The bitter peel of an orange is there to protect the fruit, and it could protect our own insides, too, if only we stopped throwing the rinds away.
The zest of oranges has now been found to contain a novel, bioactive compound, called feruloylputrescine (FP), that could benefit heart health when eaten.
Its discovery in orange peels has scientists at the University of Florida and the US Department of Agriculture excited.
In experiments, when mice were fed a nutritious orange peel extract, rich in FP, for six weeks straight, researchers noticed a reduction in blood biomarkers linked to inflammation and cardiovascular disease. Even when consuming a high-fat diet during this time, the animals fed a daily dose of FP put on less fat than the control group.
FP is a metabolite that was originally found in the leaves and juice of grapefruit. While it also appears in some oranges, it does not seem to be present in limes, lemons, tangerines, or mandarins.
The compound has received a lot of interest in recent years for its antioxidant and anti-inflammatory potential, but there is still a lot experts don’t know about it.
“This is a novel finding that highlights the previously unrecognized health potential of feruloylputrescine in reducing the risk of cardiovascular disease,” says food scientist Yu Wang from the University of Florida.
Oranges are one of the most popular fruits in the world, mostly consumed for their juice with the bitter rind typically discarded. Each year, 32 million tons of orange peels go to waste, even though the skin is perfectly edible and could be good for us. When scraps of oranges are fed to chickens, there seem to be health benefits to the animals.
In Florida, about half of the state’s orange peels are given to cattle. But perhaps there’s a reason to keep some for ourselves.
Compared to the juicy part, the skin of an orange contains an impressive concentration of vitamins, antioxidants, and limonene – a chemical that could have anti-inflammatory and anti-cancer properties. Figuring out which bioactive compounds are the most important to human health, and why, will be key if scientists want to make the healthiest extract possible.
FP should not be overlooked. When this metabolite is consumed, it seems to stop some specific bacteria in the gut from spitting out a byproduct called trimethylamine (TMA) while breaking down food.
TMA is produced by gut bacteria that are often involved in the digestion of meat, or high fat, low protein diets. When this compound enters the bloodstream via the gut, it goes to the liver and is metabolized into trimethylamine N-oxide (TMAO).
TMAO is linked to an increased risk of arterial plaque build-up, heart disease, stroke, obesity, and type 2 diabetes.
The FP in orange peels could help counter that risk.
In experiments in Florida, when mice were fed orange peel extract containing FP, their levels of TMA and TMAO were reduced, even as the bacteria that usually produced these metabolites continued munching away.
Whether the same benefits extend to humans is unclear, but the USDA is interested in finding out.
The work from Wang and her colleagues was made possible by a US$500,000 grant from the government department to investigate whether orange peel extract can improve the health of our guts and hearts.
Orange rinds are not the easiest food to incorporate into a meal, but if scientists can design a consumable product out of the skin, it could become a popular, health-boosting kitchen staple.
Several companies are already rushing to make just that. And recently, researchers found that with just a bit of work, the skin of a banana can be turned into a tasty, nutritious snack, packed to the brim with antioxidants and vitamins. The same goes for mango skin.
Orange peels are merely the latest rind to get behind.
The study was published in the Journal of Agricultural and Food Chemistry.
