WELLINGTON, New Zealand » The story of a Salvadoran fisherman who says he survived more than a year adrift on the Pacific Ocean raises many medical questions. The Associated Press spoke with Claude Piantadosi, a professor of medicine at Duke University and author of the book "The Biology of Human Survival," to find out what is physically possible and for his view on the tale of Jose Salvador Alvarenga. This is an edited version of the interview:

Question: How long can a human survive without any water or without any food?

Answer: The average is about 100 hours without water and about five or six weeks without food. You can survive much longer with just a little food, although you’ll lose weight and run into vitamin deficiency problems. So it would have been vital for Alvarenga to have collected both food and water during his journey. The Pacific’s regular squalls would have provided some rainwater that he could have scooped from the bottom of his boat.

Q: How important is shade?

A: Absolutely critical. You get significantly warmer in direct sunlight and sweat more. The pictures of the boat show a Fiberglas box in the middle which he could have sheltered in, and any type of canvas would have helped keep him out of the sun.

Q: Alvarenga described catching turtles, fish and birds with his hands and eating them. Is that plausible?

A: Over time the underside of the boat would have become its own ecosystem as barnacles, seaweed and jellyfish collected there, which in turn attracts other creatures. How often can you grab a turtle or catch a fish with your bare hands? I don’t know. Bird blood is no more salty than human blood, so would have provided some hydration.

Q: Without fruit and vegetables, wouldn’t he have developed scurvy?

A: Actually, unlike humans, birds and turtles make their own vitamin C, so fresh meat from those creatures, especially the livers, would provide sufficient vitamin C to prevent scurvy. British sailors used to get scurvy because they ate preserved meat which had oxidized and lost its vitamin C.

Q: There’s some suggestion that Alvarenga was a large man before he left. Would being overweight provide an advantage?

A: It would be a significant advantage. He could live off his own body fat and muscle for a long time, so long as he was able to get some water, vitamins, micronutrients and a little protein.

Q: Didn’t he look too healthy, even a little bloated, when he arrived?

A: The appearances of malnutrition can manifest differently depending on how short you are on calories or protein. Some underfed children in Africa look like stick figures; others get swollen. It’s only in end stage starvation that people get that really emaciated appearance.

Q: Alvarenga seemed to give confused and contradictory answers to authorities. What kind of psychological effects would such a journey have?

A: I’m not an expert in psychiatry, but we all have the feature of resilience. It can be trained or even learned on the fly. For instance, soldiers learn to deal with combat horrors. Presumably he was out on the ocean every day as a fisherman before he went missing, so he would have been familiar with the environment and with adapting his behavior to the elements.

If he had nutritional deficiencies, he may have developed some dementia or other syndromes which compromised his mental state. I’m not surprised that some of the answers he gave were a bit off and he wasn’t able to remember things.

Q: How long would it take to recover from a voyage like this?

A: Hydration can be restored in just a day or two. Re-feeding can be tricky after a long period of starvation, as the body can lose the ability to absorb nutrients. Muscle rehabilitation and physical therapy can take several weeks.

Q: Bottom line — is Alvarenga’s story plausible?

A: Yes. It’s unusual to say the least. But reports out of Mexico indicate he did go missing in late 2012. As we have gotten more information, it’s probably likely that he did survive at sea for 13 months.