A lot of you may have heard many times from your parents that carrot can improve your eyesight. When I was young, I sometimes refused to eat carrot, and in order to encourage me to eat carrot, my parents used to tell me that carrot will improve my eyesight. I did not question if this correlation (eating carrots leads to a better eyesight) is true when I was young, but now because I learned that I need to be more skeptical and question any causation relationships that we think are true, especially those that are with no science behind them. Furthermore, now that I have a better understanding on how correlations like these can be false even if they a big number of people acknowledge it, I decided to do a research about the causation (eating carrots improves vision).
Null Hypothesis: Carrots do not improve eyesight.
Alternative Hypothesis: Carrots do improve eyesight.
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According to an article in American Scientific website, carrots have a component called beta-carotene that is very useful for your eyesight. When you eat carrot, your body processes the beta-carotene in the carrot and use it to make vitamin A, which, the article claims, is proven to help your “eye convert light into a signal that can be transmitted to the brain,” which helps you see at night, but when your body does not make enough vitamin A, your vision eyesight becomes weak and will not be able to see at night.
The article mentions that a randomized control study in 2005 was done to test what is the best amount of carrots to eat to have maintain a good eyesight and whether or not carrot is the best way to improve eyesight. The study gave its participants 4.5 ounces of cooked carrots each day and for six days a week. The study has also used other food that had vitamin A components and used vitamin A supplement in the experiment. The study results found that female participants eyesight has improved to the normal level. The study has also noticed that vitamin A supplements did a better job than carrots in improving these women eyesight to the normal level. while it is true that a randomized control study provides strong evidence, the study did not mention many detail such as the results of the study when done on males nor did it mention the number of participants in the study. The study also did not mention if there were any soft points measured so that we know if the study could suffer from the Texas Shooter Problem. And in order to know if the results are correct we still need to do further research into the topic and also look for meta-analysis studies.
In addition, a study done by researchers at the University of Helsinki has conducted an experiment on whether or not beta-carotene helps improve eyesight and if yes, what amount of beta-carotene the body needs to be able to process in order to improve the eyesight of people. The experiment results showed that 20 mg. of beta-carotene given on daily basis has improved the visual acuity of 1,200 males and has also reduced cataract formation.
This study’s results are consistent with the alternative hypothesis and serve as strong evidence because of the big number of subjects being tested and also because it was a control trial (participants were given the same amount of beta-carotene). However, the study did not mention any other detail on how the experiment was done, for example, if it is a randomized double-blind placebo trial, number of participants, or what other variables were blocked out when doing the experiment. Furthermore, the study did not mention if the results were the same when it tested females, which suggests that the study results may suffer from the File Drawer Problem. However, it is highly unlikely that the results will differ when the experiment is done on females because there is no evidence or mechanism that says that women have a different eyesight system or that the results were due to chance or due to third variables because of the large number of people tested and the other meta-analysis studies that showed similar results. Additionally, the study does not seem to suffer from the Texas Shooter Problem because the study has only studied few things.
The article claims that giving vitamin A or beta-carotene to people in countries, such as Nepal or India where people suffer from vitamin A deficiencies has resulted in an improvement in their night vision, which some may argue that this could serve as an evidence for the hypothesis do improve eyesight. However, this improvement was only noticed in people who suffered from vitamin A deficiencies and has only helped them have normal vision and not a strong vision, which suggests that eating carrots could only help maintain a normal vision by providing you with vitamin A, but cannot improve your vision if your vision is normal.
Another article suggests that eating carrots can improve your night vision only if you suffer from vitamin A deficiencies, but if your vision is already normal, then carrot or any other vitamin A sources will do nothing to your eye. Furthermore, eating a lot of carrot, can dangerous as an article claims that a lot of Vitamin A can be dangerous to your body if you are already eating a balanced diet.
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Additionally, an article written by By Karl S. Kruszelnicki claims that the “myth” that carrots improve eyesight came from a rumor that was invented by the UK Royal Air Force ( RAF) to mislead the public and other countries from the truth about their RAF pilots ability to fly at night. They attributed their ability to clearly see at night to eating lots of carrots. However, the RAF has actually wanted to hide their use of what was considered a new technology back then called radar. However, this was discovered decades later, so the false truth about carrots ability to improve eyesight has spread all over the world and mane have believed it. This single anecdote shows how anecdotes are powerful in convincing big numbers of people without even having any science to prove if they were correct, false positive, or false negative.
Another study in the 1990s that was also done in Australia studied the deteriorating night vision in older people who took a lot of vitamin A. the results of the study for the participants who claimed that they ate more carrots, showed no improvement in their eyesight, which is also consistent with the other studies results that stated that if your eyesight is normal, then eating a lot of carrots will not improve your them. While it is right that the study did not mention more detail on how the study was done, we will believe the results because of their consistency with other results from the other studies.
Here is an article for ANOTHER meta-analysis studies that also say that carrot do help maintain eyesight, but do not improve them. The article talked about two experiments each studies thousands of people and suggest similar results to the other studies in the post, however, the article did not mention many detail on how the studies were done.
Here is a video that gives a similar explanation to why carrots do not improve your eyesight.
In addition, it is highly unlikely that these studies would have suffered from the Confirmation Bias problem, because of the big number of meta-analysis studies that were done and the strong evidence and mechanism suggested in the study. Not to mention that there could be more studies done on the hypothesis being tested and found out results that were consistent with the null hypothesis but did not publish them due to the File Drawer Problem.
Bottom Line: Many studies have showed strong evidence that carrots do not improve eyesight or vision if your eyesight is normal; however, studies showed that carrots do help maintain your vision indirectly, due to the beta-carotene component, which helps your body produce more vitamin A to help you see at night. Additionally, the studies results could be due to chance or due to other third variables, but because of the many well-done meta-analysis studies done on the hypothesis, the results were most likely to be correct.
In addition, if you are looking for the best way to maintain good eyes, then carrots are not the best choice, as there are many studies that confirmed that carrots are good for eyes only because of vitamin A, which, According to this article, can be found by bigger amounts in other fruit or vegetables such as sweet potatoes, dark leafy greens and, lettuce. Furthermore, vitamin A can also be found in fish