Can Our Genes Really Tell Us What, When, or How Much to Eat?
When it comes to selling weight loss, diet and nutrition companies thrive on a twofold approach. The first involves reimagining an old or dated concept; the second calls for lauding and connecting the latest innovation as it relates to nutrition.
Realizing our ancestors unintentionaly fasted due to long periods of food scarcity, marketers will rebrand this concept, and call it ‘intermittent fasting’.
Seeing a trend in slower, more focused eating, why not build an application and call this approach ‘mindful eating’.
With improving genetic analysis, some now argue the answer for optimal health or weight loss resides in our genome; enter Nutrigenomics.
Paleo, Blood Type, & Nutrigenomics
As far as diets go, eating according to our genetic code is nothing new. It’s been tried, in a broad sense, a few times before.
Two decades ago, Colorado State University Professor Dr. Loren Cordain published what remains a very popular book. In it, he argues humans evolved a hundred thousand years ago to eat specific foods, maintaining health comes down to eating these genetically matched foods now, and avoiding anything which emerged since the agricultural revolution. Though the concept had been around since the 1970s, Cordain’s book The Paleo Diet: Lose Weight and Get Healthy by Eating the Foods You Were Designed to Eat, and it’s subsequent popularity, would caused a massive surge in interest.
A genetically matched eating approach was similarly touched upon in the early 1990s. Peter D’Adamo, a naturopathic physician, began advocating Eat Right For Your Type, commonly known as The Blood Type Diet. D’Adamo believed; A Blood types should stick to vegetarian diets, O Types benefit from a high protein diet, B Types can eat a variety of the two but should avoid corn, wheat, tomatoes, peanuts, lentils and chicken, and AB Types can have tofu, dairy, and seafood, but should avoid smoked and cured meats.
The burgeoning field of Nutrigenomics promises to go a step further, tailoring a program, not according to early homo sapiens, or blood type, but specific to an individual’s genome. Those in the gene sequencing business, including 23andMe and Ancestry, have entered into partnerships or affiliations with nutritional companies advising clients on what to eat as well as which foods to avoid.
Genetics & Epigenetics
The human genome project, which sequenced and mapped our genetic code, was only completed eighteen years ago. If the field of genetics is young, than Nutrigenomics is in its infancy. Since decoding our DNA, many assumed correctly, our knowledge and understanding of how and why our genes behave a certain way, would continue to improve.
Humans have 23 chromosomes, each chromosome contains one hundred to one thousand genes, roughly translating to 30,000 genes, each of these genes makes an average of 3 proteins. Figuring out which genes code for any number of macronutrients, let alone micronutrients, is no simple task; that’s the challenge currently facing Nutrigenomics. Dr. Alun Williams of Manchester Metropolitan University, put it this way in Wired Magazine, “tying traits to DNA is like absorbing a book by reading only one word per page — you have information, but at the end you have no idea what the book was actually about.”
It’s important to make a distinction between genetics and epigenetics. While you and I have a unique, static, genetic code we inherited from our parents, we also inherit ‘tags’ on our DNA. Epigenetics are modifications in gene expression. Identical twins, for example, have the same DNA or genetic code; as they age, changes in their diet, activity, and environment will affect body features like obesity, or susceptibility to ailments including cancer and heart disease. Genetically, they remain identical, epigenetically, they differ. If our genetic code is hardware, epigenetics acts like software, changing and updating based on what we eat, where we live, and how we interact with our environment.
That said, can we use genetic information to design an optimal approach to eating? Current research says, not yet.
The Verdict (for now)
Before you splurge on an Ancestry or 23andme nutrigenomics evaluation, let’s consider the evidence.
Most promising, among several studies, seems to be The Lost Pounds Trial. Evidence suggests the fat mass and obesity-associated gene, also called the FTO-genotype, may interact with certain types of diets. In this trial, FTO (rs1558902) was genotyped in 742 obese adults, who were randomly assigned to one of four diets differing in proportions of fat, protein, and carbohydrates. Carriers of the FTO genotype had a greater reduction in weight, body fat composition, and fat distribution in response to a high-protein/low-carb diet; the opposite was observed in response to a low-protein/high-carb diet. In other words, for those with the FTO genotype, a low-carb/high-protein diet was beneficial for both weight loss, as well as body fat composition.
Outside of The Lost Pounds Trial, studies around Nutrigenomic diets have found no benefit when it comes to weight loss or reducing disease. Results of a 2018 randomized clinical trial following 600 overweight adults for 12 months found no significant difference between a healthy low-fat diet, compared to a healthy low-carb diet, and genotype pattern was not associated with weight loss.
One area of optimism though, centers around which foods to avoid, and specific nutrients or minerals subjects can tolerate less of. The NOW randomized control trial, compared groups following a Nutrigenomics approach, a general Group Lifestyle Balance, and a combination of both. Researchers found long-term dietary adherence to total fat and saturated fat guidelines were significantly greater in the Nutrigenomics + Group Lifestyle Balance population when compared to the Group Lifestyle Balance population alone.
A 2014 randomized controlled trial revealed, those who possessed the risk variant of the ACE gene (a gene that directs the body on blood pressure levels) were able to significantly reduce their sodium intake compared to the control group; they also maintained their lower sodium intake one year later. Such findings may have strong implications for decreasing the risk of heart disease.
As for some of the older genetics based diets; a 2020 study found no benefit to eating by blood type, and a plant based diet was beneficial for all participants regardless of blood type.
When it comes to The Paleo Diet, evidence gathered from anthropological studies, as well as modern tribes, points to broad variation in prehistoric eating habits, based on location and climate. The Hadza tribe in Tanzania, an African region considered the birthplace of human evolution, subsisted on plants, fruits, tubers, and game animals; with honey being a popular food group. Studies available on some Nordic tribes, revealed a seafood dominant diet.
Essentially, early (paleolithic) humans ate mostly plants, insects, and depending on region, seafood, or small game animals.
For those interested in a genetics based eating approach, cautious optimism is in order. While some with genetic markers previously studied will benefit, others may not.
As our understanding of epigenetics improves, so too will trials evaluating the effects of dietary changes on gene expression and activation.
For now, research strongly suggests, most of us would do well with a plant heavy diet, low in processed foods, higher in fiber, with lean protein sources. You can call it Paleo, Mediterranean, or a modification of both if you like; I call it healthy, balanced, eating.