Let me describe a mysterious bird that vividly illustrates some of the biological challenges that birds have had to overcome to live as long as they do.
My mystery bird is tiny, weighing about the same as a US penny. When active, it needs so much energy that to avoid starvation, it must consume food up to several times its body weight per day. During the flight, its wings beat 80 times per second, and each gram of his flying muscles produces up to 10 times more energy than the muscles of an elite athlete when both are working at maximum efficiency. In fact, it has the highest metabolic rate of any endothermic animal—and it does very endothermic. Its typical body temperature of 40°C (104°F) would be a dangerously high fever for humans. It needs so much fuel to sustain such energy expenditure that when idle it lowers its body temperature to ambient temperature so as not to starve to death while sleeping. His heart beats at a rate of 20 beats per second, similar to a machine gun. Even at rest, he breathes 250 times a minute, about the same as a panting dog, to get enough oxygen. Finally, his normal blood sugar would make him dangerously diabetic if he were human.
How long do you think he lives?
I just described a hummingbird—specifically, a ruby-throated hummingbird (Archilochus colubris), a species commonly found in parks and gardens in the eastern United States. Hummingbirds fuel their crazy lifestyle by sucking nectar – a rich mixture of sugars – from flowers. They also suck up a few small insects in search of protein along the way. Their flight is a wonder to see and hear. Their name, of course, comes from the deep hum of their wings, which beat so fast they are almost invisible.
Hummingbird special powers
About 330 species of hummingbirds – all living in the Americas – are the only birds that can fly forward, backward and hover. They can fly straight up and down like a helicopter and even do somersaults and other aerial stunts. Men in particular court women by performing aerial acrobatics that seem impossible even when you’re watching them. What’s more, ruby hummingbirds, despite their small size and high energy requirements, fly 600 miles without end across the Caribbean twice a year while migrating to their tropical wintering grounds. If birds generally perform astounding physical feats, hummingbirds are among the most astounding.
If that was all you knew about this hummingbird, you would no doubt expect them to be short-lived. After all, they live in the fastest lanes, and with few exceptions, animals that live fast die young. But you would be wrong. Ruby-throated hummingbirds can live for more than nine years in the wild, even if they make their deadly flights over the Caribbean twice a year. Nor are they the longest-lived hummingbirds. A broad-tailed hummingbird of similar size (Selasphorus platycercus), with similar energy requirements, can live in the wild for at least 12 years. The much larger mouse only lives a few months in the wild and only about three years as a well-groomed pet. Therein lies the secret that, when fully understood, can help you develop ways to stay healthy longer.
What is the secret of birds?
Hummingbirds are an extreme example, but virtually all avian biology can be understood in terms of adaptations to the unique energy requirements of powered flight. This energy requirement suggests that birds should be short-lived, but the opposite is true. Their body temperature is higher than ours; their resting metabolism is up to twice as fast as that of mammals of the same size, and while in flight their metabolism speeds up even more. Even gliding, such as that performed by seagulls, vultures, and albatrosses, may seem almost effortless to us, but it doubles or triples birds’ resting metabolic rate. Their exceptional energy requirements are fueled by blood sugar levels, which would signal uncontrolled diabetes in a human. Uncontrolled diabetes resembles accelerated aging more than any other disease.
High energy, high temperature and high blood sugar should speed up many of the major processes that contribute to aging, one of which is the production of free radicals. Recall that free radicals are molecules that can damage all classes of biological molecules, including DNA. To maintain cellular health, free radicals must be quickly destroyed by our antioxidant defenses, and the damage they inevitably cause must be repaired quickly. Birds must have extremely effective antioxidant defenses and extremely rapid repair mechanisms. In fact, some of the few studies conducted to understand birds’ longevity have shown that their cells produce fewer free radicals at the same rate of energy production as mammals of similar size. But we don’t understand how they do it. They can also withstand more free radical damage before their cells die. We don’t understand how they do it either.
Another aging process that, according to our knowledge of aging, should be accelerated in birds is protein browning. Proteins drive the chemical reactions that define life. With their role in driving chemical reactions, proteins must be assembled in a complex and precise way, like origami. Any slight deviation from perfect folding impairs their functionality. Misfolded proteins not only lose their function but become sticky, causing them to stick together with other misfolded proteins. Alzheimer’s disease plaques and tangles are particularly well-known clusters of misfolded proteins, but there are many others.
Proteins spontaneously misfold all the time in the chaotic bumper environment of our cells and are broken down and their parts regularly recycled. However, one particular type of misfolding protein is slow to recycle protein and is most suitable for birds and diabetics. This is a browning reaction caused by heat and sugars. Sugars will self-adhere to proteins, interfering with their precise folding. The higher the temperature, the more concentrated the sugar is and the faster the browning reaction occurs. This happens very quickly at the temperatures we use for cooking. Meat and toast brown when heated because of this reaction. The same thing happens in our bodies, only much slower. For example, our tendons and ligaments are made of collagen, a protein that stiffens with age due to browning. Aging athletes have been toasted to thank for the increased risk of injury. Due to birds’ higher body temperature and elevated blood sugar, their tendons, ligaments and other tissues should brown much faster than mammals. But they don’t.
How birds prevent free radical damage and browning may benefit human health. Do they have unique antioxidants that prevent free radical damage? Do they have unique ways of degrading damaged proteins? They must also have mechanisms that maintain cellular function in the face of life’s challenges. Little research has been done on the aging process of birds, but never the great sustained effort that we might have made if they had been studied for cancer prevention. Medical research remains largely mired in the study of short-lived laboratory species such as fruit flies and mice, from which we can learn little to improve or extend human health. The Manhattan Project, designed to understand the extremely slow aging of birds and their ability to maintain strength and endurance throughout their lives, would be a good use of research dollars.
This article was originally published on reader by Steven N. Austad. Read the original article here.