I recently got into a bit of a disagreement with someone in
one of the Foundations courses I’m teaching at Magnus. We try to add some nutrition discussions into
the Foundations curriculum, but we don’t have a lot of time to devote to
it. So, when trying to discuss the topic
of carbs this week, this woman in my class with a bio-chemistry background
began to push back on some of the points I wanted to make. Because I literally had 5-minutes to discuss
the topic, and because I don’t have enough of a science background to argue
with a bio-chemist, I decided to follow up with her via email. As I constructed the email with the points I
wanted to make, as well as a significant about of supporting information, I
realized this would make a good blog topic.
What follows can be considered the basics of my recommendations on
carbs…
The first point to understand about carbs is simply that
there is no such thing as an essential carbohydrate. Yes our brains run on glucose, but because
our bodies can use the gluconeogenesis process to make all the glucose that is
needed from protein, we don’t actually need to consume any carbohydrate to stay
alive. As Dr. Emily Deans put it in this article:
"...while there are essential
requirements for both fat or protein (meaning we would die without eating at
least some fat and at least some protein), we can live quite happily while
consuming no carbohydrate at all."
Next we should understand that there's good evidence
suggesting that the brain actually functions better using ketones than it does
using sugar. If you aren’t taking in any (or even very little)
carbohydrate, your body switches over to ketosis and powers the brain with
ketones. Since the 1920’s Dr.’s have
prescribed ketogenic diets for patients with epilepsy. This article by Shelly Fan from Scientific American states:
“Emerging evidence from animal
models and clinical trials suggest keto may be therapeutically used in many
other neurological disorders, including head ache, neurodegenerative diseases,
sleep disorders, bipolar disorder, autism and brain cancer. With no apparent
side effects.”
The bio-chemistry behind this point seems to come down to
the idea that the brain has more energy available in a ketogenic
environment. Again the SA article explains this concept well by saying:
"…ketones serve as an
alternative energy source to maintain normal brain cell metabolism. In fact,
BHB (a major ketone) may be an even more efficient fuel than glucose, providing
more energy per unit oxygen used. A ketogenic diet also increases the number of
mitochondria, so called “energy factories” in brain cells"
Now that we’ve established the idea that we don’t actually
need carbs, are there some good reasons to avoid carbs? Well yes, there are any number of great
reasons to avoid carbs if you’re trying to lose weight, protect your brain, or
treat a number of health conditions. I am
not however suggesting that everyone should be eating a very low carb diet,
and/or maintaining ketosis. Simply put, carbohydrate intake should vary
based on a person's lifestyle and body fat level. My general
recommendation for people is that if you have significant fat to lose, you
should eat a relatively low carb diet. I suggest people eat under 100g of
carbs per day if they are carrying significant bodyfat. If you are at a
healthy weight but do not have a very active lifestyle, you may eat a bit more
carbohydrate. I recommend people in this category stay under 150g of
carbohydrate per day. Lastly, if you do not have fat to lose AND are
highly active, I would recommend a little more carbohydrate each day. How
much more would vary from person to person, but carb intake would likely not
exceed 250g per day even for the most active folks. It's also worth
noting here that I believe there are populations of people who would thrive on
a Ketogenic approach, and there are also people who do fine eating upwards of
200g of carbs per day. Anyway, this article does a great job of laying out the basics of
the approach I suggest.
But wait, if I’m doing cardio don’t I need
carbohydrate?? The answer is no! Your body is always burning some percentage
of protein, fat, and carbs for fuel, and the percentages change based on the
intensity of the activity. This
article dispels some myths and lays this concept out in laymen’s terms, but
here’s the (very) basic idea… If you’re
doing extremely high intensity/very short duration activity (think lifting your
max weight on deadlift) you are using ATP as your primary source of fuel which
means you’re not really burning a lot of Fat or Carbs. Once you move into moderate to high
intensity/medium duration activities (regular weight training, ½ mile run),
you’re accessing your Glycolitic pathway and burning primarily carbs for
fuel. As you transition from that middle
ground into low intensity/longer duration activities (walking, jogging, riding
long distances) you move into the oxidative pathway which is primarily using
fat for fuel. Here’s
a very basic article outlining these topics.
So, in reality that plate of pasta you eat the night before running a
10K, probably does very little to help your performance.
The last thing to understand about carbs is that your carb
intake should primarily be from cruciferous vegetables. Obviously, if
someone is trying to stay below 100g per day, it's imperative that their carbs
mostly come from cruciferous vegetable sources. As carb intake goes up,
we would add in more starchy carbs, and fruits. Grains should always be
avoided for many reasons (a topic for another discussion), and we should always
strive to get the bulk of our carbs from veggies.
As you know I believe in the Paleo template as a fantastic
starting place for nutrition, and here is
a link to the basics of Paleo. I think everyone needs to do some experimenting
on their own, but Paleo provides a fantastic starting place for optimum
nutrition.
