Review: The Body - A Guide For Occupants

…where the human body is concerned, the details are often surprisingly uncertain.

How this [genetics] works in detail is still largely a mystery to us.

…only 2 percent [of DNA] does anything demonstrably and unequivocally practical. Quite what the rest is doing isn’t known.

…techniques for analyzing ancient DNA means that we are learning more all the time and much of it is surprising — and some is confusing and some disputed.

The answer is that nobody knows. Your body is a universe of mystery. A very large part of what happens on and within it happens for reasons that we don’t know — very often, no doubt, because there are no reasons.

As early as 1945, in his Nobel acceptance speech, Fleming warned that microbes could easily evolve resistance to antibiotics if they were carelessly used. Seldom has a Nobel speech been more prescient.

Thinking is our most vital and miraculous talent, yet in a profound physiological sense we don’t really know what thinking is.

But what scientists learned from [a notable brain injury patient] was not so much how memory works as how difficult it is to understand how it works.

…there is a great deal that we still don’t know about smell, including exactly how it works.

As with every other part of your head, the mouth is a realm of complexity and mystery.

Take the tonsils. We are all familiar with them, but how many of us know quite what they do? In fact, nobody knows quite what they do.

Because it is so dilute, no one is sure why it is there at all. It is so unassertive that its existence wasn’t even noticed until 2006.

For years, even textbooks spoke of a tongue map, with the elemental tastes each occupying a well-defined zone: sweet on the tip of the tongue, sour at the sides, bitter at the back. In fact, that is a myth…

That was the problem with bleeding [as a therapeutic medical treatment]. If you could tell yourself that those who survived did so because of your efforts while those who died were beyond salvation by the time you reached them, bleeding would always seem a prudent option.

Our understanding of [hormones] is far from complete, and much of what we do know is surprisingly recent.

The immune system…There is a lot of chemistry involved. If you want to understand the immune system, you need to understand antibodies, lymphocytes, cytokines, chemokines, histamine, neutrophils, B cells, T cells, NK cells, macrophages, phagocytes, granulocytes, basophils, interferons, prostaglandins, pluripotent hematopoietic stem cells, and a great deal more — and I mean a great deal more.

On top of all that, every person’s immune system is unique, making immune systems harder to generalize, harder to understand, and harder to treat when they go wrong.

Much of what happens in the immune system at the cellular level is still very imperfectly understood. Quite a lot is not understood at all.

Sinuses are strange. … [They are] riddled with a complex network of bones, which are thought to help with breathing efficiency, though no one can say quite how. … Thirty-five million Americans suffer sinusitis every year, and about 20 percent of all antibiotic prescriptions are for people with sinus conditions (even though sinus conditions are overwhelmingly viral and thus immune to antibiotics).

What is perhaps surprising is how little we sometimes understand the causes of [respiratory] problems, and of no condition is that more true than asthma.

[At the beginning of the 20th century] asthma was a rare disease and not well understood. Today it is common and still not understood. The second half of the twentieth century saw a rapid increase in asthma rates in most Western nations, and no one knows why. … Indeed, where asthma is concerned, no one knows much of anything.

"You probably think asthma is caused by dust mites or cats or chemicals or cigarette smoke or air pollution", says Neil Pearce, professor of epidemiology and biostatistics at the London School of Hygiene and Tropical Medicine. "I have spent thirty years studying asthma, and the main thing I have achieved is to show that almost none of the things people think cause asthma actually do. They can provoke attacks if you have asthma already, but they don’t cause it. We have very little idea what the primary causes are. We can do nothing to prevent it."

Vitamin D, one of the most vital of all vitamins, can both be made in the body (where it really is a hormone) or be ingested (which makes it a vitamin again). … In the case of many micronutrients, scientists don’t know quite how much you need or even what they do for you when you get them. … Chromium levels fall steadily as we age, but no one knows why they fall or what this indicates. … For nearly all vitamins and minerals, the risk of taking in too much is as great as the risk of getting too little.

For all their importance, proteins are surprisingly ill-defined. Although all proteins are made from amino acids, there is no accepted definition as to how many amino acids you need in a chain to qualify as a protein.

Eight of the twenty amino acids cannot be made in the body and must be consumed in the diet.

Trans fats are essentially a form of slow-acting poison. … [in the mid-1950s] a biochemist … reported clear evidence of a link between high intake of trans fats and clogged coronary arteries, but his findings were widely dismissed, particularly with the influence of lobbying by the food processing industry.

It’s possible for doctors to go through medical school without being taught nutrition. … Perhaps nothing is more emblematic of the unsettled state of knowledge on the modern diet than the long and unresolved controversy over salt.

A possible contributing factor to this salt controversy: A 2016 study in the International Journal of Epidemiology found that researchers on both sides of the argument overwhelmingly cite papers that support their own views and ignore or dismiss those that do not.

That’s why you are told to eat more fiber: because it keeps your gut microbes happy and at the same time, for reasons not well understood, reduces the risk of heart disease, diabetes, bowel cancer, and indeed death of all types.

…most strains do us no harm and some are positively beneficial…

The incidence of acute appendicitis in the rich world is about half today what it was in the 1970s, and no one is quite sure why. It remains more common in wealthy countries… though the rates in developing countries have been rising rapidly… but again no one knows why.

We are a long way from understanding it all.

Sleeping is the most mysterious thing we do. We know that it is vital; we just don’t know exactly why. We can’t say with any certainty what sleep is for, what is the right amount for maximum health and happiness, or why some people fall into it with ease while other struggle perpetually to attain it.

Why the eyes move during REM sleep is uncertain.

How exactly melatonin relates to sleep is still not understood.

A seventy-year-old produces only a quarter as much melatonin as a twenty-year-old. Why this should be, and what effect it has on us, remain to be determined.

We are really at the beginning of our understanding of the importance of circadian rhythms for all living things…

No one understands why we yawn.

…until recently drug trials very often excluded women, largely because it was feared their menstrual cycles could skew results…. People had been assuming that women are just 20 percent smaller then men, but otherwise are much the same. We now know that there is much more to it than that… Such findings are seriously consequential because women and men can respond to drugs in very different ways — ways often overlooked by clinical trials.

…Vaginal secretions were the only bodily fluid about which virtually nothing was known despite their importance to conception and a woman’s general sense of well-being.

Even now, there is a huge amount concerning female anatomy about which we are uncertain.

Why is this? The bottom line is that we don’t know.

Why are sperm counts in Western countries lower than they formerly were? Among the suggested causes have been diet, lifestyle, environmental factors, frequency of ejaculation, and even (seriously) wearing tight underpants, but no one knows.

…why such an extravagance of production, even at the lower end when only one sperm is required for conception, are questions that science has yet to answer.

For a decade or so [around 1900], [oophorectomy, removal of the ovaries] was the operation of choice for well-off women with menstrual cramps, back pain, vomiting, headaches, even chronic coughing. In 1906, an estimated 150,000 American women underwent oophorectomies. It more or less goes without saying that it was an entirely pointless procedure.

Despite its lavish spending, the United States has one of the highest rates of both infant and maternal death among industrialized nations… The average cost of childbirth in the United States is about $30,000 for a conventional birth and $50,000 for a Cesarean, about three times the cost for either in the Netherlands. Yet American women are 70 percent more likely to die in childbirth than women in Europe…

We are only beginning to understand the importance and nature of a woman’s vaginal microbiome. Various studies have found that people born by C-section have substantially increased risks for type 1 diabetes, asthma, celiac disease, and even obesity…

On top of all that [thwarting of microbiome functions], about four women in every ten are given antibiotics during delivery, which means that doctors are declaring war on babies' microbes just as they are acquiring them. We have no idea what the consequences this has for their long-term health, but it’s unlikely to be good.

Why can phantom pain in a lost limb last a lifetime? No one can yet explain why.

Exactly how pain works is, as you will gather, still largely a mystery.

We still don’t know exactly how the brain constructs the experience of pain…

Spinal cord injuries are dismayingly common. More than one million people in the United States are paralyzed from them.

Migraines are almost wholly a mystery.

Medical science offered very little in the way of safe, lasting relief [from pain] back then [100 years ago]. We are not much further along now… …some 75 percent to 85 percent of people get no benefit at all from even the best pain drugs, and those who do get benefit don’t usually get much. … Pharmaceutical companies have poured billions and billions into drug development but have not come up with a drug that controls pain effectively and doesn’t cause addictions.

Opioid use has become such big business that we have now reached the surreal situation that pharmaceutical companies are producing drugs to alleviate the side effects of opioid overuse. Having helped to create millions of addicts, the industry is now profiting from medications designed to make their addiction a little more comfortable.

Nobody knows quite why placebos work, but they do… Placebos don’t shrink tumors or banish plaque from narrowed arteries. But then, come to that, neither do more aggressive painkillers, and placebos at least have never sent anyone to an early grave.

A report in The Journal of the American Medical Association concluded that the victims had been suffering from a "subtle but nevertheless primarily organic illness whose effects may include exacerbation of underlying psychogenic illness." Which is another way of saying, "We have no idea."

Though Paget’s findings [about breast cancer treatment] were correct and incontestable, no one paid any attention to them for about a hundred years, during which time tens of thousands of women were disfigured to a far greater degree than was necessary.

Quite early on, it was realized that radium accumulated in the bones of people exposed to it, but this was thought to be a good thing because it was believed that radiation was wholly beneficial. Radioactive products were liberally added to many medications, with sometimes devastating consequences.

During WW1 it was realized that mustard gas slows the creation of white blood cells. Thus was born chemotherapy. "What is quite remarkable," one cancer specialist told me, "is that we are basically still using mustard gases [as a foundation for chemotherapy]."

The unfortunate bottom line is that breast cancer screening doesn’t save a lot of lives. For every thousand women screened, four will die of breast cancer anyway (either because the cancer was missed or because it was too aggressive to be treated successfully). For every thousand women who are not screened, five will die of breast cancer. So screening saves one life in every thousand.

We have reached the decidedly bizarre point in health care in which pharmaceutical companies are producing drugs that do exactly what they are designed to do but without necessarily doing any good. A case in point is the drug atenolol, a beta-blocker designed to lower blood pressure, which has been widely prescribed since 1976. A study in 2004, involving a total of 24,000 patients, found that atenolol did indeed reduce blood pressure but did not reduce heart attacks or fatalities compared with giving no treatment at all.

We rarely know, for instance, what happens when various medications are taken in combination.

We don’t have any idea why we age, or actually we have lots of ideas; we just don’t know if any of them are correct. … It may be that [multiple] factors work together… Or it may be something else altogether. No one knows.

In sum, it’s clear that telomeres are important not just for understanding aging but also for understanding cancer, but unfortunately we are still a long way from fully understanding either.

Why any animals get it is a question yet to be answered.

Nobody is quite sure what amyloids do for us when they are working properly… How tau proteins relate to amyloids and how both relate to Alzheimer’s are also uncertain…

We can’t even definitively diagnose Alzheimer’s. The only certain way to identify the condition is postmortem…

[Alzheimer’s] is the third most common cause of death among older people… and we have no effective treatment for it at all.

Antioxidants are molecules that neutralize free radicals, so the thinking is that if you take a lot of them in the form of supplements, you can counter the effects of aging. Unfortunately, there is no scientific evidence to support that.

Most of us would almost certainly never have heard of either free radicals or antioxidants if a research chemist in California named Denham Harmon had not, in 1945, read an article about aging in his wife’s Ladies' Home Journal and developed a theory that free radicals and antioxidants are at the heart of human aging. Harman’s idea was never anything more than a hunch, and subsequent research proved it to be wrong, but nonetheless the idea has taken hold and will not go away. The sale of antioxidant supplements alone is now worth well over $2 billion a year.

"It is a massive racket," David Gems of University College London told Nature in 2015. "The reason the notion of oxidation and ageing hangs around is because it is perpetuated by people making money out of it."

"Some studies have even suggested that antioxidant supplements can be harmful", The New York Times has noted. The principal learned journal of the field, Antioxidants and Redox Signaling, noted in 2013 that "antioxidant supplementation did not lower the incidence of many age-associated diseases but, in some cases, increased the risk of death."

According to the analysis, there is evidence of some benefit for just over 40 percent of them. Only 3 percent are ineffective or harmful; a further 6 percent are unlikely to be helpful. But a whopping 50 percent are of unknown effectiveness.