Can You Survive Without Carbs? | Ask The Dietitian

Trinh Le, MPH, RD
by Trinh Le, MPH, RD
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Can You Survive Without Carbs? | Ask The Dietitian

Are you carb-curious? The popularity of low-carb, ketogenic and other Atkins-style diets are fueling an intense fascination around this macronutrient. As a dietitian and self-professed science junkie, I feel the need to deepen our understanding of this topic so as to not glorify or demonize a nutrient (unless it’s well-deserved!). So, why are carbohydrates so important? Are they really essential in the diet? Read on to find out.

3 REASONS WHY CARBS ARE IMPORTANT

Carbohydrates achieve staple status in our diet because they supply a magical thing called glucose, a sugar. (OK, it’s not magic, just science.) If you weren’t automatically transported back to biology, let me explain.

1. CARBOHYDRATES ARE AN EFFICIENT FUEL SOURCE

Our body runs on calories, and it gets those calories by metabolizing carbohydrates, fat and protein from our food. Since our body smartly spares protein for rebuilding and repairing tissue, carbohydrates and fat are by far the fuel of choice. While every cell is capable of burning glucose  for energy, the same is not true for fat.

2. CERTAIN ORGANS AND TISSUES REQUIRE GLUCOSE

Our brain and red blood cells rely on the plentiful glucose in carbohydrates. Through gradual adaptation, the brain can learn to use fat in the form of ketone bodies, but our blood cells will always rely on glucose. In fact, our body fights really hard to keep our blood glucose levels within a narrow window. Once you dip below the minimum threshold of 20mg glucose/dL of blood you risk slipping into coma or having a seizure. This biological fact is partly what drives the daily recommendations for carbohydrates by major health organizations (see below).


GENERAL CARBOHYDRATE RECOMMENDATIONS


3. CARBOHYDRATES ARE EVERYWHERE

Carbs make up a large percentage of the U.S. food supply, contributing anywhere from 50–60% of calories since 1910. This makes sense given that the world’s staple crops are carb-heavy. These include cassava, corn, plantain, potato, rice, sorghum, soybean, sweet potato, wheat and yam. Fruits and vegetables, the foundation of a well-balanced diet, also contain carbohydrates. Even dairy contains milk sugar, which is a carb. Most modern societies base their diets on carbohydrate-rich foods.

3 REASONS WHY CARBS ARE NOT ESSENTIAL

Here’s where the argument that carbohydrates are essential starts to crumble:

1. PROTEIN AND FAT CAN PROVIDE GLUCOSE

The healthy human body is fully capable of reforming the amino acids from protein into glucose. Even the breakdown of fat for energy yields the tiniest bit of glucose. If an individual is eating enough calories, even if those calories are mostly from fat or protein, that person can still satisfy the glucose needs of their brain and blood cells and maintain their blood glucose at a normal level.

2. CARBOHYDRATE DEFICIENCY DOESN’T RESULT IN ILLNESS

Nutrition science defines a nutrient as “essential” if we must get it from the diet because our body can’t make enough of it to meet our needs. Deficiencies in protein, essential fats (linolenic and linoleic), vitamins and minerals all match up to an impairment or disease. This same phenomenon doesn’t exist with carbohydrates.

3. IT’S POSSIBLE TO SURVIVE ON VERY LITTLE CARBOHYDRATES

Reach outside the literature, and it’s easy to obtain anecdotal evidence of people who survive on very low-carbohydrate diets. (Note that we’re not taking into account sustainability or personal happiness when subsisting on these diets.)

  • The Atkins diet advocates followers eat as little as 20 grams of carbohydrates per day! To give you an idea of what this means: 20 grams is the amount of carbs in 1 small (6-inch) banana.
  • The classic ketogenic diet is 80–90% fat. It was originally used as a therapy for epilepsy but is now gaining popularity for use in weight loss.
  • The traditional Inuit diet, which is what the natives of northern Canada subsisted on for many years, is empty of refined sugar and grains. Instead, there’s plenty of fresh seal, walrus and other marine life on the menu. A 1980s study of that diet found that it contained, on average, 23% calories from protein, 39% calories from fat and 38% calories from carbohydrates.

READ MORE > WHAT’S THE BEST CARB, PROTEIN AND FAT BREAKDOWN FOR WEIGHT LOSS?


THE TAKEAWAY

Carbohydrates (including fiber) don’t necessarily make the cut as “essential” nutrients, but they are very important. Eliminating carbs completely from the diet is not only impossible, it’s impractical. Fruits, vegetables, whole grains and dairy all contain carbs and are foundational to a healthful diet. When it comes to choosing how low-carb you should go, keep in mind that:

  • Everyone responds differently to varying levels of carbohydrates. Our bodies are unique, so what works for one person may not work for another. The key is to do some research, then experiment to figure out what works best for you. Enlisting expert guidance from a doctor or dietitian can make this process easier.
  • The best diet is one that can be followed over time. Consistency is key to a healthy lifestyle. Setting yourself up with a plan that allows 20 grams of carbs per day may not be the best way to achieve this. A balanced diet is one that allows flexibility for you to fit in foods you enjoy regardless of carbohydrate content.
  • “Low-carb” can be a healthy lifestyle. Most low-carb diets don’t go as low as you think, hovering around 35–40% of calories from carbohydrates. For many, the term “low-carb” has become synonymous with eating less refined carbs and added sugar and eating more fruits and vegetables. Needless to say, I’m on board with that!

About the Author

Trinh Le, MPH, RD
Trinh Le, MPH, RD
Trinh is a registered dietitian by day, blogger at Fearless Food RD by night. She loves helping folks develop a better relationship with food, which includes lots of cooking, eating and learning about nutrition. When she’s not snapping mouthwatering shots of (mostly) healthy food, you can find Trinh HIIT-ing it at her local gym. For more, connect with her on FacebookInstagram and Pinterest.

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