Monday, June 07, 2010

How scared should you be of nut allergies?

The wife today was selling nuts and parents kept telling her that nuts were banned in their kids school to prevent deaths from nut allergies. How many life years are saved from banning nuts in schools versus those lost through not eating nuts?

I will look at American figures as they are available and have a large sample, which are both handy. "about 150 people die annually from serious allergic food reactions" which compares with "2,000 children drown each year" according to here. So 150 people out of the 2.5 million who die each year in America die from some food allergy. Imagine all these people had 80 years left to live. You have lost 1200 human years.

Now if you happen to be the one with the allergy you would want some reasonable precautions taken. My argument here is a guesstimate on how the over anxiety about how nuts might affect us.

“We try to relieve anxiety about nut allergy by signs saying, ‘this is a nut free zone,’ which suggests that nuts are a clear and present danger,” Dr. Christakis said. “But in doing so, we increase the anxiety.” So imagine this sort of fear of nuts made everyone stop eating nuts. How many life years would be lost? "those eating nuts daily had up to 60% fewer heart attacks than those who ate nuts less than once per month". Given four hundred and fifty thousand people die each year from heart attacks. Preventing 60% of these would be 270 000 lives. Say you only saved one year off each of these that is 270000 life years as opposed to 1200 from banning nuts. This 60% figure seems really high but other studies show massive improvements here and here says '1 ounce of nuts more than 5 times/week can result in a 25 to 39 percent reduction in coronary heart disease risk among people whose characteristics match those of the general adult U.S. population'.

Now just because people who eat nuts don't get heart attacks does not mean the nuts stop the heart attacks. But the googleable studies take this correlation versus causation problem into account. Also banning nuts in schools and telling kids they might kill people wont stop all nuts being eaten. But its not hard to imagine these warnings will severely curtail nut eating.

Not many kids have nut allergies. So a blanket ban without good reason wont save many lives. There is good evidence eating nuts is very good for your health. It is reasonable to assume telling kids nuts could kill them wont encourage them to eat them.

I think this nut fear illustrates a problem many of us have with comparing sudden risks with long term risks. For example when schools ban running by kids because they might be sued but they ignore the long term health effects of kids not exercising. There are risks everywhere but when someone wants to minimise one it is worth asking how dangerous that risk is and what consequences minimising it will have.

2 comments:

Séan Billings said...

"It is reasonable to assume telling kids nuts could kill them wont encourage them to eat them."

I have to disagree. Most kids think they are immortal and banning something can make it more attractive. Psst. Want to score some dry roasted?

And as for schools banning running to prevent being sued, that is them eliminating a risk to the school while increasing a risk to the child which the school cannot be held responsible for.

red dave said...

Good idea Séan we should make nuts as subversive as possible. Those head shops must be short of stock. That planters peanut guy would make a great frontman for a drug ring.