A number of companies have begun offering DNA tests to inform how your genetic makeup influences how you metabolize and respond to food. This exciting field of personalized dietary recommendations offers great promise. Yet, the field is new, and it can be difficult to determine what type of testing should be performed, what exactly the results mean, and the real-world implication of those results. It’s my goal to help explain this complex field. Today, we’ll start by asking, “How do genetic tests work?”
Let’s begin with your parents. Your parents each had two pairs of 23 chromosomes. When you were conceived, you randomly inherited one chromosome from each of your parents’ chromosome pairs.
Chromosomes hold our genetic potential. About 25,000 genes spread across our 23 chromosomes. The purpose of each gene is to hold the information necessary to make a protein.
Every protein has some function. Some proteins provide structure, like collagen proteins in our skin. Other proteins carry out enzymatic reactions, like detoxification of alcohol in our liver after we drink a beer at Buffalo Wild Wings.
Whatever the protein does, the structure of the protein influences how it functions. And remember, our genes provide the code that dictates the structure of every protein. So, the genes determine how the proteins function.
Since we have two pairs of every chromosome, we also have two pairs of every gene. The code of the two genes might be exactly the same, thereby producing exactly the same protein.
Or, the code might be a little different between the two gene pairs, so our bodies make two slightly different copies of each protein.
Across an entire population of people, there are often several different types (aka isoforms) of proteins that can be made based on subtle variations in a gene’s code. These different gene codes are known as genetic variants.
Geneticists have identified the areas of our genome, that is, the collection of all our genes, where genetic variants are located.
Scientists have also determined how some of these genetic variants influence our health. For example, maybe you have a slow alcohol dehydrogenase gene that makes your face turn red while drinking that beer at Buffalo Wild Wings.
Now, it has become cheap enough to test a large number of your genetic variants and provide unique insights on how your body works.
Ultimately, what makes us who we are is a mixture of our biochemistry, which is determined by our genetics, and the inputs from our external environment, like lifestyle and diet.
This field of genetic testing is new, and there is much still for scientists to understand. Learning about your genetic code might help you understand how to better match your dietary and lifestyle inputs to your unique physiology. And, as our scientific understanding expands, the public’s ability to understand themselves will also expand.