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    November 1, 2019

     

    EATING FOR YOUR GENES

     

    Nutrigenetics (matching your diet to your DNA) is touted as the future of wellness and disease prevention.  I have nearly a question a week now about this topic.  Here is some information that I hope will be helpful.

    Over time, humans have adapted to get the most from their diets.  Because early in our evolution we stayed close to home, we developed the ability to derive the most from the foods we had on hand and also the ability to survive without as much of some other nutrients that might not have been available to us at the time.  Now we move across town, across the country, across the world.  We spend time in different places and enjoy learning about different cultures and their cuisine.  We meet and marry from across the globe and all our genes are now a big happy mix, a genetic muddle not necessarily optimized for any traditional diet, per se.  That said, those genes from our ancestors are still in there, so one would think it would make sense to try to understand the genes you carry so you could optimize your diet for sparkling good health. 

    Science has actually been researching this field for some time, ever since Archibald Garrod created the field of ‘inborn errors of metabolism’ (alkaptonuria: an inherited disease that prevents the body from processing certain proteins).  His field led to the birth of nutrigenetics and nutrigenomics, the twin sciences of how your genes interact with the food you eat and, in turn, affect your health.  Science has made hundreds of links between genes, diet and physical outcomes.   For example, we’ve learned that a variation in a gene called FTO predisposes people to obesity.  We’ve learned that those with a particular alteration in the gene APOA2 lose more weight when they reduce saturated fat in their diet when compared to individuals who don’t carry this particular variation.   And we also know that more than 10% of American women have a variation in the gene MTHFR that can lead to birth defects like spina bifida in their babies, unless they supplement their intake of folate.

    When you think about how little we knew about this topic a decade ago, the growth of nutrigenetics is absolutely explosive.  On the other hand, when you think of how much there is still to know, that’s another story.  There are more than 100 million SNPs (single-nucleotide polymorphisms) and an estimated 25,000 bioactive substances in food: compounds that aren’t essential nutrients but can affect the way your body operates, including things like lycopene, resveratrol, tannins and basically every unfamiliar name you see in an article about The Next Miracle Nutrient.  It’s going to take some time to get through them all and understand how they play together.

    You are already able to get personalized dietary recommendation based on your genes from a host of different companies.   Typically, they look at SNPs from 20-30 different genes and tell you things like whether you are lactose-intolerant, prone to a number of vitamin deficiencies and how you metabolize caffeine, alcohol and different kinds of fats, and if you carry a gene that makes cilantro taste weird to you.  It’s interesting, but the advice (especially after the FDA crackdown a few years ago) tends to be soft and not really all that personalized.   Real personalized nutrition faces some big hurdles.  There are so many SNPs to test and so much research that has not been able to provide conclusive findings.  And many of the things we ‘think’ we know will not be relevant even a year from now because they’re likely based on one finding from one study that was never replicated in the research arena.    And even when knowledge about genes and diet gets more solid, there will be the question of what to do with it.  A personalized diet sounds like a wonderful thing, but if you go beyond one or two genes, things start to get incredibly complex.  Imagine if you’re trying to adjust your diet to meet a handful of gene variants: say, total calories down by 20% and saturated fat by 50%, up your folate and vitamin C by 50%, reduce your folic acid by two-thirds and get your calcium/magnesium ratio around 2.6.  So, what’s for dinner?  Most of us would have a difficult time translating that to our plates.  And even if we could, it’s not clear that we even must deal with every message we get about our genes.  Many SNPs, taken individually, aren’t impactful.  The outcomes that most of us care about: obesity, diabetes, heart disease and cancer, involve dozens of genes interacting in ways we don’t yet understand.  Genes can also be turned on and off.  They do different things at different times in the body.  So, how much does a single gene contribute to a person’s overall health?  Very little.  What’s more, it’s estimated that genes explain only about 10% of the risk linked to diet-related diseases like obesity and type 2 diabetes.   It’s arrogant to think we can’t know what to eat until we’re all individually profiled, because we’re all so unique and special.  There are fundamental truths to feeding humans, just like dolphins and pandas.  Ninety percent of health is a diet that applies to everyone.  Your body doesn’t demand a perfect diet, just a healthy one. 

    What we will be able to do with all the spectacular nutrigenetic data we’re going to acquire is use it to make better diagnoses of diseases and recommendations for dietary changes that do really matter.   The data will help us to connect the dots between symptoms, genes, diet and factors like physical activity and environment.   In the meantime, eat your vegetables, watch your intake of concentrated sweets and unhealthy fats, stay active and have a little faith in the ongoing ingenuity of the human race.  Despite occasional glitches, we’re not so dumb.

    Patrick Clinton, and read The Truth About Food by David Katz, MD, MPH