Food, science

Are Carbohydrates Necessary For Life? FAQs About Low-Carb Diets

After a tumultuous vegan era, much scientific research and self-experimentation, I have adopted a low-carbohydrate, low-sugar (apart from the occasional cookie) diet. I stay away from grains, rice, starches, fruit juices, sweets, and processed foods, but eat animal foods, veggies, fat, and not-too-sweet fruits galore.

I get questioned about my low-carb lifestyle by readers, friends, or people who barely know me but think it’s weird that I am melting butter into my coffee (especially waiters, it’s always the waiters).

The questions go something like this: “But where do you get your fiber?” “Doesn’t your brain need sugar for energy?” “Won’t you develop nutritional deficiencies?” “So you are saying the Food Pyramid is wrong?”
Or, summed up: “Aren’t carbohydrates necessary for life?”

And in case you were also wondering, here are my answers!


What are carbohydrates?
Carbohydrates can be divided into three groups:

– 1. Simple carbohydrates, aka SUGAR. Sugar occurs naturally in some foods, like fruit or honey, but the bulk of our simple carbohydrate consumption comes from sweet processed foods which contain added sugar. (soft drinks and sodas, cookies, ice cream…)

– 2. Complex carbohydrates, aka STARCH. Starch is actually plenty of little molecules of sugar attached together. When starch lands in your stomach, it is broken down into simple units of sugar. Think bread, pasta, rice, potatoes, beans and peas.

– 3. Complex ‘non-digestible’ carbohydrates, aka FIBER. Fiber occurs naturally in fruits, vegetables, whole grains, and cooked dry beans and peas. We don’t digest it, so it doesn’t really “count” as a carbohydrate in the sense that it is not digested and just passes through our digestive system.

Most plant foods contain STARCH and FIBER, in varying proportions.


And you eat absolutely zero carbs?
I stay away from sugar and starches, but eat plenty of fruits and vegetables which contain the third type of carbohydrates: fiber. (they also contain sugar, in a natural form- in quantities far smaller than those found in processed foods)

Why do you do such a thing?
We know that sugar is bad for us for many reasons (including cancer development, heart disease progression, immune deficiency) and that eating carbs promotes weight gain. Too many simple carbs over a lifetime are detrimental and cause metabolic syndromes such as Type 2 Diabetes. Personally, my body functions better when I eat low-carb. I’m not bloated, my skin is clearer, I sleep better and have more energy.

I thought the Food Pyramid told us to make carbohydrates, in the form of grains, the basis of our diet!
Indeed, the current USDA Dietary Guidelines recommend that 40-65% of daily calorie intake come from carbohydrates. So if one eats 2,000 calories a day, that translates into 900 to 1,300 calories a day from carbohydrates, or 225 to 325 grams.

However, humans can thrive on a much smaller amount of carbohydrates. For instance, our fellow Eskimos eat only fat, protein, and a little bit of berries, totalling no more than 50 grams of carbs per day.

Aren’t carbohydrates an essential part of our diet?
An essential nutrient is a nutrient required for normal human body function and which we have to obtain from our diet. The essential nutrients1 are:

energy (also called ‘ATP’, our bodies produce it from carbohydrates, fats, or protein)
protein: amino acids
fats: essential fatty acids

As you can see, carbohydrates are not essential nutrients, nor are they required for our body to function. Essential “energy” can be produced from fats and protein. Here is a quote from an article about the Eskimo diet, published in the American Anthropologist Journal : “despite its remarkably restricted composition, the native diet [which consists mainly of land and sea mammals and fish] is capable of furnishing all the essential nutritional elements when prepared and consumed according to traditional customs.”
And it’s totally awesome that the name “Eskimo” is American Indian for “eaters of raw meat”.1215-Photo-trois-enfants-inuit-couleur_g

Don’t you develop nutritional deficiencies if you don’t eat carbohydrates?
The usual way scientists discover the essentiality of nutrients is by identifying deficiency syndromes. Think about this: if you don’t eat enough protein, you develop kwashiorkor. Energy deprivation leads to marasmus, and fatty-acid deficiency leeds to allergic, visual or attention disorders. Similarly, deficiency in any vitamin, mineral, or electrolyte has severe consequences (for example, scurvy from lack of Vitamin C, or cardiac problems from Magnesium deficiency). This is why they are all essential to our functioning.

There has not been any evidence of carbohydrate deficiency syndrome in humans. It simply doesn’t exist.

The only way you could develop a deficiency by removing carbohydrates from your diet is if you used to rely solely on processed carbohydrate-rich foods for your daily vitamin and mineral intake. These foods, such as breakfast cereal or sliced bread, are virtually all carbohydrates, to which vitamins and minerals have been synthetically added during processing. Most likely, the vitamins and minerals have been sprayed onto your cornflakes, and even more likely, this is then used as a marketing device.

Rice and bread contain a lot of fiber, so where do you get yours?
The idea that carbohydrates are important for fiber intake is a myth. There is 4 times more fiber in a cup of raspberries (8g) than in a slice of whole grain bread (1.9g), and there is more fiber in a cup of brussel sprouts (4.1g) than in a cup of brown rice (3.5g).


But we need carbohydrates for energy, right?
The digestion of carbohydrates provides glucose, and glucose is the major source of fuel for most of us. However, if your diet is low in carbohydrates, some parts of our body (for instance, our brain and heart) switch over to using mostly fat for fuel. Other parts of our body which are absolutely glucose dependent (the cells in our eye for example) can make glucose from fat. Therefore, a diet rich in fats and low in carbohydrates can still satisfy our bodies and give us all the energy we need. And there is evidence that this is the way it should be.

Didn’t we evolve to eat carbohydrates?
Actually, there is evidence that a low-carbohydrate diet is closer to our optimal diet than a diet rich in grains and glucose, and that fat is the preferred fuel of our body, not carbs.

First, we have very low capacity for storing glucose (600g or 2,000 calories between our liver and our muscles), but a virtually unlimited capability to store energy as fat in adipose tissue (I did the calculation, I have 100,000 calories stored in my fat reserves). We switch to using fat for energy as soon as our glucose reserves are depleted. We could postulate that the reason we didn’t evolve with a copious potential to store glucose is because fat was the preferred fuel.

Secondly, we evolved for two-and-a-half million years with only fat and protein as the dominant macronutrients, with some foraged fruit and vegetables (when food was even available). Remember that agriculture only appeared 10,000 years ago, and with it, much greater access to carbohydrates that even cooked roots and tubers would provide.

Perhaps we became adapted to handling carbohydrate digestion, but it doesn’t seem that it is what our bodies prefer.


Our brains need glucose for energy, don’t they?
Yes. But in the context of a low-carb diet, where there is not much glucose available, our brain can switch to using ketones (from fat) as energy, either entirely, or partially.

Are there ‘Good’ and ‘Bad’ carbs?
Perhaps we can think about it this way: ‘Bad’ carbs only contain molecules of sugar, and do not bring anything else to your body (or do so artificially by fortification): sweets, deserts, bread, pasta, potato chips, etc… They also spike your insulin levels, and fan the flames of metabolic disease.
‘Good’ carbs are a vehicle for important compounds like vitamins, minerals, and fiber: think fruits and vegetables.

So what about the USDA recommendation of carbohydrate intake?
The requirements for carbohydrates are based on the minimum amount of glucose that is utilized by the brain per day. However, these recommendations presuppose a high-carb diet. If you are on a low-carb diet, your brain does not use glucose anymore, but it uses fat (ketones) for energy instead.

So does this mean that I should stop eating carbohydrates?
Well, just know that you do not need carbohydrates. Don’t eat (or drink!) carbs thinking they are vital or necessary to health. Make sure you get enough protein and fats, and eat your veggies.

Basically, as long as you get all your essential nutrients and energy from whole foods, fruits and vegetables, removing ‘bad’ carbs, i.e. sugars and starches from your diet is not a problem, nor is it unhealthy. In fact… it’s very good for you.

1Harper AE. Defining the essentiality of nutrients. In: Shils MD, Olson JA, Shihe M, Ross AC, eds. Modern nutrition in health and disease. 9th ed. Boston: William and Wilkins, 1999:3–10.

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