When it comes to vitamin A, kidney warriors start to think of their renal vitamin and supplements. Vitamin A is not commonly discussed when it comes to kidney health and nutrition goals… why is that? If looking into a supplement of vitamin A, kidney warrior beware.
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What is vitamin A?
Vitamin A is a fat-soluble vitamin. It is also known as retinol, retinal, or retinoic acid. You may be familiar with the term retinol in some skincare products. The precursor for vitamin A is beta-carotene, which is used in the body to create vitamin A.
As a fat-soluble vitamin, vitamin A requires fat in our diet for it to be absorbed into our bloodstream. The liver stores vitamin A for us. The kidneys do not play a role in vitamin A digestion or metabolism.
What does vitamin A do for us?
Vitamin A is generally known as the “eye vitamin.” Did your parents ever tell you to eat carrots when you were little so you could see in the dark? Vitamin A plays an important in vision as helping us to see from light to dark.
Besides vision, vitamin A is also known for its role in immune function. Vitamin A is an antioxidant and can help protect cells against free radicals. Free radicals are molecules we can get from radiation, smoke, even in normal metabolism and breakdowns of foods. Free radicals have been linked to diseases like cancer.
Vitamin A also helps with healthy skin, hair, nails, and bone health.
How much vitamin A do I need?
In general, the recommended amount of vitamin A for adult men is 900 mcg RAE (retinol activity equivalents) and 700 mcg RAE for women per day. The Tolerable Upper-Level intake, which can be thought of as the amount tested that will be unlikely to have harmful health effects, is 3,000 mcg per day for adults
It’s important to note here that those in the United States and other developed countries get plenty of vitamin A from their diet. A diet low in vitamin A is uncommon here. Vitamin A deficiency is seen in children and women in underdeveloped countries.
But vitamin A kidney needs are different. For those with chronic kidney disease, vitamin A supplements are not something that is promoted or encouraged.
How do I know how much vitamin A I have?
Two types of tests are available to determine how much vitamin A you have. There is a testing of the retinol-binding protein that is available to take care of your vitamin A. There is also a serum blood test that looks at actual vitamin A amounts of retinol.
An indicator of low vitamin A levels would be a retinol test result below 15 mcg/dL.
What happens if I don’t get enough vitamin A?
The most common symptom of vitamin A deficiency is night blindness. This can be tested with your eye doctor (optometrist) to see if the amount of vitamin A you have is able to help you see well enough at night and when transitioning from light to dark areas.
Again, this is mostly uncommon in the United States and other developed countries.
What happens if I get too much vitamin A?
Excessive intake of vitamin A can cause nausea, vomiting, vertigo, and blurry vision.
Highly excessive vitamin A intake – more than 10,000 mcg per day – can cause advanced health complications such as
- Bone thinning
- Liver damage
- Joint pain
- Birth defects
Don’t forget about the other kidney-specific nutrient that affects our bone health!
Is there a vitamin A kidney stones correlation?
There is a possible association that a diet with more vitamin A has been connected to more calcium stones. This may be related to how vitamin A is part of bone formation and breakdown, but the connection has not been studied enough.
One study found that those with calcium stones seemed to have a diet higher in vitamin A, whereas those with uric acid stones did not have the same correlation.
However, another study done on rats found that after a lithogenic diet, a group with a supplement of vitamin A, kidney filtration had improved. But again- this was a study on rats, not humans.
Will too much vitamin A hurt my kidneys?
While excessive amounts of vitamin A don’t appear to have a direct effect on your kidneys, a study found that end-stage kidney failure patients on hemodialysis had high calcium levels as a result of taking a multivitamin that included vitamin A.
If you have hypercalcemia, otherwise known as high calcium levels in the blood, review your supplements and talk with your doctor about the potential causes. Excessive vitamin A could be part of it, but there are other more common reasons for high calcium levels, including too much vitamin D.
Another study including children with chronic kidney disease not on dialysis found that for every 10% drop in eGFR, there was a 13% increase in vitamin A levels. It’s important to note that those with higher levels of vitamin A in their system had achieved it from supplements.
Where do we find vitamin A in our diet?
There are two types of vitamin A found in the diet. The first is known as preformed vitamin A, otherwise known as retinol. This can be found in animal products such as meat, poultry, fish, and dairy products. The preformed vitamin A is also what is in supplements and fortified foods.
The second type is provitamin A, also known as beta-carotene. This is technically not vitamin A, but is converted to vitamin A retinal and then retinol, in our body.
Vitamin A-Rich Foods: Vegan
Even though animal meats have vitamin A, so do plants! There are plenty of plants and vegan foods that have the provitamin A that the body can use.
|Vegetables||Vitamin A in a 1/2 cup serving|
|Sweet Potato, cooked||960 mcg|
|Winter Squash, cooked||268 mcg|
|Kale, cooked||86 mcg|
|Collards, cooked||361 mcg|
|Turnip Greens, cooked||275 mcg|
|Carrot, cooked||665 mcg|
|Sweet Red Pepper, raw||117 mcg|
|Swiss Chard, raw||55 mcg|
|Spinach, raw||71 mcg|
|Romaine Lettuce, raw||103 mcg|
|Fruits||Vitamin A in a 1/2 cup serving|
|Passion Fruit||76 mcg|
Again, our liver does an excellent job of storing vitamin A. The United States does not have a high risk of vitamin A deficiency. Considering the liver is where our vitamin A is stored, it makes sense that foods from liver would have very high levels of vitamin A!
Fun fact: Eating a polar bear liver would kill a person! I learned that during my undergrad… a “fun” fact I’ll never forget!
Should I get a vitamin A supplement if I have kidney disease?
You should only get a vitamin A supplement if your doctor or dietitian has directed you to take one. They should also provide guidelines for the dosing of vitamin A you need, and routinely assess your vitamin A levels to make sure you don’t get too much.
In general, a vitamin A supplement is contraindicated if you have chronic kidney disease. But what about renal vitamins?
Do renal vitamins have vitamin A?
Check your vitamin to see how much vitamin A it contains. Ideally, it should be little to none. Prorenal, for example, has no vitamin A included.
Renal vitamins are specifically designed to replete certain vitamins that those with chronic kidney disease may not get enough of, or lose through dialysis. Here is an article that includes a nice comparison of different types of renal vitamins and the nutrients they contain. See any vitamin A? Nope.
In general, those with chronic kidney disease should not be on a vitamin A supplement. This can increase your risk of high calcium levels as well as other health complications. Only take supplements under the direction and supervision of your doctor and dietitian.
If you are interested in taking a vitamin, a kidney-specific vitamin such as a renal vitamin may be the best place to start. But be sure to talk with your doctor or dietitian before starting anything new!
Interested in learning more about your best kidney health? Check out our Plant-Powered Kidneys online course, where students learn what optimal kidney health and nutrition needs are to keep their kidneys thriving!