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Nature versus nurture is a popular source for debate. Many research studies, too, trace back to this concept: everything from personality to exercise predispositions to diet. Many factors affect what we eat, but recent studies have shown that the role of DNA may play a bigger part in our overall diet and food choices than we realized.
Genetic makeup can predispose you toward a specific relationship with food by affecting tolerance, satiety, and preferences. On the flip side, the rapidly growing field of epigenetics has begun to show us the ability of environmental factors to shape the way our DNA is expressed. So exactly how much of our health is predetermined?
DNA Affects Diet
Our DNA affects what we eat. Genes can predict different predispositions towards food, including gluten sensitivity, lactose intolerance, and taste preferences. Researchers have linked specific genetic markers to specific traits. For example, a recent study found that a variant of one of the genes for bitter taste receptors influences whether or not you enjoy drinking coffee (1). People who possess this genetic marker perceive stronger bitterness and tend to like coffee more.
Other genetic markers determine the perceived intensity and taste of sugar and salt. People can be genetically predisposed to choose foods containing either more sugar or salt. Another study revealed that a particular variant contributes to the preference for oil versus butter (2). This may also play a role in determining your total calorie, fat, and starch intake. While culture and the availability of certain foods also play a role in food choices, the identification of these genetic markers reveals that we are genetically inclined to eat a certain way.
DNA, Diet, and Weight
Genetics can affect an individual’s weight both indirectly through diet and directly through metabolism. Your DNA can influence not only your food choices and intake levels, but also the expression of various hormones and enzymes critical to metabolism. Through these mechanisms, your response to dieting, predisposition to weight gain, and metabolism can be influenced by your DNA.
The genes we inherit from our parents, along with how they are expressed, determine the synthesis of several important compounds that contribute to satiety or hunger. A 2008 study identified one enzyme that is critical to the production and function of ghrelin, a hormone in humans that stimulates appetite and food intake (3). Studies on mice have identified a genetic marker, the obese (ob) gene, that when mutated results in an inability of that mouse to produce leptin, a hormone that signals satiety and decreases appetite and food intake. In humans, studies have isolated the ob gene and found it over-expressed in obese people.
In addition to affecting intake level, DNA plays a large role in the fate of the consumed nutrients. Gene expression has been shown to contribute to metabolic pathways crucial for the differentiation of muscle and fat. These factors are also important in the body’s balancing act between fat, protein, and carbohydrate.
Why Do We Have Cravings?
To some extent, our bodies crave what they need. But what about those intense, must-eat-it-now cravings? And are certain people genetically predisposed to have them? Genes certainly play their part. One study that looked at the relationship between endorphins (which are coded for by genes) and food consumption found that the two are strongly correlated, suggesting that altered endorphin activity may result in intensified food cravings (4). Another study examined neural circuitry, identifying genetic pathways that regulate food-craving behavior (5). These same pathways, influenced by genetics, also trigger impulsive, compulsive, and addictive behaviors.
Ultimately, your weight can be attributed to a variety of factors, one of which is genetic makeup. Genes can influence body composition through both dietary and metabolic mechanisms. Genes affect what we eat, but what, if anything, influences your DNA?
You Are What You Eat
Role of DNA
The emerging field of epigenetics examines all the ways that genes and their expressions may be altered by environmental factors like diet. Evidence in humans suggests that epigenetic factors can be trans-generational, meaning that environmental influences on genes can be inherited as far as two generations. Some research suggests that these influences are time-sensitive according to what stage of development a person is in. Other research suggests that the alterations are entirely reversible. Diet has been explored as one of the leading environmental factors that have the capacity to alter the way our DNA works.
One of the most potent epigenetic mechanisms is DNA methylation, which is a process that affects the expression and function of DNA. Methylation has been negatively correlated with cancer and aging. Recent studies have shown that diet has the ability to regulate DNA methylation, revealing one way in which food has the power to affect our chances of developing a tumor (6, 7, 8). Several micronutrients and vitamins have been identified as critical for patterns of DNA methylation, and deficiencies have been correlated to higher risk of disease. For example, choline deficiency is associated with a decline in memory function. Although human studies on micronutrient intake and DNA methylation have been limited, studies on animals continue to strongly support the importance of the relationship between nutrition and gene expression
The continued study of diet’s epigenetic effects has the potential to open the door to a vast array of nutritional methods for disease prevention. There are several other mechanisms by which food has the power to alter gene expression, painting a far more fluid picture of DNA than most are accustomed to. We have the ability to impact the way our genetic makeup functions through what we eat.
Genetically Modified Consumers
While genetically modified organisms (GMOs) provide financial benefits to big manufacturers, the impact of the altered genes on consumers is far less understood and poses a potential threat. Studies have shown that ingested plant microRNAs can bind to mammalian receptors and alter genes. Not only has research shown the persistence of ingested food’s genes in human tissues and serums, it now suggests that these genes can have epigenetic effects on our own DNA. This raises alarm on two levels: for the food source itself, which is being genetically modified by an outside source, and for the consumer, whose genes could be impacted through the ingestion of the food source. Due to the interplay of DNA and the environment, it is difficult to predict how one organism might respond to receiving another’s genes, whether through injection or ingestion.
Given the intimate relationship between genetics and diet, it seems almost impossible to create a successful diet outside of the context of your DNA. Now that we understand so much about the genetic basis for food preferences, intolerances, and responses, there is far more personalized data to consider that could contribute to making a logical and feasible diet plan. Knowing various markers on your DNA can, for example, allow for healthier alternatives to the indulgent foods you may be genetically predisposed to prefer.
One study presented in 2014 found that participants placed on a genetics-based diet on average experienced 33% more weight loss than those given generic diet plans (2) An ongoing clinical study at Stanford is testing whether matching diet type, either low carb or low fat, to genetic predisposition is a more successful weight-loss plan.
While there is a multitude of factors to consider for your diet and food choices, including lifestyle, mental health, culture, availability, and cost, your DNA should certainly not be ignored. Not only can your genetic makeup predispose you to respond better to certain foods and diet types, the food you decide on actually has the power to influence your genetic makeup and how it functions.