Kate Middleton and Prince William.
The duchess and her husband were offered to try UNICEF peanut paste bars. William partook but his wife declined, setting off speculation of a pregnancy. Reuters

Kate Middleton set off yet another pregnancy rumor when she refused to sample a bit of peanut paste while on a royal gig in Copenhagen, Denmark's capital.

Judging from the photos, it looks as if the duchess declined a taste of Plumpy'nut, a peanut paste which UNICEF gives to children who are severely malnourished. Prince William tasted a bit.

Plumpy'nut was made by the French company Nutriset in 1996. It contains sugar, vegetable fat, and skimmed milk powder, and is enriched with vitamins and minerals, according to the company's Web site.

Typically, a severely malnourished child will follow a peanut paste treatment programme for a month, before he or she is back to health, UNICEF says on its Web site.

Pregnant women are sometimes advised by doctors to avoid peanuts and peanut products during pregnancy. The duchess is not allergic to nuts, The Sun's royal editor Duncan Larcombe told ABC News.

Her spokesman went out of their way to stress that she has no nut allergy whatsoever, he said.

But could she possibly be allergic to gluten?

Plumpy'Nut contains maltodextrin, according to the non-profit Edesia, which manufactures ready-to-use foods, including this one. Several Web sites on gluten and celiac disease note that maltodextrin is commonly made from wheat in Europe, while in the U.S. it is made from corn, rice, or potato. This has deterred some people who are allergic to gluten to stay away from foods containing maltodextrin.

There is also the possibility that the duchess is lactose-intolerant, as the bar contains milk products. Then again, it could be nothing. She could just be keeping an eye on her slender figure (a Plumpy'nut bar contains 500 calories).

If she is pregnant there'll be absolutely no announcement until three months into her pregnancy, Larcombe told ABC News.

Still, a photo does show Prince William reading the Plumpy'Nut label with a furrowed brow.

When you report on royals often it's the very subtle things that they do which give a lot away, Larcombe said.