Food for Thought
The enzyme amylase is an important part of our carbohydrate metabolism. We secrete amylase in our saliva and digestive system, where it helps us break down starch from foods such as bread, rice and potatoes. This means amylase is especially important to someone eating an agricultural diet. When hunter-
gatherers settled down and started farming, one’s ability to digest starch became vital to health and survival. We can see the shadow of this in our genetics today.
You see, humans have evolved to have multiple copies of the amylase gene (and interestingly, so have our dogs). All the copies do the same thing – make amylase – but having multiple copies helps us make more and improves starch digestion.
Our switch to farming happened relatively recently on the evolutionary timescales, and at different times across the world. This means adaptations to agricultural diets are not yet universally distributed. For instance, scientists have found that the number of amylase genes varies from two copies in some people to more than ten in others. On average, people from populations that have farmed for a long time, such as Europeans and East Asians, have more amylase genes than agricultural latecomers. However, even among Europeans and East Asians, some individuals have few amylase genes, making them less well-suited to a high-starch diet.
Amylase is just a minor component of our metabolism, but we know of several other genetic variants that are similarly skewed in their distribution. A classic example is genetic variants that allow one to break down lactose, the sugar found in milk. Originally, only infants could digest lactose, which was needed to enable them to subsist on breast milk. However, thousands of years ago, mutations arose extending this ability into adulthood. Such mutations would be useless to hunter-
gatherers (where would they get the milk?) but to a farmer who can now subsist on dairy, they are pure gold. In my native Denmark – close to the origin of these mutations – almost every adult can digest lactose today. The mutations become rarer as you move away from Northern Europe, but that’s just because they haven’t had the time to spread yet. It’s an obvious advantage to a farmer to be lactose tolerant. If we hadn’t reached modernity lactose tolerance would continue spreading because those able to digest milk could get more calories and increase their chance at surviving and having children. For now, though, lactose tolerance is unequally distributed, and the exact same food can be a healthy source of calcium for some while giving other people explosive diarrhoea.
In some instances, there are even opposing genetic variants in different people. Take the genes FADS1 and FADS2, which encode enzymes involved in the body’s production of molecules called long-chain polyunsaturated fatty acids. Among these tongue-twisting molecules are some omega-3 fatty acids. The Inuit people of Greenland have eaten fish-heavy diets for thousands of years, which provide them with omega-3s in abundance. As a result, they have high frequencies of genetic variants in FADS1 and FADS2, which limits the body’s own production because it’s just not needed when the molecules are easily obtainable from the diet. On the other hand, there are historically vegetarian communities in Pune, India, where most people have versions of FADS2 that improve their body’s production of long-chain polyunsaturated fatty acids. This is strongly advantageous when dietary intake is low, as it is on a vegetarian diet.
So, should you eat a low-carb diet for health? Drink milk? Go vegetarian? The piece of the puzzle we’ve been missing so far is that the answer depends on your genetics. One of your friends might try a vegetarian diet and fare brilliantly, while you feel better on a low-carb diet. That doesn’t necessarily mean one of you is lying, or that one of you is healthier than the other, even though your diets are almost completely inverted.
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Most of our health efforts are still performed somewhat blindly. We hear something is ‘healthy’ and then cross our fingers that it’s true. As you might have learned by now, a lot of the time it isn’t. Something can be healthy for you without being healthy for me. For instance, when a study concludes: ‘Muscle mass was increased twenty-five per cent by eating spinach,’ that is true on average. But that doesn’t mean every single person who ate spinach gained twenty-five per cent more muscle mass. Some gained more, some gained less; some might have gained none at all or even lost muscle mass. As we’ve learned, we’re not always comparable and that’s why the blind approach often fails. So instead of guessing, we should actually measure what is going on in our bodies and tailor our approach accordingly. For instance, we could start eating spinach and actually measure how it affects our own muscle mass, strength or biomarkers of the blood. Or we could use combinations of these measurements to pick the optimal diet, exercise routine or lifestyle.
The reason we’re not already collecting data about ourselves at scale like this comes down to technological and economical limitations. In some cases, we lack knowledge – for instance, when it comes to interpreting a lot of our genetics. We can ‘read’ our genes using what is called ‘genome sequencing’, but the interpretation is harder and still at the early stages.
In other cases, we know what to do, but it is troublesome. For instance, we still need invasive blood draws to measure most biomarkers of the blood, such as hormone levels, metabolites, vitamins and markers of inflammation. In most cases, it is too expensive to measure biomarkers frequently. If you have any expertise or interest in these areas, you hereby have my strongest recommendation to give it a shot and help us all out. Gaining access to more data about our bodies could unlock a revolution in health and wellness.
As we’ve discussed already, the holy grail of biomarkers for longevity is an accurate biological clock. That is, some biomarker we can track over time to determine the rate at which our bodies are ageing. The best bets are currently telomere-shortening and epigenetic clocks. Both are useful when studying large groups of people, but unfortunately biological clocks are not precise enough to be accurate for individuals – yet.
For now, the smart choice is to use the biomarkers that are readily available to us. An obvious one is body weight, as it is well known being overweight or obese comes with significant health drawbacks. However, there are also biomarkers of the blood worth investigating, though they still require a doctor’s appointment. Let’s take a look.