Washington, Caipirinha, and the Scientific Method

Let’s start with George Washington—specifically, with his death. The first president of the United States died of what was then diagnosed as “quinsy” (literally “dog strangulation”) at the end of the 18th century. Today, historians believe that diagnosis likely referred to a throat infection caused by bacteria. Something that today would be easily treated with antibiotics and resolved within days. But medicine back then was a very different story.

In the mid-18th century, medicine attributed all diseases to an imbalance of the “humors.” It was believed that the human body contained four fluids, or “humors”: blood, phlegm, yellow bile, and black bile. Each corresponded to one of the four elements of nature—earth, fire, air, and water—and to the seasons of the year.

When these humors were out of balance, a person became ill. To cure them, physicians sought to restore balance. If one humor was in excess, the solution was to eliminate the surplus—to “purge” the body. At the time, doctors had no knowledge of hygiene, nutrition, sanitation, human anatomy, microorganisms, or infectious disease.

So when Washington was diagnosed with quinsy, his doctors decided the best treatment was a poultice of beetles applied to his throat, along with bloodletting. Bloodletting and the use of purgatives to induce vomiting or diarrhea were standard practices to “balance the humors.” Washington lost 2.5 liters of blood through this therapy. Considering the average adult has around 5.5 liters of blood, the treatment almost certainly hastened his death.

This is where the recurring idea that ancient or “millenary” treatments are valid just because they’re old and imbued with the “wisdom” of our ancestors falls apart—when we take a serious look at what medicine was like before the scientific knowledge accumulated in the past 200 years.

Thanks to science, we rapidly advanced our understanding of disease mechanisms and microorganisms. Today we enjoy treatments and medicines unimaginable in times when “traditional” was the only option. Before vaccines were discovered in the early 19th century, one in five children died before the age of five, mostly from infectious diseases. A simple cut or scratch could be fatal for a strong, healthy adult before antibiotics.

But how does this work? How does science validate medicines and treatments? For that, let’s go back further, to the mid-18th century. James Lind and the First Clinical Trial

In 1746, James Lind, an experienced surgeon in charge of the crew on HMS Salisbury of the British Navy, quietly made history. Even today, few people know his name. Yet he was probably the first to apply the scientific method to investigate the cause of a disease.

During the Age of Exploration, the British Navy lost more sailors to scurvy—a disease caused by vitamin C deficiency—than to war. Nobody knew about vitamins or their role in health, let alone that fruits contain them. At the time, all diseases were thought to result from humoral imbalance. (And shockingly, some “millenary practices” still use this logic today.)

Lind questioned this reasoning. As ship’s doctor, he saw that bleeding sailors didn’t help. So he dug into old ship logs and noticed lower rates of scurvy on vessels that carried fresh fruits and vegetables.

He then conducted his first experiment with 12 sailors in advanced stages of scurvy. He divided them into six groups of two, all receiving the same basic diet, housed in the same conditions, and given the same care. Two sailors were given a quarter pint of cider per day. Two received vitriol (a sulfur-based solution). Another pair took vinegar, another pair 150 ml of seawater. One pair was given one lemon and two oranges a day, and the last pair got nutmeg.

The result—obvious to us today but shocking then—was that the citrus fruit group recovered within days.

What Lind had done was essentially the first controlled clinical trial. He randomly divided patients into groups, gave each group a different “remedy,” and kept all other conditions equal. Today, such a study would be refined into the gold standard: a randomized, double-blind, placebo-controlled clinical trial.

A placebo group—something Lind did not include—would have received an inert substance, like water. “Double-blind” means neither doctors nor patients know who gets the real treatment and who gets the placebo, reducing psychological or emotional bias in results.

Many studies of alternative practices don’t meet these standards but are still published in low-quality journals. That’s why, to know if something really works, we rely on systematic reviews and meta-analyses—studies that pool large numbers of trials, separate them by scientific rigor, and exclude those that fail basic quality criteria.

Years later, Lind’s approach helped inspire Scottish physician Alexander Hamilton, who tested bloodletting with proper controls. He divided patients randomly: one group treated with bloodletting, the other untreated. The bloodletting group had a death rate ten times higher.

So now we see what George Washington and the scientific method have in common. But where does the caipirinha come in? From Scurvy to Limeys (and Cocktails)

It still took 40 years for the British Navy to adopt citrus fruits as a scurvy cure. Lind’s discovery was met with skepticism by the medical community.

Scurvy continued to kill sailors until 1795, when Sir Gilbert Blane, the Navy’s chief physician, decided to revisit Lind’s idea. On a 23-week voyage to India, he ordered that every sailor be given a daily drink of water, sugar, lime juice, and rum.

The drink worked—it kept the sailors scurvy-free and was an instant hit. From then on, British ships were required to carry limes and lemons, and the sailors earned the nickname Limeys.

And so, science not only cured scurvy but also gave us the prototype for the daiquiri, the mojito—and the caipirinha.
✍️ Natalia Pasternak is a researcher at the Institute of Biomedical Sciences at the University of São Paulo (USP), national coordinator of Pint of Science Brazil, and president of the Instituto Questão de Ciência.