Smart watches that tell you how many steps you've done today, apps that tell you when to drink water, sleep trackers, diet trackers, stress trackers… the list goes on. Its likely that at least one wellness-related gift was exchanged around your tree this Christmas, and its possible that one was a home DNA test.
When home DNA tests first started appearing a few years ago, the main purpose was to identify your ancestry. In the past year, in response to concerns about data privacy leading to a stagnation in sales, DNA tests are now tapping into the huge market of wellness and health. From just a saliva sample, these companies promise to reveal the likelihood that you will get certain diseases, what kind of diet you should have and what fitness regime would be best for your body. The idea of having personalised advice for your unique genetic make-up sounds pretty cool (not to mention the novelty of sending your spit off in the post) - but if simply knowing the sequence of our DNA is enough to know how to be healthier, why is it not routinely being used by pharmaceutical companies and health services like the NHS? After all, their sole purpose is to make and sell effective medicines, if moving towards 'personalised medicine', tailored to each patient by their DNA, was so much more effective, what are they waiting for?
The answer is, they aren't waiting, they're researching. But the knowledge is simply not there yet. If we think about how genes work, how they are transcribed and then translated into proteins, which in turn play a role in the cell whilst interacting with and being influence by many other proteins. At each stage of this process, things can happen to influence whether the functional protein is made or not.
The journey from DNA to functional proteins (which are the things that carry out almost all processes in the cell), is a long and torturous one, affected by factors that can either increase (green pluses) or reduce (red minuses) the amount of functional protein at every level.
Many scientists spend their entire careers researching a single protein and its formation and function in a single cell type. But humans are not just a single cell, we are made of about 30-40 trillion cells grouped into hundreds of different types, each of which transcribe and translate their genes differently. In fact, it's one of the biggest challenges in biology to relate things that happen in cell culture to what happen in the whole human body. For example in the pharmaceutical industry most medicines fail when they start being tested in animals even if they work well in cells. This is because, whilst cells can be carefully controlled in how they grow, animals such as humans are influenced strongly by their environment: their diet, lifestyle, even what they think (the placebo effect - feeling better because you feel like you have been given a medicine that works even if you haven't - works well in humans but has no effect on a dish of cells).
If the journey from DNA to effect in the cell wasn't convoluted enough, in a whole human body there are several extra layers of complication as these cells are living and communicating with each other in organs and systems like the blood and nervous system, which are also effected by environmental things like diet, climate, lifestyle and experience.
So where do these home-DNA tests get their information from?
Well, in many cases it's almost impossible to find this information. If you look into the small print of many of the flashy home-DNA tests, you find that they clearly claim not to provide any medical or dietary advice, only recreational recommendations. This may be in response to some previous clashes with regulatory authorities.
Despite this secrecy, I'd like to think that these companies aren't just throwing your spit away and making up some results. Some DNA reports identify the genes they use to make their conclusions - for example the gene ACTN3 relates to the muscle composition of an elite athlete. This link is based on research, an area of research called population genetics. Population genetics studies genes at a population level, and correlates certain gene versions (think back to Gregor's alleles) with certain traits. Population genetics is an important area of biology that looks for correlations between versions of genes and traits across lots of people (i.e. large populations). As results are based on correlations, which in turn are based on statistics and probability (covering this could fill another post), its quite possible that you might have this special gene but none of the promised effect. This makes sense if we think about all the levels of complexity that stand between your DNA and how your body actually works. There is also the added factor that one protein alone is usually not enough to make an effect, for example for a cell to become cancerous several genes need to change. Population genetics can be very useful, but if these concepts of probability and correlations are not properly communicated, results can be confusing to an individual. There are also cases of inaccuracies. A 2018 study found that 40% of results saying that a customer had a cancer-related gene were wrong. Both inaccuracies in communicating results or the results themselves can lead to unnecessary stress, and places increased pressure on the NHS as concerned customers go to their GP.
On the DNA-kit websites where genes are not named and publications not referenced, the accuracy of the results themselves, as opposed to how results are communicated, are brought into doubt. From a quick search, there seems to be a correlation between these sites and a focus on diet and fitness recommendations as opposed to probability of disease. These products claim to be able to give you a tailored diet and fitness plan based on your DNA, some even offering products that scan food item barcodes and let you know whether you should eat them or not. Although perhaps it's a little early in the development of these products to pass judgement, its hard to imagine that your DNA is going to dramatically affect what is considered a healthy diet or exercise regime, both things of which are already often disputed even without the genetic tailoring. On the other hand, if a little red light to remind you that multi-pack of chocolate cookies is not the healthiest option encourages you to live a healthier lifestyle, then at least that £100+ was not totally wasted…
Home DNA kits claim to let you free yourself from the shackles of ignorance and "fulfil your genetic potential". Strangely some prefer to keep us ignorant of how they analyse our DNA and also what they do with the information later (another topic which I haven't covered here). On the other hand, those that make an effort to educate their customers on how genes work and affect our bodies are incredibly effective in making people engaged with biology and aware of the potential of areas such as personalised medicine. Home DNA kits are fun gifts which may help us lead healthier lives and learn about ourselves, but perhaps serve mainly as a way to indulge our love for personalisation and self-discovery. It is true that we are all unique, but that’s not just because of our DNA.
Side note: when reading a few websites advertising DNA tests, I saw the phrase "keep your DNA healthy" - I'd just like to clarify that DNA cannot be 'healthy' or 'unhealthy', it's not alive like a cell or a person. It can gather mutations (check out The Changing Genome) with time and exposure to things like sunlight or radiation, but a) these changes are normally harmless and b) the number of mutations do not increase if you eat biscuits or any other food for that matter. Just to be clear - its your cells and organs in your body you want to keep healthy, not your DNA! (One less thing to worry about).