The paleo diet is very popular, and very good, but it draws ire for one peculiarity:
It posits that all grains are bad for you.
Not just corn flakes or white bread, but also wheat, barley, rye, and any other farmed carbohydrate because these weren’t eaten until 10,000 years ago when we developed modern agriculture, and our genome hasn’t had enough time to evolve to digest them properly. Excessive grain consumption of all sorts is the leading cause of the insulin resistance syndrome, the explosion in obesity and type 2 diabetes, and the metabolic syndrome in general.
To many people (me included), this seems a bit strong.
After all, if all grains were so bad then why do all those people in china stay skinny even though they eat lots of rice? What about the Incas and Mayans? Can potatoes be that evil if they fed a thriving civilization for hundreds of years? Surely there’s some sort of discrepancy here that’s not being accounted for.
I believe that someone like Mark Sisson (a champion of the paleo diet) would tell you that any society that’s lived on grains did so by jumping through hoops to prepare them in order to mediate their awful health properties. They fermented them, pickled them, soaked them, and generally did everything possible to remove the inherent toxicity in grains, but that’s a testament to human ingenuity and not the usefulness of grains themselves. The safest thing to do is to stay away from them entirely.
By and large, I think Mr. Sisson and other paleo diet champions are mistaken on this point. Unadulterated grains are fine for most people and a suitable way to get the bulk of your calories. And contrary to many people’s opinion, they’re every bit a part of our evolutionary lineage as meat, veggies, and fish.
So Why Are Grains So Bad?
First, let’s begin with the observation that refined carbohydrates are bad for you. White bread, crackers, potato chips, instant rice, and wheat thins all tack on the fat. They’re devoid of nutrients, make you hungry instead of full, and cause your body to secrete insulin which causes your body to store fat. Paleo diet people harp on this point all the time and they’re right.
But do these same observations apply to the cute little Quaker Oats guy too? Should we ditch our beans for more pork chops? No.
To lump unrefined grains with the processed kind, anti-carbohydrate people make the following three points:
- All carbohydrates are sugar, and sugar=insulin=fat. Lentils, barley, and bulgur wheat are simply one step removed from this truth.
- Grains have nasty things like lectins and phytates which are “anti-nutrients” and remove what little health benefits grains have in the first place.
- We didn’t start eating grains until 10,000 years ago, and are not biologically adapted to them. Grains aren’t in our DNA.
To varying degrees none of these statements are true. Let’s go through them one by one.
When It Comes to Carbs, Structure Matters
Insulin is the hormone that causes your body to store energy instead of burn it. It’s secretion is regulated by your blood sugar levels, and quick rises in your blood sugar after a meal causes your body to make a lot of insulin and store your calories as fat. When we went through long periods of famine this was a very useful adaptation, but now not so much.
The wisdom goes that all carbohydrates are sugar molecules stringed together, so eventually all carbs eaten push your body in the direction of fat storage.
Mark Sisson summed it up on his blog like this:
The gist is this (as many of you know): Whatever the carbohydrate, it will eventually be broken down into glucose, either in the gut or the liver.
This is definitely true refined of carbohydrates, but when it comes to insulin not all carbs are created equal.
Here are two charts that show how a kernel of wheat affects your body’s insulin response depending on its form:
Unprocessed forms of starch show almost no insulin response at all:
But when the same grains are highly refined and bought as a processed food item the insulin response jumps by 2.5x:
The reason for this disparity is due to three reasons:
- Starch is many molecules of glucose linked together, which take longer to digest, and thus have a smaller change in blood glucose levels after a meal than simple sugar which is either one or two sugar molecules linked together.
- Grinding a tuber or grain into flour increases the surface to volume ratio of the food which causes it to digest more quickly than unprocessed starch.
- Starches have a substance called phytate on them which bind to amylase, the enzyme that cleaves starch, and slows down its digestion.
And speaking of phytates…….
Are Phytates and Lectins Really Anti-Nutrients?
Per Mark Sisson, the presence of lectins and phytates are two reasons why you shouldn’t eat grains. They’re anti-nutrients. Lectins are what plants use as insecticide to fend off predators in the wild, and phytates bind with metals inside your body and carry them out of your blood, thus reducing the nutritional content of the food we eat.
With lectins, I’d counter with the following points:
- Lectins are found on practically all foods, not just grains
- Lectins are very prominent within our body and are necessary for all sorts of physiological processes
- Lectins are poorly understood in general.
Lectins are proteins that aren’t broken down in your intestine and eventually find themselves embedded on your cell walls. They’re also called glycoproteins. Your body uses the glycoproteins on the outside of your cells for various sorts of signaling.
It’s almost definitely true that when glycoproteins don’t work correctly you’ve got some problems, but there’s no doubt their presence in and of themselves isn’t a bad thing. It’s increasingly becoming appreciated that they’re very important for telling cells when and how they ought to die.
But does anybody know what the “right” amount of lectins from your diet is? From what food sources? How they change with food processing? Nope.
Phytates: The Anti-Nutrient That Nobody Appreciates
Phytates are usually located outside the germ of a grain plant and supply the embryo with phosphorus when it starts to germinate.
In your body they do one thing, and do it very well: bind to metals.
The bad news is that the presence of phytate lowers the amount of vitamins and minerals that are absorbed in a meal and lower the amount of nutrients available from grains. This is what they get the most attention for and why they get their label as an anti-nutrient.
However, for most people this mineral deficit is overcome by the rest of your diet. After all, the purported health benefits of grains, fiber, and legumes have been done with the phytates already on them.
What’s less appreciated about phytates is that their ability to bind metals also allows them to clear a whole bunch of other stuff that most people are looking to have less of: cholesterol and triglycerides. In your body phytate is a very powerful antioxidant because it prevents ions like iron and zinc from donating electrons that would create peroxides that eventually lead to dysfunctional lipids and cholesterol in your body.
Phytates are a good example of the problems with undernutrition and overnutrition. In the developing world phytates are a problem because most people don’t get enough food to eat and need whatever vitamins and minerals they can get their hands on. In the developing world we have more nutrients than our bodies know what to do with and I’m inclined to think the presence of phytates is a feature, and not a bug of complex carbohydrates.
We Were Designed to Eat Carbohydrates
The most persistent argument against carbohydrates is that they weren’t around very much until 10,000 years ago and our bodies are not adapted to eating them on a day to day basis.
I used to generally agree with this but after looking into it have decided it’s not the case and unprocessed carbohydrate is just as much in our DNA as our ability to eat meat and vegetables.
Consider the following points:
- Starch granules have been found in the tooth deposits of pre-agricultural humans and Neanderthals dating back to 100,000 years ago.
- The human genome has up to six coding regions in its DNA for amylase, the enzyme that digests starch.
- The ability to metabolize starch is possibly one of the reasons humans were able to diverge from chimpanzees in the first place.
Ancient Man Ate Minimally Processed Grain
The presence of bones and animal carcasses at ancient human archeological sites used to be considered a priori evidence that man was a natural meat eater. Grok, the prototypical caveman, got around by hunting mammoths and bludgeoning bison and using the fat and protein for calories. This is only half the truth.
Teeth preserve very well and contain their own type of fossil record for what you ate. You can strip away its layers and analyze the sediments to determine what dead people had for lunch. And it looks like they ate a lot of grain.
The teeth remnants of seven Neanderthals in Iraq and Belgium were analyzed for food deposits and the dental calculus suggested their diet consisted mostly of rye, barley, dates, and legumes. They probably hunted mammoth’s too, but definitely ate some grain in order to tide them over.
Other excavation sites done on upper paleolithic cavemen from 30,000 years ago found similar results. What’s even more interesting is they found lots of starch granules on their tools, suggesting pre-agricultural cavemen did a fair amount of food processing, possibly even making flour.
Carbohydrate Is In Our DNA
Chimps don’t eat starch. Even if you put them in a big grassy knoll with lots of tubers they’ll migrate past them in order to find other nuts and leaves they find more palatable. They just don’t like to eat it.
However, for humans this is definitely not the case. Chimps and humans share more than 99% in common with their DNA, but the differences in that last 0.01% tell a lot about why we’re different. A useful way to analyze the differences between genomes is to compare the number of differences in the amount of genes you have for a particular function. The theory is that the more genes you have that do the same thing, the more important said function is to that organism’s survival, hence the redundancy. The typical chimp has 2 copies of the amylase gene, whereas the typical human has 6. (Albeit with some variation. The human genome has differentiated itself in this regard).
Australopithecus was the first bipedal ape, and it’s been posited that a key difference between him and the chimp is that he was able to metabolize Underground Storage Units (aka starch) in plants, which allowed him to get more sugar, thus giving his brain the glucose it needed to think in a way no other animal can replicate.
So, no, you’re not forsaking your genetic destiny every time you eat a bowl of rice.
When it comes to grains, the paleo diet throws out the baby with the bath water
I like the paleo diet. It eliminates dairy, refined sugar, preservatives and processed food. That’s all good. But the stance towards grains of even some of its most articulate supporters has always thrown me off.
With a closer look I think it’s clear to see they don’t differentiate enough when it comes to carbohydrate. Gary Taubes wrote extensively about how different calories behave very differently within the body and simply counting calories isn’t likely to lead you to weight loss.
I think the metaphor is best applied to starch. There’s good carbohydrate and bad carbohydrate.
Perry, George, et. al. “Diet and the evolution of human amylase gene copy number variation”
Henry, Amanda, et. al. “Microfossils in calculus demonstrate consumption of plants and cooked foods in Neanderthal diets”
Revedin, Anna, et. al. “Thirty Thousand Year Old Evidence of Plant Food Processing”
Bornet, Francis, et. al. “Insulin and glycemic responses in healthy humans to native starches processed in different ways: correlation with
in vitro a-amylase hydrolysis”
Lichtenstein, RG, et. al. “Glycobiology of cell death: when glycans and lectins govern cell fate”
Varki, Ajit, et. al. “Nothing in Glycobiology Makes Sense, except in the Light of Evolution”
Cooper, Douglas, et. al. “God must love galectins; He made so many of them”
Eaton, John. “Phytic Acid: A Natural Antioxidant”
Thompson, Lilian, et. al. “Starch Digestibility as Affected by Polyphenols and Phytic Acid”
Yoon, Jane, et. al. “The effect of phytic acid on in vitro rate of starch digestibility and blood glucose response”