Necessary for good eyesight and skin health, Vitamin A is one of our most essential nutritional requirements.
Ask anyone where to get it— your middle school health teacher, your local nutritionist, or Livestrong.com, and you’ll be given the same answer: "Carrots, along with other orange and red vegetables are a source of vitamin A."
But is this revered refreshment of Bugs Bunny himself really the remedy for all your nutritional needs?
Unfortunately not. Because there is no vitamin A in carrots.
Beta Carotene
The FDA itself says one serving of carrots has 110% of the RDA of vitamin A.
However, carrots don't have vitamin A any more than dry ice is made of water.
How could they get away with such a blatant lie?
Because carrots contain a compound that is kind of like vitamin A. But it's not equivalent to vitamin A.
This sort-of-vitamin A is better known as beta-carotene. Most people use beta-carotene and vitamin A interchangeably; however they are not in fact the same thing.
So what exactly is vitamin A, and how does it differ from beta-carotene?
Retinol
Vitamin A refers to a group of molecules called “retinoids,” which include retinol and retinal. These compounds, also called "pre-formed vitamin A", are used directly by the body (hence “pre-formed”— they are already formed and ready to go as-is)
Given their structural similarities, people often refer to all of them as "vitamin A".
These compounds are exclusively found in the diet from foods of animal origin, and comprise the actual molecules used as vitamin A in the body.
Conversely, plant foods contain only beta-carotene, which must undergo a biological transformation before it can be used as vitamin A in the body.
And that’s how you get “carrots have vitamin A”. They actually have beta-carotene, but the FDA lets people call it vitamin A as well.
So why is the food industry allowed to use them interchangeably when talking about the nutrient content of vegetables?
Conversion
Beta-carotene is sometimes called *pro-*vitamin A. The reason being that to a certain extent and under the right conditions it can be converted by humans into actual pre-formed vitamin A (retinol).
This conversion process is highly variable, somewhat poorly understood, and dependent on a number of factors; including the amount of fat you ingest along with it, your DNA, and your current levels of vitamin A.
Estimates for conversion efficiency are around 9-22%, and the efficiency of the conversion decreases the more vitamin A you have (p. 86 of Dietary Reference Intakes).
Further, there is significant “interindividual variation of beta-carotene conversion efficiency, possibly due to genetic polymorphisms." Aka, some people are inherently better at converting it than others.
Generally, you can understand this conversion as a mechanism designed to protect your body from egregious vitamin A deficiency, and not a way to fully load your body with vitamin A.
With this understanding, it’s clear that equating beta-carotene and vitamin A is a pretty tenuous undertaking.
Yet that doesn’t stop them. The FDA invented this thing called "Retinal Activity Equivalence (RAE)", which is used to translate between beta-carotene and pre-formed vitamin A based on this expected conversion percentage.
This is the mechanism by which the FDA allows beta-carotene content to be labeled as "vitamin A". When you look at the RDA of vitamin A for carrots, for example, it's actually beta-carotene measured in RAE (the amount of pre-formed vitamin A you're "expected" to get after your body converts it).
Of course, those details are omitted from the label, and since it’s not a simple equation that applies the same to all people, this practice is deceptive at best.
It's like if you went to buy a car, and you picked out the model, wired the money, and when it's time to get the keys, the dealer gives you four wheels, an engine, a chassis, and a box of spare parts.
Technically, everything needed to make the car is there, but most of you won't actually be able to assemble those parts into a complete car, and if you can, it might take a long time and break soon after.
However, they can argue that it isn’t “lying” in the strictest sense, and people will continue to be misled about the amount of vitamin A they’re eating.
Why should we care
The main takeaway from the above is that we are not getting enough vitamin A, even if we think we are.
Despite following the FDA's RDA, if the "vitamin A" you're eating is beta-carotene, you are most likely not getting enough due to overestimated conversion.
This is a significant problem, since vitamin A is extremely important.
Bad skin, bad eyesight, improper fetal development, immune failure, reproductive problems, etc. can all be caused by vitamin A deficiency.
And the RDA is only designed to prevent deficiency– the proper amount for optimal health is unclear, and is most likely much higher.
So even if you think you’re doing everything “right”, it’s very likely you’re deficient in this importan nutrient.
What can we do?
If vitamin A is so important, and its intake so underestimated, we must increase our dietary intake, specifically from sources of actual vitamin A.
Unsurprisingly, these all come from the nutrient-dense animal foods that makeup the foundation of any health diet:
While most of the nutrient-dense animal foods in that article are high in vitamin A, a few foods particularly standout:
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