Can You Really Eat According to Your Genes? The Inside Story on Genetic Testing for Personalized Nutrition

You may have seen advertisements, read articles in the news, or even seen some of my posts about the latest nutrition game changer: genetic testing and personalized nutrition. These tests use a simple saliva sample to tell you all kinds of interesting things about your genetic makeup, and how those differences can affect your metabolism, body weight, and response to different diets or exercise regimes. You can even find out if you are at risk of some conditions like celiac disase. This cutting-edge area of nutrition science is called “nutrigenomics”, or “nutrigenetics” and it’s hella interesting.

But are these tests legit? It all really sounds like some Tony Stark level comic book fantasy. How much can your spit really tell you about your health?

As with all things in life (especially anything potentially related to weight loss) I would say a healthy dose of skepticism is always appropriate. It’s pretty rare for anything in life to be as glossy as the advertisements, and when we enter into something with sky high expectations we might be let down by the true experience. So, my goal here is to give you the REAL breakdown (both the pros and cons!) of what nutrigenomic testing can and cannot do when it comes to personalized nutrition and finding your best diet. No nutrition BS!

First, let tell you my history with nutrigenomics and how I became interested in the field….

We need to take a few steps back to 2014. I was a few years out of university and attended my first ever Dietitians of Canada National Conference. One of the speakers at the conference was a researcher in the field of nutrigenomics, and his presentation included research about genetic differences between people and their ability to metabolize caffeine. Now, I had heard a bit about this fancy new nutrition frontier during some of my University coursework, but man had the science come a long way since I was doing my degree!

(While we’re on this topic of changing times and evolving science, I want to add a side note of why it is SO IMPORTANT to go to a Registered Dietitian for Nutrition advice. Our College requires that we spend a minimum amount of time on continuing education each year in order to maintain our licence. This means you are getting the most up to date nutrition information, as opposed someone who might have completed an online nutrition program or no formal education at all, and does not need to maintain any sort of licensing…. just an FYI!)

So anyway, back to 2014 at the DC conference. I was absolutely hooked on this idea that I could  provide personalized nutrition advice to my clients, and help people optimize their health based on their genes, not guesswork. At the time there were only a few genetic testing companies on the market, and the brand of test I chose to offer was only a small, 7-gene panel. Mostly made up of vitamin and mineral information it was pretty limited in it’s scope. Interesting, sure, but not something that was going to have a huge impact on my nutrition plans. There were definitely more in-depth tests available, but what we didn’t have was enough research to tell us what to DO with that genetic information. For example since the completion of the human genome project in 2003, we can completely map the entire 20,000+ genes each of us is made up of. So, yes we know what genes we have, but how does nutrition affect each of those genes? Can any of these genes be modified with changes in nutrition? What environmental changes turn some genes on or off? Are some types of genes better than others? Even today most of these questions are still unanswered!

Fortunately though science never sleeps, and a few years later through more research and development the simple 7-Gene test I previously mentioned evolved to a much more impressive 45-Gene test. These 45 Genes include information related to the vitamin and mineral panel, caffeine, sodium, fats, protein, lactose, Celiac disease, and even eating habits and exercise. With this new test we could not only tell people what types of genes they have, but also how they can eat and exercise to best OPTIMIZE and work with these genes. Pretty cool, huh?

So, here just a few examples of the genes I personally find most useful when I’m personalizing a nutrition plan for my clients:

Caffeine (CYP1A2 rs2471300): This gene is involved in the metabolism of caffeine in the body. We describe each of us as being “slow” or “fast” caffeine metabolizers, and the population is split about 50/50. Slow caffeine metabolizers actually have an increased risk of high blood pressure, heart attack, and poorer athletic performance if they’re consuming more than 200mg of caffeine per day. To put this into perspective, a grande Starbucks Pike Place Roast coffee is estimated to have over 300mg of caffeine alone. So, if you’re a slow metabolizer and like a few cups of coffee every day, you may be putting yourself at risk. Fast caffeine metabolizers on the other hand, actually have a decreased risk of a heart attack, and enhanced athletic performance when they consume that same amount of caffeine. For these folks a little caffeine may actually be a good thing.


Energy Balance (UCP1 rs1800592): Many of us like to point to a “slow metabolism” as one of the reasons we gain weight. The UCP1 gene has been indentified as playing a role in what a person’s resting energy expenditure (aka our metabolic rate) actually is. Research estimates that about 70% of the population have a variation of this gene that results in a slightly lower metabolic rate than people with the opposite gene, about 150 calories per day. This means that individuals with the lowered metabolic rate may need to make different changes to their nutrition or exercise patterns in order to reach their goals.


Fat (TCF7L2 rs7903146, FTO rs9939609, PPARy2 rs1801282): Low Carb, High Fat (LCHF) diets have certainly been popular on and off throughout the last few decades. From the Atkins Diet to the current version, called the Ketogenic Diet, people consistently turn to cutting out carbs as a way of losing weight and becoming healthier. Interestingly though, there are a number of different genes that have been shown to influence how we each respond to different dietary fats. Some variations of these genes have been associated with weight gain, insulin resistance, and increased abdominal fat when a person consumes a high-fat, or high saturated fat diet. So we certainly know that there is no one best diet for everyone, and these differences in each of our genetics may help explain why some people do see weight loss when they follow certain dietary patterns, yet the next person sees no changes at all.


Protein (FTO rs9939609): Many trendy diets over the years have encouraged eating large amounts of protein to help boost weight loss. Similar to the high fat, low carb diets I mentioned above, a low carb and high protein diet has been a regular on the fad diet scene. Like most diets out there many people do not find success while following them (for many reasons other than just genetics!), but there are always a few who experience really significant results and find that that specific pattern of eating works best for them. Research has shown that people who have a certain variation of the FTO gene experience more weight loss when they follow a diet slightly higher in protein. For people who have the opposite gene variation, there is no benefit. Studies have shown that 1 in 6 people have the response variant, so while it isn’t the majority of us, knowing which group you fit into can certainly help finding your best nutrition plan!


Calcium (CG, rs7041 rs4588)

Iron (TMPRSS6 rs4820268, TFR2 rs7385804, TF rs381164)

Vitamin B12 (FUT2 rs601338)

These vitamins and minerals are of interest to me, because it can be challenging for some plant-based eaters to get enough. Genetic variations mean some people do not absorb or utilize calcium, iron, or B12 as efficiently as others, which puts them at risk of deficiency if they don’t carefully plan their diets. Calcium in particular, because we can’t do a simple blood test to determine if a person is getting enough. Iron and B12 are easily tested as part of routine bloodwork, but calcium levels in the blood remain the same regardless of intake (as an electrolyte having the right amount of calcium in the blood is essential to keep our heart beating!). Over time though, not having enough calcium in the body can lead to poor bone density and increased risk of fractures. To me, knowing your genetic information is absolutely key if you want to optimize your plant-based diet!


Sodium (ACE rs4343): Did you know that most North Americans eat about 30% more sodium than the upper recommended limit? It’s true! The established upper limit for sodium in a single day is 2300mg. Most of us are eating about 3500mg each and every day. For some, a little extra salt in a day might be no big deal. We may even think that because we don’t have high blood pressure that we don’t need to worry about sodium at all. Unfortunately this isn’t the case! 70% of the population have a gene variant that puts them at risk of high blood pressure if they eat too much sodium. That’s certainly enough people that I think we should ALL be cutting back on salt! BUT, what’s even more interesting is that for those who fit into this ‘salt sensitive’ category, we can still have negative health effects of a diet too high in salt, without actually having high blood pressure. So getting our salt intake down is important even if we haven’t been diagnosed with high blood pressure. Non-responders on the other hand, can struggle as well because reducing the salt they eat may actually not impact their blood pressure at all. So, if they do get diagnosed with high blood pressure they likely need alternative strategies to help bring it down.


These are just a small sample of the genes I think are most relevant and exciting for planning a personalized nutrition plan. As you can see, there is absolutely no one-size-fits-all approach when it comes to what’s best in nutrition. Being able to personalize an  eating plan can have big impacts on health, and knowing some of these genetic variations can provide incredibly useful information about what strategies will be most effective.

BUT, I did say I was going to give you both sides of the story, so I’ll share with you a few potential downsides to nutrigenomic testing that you should be aware of before you run out to spit in your test tube!

Nutrigenomic Testing can be very expensive, and may not be covered by your insurance plan. In a perfect world, we’d all have access to the genetic information we need about ourselves, just like bloodwork or medication lists. Unfortunately for now most of us need to pay out of pocket for our genetic tests and they may not be cheap depending on which company and test we use.

Lifestyle changes are enhanced with genetic information, but that doesn’t make them easy. One of the big questions we all ask when it comes to nutrigenomic testing is “does knowing more about our genes motivate us to make changes?”. Generally speaking, the research points to yes. For most people, knowing what changes they can make to optimize their nutrition based on their genetics is a very useful strategy to enhance motivation. BUT, the barriers in our lives that can interfere with making those changes don’t go away just because we have this information in hand. It’s important to understand that nutrigenomic testing isn’t a magic pill of sorts for making those changes easy. Think of it as more of a roadmap guiding us toward what changes we should make. The rest is up to us!

Not all genetic testing companies are created equally. This is especially true as the concept of direct-to-consumer testing is still somewhat new. Plenty of companies have emerged on the market that may make over the top promises, test for genes that don’t have the right science to back up their claims, or even have shady, unreliable testing practices altogether. It’s definitely buyer beware and I highly encourage you to do some homework on a genetic testing company before shelling out any cash. Make sure you know exactly what you’re spending your money on!

The science (and advice that goes with it) will change. We should always be prepared to continue to learn and evolve with this area of nutrition science because it is just so darn new. While I’m confident in what the current research says about how to personalize my nutrition plans right now, I know that a few years into the future we may have more information about some of these genes (and new genes!) that might alter the advice I’m currently providing. But, that doesn’t mean we should wait and see what changes before diving in to personalized nutrition because let’s face it, science is never done!

Nutrition science has been growing, changing, and evolving ever since it’s beginnings, and we’re still just at the tip of the iceberg when it comes to our knowledge of the human body and how it all works. New information about the complex relationship between the food we eat, our gut microbiome, and how that affects our gene expression is still a long way away from being figured out. But, working with a Registered Dietitian on any nutrition journey you take is your best bet, because you know you’ll be getting the most up to date, cutting edge information about the nutrition topics are important to you.


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