SOME relationships run aground on the perilous shoals of money, sex or religion. When Shauna James’s new romance hit the rocks, the culprit was wheat.
　　“I went out with one guy who said I seemed really great but he liked bread too much to date me,” said Ms. James, 41, a writer in Seattle who cannot eat gluten, a protein found in wheat, barley and rye.
　　Sharing meals has always been an important courtship ritual and a metaphor for love. But in an age when many people define themselves by what they will eat and what they won’t, dietary differences can put a strain on a romantic relationship. The culinary camps have become so balkanized that some factions consider interdietary dating taboo.
　　No-holds-barred carnivores, for example, may share the view of Anthony Bourdain, who wrote in his book “Kitchen Confidential” that “vegetarians, and their Hezbollah-like splinter faction, the vegans ... are the enemy of everything good and decent in the human spirit.”
　　Returning the compliment, many vegetarians say they cannot date anyone who eats meat. Vegans, who avoid eating not just animals but animal-derived products, take it further, shivering at the thought of kissing someone who has even sipped honey-sweetened tea.
　　Ben Abdalla, 42, a real estate agent in Boca Raton, Fla., said he preferred to date fellow vegetarians because meat eaters smell bad and have low energy.
　　Lisa Romano, 31, a vegan and school psychologist in Belleville, N.Y., said she recently ended a relationship with a man who enjoyed backyard grilling. He had no problem searing her vegan burgers alongside his beef patties, but she found the practice unenlightened and disturbing.
　　Her disapproval “would have become an issue later even if it wasn’t in the beginning,” Ms. Romano said. “I need someone who is ethically on the same page.”
　　While some eaters may elevate morality above hedonism, others are suspicious of anyone who does not give in to the pleasure principle.
　　June Deadrick, 40, a lobbyist in Houston, said she would have a hard time loving a man who did not share her fondness for multicourse meals including wild game and artisanal cheeses. “And I’m talking cheese from a cow, not that awful soy stuff,” she said.
　　Judging from postings at food Web sites like chowhound.com and slashfood.com, people seem more willing to date those who restrict their diet for health or religion rather than mere dislike.
　　Typical sentiments included: “Medical and religious issues I can work around as long as the person is sincere and consistent, but flaky, picky cheaters — no way” and “picky eaters are remarkably unsexy.”
　　Jennifer Esposito, 28, an image consultant who lives in Rye Brook, N.Y., lived for four years with a man who ate only pizza, noodles with butter and the occasional baked potato.