Nutrition advice is usually “one size fits all”. But there can be a wide range of metabolic responses to any food or diet which means this generic dietary advice doesn’t work well for everyone. But can diets be tailored to your genes? Is the future of nutrition personalized? On this episode we explore nutrigenomics – the study of how our individual genetic make-up interacts with the foods we eat. Could nutrigenomics be the answer for you?
M: I’m Professor Megan
S: and I’m Professor Susan, and we’re
Both: Your Nutrition Profs!
M: We are registered dietitians and college professors who have taught more than 10,000 students about health and nutrition. We have answered a LOT of questions about nutrition over the years –
S: Some questions we get asked every year and some are rarely asked but very interesting.
M: We’re here to share our answers to these common (and uncommon) nutrition questions with you.
S: So bring your curiosity and let’s get started.
Both: Welcome to our class!
S: Happy New Year everyone! Welcome to 2024. We wish you health and happiness for the upcoming year.
M: Absolutely! Many of us make New Year’s resolutions and a lot of them are health related.
S: Do you make resolutions Megan?
M: Not really.
S: I used to but I don’t anymore because I never follow through. But a lot of people do.
M: A lot of people do.
S: The top four resolutions of 2023, according to the internet, were improving mental health, improving fitness, losing weight, and improving diet.
M: So we thought we’d answer a question today related to these goals, “Can I eat for my genes?”
S: This emerging science of nutritional genomics, or also called nutrigenomics is really, really interesting. Since the advent of genetic testing, it was really only a matter of time before people applied genetic testing to their own diets.
M: Absolutely. So I’m sure some of you have seen those tests about eating for your genes? And maybe you’ve thought about taking one. Well, hopefully, we're going to provide a little bit of insight into that today. But first let’s start with a little background. I want you to think back 20 years ago. In 2003 the human genome was sequenced in the Human Genome Project.
S: It was only 20 years ago? Gosh, it seems like it’s been so much longer!
M: I know, right? This science is pretty young but it’s revolutionary, it’s groundbreaking!
S: Right. The Human Genome Project was a really big deal. Sequencing the human genome means that scientists were able to “read” our DNA, kind of like putting the letters of a book in order, to make words. In DNA speak, the letters are 300 billion base pairs, the words are combos of base pairs.
M: And these words combine to make sentences and those are genes.
S: That’s a good way to put it.
M: Yeah Genes are the basic physical and functional units of heredity and are made up of DNA.
S: Genes are packaged into structures called chromosomes. Each of us has 46 total. We inherit 23 from mom and 23 from dad, but the two copies may or may not be identical. That’s why children from the same parents do not have exactly the same DNA unless they are identical twins.
M: This science is being used for all sorts of things…identifying your ancestry, determining risk for certain diseases and conditions, choosing treatment for some of those diseases and conditions, and even catching criminals!
S: I know! It fascinates me- this whole thing!
M: Well we’re both true crime fans….I mean, it’s amazing how they’re using familial DNA to help identify perpetrators and solve cold cases.
S: I know! I’ve even had a gene test looking for a specific known gene that’s related to a heart condition that runs in my family.
M: That is amazing that we can do that!
S: Yeah, it was very cool.
M: Yeah.
S: A lot of these genes carry instructions for making specific proteins that have specific functions. Things like enzymes, hormones, neurotransmitters, your skin, your hair, your heart cells, muscle cells… Our bodies are made up of proteins. Genes also carry instructions for certain traits like the color of your eyes, or your hair, or how tall you are.
M: Gene instructions are spelled out in the form of base pairs of four different chemicals. Like Susan stated earlier, the human genome has about 300 billion base pairs. These are organized into 2 to 25,000 specific genes… Imagine it sort of like a recipe book with more than 20,000 recipes.
S: But the 20 to 25,000 recipes- that’s less than 1% of our total genome.
M: It’s- it’s hard to wrap your head around.
S: It really is.
M: So the genes in the DNA are like the list of ingredients in a recipe. But you need more than just the list of ingredients to make a cake. You need instructions for how to mix it, how to bake, and then how to cool it to get the best outcome.
S: There are chemical compounds and proteins that attach to the DNA and these tell genes to turn on or turn off. And this controls the production of proteins in particular cells. So every single cell with a nucleus in the body contains the entire recipe book, but only certain genes are turned on and work in each particular cell. Muscle cells only make more muscle cells. They don’t make hair cells even though they have the recipe for hair cells in their nuclei.
M: Specialization is the key. Our trillions of cells are specialized for different functions in the brain, the bones, the muscle, etc. But specialized cells in the eye turn on only genes that make proteins that can detect light. Specialized cells in red blood cells make proteins that carry oxygen from the air to the rest of the body. These “instructions” make up quite a bit of the rest of our genome. The remainder of the genome is made up of repetitive regions or non-coding regions whose functions we’re still learning about.
S: Let’s talk about a few more terms related to genetics, the terms genotype and phenotype.
M: Good idea! Genotype is the actual genetic formula or recipe list of ingredients. Phenotype is the trait that can be seen like eye color, hair or skin color, being tall or short, stocky or thin, and in some cases having or not having a disease or medical condition.
S: Another way you can define phenotype is gene expression- how a gene is expressed or seen in real life. This is also called epigenetics, a sciency word, or another sciency word, the epigenome. And how genes are expressed varies widely among individuals, even those in the same family. Which is certainly true in my family.
M: These sections in our DNA that turn genes on and off are the epigenome. They are passed from parents to offspring and from cell to cell as they divide in the body. Because you inherit two copies of every gene, your epigenome decides which copy to use.
S: But genes aren’t the only thing that determines how a phenotype is shown or visible or known. Lifestyle and environmental factors like whether or not you smoke, where you live whether it’s in the city or in the country or battling an infectious disease- all of these can lead to changes in the epigenome which can be potentially damaging or beneficial.
M: And all humans are genetically mostly the same. If two individuals have their entire genome sequenced, they will differ at less than 1% of their total genome.
S: Another crazy statistic! 1%! And you know what? We only differ from other species like chimpanzees or mice by just a few more percentage points.
M: We even reportedly share about ~50% of our DNA with bananas.
S: Wait- that’s bananas! That’s crazy!
M: Well the most common differences between individuals are at a single base pair. These are called single nucleotide polymorphisms or SNPs (and we’re going to call them snips).
S: Differences can also be found in the number of insertions or deletions of short DNA fragments or in how the DNA fragments are arranged.
M: Also each individual has a number of gene copies throughout their DNA. The number of these copies can vary.
S: And all of this contributes to genetic diversity. These differences are where nutrigenomics comes in. Nutrigenomics studies the relationships between our genes and nutrients in the foods we eat and how each of us might respond to these particular nutrients.
M: It’s a way to help predict what may help you reach goals based on your specific genome. It’s really the ultimate in personalized nutrition.
S: Yeah! You know, there are basically two ways to look at things. One- differences in the genes that you inherited can predict how your body will likely respond to certain nutrients. For example, your genes may signal that you’re more likely to develop high blood pressure, crave sweets, get jittery when you drink caffeine, or absorb some vitamins or minerals poorly. The other way to look at it is how do the nutrients you eat or don’t eat influence your genes? So the other way around, instead of genes influencing how your body responds, this is how you eat influences your genes. So nutrient intake is part of your environment- your epigenome.
M: Now that we’ve explained everything you ever wanted to know about genetics…
S: And probably more.
M: Let’s talk about the actual tests. Most use a simple swab of the inside of your mouth that is then sent to a lab to be analyzed. But not all genes are tested, most labs analyze 50 to 70 of your 20,000 different genes. They’re looking for differences in SNPs… tiny differences in base pairs that will slightly change the gene recipe.
S: Reputable tests will only look for SNPs where there is a known function or association with a specific disease or phenotype. It’d be way too expensive to test your entire genome right now.
M: Absolutely. And although many SNPs have been identified, we definitely don’t yet know what they all do or influence, if anything.
S: Right.
M: Some may not have any functions or links anymore at all as we evolve in local environments, these connections can get changed.
S: Right. And as humans migrated out of Africa they genetically adapted to their ancestral diets and their own local environments and over the past 100,000 years that caused wide genetic variability in humans.
M: This can help explain the observed global patterns of some health conditions. So for example, East Asians and Africans are much more likely to be lactose intolerant as adults than Northern Europeans. Knowing that, some tests can tell you your risk of becoming lactose intolerant or developing gluten intolerance or celiac disease based on these known differences.
S: But, of course, it’s complicated.
M: It always is. So just because you have a particular genotype it doesn’t mean you will definitely express a particular phenotype.
S: Right. And many phenotypes, like whether or not you’ll develop type 2 diabetes or coronary artery disease- those are the result of contributions from dozens, or even hundreds of different genes. So each small SNP variation only contributes a teeny tiny bit to the risk of developing these diseases.
M: And something else that complicates things is that single genes can have multiple effects. So in other words, one gene can affect several different and often unrelated traits, and turn on or off at different life stages.
S: So whether or not you develop a specific disease or condition related to nutrition and how severe it may be is based on a complicated web of three things. One, of course, is your actual genes.
M: Makes sense.
S: Two, is your intake or exposure to a nutrient. So how much you eat or how often you eat it or drink it or consume it. And number three, the environment where you live and this also includes your dietary history, your hormone levels, your age, other things you might consume like food additives or consuming different nutrients at the same time, or other environmental factors you’re exposed to like how much you exercise or where you live. All of those can influence this. So it’s really, really complicated.
M: Well get ready to make things even more convoluted. Both your intake or exposure and your environment can, of course, change over time. You may move to a different part of the country or change your diet or exercise patterns, which may modify gene expression.
S: Wow, so super, super, super complicated. And the science is constantly progressing and evolving. So it’s a very dynamic time.
M: Yeah, it’s exciting times for sure!
S: Mmm hmm.
M: Alright, let’s get back to the nutrigenomic tests. Since they’re not testing your entire genome, most of the genes they look for are related to how well your body absorbs and utilizes specific nutrients, how well you metabolize caffeine, whether or not a high-protein diet would be beneficial for you, or how well your body can utilize whole grains. Just to name a few.
S: These are genes that have some research associated with them. They’re not just looking for random SNPs.
M: Although you can order direct-to-consumer genetic tests, it is really important to work with a professional like a registered dietitian who has been trained to evaluate the information that you’re going to get when doing these types of tests.
S: For sure! They can explain what your results mean for you, taking into consideration all of those things we mentioned- your exposure to the nutrient, the environment where you live. and then they can help you choose foods that might reduce your disease risk or optimize your health.
M: So we’ve both had our genomes tested and the results are super interesting…. I mean, at least to us.
S: Well we’re RD nerds so…. So in my test, because of my genes I am at elevated risk for deficiency for vitamin B12, vitamin D, choline, and calcium so I need to make sure I am consuming plenty of bioavailable sources of these particular vitamins and minerals. I also have an elevated risk for high blood pressure so I need to limit my daily sodium intake. So I try to avoid processed foods as much as I can.
M: And according to my genes, I’m a mess. I am at an elevated risk of deficiency for vitamins A, B12, D, E, folate, choline, and the minerals calcium, magnesium, and zinc.
S: Yowzer!
M: So does this mean I’m doomed to micronutrient deficiency… No. If we look a bit deeper… well, let me give you an example. So let’s use vitamin A. Preformed vitamin A is only found in animal foods, while beta-carotene, which is found primarily in red and orange plant foods, is considered a provitamin because it gets converted to vitamin A in the body. Well I possess a gene variant that might make it difficult for my body to make this conversion. So if I were vegan, that could be trouble and I might need to take a supplement. But since I know this about my body, I can make sure to get adequate intake of both reformed and provitamin A which reduces my risk.
S: That makes sense. The test we did also gave us some results for some of our abilities to taste things like fat and sugar in foods, and also whether or not we’re likely to snack between meals. I am a typical taster of sugar, but a “super taster” of fats which allegedly means I can sense the taste of fats at lower levels in foods. This means I can be satisfied with a lower amount of fat in a food but it still tastes flavorful, supposedly. However, I am also more likely to snack between meals and that is definitely true for me.
M: Well my genes indicate I likely have a high preference for sugar and I can confirm that this is true. I’m also a super taster of fats! But our tests provided some information about our innate motivation to exercise, which types of exercise we might excel in, as well as our risk for muscle and tissue damage.
S: Right, the good news for me, is that according to my genes I am more likely to gain enjoyment and positive mood changes from exercising and may have a slight genetic advantage to excel in strength and power activities. I really wish I enjoyed those more! The bad news is that I am more likely to feel muscle soreness after exercise and I’m at elevated risk of sustaining an Achilles tendon injury, but I do have an enhanced pain tolerance.
M: So unlike Susan, my genes indicate I only have a “typical” motivation to and likelihood of participating in exercise… But in reality, I would say I exercise more than is “typical”.
S: I would say that too.
M: Yeah. So that just goes to show that we’re not defined or destined for things based on one gene or SNP. I’m also predisposed to excel in strength and power activities. Like Susan, I’m also more likely to feel muscle soreness but have an enhanced pain tolerance. And then I also have that elevated risk of Achilles tendon injury or rotator cuff injury.
S: So this isn’t all of our test results, just a smattering. But current nutrigenomics tests primarily focus on predicting responses related to these single SNPs and their relationship with nutrients. Less is known about how food influences gene expression.
M: The research is ongoing. Just imagine what we’ll know 20 years from now!
S: I know! Just in the last 20 years and now 20 years from now! So what would that be- 2043?
M: Wow!
S: Holy cow! I cannot even imagine… So should we change our diets based on this information? Maybe…
M: But first you’d have to know what you’re consuming. You have to know your nutrient intake or exposure. Maybe even though your genes, like mine, say I’m at risk for vitamin B12 or some other nutrient deficiency, but if I’m already consuming plenty of vitamin B12, there’s no need to add even more to your diet or take expensive supplements that may not work anyway.
S: Exactly! That’s why it’s so important to work with someone like a registered dietitian who’s been trained to interpret this information for you. Doing a diet log or food frequency questionnaire can help them help you determine if any dietary changes are recommended.
M: And maybe you’re already eating a diet that optimizes your health and no changes are necessary!
S: Right!
M: So should you be taking this sort of test to personalize your nutrition? Let’s look at the pros and cons.
S: Ok, pros first. Here’s what people say about nutrigenomics testing. Nutrigenomics can help you pinpoint the parts of your diet that have the most impact on your health. You may be able to reduce some of your risk for specific diseases or conditions by adopting some dietary changes. Another pro, is having specific and personalized information may motivate you to make those dietary changes and stick more closely to your eating plans.
M: For example, high blood pressure runs in my family. I know that, but it’s easy to ignore, especially when I was younger and thought that “it would never happen to me” or “I’m not going to need to worry about it for several years”. But now that I know I have a specific gene variant that does make me more likely to develop high blood pressure, it’s become more personal and I’m more motivated to watch my salt intake.
S: But keep this in mind, just because you have or don’t have a gene variant for a specific disease or condition, it doesn’t mean that you’ll never get the condition or the opposite- that it’s inevitable that you definitely will get that condition. Remember that genetics is just one piece of a very complicated health puzzle. Lifestyle and environment play large roles as well as we discussed earlier. So even though I may not have the gene variant for the specific heart condition that runs in my family, it doesn’t mean I am completely out of the woods and I can do whatever I want.
M: So, remember your epigenome? Lifestyle factors as we’ve said- smoking, eating high amounts of processed foods, lack of physical activity, exposure to environmental toxins- all of these can modify which genes are turned on and off which also plays a really big role in disease development.
S: And at this point nutrigenomics tests can’t tell you much about these on/off switches.
M: Right. So let’s move on and talk about some of the cons.
S: Ok, the cons. These tests are loosely regulated by FDA and the Centers for Medicare and Medicaid Services. There is largely no federal oversight.
M: The tests do not provide a clinical diagnosis. They can only say there is a certain level of risk that you might develop a certain disorder.
S: The results are most useful for those with European ancestry as most of the studies, the research studies, have used this population. If you do not have European ancestry, the results you receive may be less reliable and less applicable.
M: Testing can lead to distress and anxiety. We’re primarily talking about nutrition here, but you can get direct-to-consumer tests that give results like your risk of developing breast cancer or Alzheimer’s disease. And that can cause people a lot of anxiety, so be careful.
S: And testing may also lead to thinking that because of your genes a disease is inevitable and we already talked a little bit about this, but if you think a disease is inevitable, you may stop trying to reduce your risk.
M: Yeah.
S: So is nutrigenomics the future of nutrition?
M: Maybe. Right now nutritional recommendations are based on entire populations. Researchers have decades of data showing that disease risk tends to decrease when people eat diets high in whole plants, lean protein sources, and unsaturated fats and avoid things like solid fats, sugar, and high amounts of salt.
S: Nutritional recommendations based on your personal genetic make up will probably become much more routine. It can help you target areas more specifically based on your own body.
M: But be picky about the test you decide to use. A good test would provide both pre and post test education and genetic counseling so that consumers can understand and make the best use of their results. It’s best to have a specific goal in mind like “which nutrients should I increase or decrease” instead of something more vague like “I want to improve my health”.
S: And keep in mind that these are your genetic results- your genes! Before doing any direct-to-consumer tests, make sure you know how the company is storing and using your data. Some companies may sell your data and you won’t know who is using it or how.
M: So do your research! Make sure your name or identifying information is not linked to your genetic data… a bar code should be your only identifier.
S: Right, there are some companies out there who do not sell your data and keep it in house like the company we used for our tests.
M: Yeah.
S: These tests are usually a little more expensive and often are not direct-to-consumer but instead are provided through health professionals like registered dietitians, as we walked about earlier, who are trained to provide and interpret your results.
M: These tests are not cheap. They can range from about $150 to more than $500 with the more expensive being the most reputable.
S: Of course. So let’s bottom line it. If you’re thinking of making a New Year’s Resolution related to your diet, you may consider spending some money on a nutrigenomics test. It could help you focus your goals for improving your health. The more specific the goal the more likely you are to reach it!
M: And again we recommend that before choosing a test, do your homework, and find out as much as you can about what the company does with your data.
S: No matter which test you choose, we recommend that you work with a health professional like a registered dietitian who is trained to help you interpret your results. The data isn’t easy to understand, and most of us aren’t geneticists!
M: And that’s it for our discussion of nutrigenomics. It’s an emerging science that you will definitely be hearing more about in the future.
S: And this was kind of a sciencey episode-
M: Yeah.
S: -but I think nutrigenomics is the future so the more you know, the better.
M: Absolutely!
S: Well happy New Year! Join us next time when we’ll answer a very common question we get,
“Why does my stomach growl?”
Both: Class dismissed!
S: We hope you enjoyed this episode. You can find the show notes and a list of sources on our website, yournutritionprofs.com.
M: Your homework is to follow us at your nutrition profs on Instagram and to listen to our next episode. You can listen on Amazon Prime, Apple Podcasts, Spotify, YouTube, or anywhere podcasts are found. We’d appreciate it if you’d “like” us, write a review, subscribe, and invite your family and friends to join us too.
S: If you have a nutrition or health question you’d like answered, let us know! We may even do a show about it! Send an email to [email protected] or click on the “Contact Us” page on our website.
M: Thanks to Brian Pittman for creating our artwork. You can find him on instagram @BrianPittman77
Both: See you next time!