisonous – don’t panic. The poison protects the fruit from fungal attacks. It doesn’t hurt you directly, but it does slow sugar uptake
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Why an apple a day keeps the doctor away
It’s an old adage….
An apple a day keeps the doctor away.
Well, thanks to research carried out by a team of Japanese researchers, we know one of the reasons why, apples are SO HEALTHY ! HINT : It’s poisonous.
Eating an apple with dinner
Our team served apples and bowls of white rice to two groups of volunteers. The first group were NORMALS, the second were people who were glucose intolerant i.e. prediabetic.
In terms of the specifics : The rice (150 g) was a retorted product i.e. it was a ready to eat. You pop it in the microwave, press HEAT, peel and eat. The apple was a medium size Fuji apple (150 g).
In the study, the team mixed the order of the offering.
- On one occasion the apple came first, followed by the rice, 5 minutes later.
- On the second occasion the rice came first, followed by the apple.
In terms of the glycemic response – the order does matter.
Apples change the glucose curve
In the metabolically healthy
Above are the results for the NORMALS, the sugar spike is different. Apples change the glucose curve, when they’re eaten at the START of dinner. They lower the levels, a little
Enough to write home about………..
Nope. Although it looks quite spectacular on the graph, when they crunched the numbers, the difference was not big enough to be considered significant.
Think REAL. It could simply have happened by chance.
So why are you telling us this ? Odds are, you’re not in the metabolically NORMAL camp, you’re in the “it’s not working as well as it should”, so you’re more interested in what happened in this group of people and this is where things get interesting…
In the metabolically challenged
In the metabolically BROKEN, once again it’s pretty clear……….. eating the apple first takes the sugar spike down and keeps it down.
This time the difference IS SIGNIFICANT.
This is indicated by the little stars on the graph. Translated into plain English, the team is 95 % sure, the difference is REAL. But, if you’re like me, you’re not all that interested in whether the difference is statistically REAL, you want to know, whether it will make a difference, when you eat dinner.
And the short answer is………. YES.
If you’re glucose intolerant apples are helpful
I took the liberty of superimposing the graphs so you can see the impact….
The pattern that they observed would be clinically relevant.
Eating the apple, does not normalize the situation completely, the sugar levels still remain high for a protracted period of time. But it puts the initial sugar spike in the zone of what is seen in a NORMAL, eating a bowl of rice.
Apples are not magic
Unfortunately, the sugar levels still remain high for a protracted period of time.
This is not a licence to eat bowls of rice for dinner.
NOTE : Your biology is making you carb intolerant. Smalls amounts are okay, but big amounts are going to have nasty consequences……….. it is what it is.
But, it might be a tool to put in your tool bag, for times when you’re on the run………….and faced with an eating dilemma.
When it’s a high carb meal OR NOTHING
Now, NOTHING…………. would be first prize. This is what I would typically do, the body chemistry fall out from a sugar spike, is just not worth it.
Yes. It can be super awkward and very anti-social.
The second prize would be to add protein and/or fat, to the meal and this should be your standard operating procedure. For more information on the Adding protein, fat and fibre to your diet, go here.
Both of these are great options, but not always practical. Protein is not an ON THE GO food, apples ARE !
Apples the easy fix
- relatively inexpensive
- available all year round
- easy to eat
They’re small, don’t need refrigeration and fairly durable. You can pop them in a bag and use it for “EMERGENCIES”.
Munching on an apple, just before your carb heavy meal, can offer a little respite.
But isn’t the apple FULL OF SUGAR ?
Yes. Apples are NOT by definition low carb…………… and if you are counting carbs, your default response to an apple, might be, I don’t think so. Although, if you use taste as a guide, you could be duped.
The carb count can be higher than one would think.
Not all sugars are created equal
Apples actually don’t trigger an enormous “sugar” spike, because the sugar they’re made of is………..FRUCTOSE, not glucose. Fructose has different biology to glucose – you can learn more about this on the fructose library page.
And for the record, your glucose meter is not equipped to measure fructose levels. In fact, fructose levels are not routinely measured, but there are a number of studies that hint, high serum fructose levels, are something that goes hand in hand with metabolic problems and is NOT a good thing.
Fuji apples are full of fructose
Our team confirmed the Fuji apple that was being munched on in this study was predominantly fructose, by running mushed up apple samples through an HPLC machine.
It came back…
But it is highly unlikely that the fructose is responsible for the glycemic benefits seen in this study. The fructose might help give the apple a free pass, because insulin doesn’t respond to fructose. But the magic is more than likely due to a pesticide found inside the apple.
Phlorizin – the apple pesticide
Pesticide – don’t panic. This pesticide is all natural, it is produced by apple trees – to stop fungal growth. It’s primarily found in the bark of the trees, but small amounts pop up in apples.
The highest concentrations are in the peel, but it also shows up in the flesh.
Exactly how much, depends on the variety of apple, as well as how mature the apple is. As a rule, the “younger” the apple, the more is present.
The poison apple
Fortunately, you are not a fungi, so the tiny amounts of phlorizin, leave you largely untouched. Largely. It turns out, that the protein (SGLT1 transporter) responsible for getting glucose from inside your gut, to inside your circulation, is a little sensitive to phlorizin, because….
Slowing glucose uptake
The phlorizin is actually a glucose molecule, with a huge ring structure plopped on top. And that enormous ring structure, gets caught in the transporter.
Leaving the transporter unable to move the sugars across efficiently.
The sugar molecules get stuck in no man’s land.
A fortuitious delay
The sugar is there………..
WAITING TO ENTER.
And eventually it does, but instead of a flood, hitting the liver, causing panic and consternation, the sugar trickles in. The liver has more time to process it and insulin, arrives on the scene IN TIME, even if you’re metabolically challenged. Yah !
But, the process of “dinner” is somewhat protracted.
And glucose levels end up taking a bit longer to return to NORMAL.
An unseen benefit
If you’re monitoring your glucose levels, this benefit might appear as a non-event or even a FAIL, since the sugar reading is taken at the tail end of the drama. But, this is not where the benefit happens.
The sugar peak was never as high as it might have been.
So, your body chemistry is BETTER.
Prudent to carry an apple in your backpack
Poisoning your SGLT1 transporter is a strategy worth deploying …….especially if you’re glycemically challenged.
NOTE : In this study it only “worked” in those who were metabolically challenged, probably because their SGLT1 transporters are typically over expressed and this amplified the benefit. Blame insulin he is responsible for their deployment.
The dose makes the poison
Exploiting this biology is not a new idea, numerous attempts have been made to bottle the apple poison and hit the drug development jackpot.
But phlorizin itself, is not very stable and at high doses, it can be potentially toxic.
Plus it can’t be patented.
Nevertheless, phlorizin has served as the inspiration behind the family of drugs, collectively known as the glifozins, they selectively inhibit the glucose transporter (SGLT2) in the kidney, causing you to pee out excess glucose. The class includes canagliflozin, dapagliflozin, and empagliflozin – maybe I’ll tell you their story in an upcoming post.
You can exploit this chemistry
By eating apples………apples, unpeeled. Not apple juice. The phlorizin content of apple juice will be pretty low, because heating destroys it and a BIG fructose hit, without fibre is going to upset your liver. BIG TIME !
Too much fructose is definitely NOT YOUR FRIEND.
For more ideas on how to use science to minimize meal time sugar spikes visit this page.
The milk machine is just not keeping junior adequately nourished………..
Phlorizin: a review. Diabetes Metab Res Rev 2005; 21: 31–38. Joel R. L. Ehrenkranz, Norman G. Lewis, C. Ronald Kahn, Jesse Roth
Comparing the efficacy of apple peels and a sodium-glucose cotransporter 2 inhibitor (ipragliflozin) on interstitial glucose levels: A pilot case study. Current Therapeutic Research 93 (2020) 100597. Junichi Okada, Eijiro Yamada, Kazuya Okada, Shuichi Okada, Masanobu Yamada
Inhibition of the intestinal sodium-coupled glucose transporter 1 (SGLT1) by extracts and polyphenols from apple reduces postprandial blood glucose levels in mice and humans. Mol. Nutr. Food Res. (2014) 58 : 1795–1808. Christine Schulze, Adina Bangert, Gabor Kottra, Kerstin Elisabeth Geillinger, Bettina Schwanck, Henning Vollert, Wolfgang Blaschek and Hannelore Daniel.
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