According to Iranian researchers, a fruit frequently consumed in autumn – and often presented in the form of jam – could significantly reduce your blood pressure. But how can we explain these effects? A nutrition expert answers us.
Quince and blood pressure: a promising link
The report in question, which brings together a dozen studies carried out on animal models or in vitro, reveals that quince would have an interesting impact on blood pressure.
“Quince extracts, derived from the leaves, seeds and fruits, have shown positive effects on blood pressure, glucose metabolism, lipid profile, body weight and liver function“, confirm the researchers.
In detail, the antihypertensive effect of quince was comparable to that of captopril (a drug used in the treatment of high blood pressure), and its hypolipidemic effect (which reduces the level of bad cholesterol) to that of simvastatin.
Additionally, two studies evaluated the effect of quince fruit extract on insulin levels. “One reported no effects, while the other observed a significant positive effect. Quince also showed strong anti-inflammatory and antioxidant capacity,” say the scientists.
The results therefore suggest that different parts of the quince could be used to treat hypertension. However, they also have some limitations, notes Julie Boët, dietitian-nutritionist.
“If quince extracts have indeed shown a reduction in blood pressure in hypertensive rats, this work was carried out on animals, with standardized extracts, highly concentrated in active compounds, often administered in the form of capsules or injections, and not with culinary preparations. All of this is therefore not yet 100% reliable”, she warns.
How to explain these benefits?
Still according to our expert, the supposed mechanism of these effects is based on several simultaneous actions.
“Quince polyphenols have powerful antioxidant and anti-inflammatory activity: they protect our arteries, and promote the production of nitric oxide, a chemical messenger which naturally dilates blood vessels. Certain extracts also seem to modulate the renin-angiotensin system, which regulates blood pressure: they reduce the production of angiotensin II, a vasoconstrictor hormone, which brings their effect closer to that of antihypertensive drugs,” she reveals.
Other researchers have also observed an improvement in blood viscosity and better elasticity of red blood cells, suggesting that blood circulates more easily in small vessels.
“Finally, some work shows complementary effects on cholesterol and blood sugar, two aggravating factors in cardiovascular risk. All this suggests that quince acts through a set of mechanisms, rather than just one,” notes the expert.
Quince: the parts of the fruit to favor
Of course, not all parts of the quince are equal. “The leaves, widely used in studies, are particularly rich in flavonoids and polyphenols. The flesh of the fruit also contains them, as does the skin, which concentrates even more, as in most fruits. The seeds contain mucilage and certain bioactive compounds which have also been studied. These elements are interesting in their raw or lightly processed form”,
confides the dietician.
On the other hand, processing into jam involves prolonged cooking of the fruit with sugar, sometimes in almost equivalent proportions. Heat also degrades some of the antioxidant compounds.
“Studies show that between 50 and 70% of polyphenols can be preserved if cooking is short or carried out at moderate temperatures. However, the longer you heat, the more sugar you add, and the more these fragile molecules disappear!” warns the expert.
Added to this is an essential point: quince jam contains a lot of added sugars, but an excess of sugar in the diet is itself associated “increased blood pressure, weight gain (especially around the abdomen), insulin resistance. Sugar also indirectly increases the stiffness of the arteries, stimulates certain stress hormones, promotes chronic inflammation. continues the specialist.
No, jam cannot replace medicine
Not surprisingly, traditional jam cannot in any way replace antihypertensive treatment.
“On the other hand, integrating quince into the diet is a great idea: lightly sweetened quince compote, poached fruits without added sugars, inclusion of the skin when possible, leaf teas (practiced in certain cultures), and more generally a diet rich in fiber, plants, low in salt, sugars and saturated fats”, underlines the expert.
“Quince is not dangerous, quite the contrary, but it does not exempt you from prescribed treatment or regular blood pressure monitoring.“, she concludes.
Our expert insists on the need to favor a global approach.
“What I recommend to a hypertensive person is not to look for a miracle food, but for overall consistency.“, says Julie Boët. “Less salt, less alcohol, less sugary industrial products, more regular physical activity, maintaining an appropriate weight, stopping smoking, stress management, and rigorous medical monitoring.”
Quince can fit into this framework, as an interesting seasonal fruit, but not as a natural medicine.