The spinach-eating cartoon character Popeye has much to teach us, new research from the Swedish medical university Karolinska Institutet shows. The muscles' cellular power plants - the mitochondria - are boosted by nitrate, a substance found in abundance in vegetables such as lettuce, spinach and beetroot.
For half a century, inorganic nitrate has been associated with negative health effects, but more recently, evidence of the contrary has mounted. In the 1990s, a research group at Karolinska Institutet demonstrated how the body can convert nitrate to NO, a molecule involved in many important bodily functions, such as blood pressure regulation, the immune defence and cell metabolism.
In this new study, the same team had healthy people take nitrate equivalent to 200-300g of spinach or lettuce for three days, after which they were given a cycling task to perform. The researchers then analysed samples from their thigh muscles and compared them with similar samples from the same subjects when they had taken a placebo instead. After nitrate ingestion, a significant improvement was seen in the efficiency of the mitochondria, which consumed less oxygen and produced more of the energy-rich substance ATP per consumed oxygen molecule.
"The mitochondria play a key role in cellular metabolism", says Professor Eddie Weitzberg, who is heading the study with Professor Jon Lundberg. "Improved mitochondrial function probably has many positive effects on the body, and could explain some of the health benefits of vegetables."
The results, which are published in Cell Metabolism, are of sports-physiological interest, as they show that nitrate reduces oxygen consumption during physical exercise; however, they are also of potential significance to diseases involving mitochondrial dysfunction, such as diabetes and cardiovascular disease.
The group has also recently shown that nitrate reduces the blood pressure of healthy individuals and that in laboratory animals it counteracts components of the metabolic syndrome, a pre-stage of diabetes. Other scientists have demonstrated protective effects of nitrate and nitrite in animal models against heart attack and stroke.
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