Citrus flavonoids have been under study for about the last decade or two as their value in maintaining human health and even potential to cure disease is being discovered.
Like other flavonoids, nobiletin is found in stems, seeds, root tissues, the flesh, and most importantly, the peel of citrus fruits. Even in the plant, they have beneficial effects, protecting the leaves and fruit against the effects of too much sunlight by shielding mesophyll cells and scavenging radicals – the same activity that has been reported in human and animal medical studies.
The Study of Citrus Flavonoid Nobiletin
Researchers from the University of Western Ontario, McMaster University, and the University of Ottawa, all in Ontario Canada, published a study targeting the effect of a flavonoid found in oranges, lemons, tangerines and other citrus fruits on the regulation of fats in the blood.
The study was published in the Journal of Lipid Research in 2020, and specifically studied the effects of nobiletin, a flavonoid found in high concentrations in citrus peel, particularly oranges and tangerines, and its effects on mice who were fed a diet high in fats.
The researchers were attempting to test a theory behind the results of a previous study published in 2017. In that study, Japanese researchers used a group of mice who were fed a diet high in fats and cholesterol. One segment of the group was also fed nobiletin.
• Those mice were significantly leaner than the non-nobiletin group.
• As well as less body fat, they had lower levels of fats in their blood, and increased sensitivity to insulin (i.e. decreased insulin resistance.)The researchers posited that nobiletin worked by affecting a specific regulator in the body responsible for how fat is processed, called AMP Kinase.
Testing the Theory
In the new study, the Canadian researchers used mice which had been genetically altered to remove the AMP Kinase from their bodies. If the theory was correct, then the addition of nobiletin would have no effect on these mice.
However, their theory proved incorrect.
In other words, the mice continued to show the beneficial effects of nobiletin, being leaner bodies, lower lipid levels in the blood, and reduced levels of insulin resistance.
“This result told us that nobiletin is not acting on AMP Kinase and is bypassing this major regulator of how fat is used in the body.”
Why It’s Important
• Insulin resistance and metabolic syndrome are increasing across North America.
• Many of the drugs used to treat it and type II diabetes affect the AMP Kinase pathway.
• Since nobiletin does not, it has great potential for therapeutic use. Lead researcher Murray Huff is quoted in the paper.
“We’ve shown that in mice that already have all the negative symptoms of obesity, we can use nobiletin to reverse those symptoms, and even start to regress plaque-like build-up on arteries, known as atherosclerosis.”
Nobiletin has also been studied for its protective and therapeutic effects in the treatment of dementia and other uses. It’s just another reason to use citrus – and in this case, particularly orange – zest in your cooking on a daily basis.
