This week, we will turn our attention to our first vitamin: vitamin A.  Up until this point, we have covered all sorts of nutrients found in our food from macro to micro.  Now, we will turn our attention to the substances you can find in a multivitamin.  Remember, a vitamin supplement can provide some of what you need, but not all of your nutritional needs - only a balanced and varied diet can do this. 

Supplements become an important part of our health when we cannot meet our needs with diet alone.  Take a moment to review some of the common causes of nutrient depletion as well as the symptoms of nutrient deficiency if you like. 

As we explore vitamins and minerals over the remainder of this year, try to avoid the impulse to run out and start making supplement purchases.  Instead, focus on the food sources of nutrients, consider tracking your nutritional intake to assess your current status, talk with your healthcare team if you believe you may have additional nutritional needs, and be sure to thoroughly evaluate any potential supplements and their manufacturers before making a purchase; there are a lot of people and companies looking to turn a profit, which at times means putting their bottom line before quality and safety - the flashier the product and the bigger the claims, the more scrutiny is needed. 

On to vitamin A!

What is Vitamin A:

Vitamin A isn’t actually just one substance.  It is a group of fat-soluble vitamins found in animals (retinol) and plants (carotenoids).

Once inside an animal body, vitamin A is found as retinol, retinal, and retinoic acid.  It is found concentrated in our livers.  When needed, vitamin A is released from the liver, bound to a protein and delivered to the needed tissues through the bloodstream. 

What Does Vitamin A Do:

Vitamin A plays multiple important roles in the body.  

Vision:

Many of us probably associate carrots with eye health.  This is due to their high content of beta carotene - a vitamin A precursor.  We do see vitamin A playing a vital role in vision, and vitamin A deficiency is the leading cause of blindness worldwide!

Vitamin A in the form of trans-retinol is found abundantly in the retina.  When you see the term trans in biochemistry, we are effectively referring to a bend in the molecule.  The opposite bend is referred to as cis; sound familiar?  When a photon of light hits vitamin A in the retina the bend will change.  This physical change in structure triggers a chain of events that end up with a nerve signal traveling through the optic nerve into the brain and our perception of sight!  All from a tiny bend in a molecule of vitamin A.

Vitamin A is especially important for our ability to see in low-light conditions and the detection of motion, making it especially valuable for night vision and driving in dark conditions. 

Immune Health: 

Vitamin A is necessary for our immune cells to scout for possible infection, alert other cells to an infection, and initiate the cascade of events that results in our ability to fight an infection and develop immunity.  No vitamin A - no immune response.  Studies have shown that providing vitamin A drops along with vaccinations help children develop immunity - especially when children are malnourished. 

Growth and Development: 

During fetal development, vitamin A excess and deficiency have both been shown to cause birth defects.  Balanced levels of vitamin A are especially important for the development of the internal organs including the heart, eyes, and lungs.  Vitamin A plays a role in the creation of the extracellular matrix - the complex collection of proteins between cells that provide the structure of an organ and where communication between cells occurs. 

Red Blood Cell Production: 

Vitamin A has been shown to help red blood cell precursor cells (stem cells) develop into mature functional oxygen carriers.  We also see vitamin A having a role in moving iron from storage sites into red blood cells and increasing their oxygen carrying capacity.  Vitamin A is now being seen as an important part of the treatment of anemia that has often been overlooked. 

Disease Prevention: 

Vitamin A supplementation has been successfully used to encourage the development and health of the lungs, eyes, and gastrointestinal tracts of premature infants.  Rates of a quite common chronic illness known as bronchopulmonary dysplasia were significantly reduced in infants treated with injections of vitamin A during their ICU stays. 

Overall illness and death in children seems to be related to vitamin A levels.  The better their vitamin A status, the less illness and injury. 

Additionally, measles infections have been shown to be significantly less severe when children received doses of Vitamin A as part of their treatment. 

Finally, for those at high risk of lung cancer, supplementation with vitamin A has been shown to reduce the overall risk. 

Disease Treatment: 

Please note, using vitamin A at high doses must be monitored closely to prevent liver damage.  Do not self-treat any conditions with high dose vitamin A without the support of your doctor.  This information is provided for your education and to encourage you to have a conversation with your physician.  

Diseases that have been shown to respond to vitamin A treatment include: 

• Acute Promyelocytic Leukemia

• Psoriasis

• Acne

• Retinitis pigmentosa

Where to Find Vitamin A: 

Vitamin A is a relatively easy to obtain nutrient.  

Animal Sources: 

• Liver (all forms including fish)

• Cod liver oil

• Eggs

• Butter

• milk

Plant Sources: 

• Fortified cereals

• Sweet potatoes

• Pumpkin

• Carrot

• Cantaloupe

• Mango

• Spinach

• Collards

• Kale

• Broccoli

• Squash - butternut and others 

Applications:

The average adult requires between 900 and 700 micrograms of Vitamin A daily. This amount is easily obtained in a single ½ cup serving of cooked pumpkin or sweet potato. 

Most multivitamins sold in North America contain around 900 micrograms or 100% of the recommended dose.

Toxicity is an issue to be taken seriously and tends to be an issue with people consuming around 8-10,000 micrograms daily over an extended period of time.  

“Acute vitamin A toxicity is relatively rare, and symptoms include nausea, headache, fatigue, loss of appetite, dizziness, dry skin, desquamation, and cerebral edema. Signs of chronic toxicity include dry itchy skin, desquamation, anorexia, weight loss, headache, cerebral edema, enlarged liver, enlarged spleen, anemia, and bone and joint pain. Also, symptoms of vitamin A toxicity in infants include bulging fontanels. Severe cases of hypervitaminosis A may result in liver damage, hemorrhage, and coma.” (1)

Problems with vitamin A toxicity tend to arise with prolonged high level supplementation and retinol-based acne treatments.  Most cases of high level supplementation are associated with those taking multiple complex formulas over a long period of time.  It’s important to take into account how much of each nutrient you are supplementing across your different products.  I’ve seen unethical prescribing in effect several times over the course of my career and helped many people heal through reducing or eliminating their supplements. 

Watch for exploitative prescribing practices among providers recommending supplementation!

In my practice, I rarely recommend vitamin A supplementation on its own and have done so only at the onset of intense viral infections and for a short period of time.  This does not mean supplementing with vitamin A is uncalled for, but it should be done with a good dose of caution. 

Next Week:

Next week, we will begin our exploration of the fat soluble vitamins by discussing vitamin D.  This is always an interesting topic, so be sure to check it out.

To our health!

References: 

Higdon, J, Vitamin A, Linus Pauling Micronutrient Center, 2000, updated 2015, https://lpi.oregonstate.edu/mic/vitamins/vitamin-A accessed 6/9/2021