A study from Hong Kong published in 2025 showed that olive oil and walnuts strengthen special immune cells that recognize and destroy tumor cells, even before they develop into cancer.
What actually happens in the body?
You can imagine our immune system as a small but incredibly effective army. Among its fastest soldiers are gamma-delta T-cells—special white blood cells that patrol the body looking for suspicious cells. When they find them, they destroy them. These cells act like a personal bodyguard, making sure, 24 hours a day, that intruders do not invade your body.
Scientists at the University of Hong Kong (HKUMed) found that these cells have their own fuel, which isn’t sugar or coffee, but fat that we eat.
The study tested two types of fatty acids:
- Oleic acid (OA) – this is a healthy, unsaturated fat found in olive oil, avocados, walnuts, almonds, and sunflower seeds.
- Palmitic acid (PA) – this is a saturated fat found in butter, fatty meat, cheese, and especially palm oil, which often hides in industrial cookies and chocolate bars.
The result was surprising ... When the gamma-delta cells were fed oleic acid, they became stronger, more resilient, and more effective at destroying tumors. Their mitochondria—tiny power plants inside the cells that produce energy—functioned steadily, like a well-oiled engine.
In contrast, the cells exposed to palmitic acid began to visibly die off. Their internal energy literally collapsed, inflammation appeared, and the surrounding environment became ideal for the spread of cancerous changes.
Professor Tu Wenwei, head of the research, commented: Foods rich in oleic acid, such as olive oil and avocados, can improve immune monitoring and help the body fight cancer more effectively.
This means that fat we consume is not just a source of energy, but also has a direct effect on how effectively our body detects and destroys dangerous cells.
Why our grandmothers knew more than they thought
Our ancestors knew, even without laboratories, what science confirms today: a spoonful of olive oil on an empty stomach and a handful of walnuts a day keeps the doctor away.
In the past, people used olive oil not just for cooking, but as a remedy for skin, digestion, and the immune system. Walnuts have always been a symbol of strength and wisdom—ancient Romans believed they strengthened the brain.
In 2023, the Harvard School of Public Health published data showing that people who eat 20g of nuts daily live, on average, 3 years longer than those who don’t.
The Spanish PREDIMED study found that 1 to 2 spoonfuls of olive oil daily lowers the risk of stroke by 30% and improves immune response after just 12 weeks of regular use.
In 2024, Italian researchers from Parma found that oleic acid reduces the activity of inflammatory genes by as much as 40% in people with weakened immune systems.
Even though we’re talking about modern research, we keep coming back to old, simple solutions.
What does immunometabolism mean and why is it important
The word immunometabolism may sound complicated, but it means something simple: it is the science that studies how food affects the functioning of our immune system. It matters what we feed our immune system. If we give it the right fuel, it works well; if we give it the wrong one, it gets tired, blocked, or even attacks its own cells.
According to Nature Immunology journal data from 2025, as many as 65% of immune disorders originate from poor diet, especially due to excess saturated fats, sugar, and artificial additives.
That’s why researchers from Hong Kong went a step further and checked how dietary changes can support immunotherapy—which is becoming an increasingly modern way of treating cancer, where doctors help the immune system to attack the tumor itself. The result was that the combination of medication and a diet rich in oleic acid increased therapy effectiveness by up to 25%, which is a huge step forward.
How to strengthen the immune system
The good news: you don’t need special capsules, powders, or supplements for this. Small changes in daily diet are enough. If you’d like to take a first step, try the following:
- Instead of butter for baking, use a spoonful of extra virgin olive oil.
- Replace industrial snacks with a handful of walnuts, almonds, or sunflower seeds.
- Add avocado to salads or make a simple spread from it (mash avocado with a spoon of lemon juice and a pinch of salt).
- Instead of cream, use plant-based milk or homemade cream made from blended cashews with a little water.
Such changes are not just healthy, but also affordable. If every family replaced 100g of butter with olive oil every week, that would mean 1.3 million liters less saturated fat per year, which, according to estimates from the WHO, would lower the incidence of cardiovascular diseases by 10%.
How walnuts work – more than just healthy fat
Walnuts are not only a source of oleic acid, but also contain alpha-linolenic acid (ALA), which the body converts into omega-3 fatty acids. According to a study by Yale University in 2022, just 7 walnuts a day improve brain function and memory in adults by 19% after two months of regular intake. Walnuts also contain melatonin, a natural sleep hormone, so they help regenerate the immune system overnight.
Old healers often recommended walnuts to people after illnesses and surgeries because they nourished the blood and soul. Today we’d say: they regenerate cells and reduce oxidative stress—something modern measurements confirm. Many studies have recorded a reduction in oxidative markers by 15–25% in just 4 weeks.
Why not all olive oil is the same
When choosing olive oil, quality is key. The most oleic acid is found in extra virgin olive oil (more than 75% of all fats), so that's the right choice. You don't need to heat the oil to a boil—use it cold or lightly warmed, because beneficial substances begin to break down at too high a temperature. Interesting: a Spanish study from 2021 showed that just 1 tablespoon of cold-pressed olive oil daily reduces bad LDL cholesterol by 12% in 6 weeks.
If you store olive oil in a dark bottle at room temperature, it keeps its quality for up to 18 months. In light or in plastic, beneficial substances begin to degrade after just 3 months.
Food as the medicine of the future
Scientists predict that in the next ten years, nutrition will become part of official therapy for treating cancer and chronic diseases. The European Research Agency already estimated in 2025 that proper nutrition can prevent up to 30% of all cancer cases—that’s more than 2 million lives annually around the world.
But beware! This doesn’t mean we should eat only oil and walnuts. As with all natural remedies, moderation and balance are key. Too much fat, even if healthy, can burden the liver. It is enough that healthy fats make up 25 to 30% of daily calorie intake, which means about 2 tablespoons of olive oil and a handful of nuts per day.
How each of us can make a difference
Even if it seems unimportant, every purchase we make has an impact. If we choose olive oil instead of palm oil, we’re not just helping ourselves, but also the environment. Palm oil is responsible for as much as 8% of global deforestation, meaning the loss of thousands of hectares of tropical forests every year.
So, with every liter of olive oil replacing palm oil on the shelf, we take a step towards a cleaner planet—and at the same time towards a stronger immune system.
Small spoon, big effect
In a world that's becoming more artificial and rushed, nature quietly reminds us that it still holds all the answers to everyday problems we face. Olive oil, walnuts, almonds, and avocados are not a fad. They are proven tools to strengthen the body, mind, and immune system. And most importantly: all of this is within reach—without a prescription or laboratories.
So, next time you cook, try using a spoonful of olive oil instead of butter, and eat a handful of walnuts instead of chips. Your body will be grateful, and your immune system will work better.
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