Fun Post Friday: Fact Checker – Carrots?

Happy Friday, guys!

First things first: After seeing the response to last week’s Fun Post Friday, and realizing how nice it is to end the work week with something less mentally taxing, I’ve officially decided to make Fun Post Friday’s a thing!

With that in mind, I honestly don’t know yet what all these posts will look like – I’ll just try to keep them fun, probably a bit shorter, but still informative.

And with that, let’s dive in to this week’s post!

Since it’s political season… again… (does that season ever end?), it only feels fitting to write a fact checker post about a common claim involving your eyes – carrots!

Claim: Eating Carrots Improves Vision

I’m firmly convinced that this is a parent’s favorite way of convincing their child to eat veggies – especially carrots.  I mean, who wouldn’t want to have bionic vision from eating healthy foods?!

Unfortunately, for all the hopeful parents and children out there, this notion is (almost) completely false!

So, where did it come from?  Supposedly, this myth originated in WWII, after the British Royal Air Force developed a new type of radar technology that allowed them to shoot down German planes at night.  Rather than divulging their newfound technological advancement to the public (which would not be particularly advantageous for *ahem* winning the war…), they reported that the pilots’ “incredible night vision” was due to carrots.

Interestingly enough, however, vitamin A, one of the primary vitamins in carrots, is actually vital for night vision, as it is a precursor molecule for the photopigment rhodopsin.  This pigment is responsible for absorbing light, as part of the phototransduction cascade, in which light is converted to a neurological signal that is then transmitted to the brain.

Additionally, vitamin A is important in maintaining the health of the front surface of your eye.

Hold up.
Now where’s the fact checker – this post is literally disagreeing with itself – right?

Not so fast.
While vitamin A is important for vision, increased consumption will only improve vision in the case of vitamin A deficiencies, which are rare in the United States and other first world countries.  Additionally, excess vitamin A intake can actually be detrimental to your health.

Vitamin A toxicity is a condition that can present either either acutely or chronically, depending on the extent and duration of excess vitamin A intake.  In the acute form, common signs and symptoms are:

  • Drowsiness
  • Irritability
  • Nausea
  • Vomiting

 which may or may not be associated with increased intracranial pressure.

Chronic vitamin A toxicity more commonly presents with:

  • Hair and skin changes
  • Headache
  • Weakness
  • Fractures
  • Pseudotumor cerebri

In both of these, the most concerning presentation is often observable ocularly: increased intracranial pressure/pseudotumor cerebri.

As the name implies, vitamin A can cause increase in the fluid pressure inside the skull.  Since this is a confined space, the increased pressure acts somewhat like a tumor (hence pseudo, or false, tumor). With nowhere else to go, the increased fluid is transmitted through the optic nerve, disrupting the normal layers, and presenting as swelling, or papilledema (by definition swelling of both optic nerves secondary to an increase in intracranial pressure).

Unfortuantely, this swelling of the optic nerve causes compression of the nerve fibers, and, if left untreated, may result in permanent vision loss.

Now, granted, it can be difficult to consume enough carrots to create this type of scenario.  Vitamin A toxicity is more often associated with vitamin A supplement use.  More commonly, an excessive carrot consumption will only turn your skin – specifically in the palms of your hands and soles of your feet – orange (caretenosis).  However (not from personal experience or anything), eating around a pound of carrots/day for three months is a really bad idea.

Takeaway: Vitamin A, which is found in carrots is necessary for vision, but will only improve vision in rare cases of deficiency.  Excess vitamin A intake can result in vitamin A toxicity, which, if left untreated, may cause permanent vision loss.

And there you have it!

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