In the cartoon Popeye the sailor man became super-strong after eating spinach. Is it just fiction or is it a scientific explanation behind it?
Each year millions of adventurers visit high altitude regions higher than 2500 meters(HA) around the world. When ascending in HA, the pressure in the atmosphere decreases, resulting in reduction in available oxygen per breath, “thin air”. Since processes in the human body are dependent on adequate oxygen delivery, the body needs to respond to the “thin air” in a process known as acclimatization. Two important physiological responses occur in the early acclimatization phase to optimize oxygen delivery to the tissues: You start breathing faster, hyperventilating, and more blood is pumped per minute since your heart rate goes up. At the same time blood pressure will increase since your blood vessels are becoming smaller, and to ensure adequate O2 delivery at HA, it is crucial that blood vessels are able to function properly. The next sections will describe how beetroot juice may play a beneficial role in regulating the function of blood vessels in HA.
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Many factors influence the ability to increase the blood vessel diameter, but the most important factor is named nitric oxide (NO). One of the ways humans produce NO is by eating food that contains NO3–, especially beetroot and spinach have high concentrations of this. Studies conducted at sea level under artificial low oxygen concentrations, showed that the ability to produce NO from NO3–increased. Until CERG in collaboration with the Mid- Sweden University went on a HA research project to Nepal in 2013, the effect of dietary (beetroot juice) NO3– supplementation to improve blood vessel function at HA had not been studied before.
After seven days of walking from the capital Kathmandu at 1370, the students of the Outdoor and Adventure Management program in Åre, Sweden, reached 3700 meters. Here the function of the blood vessel in the upper arm, brachial artery, was studied with an ultrasound-based technique after the students either drank 70 ml of Beet-it juice containing high doses of NO3– or 70 ml of Beet-it juice without NO3-, placebo juice. At 3700 meters we saw a reduction in blood vessel function because of the “thin air”, and as expected placebo juice without any NO3– showed no beneficial effects. However, when the students drank juice containing high doses of NO3–, there was a great improvement of blood vessel function. So in other words, beetroot has the ability to improve blood vessel function in HA and maybe it is worth carrying a bottle of beetroot when you want to stand on the top of a high mountain.
We chose to use beetroot in this experiment, but Popeye the sailor man ate spinach that is also full of NO3– supplement. So maybe spinach made Popeye the sailor super-strong after all?
Svein Erik Gaustad, Post Doc CERG