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How can carbohydrate restriction be healthy if it means limiting “natural foods” like fruits and vegetables?

I’d like to tackle one of the
most important questions that I get asked.  However, before getting to the
question, I think it’s worth investing a few minutes to frame this discussion
around a theme tightly linked to it — sugar.

If you’ve been following the nutrition news lately, you may
have noticed that Dr. Rob Lustig has made some headlines.  If you’ll
recall, Dr. Lustig is arguably the world’s expert on fructose (i.e., fruit
sugar) metabolism, and I included a link to his now-gone-viral YouTube video on
fructose toxicity from 2+ years ago in my post, Sugar 101.  In the February 2nd issue of the journal Nature, Dr. Lustig and his two colleagues make the
following case:

1.   
Sugar consumption is linked to the dramatic rise in obesity, diabetes,
cancer, heart disease, and Alzheimer’s disease (i.e., the diseases that cluster
around metabolic syndrome).  Effectively, sugar speeds up our
aging process.

2.   
The metabolic effect
of sugar, and fructose in particular (fructose makes up half of sugar – sucrose
is 50% glucose, 50% fructose; HFCS is 45% glucose, 55% fructose), is nearly
identical to that of ethanol (drinking alcohol).

3.   
As such, sugar should
be regulated in a manner commensurate with the damage it causes.

If you have access to Nature (or are
willing to buy the article for $32), I highly recommend reading it.

Let me lay out a few facts. 
First, our consumption of sugar is increasing at a staggering rate.  We
consume, on average, about four times the amount of sugar today that we did 40
years ago, even though our consumption of sucrose (the white crystals) is going
down.  How, you ask?  Because we have more than made up for it with
the ubiquitous addition of high fructose corn syrup (HFCS) to darn near
everything we eat (e.g., cereal, pasta sauce, salad dressing, virtually every form
of “low-fat” food out there, condiments).   Remember the “Peter
Principle” – when you see “low fat,” run the other way, as it is almost
synonymous with “high sugar.”

The figure, below, from the Nature paper
shows the amount of sugar (excluding fruit) that each country produces,
in per capita figures.  If you factor in fruit,
obviously the numbers are much greater.  A quick glance at this figure
shows that (excluding fruit), the U.S. is the reigning undisputed champion of
sugar production at over 600 calories per person per day, which means over 175
gm of sugar per person per day, (excluding fruit and fruit juice).  
To fully understand why we produce
so much sugar requires a discussion beyond the scope of what I want to write
about today, but I’m sure most of you already have a pretty good idea: economic
incentives.

There’s another interesting observation that can’t help but
poke you in the eye when looking at this figure.  How many times do you
ask (or get asked), “Why do some cultures eat carbs
like rice and not get the same diseases we do?”
  A quick glance
at China, for example, sheds some light on this.  They may eat rice, but
they sure aren’t producing (or eating) much sugar, on average. 
Furthermore, the distribution of sugar consumption within the country is
wide.  In other words, while the few wealthy people do eat amounts of
sugar approaching Western amounts (along with other simple refined grains), the
vast majority of non-wealthy inhabitants do not.  So while some have
asserted that animal products and fats are the clear culprits explaining the
different disease patterns in Asia, they’re missing this important point:
 Given the absence of mechanistic and evolutionary reasons why animal
products and fats are bad for us, is it more likely that sugar consumption is
the single biggest factor differentiating the state of disease across these
populations?


So what’s the upshot of this graph?  Well, for starters we eat a lot of this sugar.  Second, we export a lot of sugar, too.  This wouldn’t be a
problem if sugar were not so harmful.   How harmful is sugar? 
For a long reminder, read Sugar 101.  For a
very quick (by proxy) explanation take a look at the following table, also from
the Nature paper, and previously presented by Lustig.

 


This table shows, side-by-side, the
health problems that occur with chronic ingestion of ethanol (i.e., drinking
alcohol) and fructose.  [Remember: fructose is the sugar found in fruit
and fruit juice, but it also makes up 50% of table sugar (i.e., sucrose) and
55% of HFCS.]

I think the figure speaks for itself
and suggests that about two-thirds of the pathology that afflicts a heavy
consumer of ethanol also afflicts a heavy consumer of fructose.   As
Lustig points out, this should not be terribly surprising, given that we
ferment ethanol from fructose.

Let’s summarize:

1.   
We produce and eat
more sugar than any other country on earth, and do so more than at any other
time in history.

2.   
Consuming sugar is
not just “bad” because of the “empty calorie” hypothesis (i.e., the reason one
should limit sugar is because the calories from sugar are not as valuable as
those from, say, protein); it’s bad because sugar is a chronic toxin.

One last point before we jump in:  Before you angrily email me, or say awful things about me
for daring to suggest that Michelle Obama and the USDA might be wrong in
recommending we eat 5-6 servings of fruits and vegetables (many vegetables are
full of fructose, too) per day, keep one thing in mind.  I am simply making a few points and you need to decide how you
want to interpret them and make personal choices around them
.  We are all genetically different, and therefore have
a very different genetic predisposition in our sensitivities around these foods
(and all foods in general).

There are some folks out there who can
eat enormous amounts of sugar and experience very little ill effect.  My
wife is the poster child for this phenotype – though she doesn’t any longer,
she could eat unlimited amounts of sugar and not gain weight*. 
Furthermore, as we age, we generally get less adept at processing sugar, and
therefore with each passing year a “fixed dose” of sugar appears to cause
greater and greater harm to an individual.

*Note that I only commented on the “weight” portion of her
phenotype.  When my wife did reduce her sugar intake, she experienced many
benefits in her health, perhaps most importantly, her improved cardiac disease
risk profile measured by advanced lipid testing.

Here are the points with which I want
to challenge you:

1.   
Before you assert something is
“natural,” be sure to understand what you mean by “natural.”

2.   
Don’t be afraid to question the
notion that all things “natural” must be healthy (and by extension, that all
things “un-natural” are unhealthy).

Let’s address these points in order.

Point I: How do you define “natural?”

Most people assume the fruits and
vegetables we eat are “natural,” but in reality fruits and vegetables of today
bear little, if any, resemblance to their original form.  Let’s take corn
as an example.  [I’m choosing corn because (i) it’s illustrative of the
broad science and progression of agriculture, and (ii) I happen to read a lot
about it, as I find the evolution of corn cultivation fascinating.]
  Bear with me for a moment, as I tell this story.

7,000 years ago — a sliver of time on the evolutionary scale
— corn was a plant called teosinte
Teosinte was about the size of your thumb and had a few (maybe 4 or 5)
kernels.  Over the next few thousand years we began the shockingly quick
(by evolutionary standards) process of “domesticating” this crop from its
“natural” state into subsequent states of what we now refer to as maize. By
domestication I mean the process of successive selection of crops that had the
most advantageous features for our needs.  Sort of like “domesticating”
animals so they would cuddle up with us on the couch instead of trying to eat
us.

How did the process of domestication
work?  As an example, farmers selected teosinte crops which were larger,
had more kernels, were more resistant to drought, and were more resistant to
pests and predators.  This process went on, growing season after growing
season, until about the period of time leading up to World War II and morphed
teosinte into a very different looking crop.  At that time, the average
farmer in the U.S. could grow about 18 bushels of corn per acre per year,
though progress in yield increase had been stagnant for a few hundred years.

Around 1940, however, the productivity (i.e., the
yield improvement) and morphology (i.e., the physical “look”) of corn growth began to
change dramatically for two main reasons.  First, this change was driven
by the introduction of technologies to make cultivation more efficient (e.g.,
crop rotation, use of fertilizer and pesticides, improved irrigation). 
This was referred to as the “industrialization” of agriculture.  Roughly
in parallel to this effort, advanced biologic techniques of active breeding (genetically crossing one plant
with another so they could mix genes – the same things animals do when they
mate) and mutagenesis (disrupting the
genes of the crop, typically using chemicals or other agents, like radiation,
to change the genes of crops) significantly increased the functional genetic
diversity of the crops, year after year, further increasing yields and other
desirable crop properties, such as cost of production.

Furthermore, in the last 20 years or so, the introduction
of genetic modification (GM) has made maize even more
robust and genetically fit.  Today U.S. farmers can grow nearly 200
bushels of corn per acre per year, up from less than 20 bushels per acres per
year in 1940.   Below is a figure showing corn yield data from the
National Agricultural Statistics Service, which shows the almost unrelenting
productivity gains in corn cultivation over the past 70 years.  The
world’s leading technology companies leading this charge (Monsanto, Pioneer,
Syngenta) are projecting yields of 300 bushels per acre per year by 2030. 
In other words, with each passing year, technology is making corn more and more
robust, and therefore more and more distant from what is “natural.”


What about apples? Oranges? Strawberries? Peas? Carrots? It
turns out the story I’ve told for corn is virtually identical for every “crop”
we grow today, including all of our fruits, vegetables, and grains.  I
know what some of you are thinking, “I only eat organic non-GM
fruits and vegetables, so I’m ok, right?”
  Unfortunately
not.  Genetically modified (GM) plants and crops are different from non-GM
plants and crops in small genetic ways that generally make them more resistant
to pests.  But the hallmark differences between, say, teosinte and modern
maize are 95% accounted for without the addition of genetic manipulations.
 For the purpose of this discussion, genetically modified crops are a moot
point.  In other words, what we grow
and eat today, even if we buy “organic” or “non-GM” has absolutely no resemblance
to what was “natural,” say, 10,000 years ago.

So the next time you bite into a Fuji
apple half the size of your head (these used to be my absolute favorite things
to eat, by the way, and I’d easily consume 3 or 4 per day), ask yourself what
it has in common with the “apples” your ancestors ate.  The answer, not
surprisingly, is very little.


Point 2: Who says everything “natural” is good for you?

The next point I’d like to address is dispelling the myth
that all “natural” substances (notwithstanding the argument, above) are
healthy.  Let’s examine the role of toxicity in natural things we ingest
by first distinguishing between two types of toxicity: acute toxicity and chronic toxicity.  Simply speaking, acute toxins are toxins that can
kill you quickly, if you are exposed to a single dose, or a series of repeated
doses in a short period of time. Conversely, chronic toxins are toxins that
don’t kill you from a single exposure, but over time multiple exposures can
kill you.

While there is no shortage of
“man-made” toxins in the world, you might be surprised to learn how many
“natural” toxins exist, too.  Let’s examine a naturally occurring acute
toxin, a naturally occurring chronic toxin, and a naturally occurring toxin
that is both acute and chronic.   The figure (below) shows each.

1.   
Perhaps the most
singularly potent acute toxin on earth is a molecule called tetrodotoxin, or TTX.  Tetrodotoxin is a nerve
toxin that blocks sodium channels in our cells.  TTX is so potent that
less than 200 pounds of this compound would kill every person living in the
United States. In other words, it’s about 10 times more potent that
cyanide.  Here’s the catch: TTX is found in nature – it’s 100% natural. 
It’s found in puffer fish, newts, toads, and several other sources. 
Several people die each year from exposure to TTX when they unknowingly consume
animals containing the toxin.  

2.   
Tobacco is also a naturally occurring substance.  Whether
smoked or chewed, however, it has many forms of chronic toxicity, primarily
related to its carcinogenic (i.e., cancer-causing) properties.  In other
words, you won’t die from smoking one cigarette or chewing one pack of dip, but
if you do it enough, you might.

3.   
Finally, ethanol is both an acute and chronic toxic.
 While acute toxicity is rare, it is possible to overdose on ethanol
(toxicity in this case is usually related to respiratory depression – that is,
you stop breathing).  More common, of course, is the chronic toxicity of
ethanol, which is well understood and well-documented.  For a quick
reminder, take a look at the table I showed earlier in this post from the Nature paper.


So there you have it.  There are plenty of “natural” compounds on earth that are harmful.  I am not suggesting that eating a Fuji apple is as toxic as smoking a pack of cigarettes, but I am saying that once you begin to understand the metabolic pathways of fructose (there are about 25 grams of fructose in a large apple) you’ll see that an apple, just because it grows on a tree, is not actually “good for you,” even though it is supposedly “natural.”  For some people, eating 10 apples a day causes no harm.  For others, eating 1 apple a day causes harm.  The goal should be to figure out what your “toxic” dose is — and stay well below it.

If you’re reading this and wondering how much sugar you can eat, it’s a bit like asking how much can you drink or smoke.  It depends.   How genetically susceptible are you to the effects of these toxins?  What are you optimizing for — short-term pleasure or long-term health?  This is where we get into the idea of dose-response.  I will address this in a future post, as it really deserves a discussion of its own.

The news letter was a blog post from the- The Eating Academy | Peter Attia, M.D

http://eatingacademy.com/nutrition/how-can-carbohydrate-restriction-be-healthy-if-it-means-limiting-natural-foods-like-fruits-and-vegetables

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