Did you get 23andMe, AncestryDNA, or MyHeritage results back?
Upload your raw DNA data to access 25+ traits for FREE at Genomelink!
July 29, 2019
Science
Why does everyone seem so worried about Carbohydrate Intake?
No matter who you are, you probably know someone on a ‘low carb’ diet.
By
Tomohiro Takano

No matter who you are, you probably know someone on a ‘low carb’ diet. You may have even tried a low carb diet yourself. But what are they, and why does everyone seem so worried about carbohydrate intake?

This article looks at carbohydrates, the good and the bad, the science behind our love of whole grain bread, and shows how our genetic makeup pushes us to prefer protein or carbs.

Why go low carb?

Spend too long looking through weight loss sites and you’ll start to feel a bit lost. Fat intake, carbohydrates - what should you cut first to lose weight, reduce your body-mass index (BMI), and avoid cardiovascular disease?

The typical answer, one held by weight loss and low carbohydrate diets around the world, is to drop your carbohydrate intake. Cut carbs, enjoy the high-fat diet, and there you go. Consistent weight loss and all the bacon you can eat. This sounds almost too good to be true, and this simplicity led to low-carb diets taking the world by storm. At one point 1 in 10 Americans were trying some form of low-carb diet to lose weight.

So what exactly are carbohydrates, and why does everyone keep going on about them?

Despite the complex name, you’re undoubtedly familiar with carbs - you know it as “sugar” or “starch”. There are many different types of carbs and they pop up in many different places - the added sugars we see in white bread is sucrose, starchy potatoes are full of molecular ‘strings’ of glucose, fruit is packed with fructose, and milk contains lactose.

This is clear enough, but the real question we’re asking is: are carbohydrates bad for me? Well, that’s actually quite a tough question, and the answer is “it depends”.

So what exactly is a carb?

Carbohydrates provide the basic fuel required by your body - the minute-by-minute energy which you need simply to survive. This is very different to fats, which let the body store energy away for later use. Instead, sugars such as glucose in the blood are there to be used, and fast!

Your brain runs almost exclusively on glucose, keeping thoughts snappy and our senses sharp. Your muscles are the same - the rapid energy from glucose lets us flee from saber-toothed tigers or catch a thrown beer.

But glucose isn’t all good all the time. There are a number of vital and complex mechanisms which keep the levels in your blood under control. Too much glucose and you burn them out, leading to diabetes. Too little and you simply run out of energy, dropping into a coma. This is not good, obviously, so your body prefers the ‘too much glucose’ side rather than ‘too little’. Extra glucose is converted into fat and packed away - the last thing your weight loss program needs!

Carbs can be ‘simple’ and ‘complex’. Simple carbs are basic sugars such as glucose - easily digested by the gut and quick to raise your glycemic index. Complex carbs from whole grains are long, interlinked chains of sugars - these are much more complicated to break down and take far longer to enter the blood. Starch, for example, takes a few hours to be digested. More complex carbs like cellulose can’t be digested at all - this is why celery is so good for weight loss.

The speed at which carbs are digested is also dependent on what else you eat. Stuff your face with sweets and you’ll send your blood glucose haywire. Stuff it with a whole-grain sandwich containing many complex carbs and your blood glucose will slowly rise, well within the control of your body.

You can probably guess that one of these is better for your health than the other. This is why carbohydrates, as with most things in life, should have a bit of variety.

Does DNA affect your low-carb diet success?

So carbs are sometimes good, sometimes bad. But you’re here to find out how your genes affect your taste for carbs or protein. How can we even know this?

We know this because a group of scientists examined the genomes of almost 40,000 volunteers to link their DNA and their choice of foods. They found 35 possible markers of food preference, which they cross-checked in another 33,000 genomes.

The same discovery was made by an independent group of researchers, checking 33,500 genomes. That’s an awful lot of testing, but it meant that the researchers were very certain of their results.

So what did they find?

A single protein, FGF21, is vital for metabolism of sugars and fats. People with one variant of this protein were more likely to prefer protein-rich foods than those with the other version, who preferred carbohydrates. This association was very significant (i.e. a one-in-a-billion chance of happening randomly), and was independent of weight. In other words, fat or thin, the gene affects your favorite nutrition.

Unfortunately, scientists still aren’t certain what is going on. FGF21 is part of many different metabolic processes, but the link explaining this gene and our love for garlic bread is still missing.

More Questions?

My results say I don’t have a high tendency to seek out carbs, but I’m obsessed with bread. What’s going on?

The DNA test results you get from us show your potential to prefer high carbohydrate diets. But our environment, our upbringing, our friends - all of these influence our lifestyle. Genetics sets the stage, but our lives fill in the theater, so you shouldn’t be surprised if your love of sourdough outweighs your genes.

Is it dangerous to eat too much or too little carbohydrates?

It certainly is! Like everything in life, your body wants variety. Doctors generally recommend that you get about half your daily nutrition from carbohydrates, mostly whole grains rather than simple sugars. If you want to lose weight via a low-carb diet, then consult a doctor first.

So what now?

At the moment we know that the FGF21 gene affects on carb intake, but we don’t know how this is occurring. It also isn’t particularly strong - the gene variant matches less than 1 percent of your carbohydrate intake preference, increasing to 6-17% with other genetic factors. Researchers now need to see how exactly these genes change our diet, how that helps us lose weight, and how to control them.

Find out what your DNA says

Carbs! Good and bad, essential for your health and wellbeing. Are you genetically predisposed to eat carbs, protein, or fat? Find out by checking your “Carbohydrate Intake” trait at Genomelink.


Did you get 23andMe, AncestryDNA, or MyHeritage results back?
Upload your raw DNA data to access 25+ traits for FREE at Genomelink!
Tomohiro Takano
Tomohiro Takano
Co-Founder and CEO
Up next
Why is my Genomelink result inaccurate?
Why is my Genomelink result inaccurate?
Your Genomelink result indicates the most likely outcome for the trait in question based solely on the raw data file you uploaded.
By
Tomohiro Takano