Two checkout belts at the supermarket
Friday evening, the queue at the checkout is long, and since you have to wait anyway, your gaze wanders over the checkout belts. On one there is a frozen pizza, a family pack of salami, two bottles of cola and a bag of crisps. On the other, tomatoes and peppers roll towards the till, along with a net of apples, a packet of lentils, oats, a piece of salmon and a six-pack of mineral water.
Then your eyes land on your own belt. There is probably a bit of both on it.
Of course, this is exaggerated. Hardly anyone buys only the one or only the other, and a single shop says little. But whatever keeps showing up on your belt week after week eventually reaches your cells. That is exactly what makes nutrition one of the big levers for your biological age. Your chronological age counts the years since you were born. Your biological age, on the other hand, describes the actual condition of your body, for example how much silent inflammation is wearing it down and how well its cells still renew themselves. But how much difference does what ends up on your plate actually make?
How many years of life are in your diet
A research team at the University of Bergen in Norway set out to answer this question. Instead of following thousands of people themselves, Lars Fadnes and his colleagues pooled the results of numerous large studies. With them, they calculated what happens when someone switches from a typical Western diet to a balanced one: more pulses, wholegrains, nuts, vegetables and fruit, and less red meat, processed meat and sugary drinks.
The result was clearer than expected. According to these calculations, someone who switches at 20 could gain a good ten years of life on average, and men even around 13. Switching at 60 still meant about eight years, and at 80 a good three. The biggest share came not from exotic superfoods but from completely everyday foods: lentils, beans and chickpeas, wholegrain bread and a handful of nuts.
A modelling study like this is no promise for any individual. But it does show the order of magnitude nutrition is operating on.
The earlier you switch, the more you gain, but even at 80 the step is still worth it.
That leaves the question of what actually happens in your body.
Silent inflammation: How your food feeds or dampens a smouldering fire
Picture a smouldering fire in an old woodpile. There are no flames and hardly any smoke, just embers slowly and unnoticed eating their way through the wood. The more dry material is added, the longer it keeps glowing.
Silent inflammation in the body behaves in a similar way. It does not hurt and causes no fever, but it keeps the tissue in constant repair for years. To do this, the cells have to divide more often, and their telomeres, the protective caps at the ends of the chromosomes, get shorter faster as a result. Read more here (Article: Biological age).
What you eat can feed or dampen this smouldering fire. Highly sugared and highly processed foods make your blood sugar spike again and again and fuel the inflammation. Vegetables and fruit work in the other direction. They provide fibre, from which your gut bacteria produce anti-inflammatory substances, and a wealth of plant compounds that protect your cells. The more colourful your plate, the greater this variety.
US researcher Larry Tucker examined in almost 5,500 adults whether this can be traced all the way into the cells. People who ate a good three handfuls of fruit and vegetables a day had telomeres whose length corresponded on average to around 4.4 years less cellular ageing than in people who ate hardly any fruit and vegetables. In men, this link was mainly down to the vegetables.
Something similar shows up with oily fish such as salmon, herring or mackerel. It contains omega-3 fatty acids, which can slow down inflammatory processes in the body. A team from San Francisco measured the omega-3 levels in the blood of around 600 heart patients and observed their telomeres over five years. In participants with the highest levels, the telomeres shortened most slowly; in those with the lowest, most quickly.
If you don't like fish, you can turn to algae oil, which provides the same fatty acids. Fish on your plate has the better data, though. In large studies with tens of thousands of participants, low-dose omega-3 capsules brought no clear overall benefit for the heart and circulation. Whole fish also provides iodine, selenium and vitamin D.
But nutrition does not only work through inflammation. Some foods act directly on your genetic material.
Processed meat and DNA: Where copying errors creep in
Imagine you had to copy out a thick recipe book by hand over and over again, with each copy serving as the template for the next. You notice most mistakes and correct them. But the more often you copy and the more restless your surroundings, the more likely one slips through, and it then travels into every following copy.
Your cells face a similar task. With every division, they copy their entire genetic material. A sophisticated repair system finds and fixes most of the damage along the way. But the more there is to repair, the more likely something is left behind. Such errors add up over the years and are among the causes of ageing.
This is where processed meat comes in. Curing, smoking and strongly heating sausages, ham and salami creates substances that can directly damage genetic material. In 2015, 22 experts from ten countries reviewed more than 800 studies on behalf of the World Health Organization. They classified processed meat as carcinogenic, mainly with regard to bowel cancer. Unprocessed red meat such as steak or mince is considered probably carcinogenic; here the evidence is less clear-cut.
This classification describes how firmly a link has been established, not how large it is. So a slice of salami cannot be compared to a cigarette. For your biological age, what matters most is the amount that adds up over weeks and years. The bratwurst at a summer barbecue hardly counts, whereas salami on your bread every morning is more likely to. Poultry, fish, eggs and pulses are good alternatives if you want to cut down.
Besides what ends up on your plate, there is one more area that is often overlooked: what you drink.
Drinks: How much sugar is in your glass
A half-litre bottle of cola contains around 53 grams of sugar, which is about 17 sugar cubes. Hardly anyone would eat that much sugar in one go. Drinking it, on the other hand, happens quickly, and because liquid sugar comes without fibre or chewing, it rushes into the blood particularly fast. That makes it perfect fuel for the smouldering fire.
A team at the University of California, San Francisco analysed data from more than 5,300 adults. People who drank around 0.6 litres of sugary soft drinks a day had telomeres whose length corresponded on average to about 4.6 years of additional cellular ageing. For other drinks, the team found no such link.
The good news: the alternative could hardly be simpler. The German Nutrition Society (DGE) recommends around 1.5 litres a day, ideally water or unsweetened tea, and correspondingly more in hot weather or when exercising. A useful rule of thumb is the colour of your urine: if it is pale yellow, you are drinking enough. By the way, unsweetened coffee in normal amounts also counts towards your fluid intake.
The pattern counts, not the single food
Vegetables, fish, processed meat and drinks work in different ways. But their influence becomes clearest when you look at them together.
A Harvard study of 4,676 women shows this. The researchers examined how closely the participants' diet matched classic Mediterranean cuisine: lots of vegetables, pulses, wholegrains, fish, olive oil and nuts, and little meat and processed meat. The closer it was, the longer the telomeres. Just one more point on the Mediterranean scale corresponded on average to around one and a half years less cellular ageing. Strikingly, no single food showed a clear link on its own. It only became visible in combination.
This is where the stories in this article come together.
For your biological age, what counts is not the one superfood, but the pattern that repeats itself on your plate day after day.
What a plate that keeps you young looks like
The German Nutrition Society (DGE) revised its recommendations in 2024. At their core, around three quarters of your diet should consist of plant foods. That includes three portions of vegetables and two portions of fruit a day, with one portion being about a handful. Conveniently, this measure grows with you. Pulses should be on the table at least once a week, along with a small handful of nuts every day and, for bread, pasta and rice, preferably the wholegrain version. The society recommends fish once or twice a week, and meat and processed meat together at most 300 grams a week. That is roughly two small portions.
A simple rule of thumb for every meal: half the plate is vegetables, a quarter protein, for example from pulses, fish or eggs, and a quarter wholegrains.
In everyday life, this can look completely unspectacular. A few slices of cucumber and tomato with your breakfast bread, half the mince in your bolognese replaced with lentils, a handful of nuts instead of crisps in the evening and a jug of water on your desk. For stressful days, it is worth keeping a supply of frozen vegetables, which contain hardly fewer nutrients than fresh ones.
Small swaps instead of a strict diet
The researchers from Bergen also calculated a more realistic scenario in which someone only gets about halfway there. Even this still brought young adults six to seven years of life. So you do not need a perfect diet.
That is why it is worth starting small. Instead of overhauling your diet overnight, you can swap one thing each week: water instead of a fizzy drink at lunch, lentil soup instead of currywurst, fruit instead of a chocolate bar in the afternoon. Swaps like these hardly feel like giving something up, and that is exactly why they stick.
As with exercise, the same applies here: for your biological age, what counts is not the perfect day, but what you eat on most days.
Where you stand on nutrition
The BioAge test asks how much fruit and vegetables, fish and meat you eat and what you drink in four short questions, plus your body mass index. Together with the other questions, this produces an estimate of your biological age and an overview of where you have the most to gain.
Frequently asked questions about nutrition and biological age
Is a vegetarian or vegan diet better for biological age?
It can be, but it does not have to be. What matters is what ends up on your plate instead of meat: pulses, wholegrains, nuts and vegetables bring the benefit, whereas white bread, sweets and ready meals do not. A diet with the occasional bit of meat can also be very healthy.
Does intermittent fasting help with biological age?
Intermittent fasting can help with weight loss and improve blood sugar and blood pressure. In comparative studies, however, it performed hardly any better than an ordinary reduction in calories. Whether it slows biological ageing in humans beyond that has not yet been proven. If it helps you eat more mindfully, though, there is nothing against it.
Which protein sources are the best?
Good sources are pulses, nuts, wholegrains, fish, eggs and dairy products. In a large Harvard analysis, people who ate more plant protein lived longer on average, especially when it replaced processed and red meat. You can read how much protein you need for strength training here (Article: Strength training).
Are processed foods bad in general?
No. Frozen vegetables, tinned tomatoes, oats or plain yoghurt are processed, but valuable. It is a different story with highly processed products with long ingredient lists, such as sweet snacks, many ready meals and soft drinks. A large review linked a high share of these to numerous health problems. A good rule of thumb: the shorter the ingredient list, the better.
Do I need dietary supplements?
With a balanced diet, usually not. Exceptions are vitamin B12 on a vegan diet, because it occurs almost exclusively in animal foods, and omega-3 from algae oil if you don't eat fish. Whether you need vitamin D in the winter months is best discussed with your GP.