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Bunny Vision

ctreed's picture

For years mothers have told their children to eattheir vegetables.  When it came tothose odd orange ones called carrots, they often gave the reason that eatingcarrots would improve eyesight, especially vision in the dark – just likerabbits.  By some this isconsidered an old wives’ tale, others think of the link between vitamin A andeyesight and dutifully eat their carrots. The story of carrots being linked to good eyesight first became widespreadin Britain during World War II. Coinciding with more successes at shooting down enemy bombers, newsstories appeared in Britain crediting a special new diet with an increasedamount of carrots as improving the night vision and therefore effectiveness ofthe Royal Air Force pilots like John “Cat Eyes” Cunningham.  People were also encouraged to eatcarrots to help them see in the dark during blackouts.  The story took off and successfullydiverted attention away from what the British Air Ministry had not wanted tobecome common knowledge – they had developed and put to use AirborneInterception Radar [1]. 

However, the link between carrots and good eyesightis not entirely unfounded. Carrots, along with other leafy green vegetables, are rich in beta-carotene,a precursor form of vitamin A.  Inthe small intestine, the beta-carotene is made into vitamin A [2], which inturn is converted to rhodopsin, the light sensitive pigment responsible forvision in dim light [3]. 

Sufficient amounts of vitamin A are thereforenecessary to keep the retina, and other parts of the eye working normally[2].  A deficiency in vitamin Aleads to a multitude of eye problems. Initially it leads to night blindness or nyctalopia, an inability “todiscern contrasting images under low lighting conditions” [4].  More severe deficiency leads to “dryingof the tear ducts (xerophthalmia) and ulceration of the cornea (keratomalacia)resulting in blindness” [2]. 

In regard to night blindness, maintaining abalanced died that includes enough vitamin A, or taking supplements is noted toaid in prevention, as it would lower a person’s risk of deficiency [4].  A study to this effect was conducted in1998 by a group of Johns Hopkins researchers.  They studied 30,000 South Asian women who were believed tobe in danger of developing vitamin deficiencies due to the nature of theirdiet.  “A group that receivedvitamin A tablets had 67% fewer cases of night blindness than a group thatreceived a placebo” [7].  Takingvitamin A supplements appears to be quite effective in reversing the deficiencythat results in night blindness. 

It has also been suggested that beta-carotene andvitamin A supplements may lower the risk of macular degeneration [5].  One source does indeed list eating anantioxidant-rich died including “leafy greens, fruits and other vegetables” asa preventative measure since they are essential for healthy eyes [6].  This source also states that theAge-Related Eye Disease Study found that taking supplements including, amongmany other components, beta-carotene, produced a 25% decrease in “the risk ofprogressing to moderate or severe vision loss”, and “for people with moderateto advanced macular degeneration, the findings from AREDS indicate that takinghigh doses of zinc, beta-carotene, and vitamins C & E is effective inreducing the risk of further vision loss” [6].  It is unclear whether vitamin A deficiency is a cause ofmacular degeneration, however, poor nutrition was cited as a risk factor [6].

Another study from March 2003 [8] discounted theeffectiveness of beta-carotene alone in preventing the deterioration ofeyesight through macular degeneration. The study divided over 21,000 male physicians into two groups.  Over a period of twelve years, onegroup took 50mg of beta-carotene every other day, and the other group took aplacebo in the same fashion.  Thedifference in numbers of doctors that developed macular degeneration betweenthe groups was not statistically significant, suggesting that beta-carotene maynot be as vital as previously thought [9]. 

The most direct answer to the carrot question comesin form of an experiment conducted by Dr. Andrew Rochford to see ifspecifically eating carrots, rather than taking a supplement of some kind,would directly improve his vision. He had his vision checked before starting, and then preceded to eatfifteen kilograms of carrots in a period of ten days.  After having his eyes checked again, Dr. Rochford learnedthat his eyesight had not changed at all, and concluded that “unless you aredeficient in vitamin A, carrots won’t help you see better in the dark”[10]. 

In the interest of accuracy to observations, itappears a revision is in order.  Eating carrots is definitely good for you, and vitamin A is important tomaintaining healthy eyes (though toxic in large amounts of its retinol form)[2], but it will not necessarily improve your night vision.  On the other hand, if the story thatcarrots help you see in the dark gets kids to eat their vegetables, perhaps itshould be left alone. 


Works Cited