Seth Roberts is the author of The Shangri-La Diet and posts at Seth's Blog about personal science, self-experimentation, and the scientific method.

In 2008, Rachael Hoffman-Dachelet's eight-year-old son started having frequent sore throats. He'd run a fever, feel stiff and tired, and miss a few days of school. After six sore throats in a year, her pediatrician said This is crazy. I'm going to refer you to an ear nose and throat specialist. I think he'll recommend a tonsillectomy (tonsil removal).

Rachael and her son saw the specialist, who did recommend a tonsillectomy. Tonsils are part of the lymphatic system, a network of tiny tubes and nodes all over the body. It is mostly a drainage system. Lymph drains into the tubes, which carry it to the heart, where it reenters the blood. En route to the heart, lymph passes through nodes. How can lymph move through the system if you remove part of it? Rachael asked the specialist. If there were any bad long-term consequences we'd know because so many tonsillectomies have been done, he said. The correct answer is that lymph does not pass through the tonsils. Rachael asked about the benefits of the surgery. Your son will miss a lot less school, he said.

Rachael teaches art at a Minnesota middle school. Her experience with doctors had made her skeptical of their predictions. To decide for herself if a tonsillectomy was a good idea, she googled "pubmed tonsillectomy meta-analysis" and found a Cochrane Review about tonsillectomies and tonsillitis. There are thousands of Cochrane Reviews. Each tries to summarize the evidence about the effect of a treatment on a health problem (e.g., "Antibiotics for sore throats"). They are meant to be practical — to help everyone, including outsiders like Rachael, make treatment decisions (such as "should my son have a tonsillectomy?"). They are produced by the Cochrane Collaboration, a British non-profit, which says its reviews are "internationally recognised as the highest standard in evidence-based health care".

The Cochrane Review that Rachael found ("Tonsillectomy or adeno-tonsillectomy versus non-surgical treatment for chronic/recurrent acute tonsillitis") was published in 2009. It describes four experiments that compared tonsillectomy to the care a sick child would otherwise receive. All four involved children like Rachael's son, and all four had similar results: Tonsillectomies had only a small benefit. (Contrary to what Rachael was told.) During the year after random assignment to treatment — the point at which some children had their tonsils removed, other children did not — children whose tonsils were removed had one less sore throat than children who were not operated on (two instead of three for children like Rachael's son). Because the benefits were small, the decision was easy. "The time, expense, and risk of surgery vs. one [sore throat]," Rachael wrote on my blog, "Not a tough choice."

Rachael believes "when things are going badly with your body, nutrition is a good place to start" looking for help. After she decided against tonsillectomy, Rachael and her son went to see a naturopath that a neighbor had recommended. The naturopath was especially knowledgeable about nutrition and supplements. After an hour interview, she suggested Vitamin D3 (5000 IU/day), a multivitamin, Vitamin C (500 mg/day), and powdered larch bark. Rachael searched for research about these recommendations. She found many studies that suggested Vitamin D might help. Her son is a pale redhead and used sunblock a lot. It was easy to believe he wasn't getting enough Vitamin D. Because Vitamin D won't work properly without other vitamins (called co-factors), a multivitamin was a good idea. Rachael found studies that implied that a multivitamin was very unlikely to be very harmful. She found few relevant studies about Vitamin C. Maybe extreme claims about its benefits had scared off researchers — "Linus Pauling burned that bridge," said Rachael. But she took the Vitamin C recommendation seriously because the naturopath had made other reasonable recommendations, the recommended dose was not large, Vitamin C is easily excreted in urine (in contrast to building up in the body), and Rachael had never heard of anyone having trouble at that dose. The naturopath had said that larch bark had reduced ear infections in children with chronic ear infections. A little bit of theory supported this, Rachael found, but overall the larch-bark research was "dodgy," she said. A considerable virtue of the naturopath's recommendations was that if they didn't work or had bad effects, you could stop them (e.g., stop taking Vitamin D). A tonsillectomy is forever.

As it happened, the larch bark tasted awful and her son only took it for a few days. He took Vitamin C for a month or two. He still takes Vitamin D3 and a multivitamin. Because he took the Vitamin D3 at 7 am, maybe it improved his sleep (and better sleep = better immune function). He had no more sore throats.

Tonsillectomies are ancient and, as the ear nose and throat doctor said, very common. "For much of the twentieth century," says this book,"tonsillectomy (generally with adenoidectomy) was the most common surgical procedure in the United States." They are still very common. In 2006, half a million were done just in America.

What do tonsils do? Tonsils, like other parts of the lymphatic system, contain large numbers of lymphocytes. Lymphocytes are usually called a type of white blood cell, but that is misleading because relatively few are in the blood. Almost all your lymphocytes are in your lymphatic system, which is why they're called lymphocytes. As recently as the 1950s, their function was unknown. In 1953, for example, this ignorance was called "a disgraceful gap in medical knowledge". Failure to understand what lymphocytes do made it unclear what tonsils do. It is dangerous, to say the least, to cut off part of the body whose function you don't know. In spite of this, tonsillectomies were extremely popular from the 1920s through the 1940s. Tens of millions were done.

Around 1900, America started to have frequent polio epidemics. Starting in 1916, they happened every summer, which came to be called "polio season". Over the years, they got worse. In 1951, thousands of children died, and tens of thousands were crippled. The level of fear can be seen from a booklet called Polio Pointers for 1951. Along with practical advice ("keep [your children] away from new people"), it tried to reassure: "Remember — at least half of polio patients get well without any crippling." As both tonsillectomies and polio increased, a horrifying correlation emerged: Children who'd had a tonsillectomy were more likely to get a certain type of polio (infection of the bulbar region of the brain stem) than children who had not had a tonsillectomy. This became common knowledge. Polio Pointers said "don't have mouth or throat operations during a polio outbreak." In 1954, the American Journal of Public Health ran an editorial summarizing the link between tonsillectomy and polio. The main evidence was that within a group of children with polio, the ones with bulbar polio were about three times more likely to have had their tonsils removed than the ones with spinal polio (infection of the spinal cord). This resembles some of the first evidence connecting smoking and lung cancer: Hospital patients with lung cancer were much more likely to be heavy smokers than hospital patients with other diseases. Although Polio Pointers implied that tonsillectomies were unsafe only "during a polio outbreak," this was false. The data implied they were always unsafe: "This higher proportion of bulbar cases in tonsillectomized persons occurs at all ages regardless of the time elapsed since operation," said the editorial. A 1957 paper about the tonsillectomy/polio association cited 19 studies that had observed it. "The association is generally regarded as an underlying causal relationship," said the paper, meaning that the usual explanation was that tonsillectomy increased risk of bulbar polio. The paper found more evidence for this explanation. Researchers considered other explanations for the polio/tonsillectomy association (for example, are tonsillectomies more common among rich children? among sickly children? ) but failed to find supporting evidence. The tonsillectomy/polio connection is probably why tonsillectomies became less popular starting in the 1950s. They declined from extremely common (the most common of any operation) to very common (the most common operation done on children).

By 1960, the tonsillectomy/polio association was firmly established, but its explanation was a mystery. If it reflected cause and effect, why would tonsils protect against infection? Around this time, work by James Gowans and others started to answer this question by figuring out that lymphocytes are the main cells of our immune system. They detect bacteria and viruses and make antibodies against them. T cells, B cells, and natural killer (NK) cells — all lymphocytes. In one experiment, Gowans and his co-workers drained the lymphocytes from rats. The rats lost the ability to make antibodies. When the researchers put the lymphocytes back into the rats, they regained the ability to make antibodies. That's just an example. Our understanding of what lymphocytes do comes from thousands of experiments.

When the function of lymphocytes became clear, the lymphatic system made much more sense. Lymph washes germs out of tissue and into lymph nodes, where lymphocytes detect and try to kill them. The high density of lymphocytes in the nodes ensures that germs will bump into them and be detected. When lymphocytes detect more germs than usual, they multiply and the nodes enlarge. Tonsils do not filter lymph, as I said, but like lymph nodes are full of lymphocytes. Their shape and placement causes them to sample the bacteria in your mouth, so they protect you against the bacteria in your mouth. Tonsils become swollen and sore during infections because the number of lymphocytes inside has increased — the lymphocytes are fighting off the infection. These facts about the immune system and the lymphatic system, including the function of lymphocytes, are part of high school biology. For example, this lecture.

Removal of your tonsils is removal of part of your immune system. Our understanding of the immune system implies that removal of tonsils reduces ability to fight off infection. We cannot say exactly what tonsils do, just as we cannot say exactly what many parts of the brain do, but our general understanding of the immune system (based on thousands of experiments) implies that removal of any part of it is very dangerous, just as our general understanding of the brain (based on thousands of experiments) implies that removal of any part of it is very dangerous. When a child gets a sore throat, it suggests that his immune system is not doing a good job fighting off infections; a better-functioning system would have killed the germs sooner. Cutting off part of the body that fights infections because of too many infections makes as much sense as getting rid of fire houses because of too many fires. If your outcome measure is narrow, you may conclude that damaging a vital organ is beneficial. For example, prefrontal lobotomies were once claimed to be a a good thing (some people became less disruptive). In rare cases, the benefits of removing part of a vital organ may outweigh the risks. If I were in intractable pain, I might agree to have part of my brain removed. But not because of six sore throats.

The tonsillectomy/polio association was the first large batch of evidence that tonsillectomies do serious harm. The studies that showed what lymphocytes do was the second large batch — so large and clear that tonsillectomies should have stopped. But they didn't, and the evidence that they do serious damage has increased. In recent years, they have been repeatedly associated with obesity. A 2011 review of nine articles found that "a large population of normal and overweight children undergoing [adeno-tonsillectomy — removal of both adenoids and tonsils] gained a greater than expected amount of weight postoperatively." Another study concluded "risk of overweight should be mentioned as a probable undesirable outcome of adenotonsillectomy." A third study points in the same direction. To see more evidence, search "obesity tonsillectomy".

Another recent association is with heart attacks. A 2011 study found that people who had had tonsillectomies before age 20 had a much higher rate of heart attacks (about 50% higher) than matched controls over the next twenty years. The study cites other evidence that immune dysfunction increases heart attacks. The same study found that hernia operations at a young age were not associated with heart attacks. A 2010 study based on different people found that "tonsillectomy before age 7 years was associated with a 1.5-fold increase in mortality" from age 18 to 44. This supports the association of tonsillectomies with a large percentage increase in a common cause of death (heart attacks). That tonsillectomies increase heart attacks is made more plausible by the well-established association of gum disease and heart disease. Gum disease is caused by bacteria in the mouth; tonsils protect against bacteria in the mouth.

After Rachael read the Cochrane Review about tonsillectomies, she decided they're a bad idea. This is like Vladimir Putin's party getting only 49% of the vote in the recent election in spite of ballot stuffing. Cochrane Reviews are supposed to be unbiased, but this one omitted (without saying so) a great deal of anti-tonsillectomy information:

1. It does not say that tonsils are part of the immune system, nor that removing the tonsils damages the immune system. It says nothing about lymphocytes and their function. It does not say that the tonsils are full of lymphocytes. It does not say that the nodes of the lymphatic system, including the tonsils, are the main places the immune system does its work.

2. It says nothing about the tonsillectomy/polio association. It says nothing about the tonsillectomy/obesity association.

3. "Those who choose surgery for themselves or their child must be fully informed of the risks of the procedure," say the authors. I agree. Do the authors follow the advice they give to others? Here is how they answer the question "what are the risks of [tonsillectomy] surgery?": "Tonsillectomy is associated with a small but significant degree of morbidity in the form of primary and secondary haemorrhage and, even with good analgesia, is particularly uncomfortable for adults." That's their whole answer.

If you search tonsillectomy/adverse effects on PubMed, you will get more than 1000 references. There is no sign in the review that the authors did that search or any other search for bad effects of tonsillectomies. If the authors had looked at the PubMed articles published before their review (about 900), they would have learned that the risks of tonsillectomy include polio, weight gain, vomiting (many articles), taste distortion (here, here, here), Hodgkin's disease (here, here, here, here, here, but here is evidence that disputes the association), Creutzfeld-Jacob disease (e.g., here, here), inflammatory bowel disease and Crohn's disease, rheumatoid arthritis, severe spine infection, neck infection (here, here), speech problems (here, here), hearing loss, ear pain, visual loss (here, here), depression, several other serious problems, and immunological abnormalities (e.g., here, here, here). They would have learned that tonsillectomy "is associated with a relatively high risk of postoperative complications" and that "the actual post-tonsillectomy haemorrhage rate is much higher than that recorded in hospital statistics." (The Cochrane Review says this risk is "small".) They would have learned, if they didn't already know, that "the tonsils have a large immune function."

4. At the end of the review, it says, "If adeno-/tonsillectomy has an effect on aspects of an individual's health other than sore throats – general well-being, for example – these outcomes should also be evaluated." "If"? This is misleading. By 2009, as I've shown, there was plenty of evidence of bad effects.

The Cochrane Review deserves credit for summarizing some relevant evidence. It deserves criticism for silently omitting a large amount of anti-tonsillectomy information (polio, lymphocytes, obesity, and so on) and posing as a reasonable guide to the value of tonsillectomies. (It comes with a "plain language summary" that says nothing about omitted information.) The review is by Martin Burton and Paul Glasziou, both at Oxford at the time. Both declined to comment for this post on my criticisms. Burton now heads the United Kingdom Cochrane Centre. Glasziou specializes in evidence-based medicine (which I have criticized). He has co-authored a book on systematic reviews and a consumer's guide to evidence-based medicine. He now heads the Centre for Research in Evidence-Based Practice at Bond University in Australia.

Any review must omit information. The Cochrane Review, however, omits a vast amount of anti-tonsillectomy information that could easily have been included. It does not omit a vast amount of pro-tonsillectomy information. There has been no series of devastating epidemics in which tonsillectomy was associated with less disability and death. There have not been thousands of experiments that imply tonsils reduce resistance to infection. In that sense, the review is badly biased. One reason may be conflict of interest. Burton is an ear nose and throat surgeon; he does tonsillectomies for a living. This is not disclosed in the review. I don't know if his finances depend on how many tonsillectomies he does, but I am sure he has done many of them (biasing him to think they are good) and has many tonsillectomy surgeons among his friends and colleagues. He must care what they think. Negative comments about tonsillectomies would surely displease them. Burton declined to comment on this criticism.

In its omission of anti-tonsillectomy information, the Cochrane Review reflects this area of medicine. While doing research for this post, I was unable to find a single instance in which any doctor — including pediatricians, ear nose and throat doctors, and tonsillectomy surgeons — or doctor-run website told any parent (or anyone else) anything like the truth about the risks of tonsillectomies. On the Mayo Clinic website, for example, a pediatrician tells parents that "the decision to remove a child's tonsils must be weighed against the risks of anesthesia and bleeding, as well as the missed school days to recover from the procedure." That's all he says about risks.

False claims about tonsillectomies are nothing new. In 1933, an American writer named Kenneth Roberts (no relation) visited England. His shoulder started to hurt. It became so painful he had trouble sleeping. He consulted a London surgeon, who recommended a tonsillectomy:

"Then you think this pain in my shoulders is due to my tonsils?" I asked him. "My dear boy!" he expostulated. "Of course! You're poisoned! It might crop out anywhere! Arms, legs, body, head, feet, brain — positively anywhere! Not an instant to lose, my dear boy."

Roberts encountered similar behavior by other doctors. His account of it is called "It Must Be Your Tonsils". Given this history (overstatement of the benefits of tonsillectomy), it is especially remarkable that the Cochrane Review is so biased. Professional groups are worse. The American Academy of Otolaryngology-Head and Neck Surgery currently recommends that "children who have three or more tonsillar infections a year undergo a tonsillectomy". The corresponding Canadian group has a higher threshold: six infections in a year. Those are low bars for cutting off part of a vital organ. Both groups claim that a good solution to too many infections may be removal of part of the body that fights infection.

Overtreatment — wasteful and harmful medicine — is an enormous problem. It is the subject of two recent books (Overtreated and Overdiagnosed) and a Newsweek article. Tonsillectomies are an example. The last sixty years have produced a mountain of anti-tonsillectomy evidence (polio, lymphocytes, obesity, heart attacks, and so on) that doctors, such as the Cochrane reviewers, seem to ignore. People like Rachael suggest a solution: help non-doctors look at evidence.