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DNA and what It Tells us
I have always been interested in family history — which makes me interested in genetics as well. What do we inherit from our mothers and fathers, our grandparents, and even people in our family tree from generations ago? As a genealogist, I have always wanted to know more about personality and physical traits than birthdates and anniversaries (although those can be interesting, too).
About a year ago, I decided to get my DNA tested. Different companies provide different information: I chose a company 2 that was mainly testing for ancestry composition. However, they also provided some interesting information about inherited personality traits and potential diseases or disorders (which I had not even expected).
In the end, I received information on:
- Ancestry Composition: Mine is 99.8% European, mostly British, Irish, French, German, and Scandinavian. (None of this was a surprise to me, but it was nice to have it confirmed.)
- DNA Relatives: On this particular website, there are 15 people who could be my 2nd or 3rd cousin. I have the option to contact them if I wish.
- A Summary of My Ancestry: This includes the information already mentioned above, as well as adding my mother's ancestry specifically.
- My Neanderthal Ancestry: An estimated 2.5% of my ancestry is of Neanderthal descent which is common for the average European.
- Genetic Risk Factors: This does not list every possible disease or condition I could inherit and fortunately I do not have the variants necessary for many conditions which they tested (which is obviously somewhat of a comfort). However, I am cautioned by the company to understand that these gene variants are not the only reason I might not get the disease or disorder — there are other factors which are not part of the DNA make-up.
- Drug Response: As with genetic risk factors for various diseases and conditions, I am told what drugs I might have a negative reaction to. In particular, for example, my genetics say that I might have a "higher risk" of reacting to statins, the drugs used to lower cholesterol. Since I have hypercholesterolemia (genetically high cholesterol), I have been taking statins for several years. I had already learned that I could not tolerate higher doses of this drug, so although the information was not new, it was interesting to discover this was actually a part of my DNA.
- Inherited Conditions: A list of nearly 50 inherited conditions reveals that I do not have the variant required for any of those on the list. However, this does not mean I could not get any of those conditions; it simply means my risk is lower.
- Inherited Traits: This was the most interesting (in my view) and where I will focus my comments for this article.
Inherited traits are those small things that make up you who you are: height, weight, colour of eyes and hair, curly or not so curly hair, and many other traits. Often it's obvious that we have inherited a trait from our mother or our father, but sometimes it's less obvious. Some of these traits, therefore, can be most surprising but many are totally predictable.
Some of these, for instance, were no surprise to me:
- Blond Hair: 28% likely (I was a brunette until most of it turned gray);
- Muscle Performance: An unlikely sprinter (definitely true);
- Red Hair: <1% likely (I know of no one in my genetic pool who is a redhead);
- Eye Colour: Likely Brown (very true!);
- Hair Curl: Slightly curlier hair on average (also true, as was my father's).
And on it goes.
But the one that hit home — and was not a surprise but certainly a great vindication — was this one: Bitter Taste Perception. It was not a surprise because many foods taste bitter to me — what I did not know was that I carry a gene that determines that.
So why was it a vindication for me?
I have always been what most people would call a "picky eater." I never had an explanation for it, but it certainly never occurred to me that what I tasted was different from what other people tasted. To learn that I had this particular gene was an eye-opener, to say the least. For the first time in my life, I had an explanation for why some foods just didn't taste good to me.
Bitter Taste Perception: an inherited genetic trait. Fascinating! I had to delve into this more.
The Bitter Taste Perception: What is it?
Why do some people seem to enjoy brussels sprouts, while others can't stand them?
The answer is that there is a genetic variation which causes some people to taste a chemical called propylthiouracil (PROP) similar to the bitter components found in cabbage, raw broccoli, coffee, tonic water, and dark beers.
It turns out that sensitivity to this kind of taste is due almost entirely to a single gene 3 that encodes receptors in taste buds on the tongue. A specific SNP 4 in this gene is responsible for whether a person tastes bitter or is taste-blind.
We have two copies of most genes: one from your mother and one from your father. The G version of the SNP in TAS2R38 is dominant, meaning it allows a person to taste PROP-like chemicals whether they have two copies or just one. I have an SNP with two G versions — tasting bitter is a certainty for me. We are sometimes referred to as "super-tasters."
People who cannot taste PROP, are considered to be "taste-blind." They find most food and drink to be less bitter, or not bitter at all. People who can taste PROP are sometimes referred to as supertasters.
Sensitivity to bitter tastes is highly heritable, meaning that the trait is controlled almost entirely by your genes — environmental factors play little or no role. Because of this, simply knowing your genotype is almost enough to know your sensitivity to PROP-like bitter tastes.
According to a Wikipedia article, there are some foods more likely to taste bitter to super-tasters; although individual food preference for supertasters cannot be typified, documented examples for either lessened preference or consumption include:
- Certain alcoholic beverages: gins, tequilas, and hoppy beers
- Brassica oleracea cultivars (these become very sulfurous, especially if overcooked): brussels sprouts, most types of cabbage, cauliflower, collards, savoy, collard greens, and kale
- Grapefruit juice
- Green tea
- Soy products
- Carbonated water
- Anise and licorice
- Lower-sodium foods
And possibly, according to Wikipedia, these two could be added:
- Tonic water – Quinine is more bitter to supertasters
- Olives – for a given concentration, salt is more intense in supertasters
NOW I know why I find some foods to taste very bitter and therefore I don't like to eat them. I am NOT taste-blind. I taste the bitter! Genetically, this was a good thing because it protected me from eating things that might be harmful to me.
What has been my experience with these foods?
I was a slow grower, and tiny for my age, so my parents worried that I wouldn't grow. They encouraged me to eat the food on my plate, but from the beginning I wasn't willing to eat many of the foods they gave me. I'm sure I frustrated them greatly — even as I frustrate my husband to this day (who does most of the cooking in our family). I always considered myself just a little bit "weird" and I wondered why so many foods did not appeal to me.
Learning that I had this bitter-taste gene, suddenly I understood why a lot of foods just didn't taste good to me. Many of these showed up very early in my life and I either refused to drink or eat them....or I drank or ate little of them:
The Gemmifera Group of cabbages: I have always disliked cabbage, broccoli and brussel sprouts. I can usually manage cauliflower if it's fresh, but once it begins to be "old," the bitter taste comes through.
Green Tea and Coffee: When I was a kid, my mother drank a cup of coffee a day — usually black. She once let me take a taste, and I found it extremely bitter. I swore I'd never drink coffee — and I never have. My father did not drink coffee at all — I'm guessing he had the bitter-tasting gene. As with coffee, I have never liked most teas, but green tea is probably one of my least favourites.
Beer and Hard Liquor: I found some studies that are trying to find a link between taste-blind persons and alcoholism. Those of us who find alcohol bitter are not likely to become alcoholics. But those who do not taste the bitter might be more inclined to drink too much. This research isn't complete yet, but it is an interesting theory. There was no alcohol in my childhood home as my father banned it. I always believed their non-drinking values were just that — values. It never occurred to me that they might simply be supertasters. My first taste of alcohol came in my 20's and I did not like it at all.
Lower Sodium Foods: I've always preferred salty foods and I will use salt on a lot of my food. Of course, using extra salt has been much frowned upon in health circles in recent years, but it is usually a warning to people with high blood pressure. Fortunately, I have always had low blood pressure.
Licorice: I always hated to see licorice in my Hallowe'en trick-or-treat bag. I almost always gave it away or traded it for something else. If I went to the store to buy a "treat" for myself, it was certainly not licorice!
So who cares that I now know this?
I do. For years I have been teased by others that I wouldn't drink alcohol and that I had such limited food preferences. I think that I always tasted new food with a great deal of caution, fearing it would taste bitter. I stuck to the foods that I knew would taste all right to me.
If tasting bitter chemicals like PROP is so important to health and therefore reproductive fitness, why wouldn't everyone have two copies of the taster version? There are probably two reasons: First, the goiter-causing compound in cabbage isn't so toxic that it can kill us directly (although there may be unknown, related compounds with more severe effects). The second is that while the taste-blind C version of the gene cannot detect PROP, it might be able to sense some other class of plant chemicals that researchers have not yet identified. In our evolutionary past, our ancestors' survival may have depended on the ability to detect this other compound.
I have learned that we inherit a lot of things and it's helpful to understand what we have inherited. I rather like that new label — supertaster!
Other articles you might find interesting:
- Metabolism, Calorie Intake, and False Promises: Getting Through the Dieting Maze — NEW!
- Canada's Food Guide: Nutrition and the Older Adult
I am a BCRPA-certified fitness instructor in Vancouver, BC. I teach four classes at the West End Community Centre in Vancouver, BC, mostly designed for the older adult. The Inevitable Disclaimer: Everything published here expresses only my opinion, based on my training and research. What you do with the information is entirely your own responsibility. I am not liable for any injury you suffer that seems to be related to anything you read here. Always consult your doctor before beginning an exercise program. For other articles, return to the table of contents.
These three dots behave exactly like a footnote. Click on them and you will get more information about the topic. ↩
I used a company named 23 and Me. I chose it mainly because it is Canadian. ↩
Each kind of protein has its own blueprint, or gene, located in the cell's nucleus. Genes can be turned on or off in different cells at different times. For example, the gene for the protein that detects bitter things is on in your tongue cells, but off in your skin cells. ↩
An SNP is a site in the genome where a single DNA “letter” often differs from person to person. (SNP stands for Single Nucleotide Polymorphism.) Some, but not all SNPs appear to be associated with variation in different people's phenotypes. ↩