Takaki returned to Japan in November 1880, and soon became director of the Tokyo Naval Hospital. The navy was growing but the beriberi problem was as bad as ever. There were so many patients in the summer that they overflowed the hospitals and had to be carted into nearby temples.

“Such conditions used to strike my heart cold whenever I came to think of the future of our empire,” he wrote, “because if such a state of health went on without discovering the cause and treatment of beriberi, our navy would be of no use in time of need.”

Takaki resolved to end the crisis. “If the cause of this condition is discovered by someone outside of Japan, it would be dishonorable,” he told the emperor.

The Naval Medical Bureau had only collected the most basic of statistics between 1872 and 1877—treatment results, lists of known diseases and the names of hospitalized patients. From 1878, practitioners added facts about non-hospitalized patients and hygiene, but it wasn’t until 1884 that a truly holistic approach to record-keeping took hold.

There wasn’t enough data for Takaki to really investigate the disease, so he started from zero.

In February 1882, Takaki became vice-director of the Naval Medical Bureau. He was now in a position to investigate beriberi in the fleet. He compiled everything he knew about the disease.

Beriberi was more prevalent at the end of spring to summer, but occurred at some level throughout the year. It affected both ships and bases, skipping some units entirely. And the state of quarters and clothing seemed to have no impact on the disease.

Looking more broadly, Takaki noted that sailors from higher social classes rarely came down with beriberi. The disease mainly struck large cities … smaller towns sporadically.

Takaki rejected Western doctors’ hypothesis that beriberi resulted from “high temperature, moisture, marshy air, over-crowding, hard labors, nervous exhaustion, coarse food, etc.” All navies had to contend with these conditions, but the beriberi problem was seemingly unique to the Japanese.

Takaki began to suspect the navy diet. He petitioned the navy ministry to give him a broad remit to investigate the problem—but the navy was skeptical. The German-trained doctors at the elite Tokyo Imperial University all pointed to a microbiological cause.

Falling back on his Satsuma connections, Takaki finally managed to persuade the ministry to approve an investigation into the navy’s great shame.

Takaki surveyed living conditions, including the length of the workday, sanitation, clothing and diet. In the data he spotted a “great deal of difference” in sailors’ eating habits. Cross-referencing similar British studies, he finally pinpointed the culprit—protein deficiency.

The proof is in the eating

Sailors were consuming too many carbohydrates. Earlier German research had demonstrated that a healthy diet required at least one unit of protein per 15 units of carbohydrates. By contrast, the average Japanese sailor ate one unit of protein per 28 units of carbs.

“The greater the difference in these proportions the more beriberi occurred, and the lesser the difference the less,” Takaki noted. He had cracked the beriberi secret. To improve the health of its men, the Imperial Japanese Navy simply had to ensure they ate better.

But the navy was having none of it. Officers recalled the unrest that had hit the Italian navy after a change of diet—and they defended the current money-based system.

Under this system, ships’ crews were required to buy their food from the galley. Only white rice was free. Officers had the money to afford a more nutritious diet while sailors frequently resorted to surviving just on the free rice.

Takaki fought hard to institute fixed diets—but the navy resisted, saying it would double the cost of feeding crews.

Takaki became the director of the Naval Medical Bureau in October 1883. His biggest break soon followed—a telegram that read, “Many patients, voyage impossible, send money.”

The telegram was from Ryujo, a Japanese naval vessel on a training cruise around the Pacific Rim. Ryujo eventually returned from her voyage with 25 dead sailors on her manifest. Forty-five percent of her 376-strong crew had developed beriberi.

It sent a shock through the Ministry of the Navy … and all eyes turned to Takaki.

He asked the navy to give him control of the diet aboard Tsukuba, another vessel about to set out on a training voyage. He demanded the Tsukuba follow the same route as Ryujo to minimize the variables of time and location.

Takaki asked his fellow Satsuma statesmen to secure Imperial backing. He met with the emperor and explained his theory. “We must investigate the cause of this disease, and if we should succeed in preventing this condition it would be a great honor for the Japanese people,” Takaki said.

With Imperial assent and money from the Ministry of Finance, Takaki assigned Tsukuba a simple set of rules to ensure that sailors kept to a 1:15 ratio of protein to carbohydrates. The navy ministry formalized the new food system on Nov. 29, 1883, and Takaki issued a detailed handbook to the fleet in February 1884.

Tsukuba set out on Feb. 2, 1884. Takaki was uneasy. He had promised the emperor success—his life was on the line. “I would have immediately committed harakiri, begging pardon for the great mistake,” he said when asked what he would have done in the event of failure.

But Takaki needn’t have worried. A telegram followed in September. “Not one patient; set your mind at ease.” The ship returned on Nov. 16 with incredible results reminiscent of the British success with the HMS Suffolk.

Only 14 of the 333 sailors aboard the Tsukuba had suffered from beriberi. Those 14 had not been eating their food rations properly.

Tsukuba’s voyage cemented support for Takaki throughout the navy. Within one year, the incidence of beriberi dropped by 94 percent and deaths from the disease ceased.

Takaki had also improved the general health of the fleet. Better-nourished crews were suffering from 50-percent less overall disease and injury.

Unpalatable solutions

Takaki had identified the nutritional causes of beriberi and reduced the disease significantly, but some sailors were still succumbing. The reason—finicky eating and socially-constructed ideas of “good” food.

The navy gave sailors bread and biscuits to boost the protein in their diets. Rumors spread that the sailors only had to eat the soft doughy parts of the bread to improve their health, and so many sailors threw the crust overboard, luring flocks of seagulls to the ships … and sending Takaki back to the drawing board.

In March 1885, he instituted his solution—protein-rich barley mixed with rice. Many of the enlisted personnel in the navy came from the lowest strata of Japanese society. They grew up in poor villages on a diet of brown rice and millet.

Too poor to eat fish and vegetables, the highest they could aspire to was the all-you-can-eat polished white rice of the navy and army. These sailors resisted a return to a poor man’s diet.

“By last year’s experience, we have found that most of the men dislike meat as well as bread, and we do not know what we shall do next,” Takaki said. “But if we leave the matter to their own choice, we shall certainly have a great many cases of beriberi as has hitherto been the case.”

But Takaki also faced severe criticism from army doctors and academics.

The Japanese Imperial Army—with its close ties to the Prussian army and German-style medical practice—continued to believe beriberi was an infectious disease even after Takaki’s successes.

For thousands of years, diseases had been seen through the lens of kampo, traditional Chinese herbal medicine. In kampo, disease was caused by heat or evils and was treated with herbal remedies.

Sometimes the medicine was hokey, but other times it worked—as was the case with azuki and barley supplements for beriberi. But many Japanese now viewed kampo as backward and even shameful. Likewise, they considered Takaki’s prescription archaic nonsense, owing to its kampo roots.

Takaki’s statistical claims sometimes fell on deaf ears. The establishment was more comfortable with laboratory experiments and cold detachment from the human element of medicine. Takaki’s success, they argued, was due to the sanitation benefits of living on a warship, where everything could be disinfected.

Sanitation, white rice, experimental medicine—this is what it meant to be modern in Meiji-era Japan.

While it dismissed Takaki’s theory, the army was acutely aware of its own beriberi problem. “In the army the severity of beriberi fluctuated from year to year,” army surgeon Tadanori Ishiguro said, “but among all diseases it was the most prevalent and correspondingly produced the most deaths.”

“Since it is so widespread in the army, the urgent matter at hand for military physicians is to research, prevent and treat this illness,” Ishiguro added.

But the army dealt with its beriberi problem very differently than the navy did. The ground branch’s insistence on a microbiological cause led it to focus on sanitation—but all the sanitation in the world wouldn’t give their soldiers the dose of vitamin B1 they needed to survive.