Why did beriberi strike people eating white rice?
― A warship and a chicken cracked the case

There was no poison in the white rice. What was missing was just a pinch of one nutrient, thrown away with the "bran" during milling. It took Japan and other Asian countries decades — and countless lives — to figure that out.

Only two reasons white rice caused illness

In short, an all-white-rice diet meant "plenty of fuel, but not enough tool to light it." That's easy to say now. At the time, reaching this answer was extraordinarily hard.

Why was the cause so hard to find? ― Disease was assumed to mean "something got in"

The late 19th century was an age when one disease-causing bacterium after another was being discovered. The tuberculosis and cholera bacilli had just been found, and medicine was advancing fast.

So most doctors assumed beriberi, too, must be caused by a germ or a poison. The idea that illness could come from something *missing* wasn't yet widely accepted.

And yet beriberi would sweep through a whole group eating the same food, while showing no sign of spreading person to person. It struck soldiers and students — and anyone given generous rations of white rice — far more than ordinary townspeople.

The first clue came from two warships ― Takaki Kanehiro's voyage experiment

Takaki Kanehiro, a naval doctor who had trained in medicine in England, had noticed that the British Royal Navy had almost no beriberi.

In Japan's navy, the warship Ryūjō made a long ocean voyage from 1882 into the following year. Of its 376 crew, 169 are said to have developed beriberi, and 25 died.

Takaki suspected the diet was to blame. So in 1884 he sent the warship Tsukuba on the same route. The only thing that changed was the food: less white rice, more barley, meat, and milk.

The results: only 14 crew developed beriberi, and none died. And those 14, it's said, were the ones who hadn't eaten some of the new rations. Afterward the navy adopted rice mixed with barley, and beriberi nearly disappeared.

Takaki himself, though, believed the cause was a lack of protein. His remedy was right — but his explanation for why was wrong.

Why didn't the army follow suit?

Army doctors refused to accept Takaki's explanation. A germ theory looked more scientific to them than a remedy with no clear explanation. Among the skeptics was Mori Ōgai, also known as a novelist.

The army kept issuing soldiers six gō (about 900g) of white rice a day. During the Russo-Japanese War, an estimated 250,000 army soldiers developed beriberi, and around 27,000 died — a toll said to rival the number killed in combat.

What the chickens revealed ― something was missing

Around the same time, the Dutch physician Christiaan Eijkman was searching for the cause of beriberi in what is now Indonesia. He was hunting for a germ.

One day, chickens kept at his hospital began wobbling with symptoms much like beriberi. Their feed was leftover white rice from the hospital kitchen.

Then a new administrator arrived and said, "Don't feed military-issue white rice to the chickens," so their feed switched to cheaper brown rice. The chickens recovered.

Eijkman confirmed that a white-rice-only diet caused the illness, and adding back the bran cured it. This was a huge step toward the idea that a disease can arise from something missing in food. He later won a Nobel Prize for this work.

Extracting the culprit from rice bran ― Suzuki Umetarō

In 1910, agricultural chemist Suzuki Umetarō announced that he had extracted a substance effective against beriberi from rice bran. It was later named "Oryzanin."

But when his paper was translated into German, the crucial line stating it was "a new nutrient" is said to have been dropped. As a result, it was the Polish-born chemist Casimir Funk — who named a similar substance "vitamine" the following year — who became widely known around the world instead.

This substance is what we now call vitamin B1.

How big was the shortfall? ― The more you ate, the bigger it got

Here's where reason 2 — "burning rice needs that nutrient" — comes into play. The amount of vitamin B1 the body needs is thought to scale roughly with the energy you eat.

Eat more white rice, and you take in more B1. But your requirement grows by the same proportion. Look at Figure 2: whether it's 3 gō or 6 gō of white rice, it only covers about 43% of what's needed.

This is why the people who ate their fill of white rice were the ones most likely to get beriberi. Soldiers of the era ate few side dishes and relied on rice for energy. The more they ate, the bigger the shortfall grew alongside it.

Summary

Beriberi wasn't caused by anything bad in white rice — it happened because something essential was being thrown away along with the bran. And because eating more rice also raised the requirement, you couldn't fix it just by eating more. The truth only came into focus once three separate lines of research — a warship voyage, chicken observations, and the chemistry of rice bran — converged from entirely different places.

The cause wasn't something present — it was something absent.
Beriberi is the disease that taught humanity that a deficiency, too, can be a disease.

We counted how many grains are in a bowl of rice in "How many grains of rice are in a bowl of rice?" And for how the body burns food for fuel, see "What exactly does a food "calorie" measure?"

※This article is a general-audience science explainer. The figures given are approximate, meant to illustrate the underlying mechanism. Historical casualty numbers vary by source. If you have concerns about your health or diet, please consult a doctor or registered dietitian.