A new study by the National Cancer Institute has revealed that a seaweed extract called carrageenan can prevent human papillomavirus (HPV) -- a sexually transmitted disease linked to cervical cancer -- from entering human cells.

Researchers found that carrageenan -- derived from red algae -- strongly inhibits HPV from attaching to human cells, which prevents it from entering and infecting the cells. "We were floored by how much better it worked than anything else we have tested," said researcher John Schiller of the National Cancer Institute.

Carrageenan is already in use in sexual lubricants as a thickener, and researchers hope to eventually develop the seaweed extract into an inexpensive gel that could help curb the spread of HPV, which infects 50 percent of sexually active women between the ages of 18 and 22.

An inexpensive gel would compete with Merck's new HPV vaccine called Gardasil. An influential U.S. advisory panel recently advised all 11- and 12-year-old girls to be vaccinated with Gardasil, which is nearly 100 percent effective against the most dangerous strains of HPV. However, the three-course Gardasil vaccination costs $360, which many people cannot afford, especially in developing countries.

The researchers said carrageenan was shown to somewhat affect HIV and herpes, but that genital HPV was a thousand times more susceptible to the seaweed extract. While Gardasil comes with possible side effects including pain, swelling, erythema (redness of the skin), pruritus (itching) and fever, carrageenan is widely used in baby formula as a thickener, and is completely safe to ingest.