You must understand the problems faced by seamen in the great days of exploration and trade. Ships were at sea for months, and the food situation was atrocious. To quote Willy Ley in Exotic Zoology (1941):
Since the existence of bacteria was still unknown, the relatively simple process of canning food was still in the future. Refrigeration was an impossibility which nobody had ever dreamed of, though on land the ice house was in use. Insect-killing poisons were unknown. So the food on board these ships consisted of heavily oversalted meat, sometimes beef, more often horse meat, dished out with the brine in which it floated. The other staple was hardtack, a bread so dry that no mould could get a root-hold (unless the hardtack was swamped by water and could not be dried out fast enough), and limited quantities of dried beans and peas and lentils which were used up quickly before the weevils got into them.That a ship would lose part of its crew through injury, scurvy, or disease before the end of the voyage was taken for granted. And, of course, hygiene was non-existent, and tropical diseases ubiquitous. On the way to Japan, the Clove had to put it at the Javanese port of Bantam, which was a tropical cesspit, whence the survivors emerged with a new complement of infectious diseases. By the time they reached Japan there were few of them who were not sick.
Not only that, but they had lacked the facilities, and quite probably the desire, to wash either their bodies or their clothing for months, and if there was one thing the Japanese despised, it was filth. Just the same, they were eager to welcome the dirty, smelly, hairy foreigners. "King Foyne" came aboard to greet them, and the following day he returned with his nobleman and their wives and daughters. Now, Captain Saris had a large portfolio of - ahem! - dirty pictures, with which he used to regale honoured guests, and on this occasion he decided to show them to the women. Much to his surprise, however, when they saw, hanging from the wall of his cabin, this pride and joy: a picture of Venus in all her unclothed glory, they fell down and worshiped it. It turned out they were secret Christians, who mistook the naked goddess for the Virgin Mary. (For that matter, Vasco da Gama's crew made the same mistake in bowing to a Hindu idol when they first arrived in India.)
The Japanese had peculiar customs. For a start, their doctors didn't believe in bleeding their patients. Instead, they stuck needles into them (acupuncture).
Justice was enforced with strict surveillance and draconian punishments. On the one hand, curfews and neighbourhood spies kept the population in place. On the other hand, death was inflicted for what would elsewhere be considered minor offences. A sixteen year boy old stole a little boat: off with his head! Execution normally took place immediately after judgment - none of this nonsence about setting a date for the punishment, let alone an appeal, or - unheard of! - a jury. Jacobean Englishmen were familiar with public executions, but the casual violence of Japan took some getting used to. Beheading was regularly followed by the body being hacked to pieces by the samurai testing their swords on it. Bodies lying by the roadside were a common sight, even on that small island.
But there was one peculiar custom which the English decided to copy: cleanliness. A bathroom graced every upper class dwelling, while the lower ranks enjoyed the public bathhouses. The Japanese bathed at least once, and often twice a day (uh!), on each occasion a relaxing steam bath being followed by a cooler one. The English tried it, and it wasn't so bad, so it became a regular habit.
None of the overflowing excrement of English towns affected those of Hirado. Over there special latrines, each with a perfume pan and new paper cut for use were strung along the paved road. They did not smell; the owner would clean them after his guests departed and, in any case, a team of cleaners would come and pay the owner for the privilege of removing the waste for use as fertiliser.
Easy to hire were cooks who, as a matter of course, scrubbed all the household pots and pans. The food was cut up on spotless tables with iron forks, knives, and cleavers in such a way as to avoid any touch of human hands. Should some uncooked food be accidently touched, it would be immediately washed and sterilised. Needless to say, eating with the fingers was not encouraged.
Once the English had adopted these habits - surprise! surprise! - those who were sick (nearly all of them) got better, and stayed better.
And this is where the irony celebrated in the title of this article comes in. The English paid regular visits to the daimyō, and on each occasion an exchange of presents was expected. But then one of the chief merchants, Richard Cocks discovered that his lordship had developed a taste for traditional English cooking - in particular, hearty stews of beef and pork with onions, turnips, and thick gravy.
Thus began a bizarre exchange: Foyne would present Cocks with local fish - yellowtail, red snapper, shellfish and crabs - and Cocks would hand over chunks of two-year-old meat, some of which had travelled all the way from England.Oh well, as the Romans used to say, concerning taste there can be no dispute.
Reference: Giles Milton (2002), Samurai William, the Adventurer Who Unlocked Japan