Have you ever wondered why people can have such different responses to certain foods? Not just allergies or different tastes, but actually how you process or react to food.

Some people can digest dairy, others cannot.

Some people get energized after drinking coffee, others get sleepy.

Some people gain weight easily, others do not.

These kinds of differences are what make it so hard to find dietary advice that actually works for you.

What foods you should eat to get you the health outcome you want, depends on your genes and something called nutrigenomics.

What is Nutrigenomics?

Nutrigenomics, also known as nutrigenetics, is the intersection between nutrition and genetics.

It looks at how the nutrients we eat interact with our genes to impact our health and performance.

If all these words are sounding like mumbo jumbo to you, let’s back up a bit and clarify what exactly genetics and genes are and how they work.

What is Genetics?

Genetics is a general term for the study of genes.

What Are Genes?

Genes are little sections of DNA, which is the hereditary material that is passed on from parents to their offspring.

If you’ve ever heard that you have your mother’s eyes, or you’re the spitting image of your grandfather, or your child has your hair – this is because you inherited, or passed on, certain genes that encoded for those traits of eye colour, hair colour, etc.

Genes are basically instructions that tell the cells in your body what to do. What protein to make, what eye colour, what facial features, etc.

Every cell in your body contains genes that code for all sorts of different things. Your physical features and appearance for one, but also pretty much everything else about you – all your bodily functions, all the proteins and molecules that keep your body running, your susceptibility to health conditions and diseases, and more.

Differences in Genes

The differences or similarities between people come from the differences/similarities in their genes.

Different people can have different versions of the same gene.

We inherit two copies of each gene – one from each parent. Each gene can come in two possible forms. So there are three possible combinations of what you can inherit for one gene.

Depending on what versions of the gene you inherit, you may have a trait/feature that is different from someone else who inherited different versions of that gene.

Genes can also acquire small mutations that can be passed down and inherited. A gene with a mutation may function differently than the same gene without the mutation.

These same genes with different functions are known as gene variants.

Genes and Nutrition

Just like your genes determine all your traits, your genes can also have a profound effect on how your body responds to food.

Variations in genes can affect what food you eat, your metabolism, eating behaviours, smell, taste, appetite, absorption, digestion, excretion, etc.

Let’s look at a few examples…

How Your Genes Affect Your Diet

Your genes can affect how you respond to certain foods such as coffee, dairy, and sugar.

These are just a few of many examples of how nutrition and genetics can interact:

  1. Lactose intolerance

A familiar and common example of how your genes can affect your food choices, is lactose intolerance.

People who are lactose-intolerant cannot digest lactose, which is the sugar found in milk and other dairy products.

This is because they have inherited a mutation in the gene that encodes the lactase enzyme, which leads to a less active lactase enzyme.

The lactase enzyme is what breaks down the lactose that you consume from dairy products.

Individuals with lactose intolerance do not produce enough active lactase to digest lactose, so they experience gut discomfort when they consume foods containing lactose.

2. Coffee consumption

Your genes also play a role in how much coffee you should be drinking.

We have a gene called CYP1A2 which encodes the enzyme that breaks down the caffeine in coffee.

People with a specific variant of this gene are classified as “fast metabolizers” because they can break down caffeine a lot quicker than people with a different CYP1A2 gene variant (aka “slow metabolizers” who have a less active enzyme).

This determines how much caffeine your body is exposed to – a fast metabolism means the caffeine is cleared out of your system faster.

This has implications for how much coffee you should be drinking. Depending on who you ask, you may hear that coffee does or does not increase your risk of heart attack. As it turns out, this may depend on what kind of caffeine metabolizer you are.

Research has shown that slow metabolizers have an increased risk of heart attack when drinking more than 2 cups of coffee daily (1).

For fast metabolizers, even over 4 cups of coffee daily does not increase heart attack risk in fast metabolizers who are over 60 years old. And for fast metabolizers who are younger than 60 years old, there is actually a protective effect of drinking 1-3 cups per day (meaning drinking coffee actually reduces the risk of heart attack for these people).

So if you’re a fast metabolizer, go right on ahead and drink that third cup of coffee today. And if you’re a slow metabolizer…maybe cut back or opt for decaf.

3. Asparagus…odours

Okay, this is going to sound a little weird, but after you eat asparagus, do you notice that your pee smells funny?

You’re either wondering what the heck I’m talking about right now…..or you know exactly what I mean.

Believe it or not, there are actually certain gene variants that determine if you are able to smell the odour that asparagus causes your urine to have!

4. Sugar consumption

Whether or not you are a sweet tooth may also depend on your genes!

A variant in the GLUT2 transporter gene is associated with higher sugar consumption (2). Is is thought that individuals with this variant have a lower glucose-sensing ability, causing them to consume more sugar before satiety.

So next time the sugar cravings kick in, you may be able to blame it on your genes.

5. Vitamin C deficiency

Your genes may also determine if you are prone to certain nutrient deficiencies.

One variant of the gene that encodes what are known as GST enzymes, leads to inactive GST enzymes.

Individuals with this variant have an increased risk of vitamin C deficiency if they do not keep up with the recommended daily intake of vitamin C (75-90mg/day (3)) (4).

Individuals with the other gene variant, who have functional GST enzymes, are protected against any drop in their blood’s vitamin C levels, even if vitamin C intake is less than the recommended daily intake.

Why is Nutrigenomics Important?

Understanding how genes can affect the way you respond to food, helps explain why dietary advice tends to be so confusing and contradictory.

It’s hard to find clear-cut answers to questions like, What constitutes a healthy diet? Or, Is this food good for me? Or, What should I eat to prevent this disease?

As you saw in the above examples, one nutrition factor can have different outcomes based on which variant of a gene you have.

When it comes to diet, one size does not fit all.

It is difficult to make accurate claims of what is healthy or unhealthy for you, without taking genetics into account.

The only way to find out if you actually have certain gene variants, is to get your genes tested. Fortunately, genetic testing kits (where you spit in a tube and send it in to get your DNA analyzed) are becoming more and more popular and affordable.

Understanding the influence that your genes have on your diet is the first step to a more personalized approach to health and medicine.


Different people can have different versions of the same gene. Depending on what gene variant you have, certain foods may cause different reactions or health outcomes. Your personal genetics need to be taken into account in order to know what foods you should or shouldn’t eat.

I hope you enjoyed this article on how your genes affect what foods you should eat. If you liked this article, or have any questions, be sure to comment below!

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