These are conclusions from several research studies that have investigated the effects of eating different types of citrus fruits. Some have shown that eating citrus increases circulation, while others have shown that eating more citrus reduces the risk of strokes. Still others have found citrus fruits boost cognition even right after consuming it. Let’s review the evidence.Citrus increases circulation
Research from the UK’s University of Reading studied 28 people. They were between 30 and 65 years old and healthy. On different days, the researchers gave the subjects different types of citrus juices or not with their meals. These included typical commercial orange juice, homogenized orange juice and flavanone-rich orange juice.
The meals given to the subjects were considered double meals. This means an excess of fat content in the meal. In this case, over 80 grams. Typically, eating a double meal with excess fat will cause a reduction of circulation within hours of the meal. This reduced blood flow will often continue for seven or eight hours after such a meal and even longer.
The researchers were testing the ability of orange juice to possibly reduce this circulation reduction if orange juice was consumed with the meal.
After the meals, the researchers tested the subjects' circulation. This included their flow-mediated dilation (FMD) levels and their plasma nitrite levels. Flow-mediated dilation was measured at the brachial artery right after eating the meal, and after two hours, five hours and seven hours after the meal.
The researchers found that consuming the citrus significantly reversed the reduced flow-mediated dilation levels of the meal. In other words, the citrus increased their circulation.
Citrus boosts cognition
A 2015 study from the University of Reading tested orange juice and cognition on 37 healthy older adults. They gave the subjects high-flavanone orange juice or low-flavanone orange juice for 8 weeks using a crossover design.
Using standardized cognition tests, the researchers discovered that the flavanone orange juice boosted cognition among the adults. This included increased executive function.
A 2016 study on 24 healthy men between 30 and 65 had similar results. This one, however, found cognition boosted over a six-hour period after consumption of the juice in a two-day period. They drank 240 milliliters each time.
Again, this is orange juice with greater flavanone content. But in both studies, the effects occurred rather quickly.
But other research has found that regularly consuming citrus over a longer time reduces the risk of dementia. It also increases cognitive function over the long run. In a 2012 study from the University of Paris, 2,574 people were followed for 13 years. They were tested for cognitive function and their diets were assessed.
The study found those who had more polyphenol consumption – such as flavanones from citrus – had better verbal memory and episodic memory.
Citrus reduces stroke risk
Researchers from the Norwich Medical School of the UK’s University of East Anglia found in 2012 that the consumption of citrus is associated with a reduction of strokes among women.
The researchers studied 69,622 women for 14 years. There were 1,803 strokes among the women during that period. The researchers found that those who consumed the highest amounts of citrus fruits or juice had a nearly 20% lower incidence of ischemic strokes, and a 10% lower incidence of all strokes.
An ischemic stroke is caused by a blockage of blood flow that feeds the brain. This can produce a loss of physical, nervous or cognition function. The source of the blockage can be caused by a blood clot somewhere else in the bloodstream, causing thrombosis. This is often related to atherosclerosis – the build of plaque within the artery walls.
Do the flavanones reduce strokes?
The UK researchers initially attributed the effect to the increased level of flavanones from the citrus. Flavanones are a type of flavonoid that typically contain glycosides. Examples of flavanones are Hesperetin, Hesperidon, Naringin and Naringenin – all of which are contained in citrus fruits.
However, further investigation found that flavanone consumption did not specifically relate to the stroke reduction found in the study.
What caused the reduction? Citrus contains a variety of bioactive substances other than flavanones, many of which are potent antioxidants.
This was underscored in a 2012 study published in the Journal Agricultural Food Chemistry. The researchers found that lemon juice supplies potent antioxidants that break down a variety of free radicals.
Plaque buildup in the arteries is associated with an increase in oxidative radicals such as oxidized LDL-cholesterol. The ability of antioxidants to neutralize oxidized LDL has been shown in numerous nutraceutical studies.
The researchers also found that lemon juice in particular inhibits cholinesterases such as acetylcholinesterase and butyrylcholinesterase. The ability to reduce these cholinesterases gives lemon therapeutic properties against a variety of neuromuscular disorders and chronic nervous issues.
We’ve also discussed research showing how citrus reduces the risk of diabetes. We’ve also provided the evidence showing that citrus peels lower LDL-cholesterol and reduce disease in general. So eating fresh citrus – which includes a good portion of the peel – is the best strategy.
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