Is olive oil REALLY better for you than butter? I did a month-long experiment on myself to find out… the final blood test results surprised me

It’s one of the biggest – and surprisingly most fierce – debates in the nutrition world at present. Which is healthier: butter or olive oil?

For years, experts have argued that olive oil is by far the better option because butter is filled with saturated fats – a form that raises so-called ‘bad’ cholesterol levels, increasing the chances of a deadly heart attack or stroke. Olive oil, meanwhile, is thought to boost levels of ‘good’ cholesterol, which actually protect against heart issues. It is also a cornerstone of the Mediterranean diet, which has, in numerous major studies, been linked to a far healthier and longer life.

However, in recent years, a new school of thought has emerged, driven largely by social media influencers such as the massively popular US podcast host Joe Rogan. He claims that oils are ‘poisoning’ people, while butter has health-boosting properties.

Earlier this year, the idea even won the support of Robert F Kennedy Jr, the US Health Secretary known for his alternative views on healthcare, whose department published a controversial set of diet recommendations that included eating more saturated fats such as butter.

‘Our message is clear: Eat real food,’ Mr Kennedy said. ‘Protein and healthy fats are essential and were wrongly discouraged in prior guidelines.’

And the need for a clear answer to this question is obvious. Every year, 175,000 people in the UK die from cardiovascular disease, making it one of Britain’s biggest killers – and about a quarter of those deaths are thought to be linked to high cholesterol levels.

So who is right? I decided to put to the test the theory that butter is actually not something to avoid.

For one month, where possible, I planned to swap out olive oil for butter. I would get my blood tested before and after the experiment, in order to work out whether the change had improved or worsened my health.

I felt like I was better placed than most to be the guinea pig for this unconventional piece of research. I’ve never been much of a butter fan, preferring to cook mainly with extra-virgin olive oil – the most expensive and, according to scientists, the healthiest kind. I take good care of myself – my weight has stayed steady for years at 8st 10 lb, which at 5ft 4in gives me a healthy BMI of just under 21 – and I believe I eat well.

My weekly shop tends to include soups, salad leaves, tinned fish, fresh bread and picky bits (ham, cheese, olives, pickles), with the addition of pasta, rice noodles and the necessary ingredients of a Sunday roast – typically chicken rather than red meat.

I try to eat the 30 vegetables weekly, as recommended by gut health specialists, plus lots of legumes to add fibre.

However, I do worry about heart disease. At 59, I’m entering the age-range when these health issues go from hypotheticals to very real risks. Cardiovascular disease also runs in the family. My grandfather died aged 60 of a heart attack on the day he retired.

So you could argue that I have more to lose than many by abandoning my olive oil-based diet.

The first step was the blood test – which I did with One Day Tests.

The initial results were unexpected, not to mention unwelcome. My cholesterol was higher than I’d expected. My total score was 6.5 – the NHS considers anything above five to be worrying.

It was explained that this was most likely raised due to my age – it’s normal for cholesterol to slowly tick up as we get older.

However, this made me even more nervous about embarking on this experiment. What would one month of excessive butter consumption do to that level?

Nonetheless, in the name of science, I pressed ahead, swerving the olive oil shelf on my weekly shop and instead picking up two large sticks of butter.

I started cooking my weekly soups by sauteing onions in a big blob of butter. Meanwhile, pasta and stir fries, which would have normally been drizzled with olive oil, were coated with butter.

The Sunday roast chicken also got basted in butter – much to the enjoyment of my American husband, Fabian, who would, I suspect, cook everything in butter if he could.

Did I like it? Well, I didn’t hate it. But I don’t think it improved the taste. It did give it a much softer, creamier flavour – compared to the tangy finish of olive oil. The best way I can describe it is that everything tasted very French.

I ended up following the butter diet for five weeks. And when I arrived for my second blood test I was certainly nervous about what the results would show.

According to the British Heart Foundation, a month is enough time for a significant diet change – whether healthy or unhealthy – to show up on a blood test.

But I was pleasantly surprised. Yes, my bad cholesterol – also known as LDL cholesterol – had gone up. My healthy cholesterol levels – or HDL cholesterol – had also gone down. However, the changes were slight. My LDL levels rose from 3.77 to 3.89, while my HDL went from 2.72 to 2.32.

According to the doctor who analysed my results, these changes were ‘not clinically significant’. Moreover, my weight did not change at all. And this made me question whether everything I had been told about the danger of butter was true.

If saturated fats were so bad for you, surely consuming large quantities on a daily basis for five weeks should have had more of an impact?

Experts say that these findings are, in fact, in line with what the research into butter shows – and argue that much of the concern over the unhealthiness of butter is overblown.

‘It’s certainly true that olive oil is better for you,’ says Professor Jules Griffin, a food researcher at the University of Aberdeen. ‘But butter is not nearly as bad as many people make it out to be.’

To understand why, it’s important to know the key differences between butter and olive oil.

Butter is a saturated fat, which means that it contains something called palmitic acid, which suppresses the body’s ability to clear LDL cholesterol. As a result, a diet high in saturated fats leads to higher LDL cholesterol levels.

Olive oil, by contrast, is a monounsaturated fat, which does not have this affect on LDL levels.

In fact, Prof Griffin adds, some studies suggest that monounsaturated fats may even raise HDL levels – lowering the risk of heart problems.

A 2025 Harvard Study that analysed the health data of 220,000 adults over 30 years found those with the highest butter intake were 15 per cent more likely to die prematurely than the average, while those with the highest olive oil consumption were 16 per cent less likely to die young.

However, experts say this study, and other similar research, shows the dangers of eating extremely high levels of butter, rather than the more moderate amounts that most people consume. Moreover, studies show that the body does need some amount of saturated fats.

‘Saturated fats are a great source of energy and are definitely part of a healthy diet,’ says Prof Griffin. ‘The problem is that, in the UK, many people eat dangerously high levels of saturated fats. That’s because saturated fats are often found in takeaways and ready meals.’

Studies show that Britons get about 15 per cent of their food energy from saturated fats, noticeably higher levels than in other European countries, such as Greece and Spain where levels are closer to 9 per cent. But, as this data shows, even healthy nations still regularly consume saturated fats.

‘We think of Mediterranean countries as having the healthiest diets,’ says Prof Griffin. ‘But the Mediterranean diet includes plenty of saturated fats in the form of cheese and meat. The difference is that this is not combined with large amounts of processed, fatty foods like in the UK.’

There is even growing evidence that not eating enough saturated fats can have negative health consequences. Studies show that saturated fat products such as butter, milk and cheese contain crucial nutrients, such as vitamin A, B and B12. Meat is also a source of saturated fats and contains important minerals such as zinc and iron.

Iodine, a nutrient needed for a healthy thyroid gland, is also gained through saturated fat products. In the UK, studies show that the number of iodine-deficient patients is on the rise – and sufferers appear to be disproportionally young women. Some experts have theorised this is because many young women consume dairy alternatives such as oat milk in place of the real deal.

Prof Griffin also points to research that shows people who consume healthy amounts of saturated fat are less likely to develop diabetes than those who have significantly low levels.

‘This is the research that many influencers online have caught on to as proof of the health benefits of butter,’ he says.

‘However, the problem is that they have taken it way too far and now say that people should be consuming butter with every meal. The truth is somewhere in the middle.

‘A diet that includes excessive amounts of butter will almost certainly increase the risk of heart disease. But people who have a relatively healthy, balanced diet have nothing to fear from eating butter.

‘I eat plenty of butter myself – I’d say it’s my main source of dairy. I always put it on my toast and sandwiches, though I try not to cook with it because when you do it’s easy to consume too much.’

And as for me? Previously, I’d viewed butter as a guilty treat. I’d always given my husband a hard time for the amount of butter he cooks with, believing that he was sending himself to an early grave. However, after my five weeks of butter-eating, I feel more confident that it can be part of a healthy diet.

Funnily enough, it makes me think of my grandmother and her diet.

Growing up in the 70s, one of my strongest memories is going shopping with her. We would always buy fresh produce from the local butcher, baker and greengrocer. There was no fast food, additives, preservatives, or packaged foods in her shopping basket.

But, equally, she did not overthink what she ate.

She never counted calories and she certainly never worried about her saturated fats – eating plenty of butter and cheese like any average Briton did back in those days.

And, despite this, she remained in good health all the way up until her 90s.

It makes me wonder whether, despite all the food warnings we receive today about what we should and shouldn’t eat, my grandma had it right all along.

Going forwards, I’ve decided to add a bit of butter into my diet. I might smear it on a crumpet or a jacket potato – or snack on butter-coated crackers.

Olive oil will always be my preferred option and, as the scientists explain, all things being equal, it’s definitely the healthier choice. But I now realise there’s much less to fear from butter than I had thought.