"Eat your greens, they're good for you." This is statement that many of us heard as a child while pushing vegetables around the plate in disgust at dinner time. But it seems our parents may have had a point; three new studies reveal that a chemical called nitrate - found in green vegetables including spinach, lettuce and celery - may aid heart health and reduce the risk of obesity and diabetes.
The three studies were conducted by researchers from the University of Cambridge and the University of Southampton - both in the UK.
In the first study, co-led by Dr. Andrew Murray from the University of Cambridge and published in The FASEB Journal, researchers found that eating more vegetables rich in nitrate may reduce production of a hormone made by the liver and kidneys, called erythropoietin. This hormone regulates the number of red blood cells in the body.
The team explains that at high altitudes or in cardiovascular diseases, the body is subject to a shortage of oxygen. In order to get more oxygen around the body, erythropoietin increases its production of blood cells.
However, high numbers of blood cells can cause the blood to become too thick. This means that the body's organs and tissues may be starved of oxygen because the blood is unable to flow through small blood vessels to get to them.
But the findings from the team indicate that eating more nitrate-rich vegetables could thin the blood by lowering the number of red blood cells produced, which could have important implications for health. Dr. Murray says:
"Here we show that nitrate from the diet can help regulate the delivery of oxygen to cells and tissues and its use, matching oxygen supply and demand. This ensures cells and tissues in the body have enough oxygen to function without needing to overproduce red blood cells, which can make the blood too thick and compromise health.
In addition, the researchers note that their findings could lead to the discovery of better ways to deliver oxygen to cells, which may help the recovery of patients in intensive care units.
Dietary nitrate 'protects against heart, circulatory conditions'
Dr. Murray led the second study, which was recently published in The Journal of Physiology.
In this research, the team exposed rats to high altitudes in order to trigger increased production of red blood cells.
They found that rats fed a diet with nitrate - the equivalent to humans adding slightly more green vegetables to their diets - were better protected against an array of heart and circulatory conditions than rats fed a nitrate-free diet.
This is because nitrate increases production of a compound that widens the blood vessels, according to the researchers, improving blood flow. What is more, the researchers found that nitrate protects proteins in heart cells that are crucial for heart health.
"Nitrate supplementation may thus be of benefit to individuals exposed to hypobaric hypoxia at altitude or in patients with diseases characterized by tissue hypoxia and energetic impairment, such as heart failure and chronic obstructive pulmonary disease, or in the critically ill," the team says.
Nitrate converts 'bad' fat cells into 'good' fat cells
In the third study - published in the journal Diabetes and led by Lee Roberts from the University of Cambridge - the team found that nitrate subjects "bad" white fat cells to a process called "browning," which converts them into beige cells.
The researchers explain that beige cells are similar to "good" brown fat cells, which burn fat in order to generate heat. Increased levels of brown fat have been associated with reduced risk of obesity and diabetes, therefore the team hypothesizes that incorporating nitrate into the diet could protect against these conditions.
Commenting on the findings of all three studies, Dr. Murray says:
"There have been a great many findings demonstrating a role for nitrate in reducing blood pressure and regulating the body's metabolism.
These studies represent three further ways in which simple changes in the diet can modify people's risk of type 2 diabetes and obesity as well as potentially alleviating symptoms of existing cardiovascular conditions to achieve an overall healthier life."