Since we were children, our parents have told us that eating vegetables would make us as strong as our favorite superhero. Specifically, our parents would tell some of us that eating carrots would give us 20/20 vision. How true is this statement? After growing up eating plates full of carrots, I was still given a prescription for glasses a few years ago. I decided that this question needed some further research in order to determine if eating carrots caused an improvement in one’s eyesight.
Before I began searching the internet and critically thinking through all of the information I would find, I wanted to think about the null hypothesis and the alternative hypothesis.
The null hypothesis in this case would be there eating carrots do not improve eyesight. The alternative hypothesis would state that eating carrots does improve eyesight. When scientists conduct experiments and research, they use the null and alternative hypothesis to create a conclusion to their findings. As Andrew taught us in class, if scientists conclude that the null hypothesis is false (reject the null), meaning carrots do improve eyesight, but in reality carrots do not, then this is called a false positive. In science there is a 5% chance of this happening. On the other hand, if a scientist concludes that the null hypothesis is indeed true (accept the null), meaning carrots do not improve eyesight, and in reality they do improve eyesight, this is called a false negative.
After doing research, I found that carrots, and other organically-colored orange foods, are high in Vitamin A. It was said that Vitamin A plays a critical role in supporting strong eyes and those that have a Vitamin A deficiency could lead to a condition known as Keratomalacia. With this condition, one could experience incredibly dry eyes, night blindness, and other symptoms.
A randomized, control study in Nepal was conducted in 2005, and published in the American Journal of Clinical Nutrition, where pregnant woman were given different types of locally grown Vitamin A foods, such as carrots and goat liver, in addition to a Vitamin A supplement, and then tested for the affect on their night vision. The pregnant and blind woman were randomly assigned to many different combinations of foods and high/low dose vitamin A supplements. The control group in this study were non-blind woman. A control group of blind, pregnant woman was not used due to unethical practices; pregnant woman in Nepal are more susceptible to death when pregnant and night blind, therefore they must use non-blind woman in order to reduce risk. (Side note: this unethical control group practice reminded me of the class where Andrew talked about childhood cancers, and that it is unethical to place a child in a control group for a clinical cancer treatment.) The control group was not given any other Vitamin A foods or supplements that what they already regularly consumed.
The conclusion of the study found that there was no clear different between a Vitamin A supplement versus regular, Vitamin A rich foods on the affect of night blindness in pregnant woman. Although, the study did find that Vitamin A as a whole did improve eyesight in the woman being tested. The study above contains strong evidence, where about 100% of night blind woman reported improvement in their eyesight after consuming Vitamin A.
(Picture source: http://ajcn.nutrition.org/content/81/2/461/F4.large.jpg)
In conclusion, I think it is safe to say that Vitamin A can help improve eyesight when included in a normal diet. Although this study was conducted in Nepal, where vitamin A rich foods may be more scarce than here in the United States, the study controlled for that variable. They brought food and supplements to the woman in different villages, allowing them access to this nutrition.
Next time you load up your plate at the dinner table, it may be wise to add a few more carrots to your plate!