The science myths that will not die

False beliefs and wishful thinking about the human experience are common. They are hurting people — and holding back science

Megan Scudellari, Nature (abridged and modified by Hikmet Geckil)

In 1997, physicians in southwest Korea began to offer ultrasound screening for early detection of thyroid cancer. News of the programme spread, and soon physicians around the region began to offer the service. Eventually it went nationwide, piggybacking on a government initiative to screen for other cancers. Hundreds of thousands took the test for just US$30–50.

Across the country, detection of thyroid cancer soared, from 5 cases per 100,000 people in 1999 to 70 per 100,000 in 2011. Two-thirds of those diagnosed had their thyroid glands removed and were placed on lifelong drug regimens, both of which carry risks.

Such a costly and extensive public-health programme might be expected to save lives. But this one did not. Thyroid cancer is now the most common type of cancer diagnosed in South Korea, but the number of people who die from it has remained exactly the same — about 1 per 100,000. Even when some physicians in Korea realized this, and suggested that thyroid screening be stopped in 2014, the Korean Thyroid Association, a professional society of endocrinologists and thyroid surgeons, argued that screening and treatment were basic human rights.

In Korea, as elsewhere, the idea that the early detection of any cancer saves lives had become an unshakeable belief.

This blind faith in cancer screening is an example of how ideas about human biology and behaviour can persist among people — including scientists — even though the scientific evidence shows the concepts to be false.

These myths often blossom from a seed of a fact — early detection does save lives for some cancers — and thrive on human desires or anxieties, such as a fear of death. But they can do harm by, for instance, driving people to pursue unnecessary treatment or spend money on unproven products. They can also derail or forestall promising research by distracting scientists or monopolizing funding. And dispelling them is tricky.

Some dangerous myths get plenty of air time: vaccines cause autism, HIV doesn’t cause AIDS. But many others swirl about, too, harming people, sucking up money, muddying the scientific enterprise — or simply getting on scientists’ nerves.

Here, are three myths that refuse to die.

Myth 1: Screening saves lives for all types of cancer

Regular screening might be beneficial for some groups at risk of certain cancers, such as lung, cervical and colon, but this isn’t the case for all tests. Still, some patients and clinicians defend the ineffective ones fiercely.

The belief that early detection saves lives originated in the early twentieth century, when doctors realized that they got the best outcomes when tumours were identified and treated just after the onset of symptoms. The next logical leap was to assume that the earlier a tumour was found, the better the chance of survival.

But evidence from large randomized trials for cancers such as thyroid, prostate and breast has shown that early screening is not the lifesaver it is often advertised as.

Myth 2: Antioxidants are good and free radicals are bad

In December 1945, chemist Denham Harman’s wife suggested that he read an article in Ladies’ Home Journal entitled ‘Tomorrow You May Be Younger’. It sparked his interest in ageing, and years later, as a research associate at the University of California, Berkeley, Harman had a thought “out of the blue”, as he later recalled. Ageing, he proposed, is caused by free radicals, reactive molecules that build up in the body as by-products of metabolism and lead to cellular damage.

Scientists rallied around the free-radical theory of ageing, including the corollary that antioxidants, molecules that neutralize free radicals, are good for human health. By the 1990s, many people were taking antioxidant supplements, such as vitamin C and β-carotene (the precursor to vitamin A).

Yet in the early 2000s, scientists trying to build on the theory encountered bewildering results: mice genetically engineered to overproduce free radicals lived just as long as normal mice, and those engineered to overproduce antioxidants didn’t live any longer than normal. It was the first of an onslaught of negative data, which initially proved difficult to publish.

None of those results has slowed the global antioxidant market, which ranges from food and beverages to livestock feed additives. It is projected to grow from US$2.1 billion in 2013 to $3.1 billion in 2020.

Today, most researchers working on ageing agree that free radicals can cause cellular damage, but that this seems to be a normal part of the body’s reaction to stress. Still, the field has wasted time and resources as a result.

Myth 3: Humans have exceptionally large brains

The human brain — with its remarkable cognition — is often considered to be the pinnacle of brain evolution. That dominance is often attributed to the brain’s exceptionally large size in comparison to the body, as well as its density of neurons and supporting cells, called glia.

None of that, however, is true. Human brains are about seven times larger than one might expect relative to similarly sized animals. But mice and dolphins have about the same proportions, and some birds have a larger ratio.

Human brains are different from those of other primates in other ways: Homo sapiens evolved an expanded cerebral cortex — the part of the brain involved in functions such as thought and language — and unique changes in neural structure and function in other areas of the brain.

The myth that our brains are unique because of an exceptional number of neurons has done a disservice to neuroscience because other possible differences such as energy metabolism, are rarely investigated.

Myths that persist

Nature polled doctors and scientists for the medical myths that they find most frustrating. Here’s what turned up.

Vaccines cause autism
Although there are some risks associated with vaccines, the connection to neurological disorders has been debunked many times over.

Paracetamol (acetaminophen) works through known mechanisms
Although it is widely used, there are only hints as to how it and other common drugs actually work.

The brain is walled off from the immune system
The brain has its own immune cells, and a lymphatic system that connects the brain to the body’s immune system has recently been discovered.

Homeopathy works.

It doesn’t.

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