Vitamin A has been given the distinguished honor of kicking off what is sure to be an enlightening series on micronutrients I’ll be writing for you over the next several weeks.
I’ve spent enough time researching the most detailed information available on micronutrients over the years to know that it can get quite dry, boring and painstakingly multisyllabic where we’re going.
But you know I would never subject you to such torturous fare except for when it’s absolutely necessary to do so. Yes, I will have to wax scientific at times in order to adequately communicate the biological processes involved with the body’s utilization of the myriad micronutrients I’ll be breaking down for you.
That said, in the interest of educating you – and saving you from the temptation to throw your smartphone, ipad, tablet or laptop through the nearest window – you have my word that I will keep the scientific prose minimized as much as possible.
As I laid out within the preamble to this series of articles, I want to quickly reiterate how important it is for your health and physical appearance that you gain an appreciation for, and understanding of, the powerful benefits the vitamins and minerals in our foods afford us.
There’s no denying that Americans are largely ignorant to these benefits, as is evidenced by the staggering sums of money spent on processed foods and skyrocketing rates of sickness, disease and obesity running rampant in our country that are showing no signs of reversing course any time soon.
If we are going to take back our collective health it will begin and end with nutrition – and, more specifically, nutritional education.
Carbs, proteins and fats are as far as most people’s nutritional knowledge extends. But the microscopic complexities within the nutritional spectrum of our foods contain a wealth of health-promoting properties for us to learn about, appreciate and benefit from.
I believe that gaining an understanding of these properties will motivate you away from the toxic and nutritionally bankrupt diets that are so prevalent today – leading to obesity, insurmountable medical bills, disease, death and suffering – and towards a diet that promotes optimal health and wellness.
Let’s start this educational journey by diving into the wonderful world of Vitamin A.
If you prefer audio format, you can click the play button below to listen to the podcast I’ve recorded on the topic of vitamin A to hear me talk through everything presented below:
Vitamin A: Basic Overview
The name “Vitamin A” gives the false impression that it’s a single micronutrient. This impression is false because the term “Vitamin A” actually refers to a subset of several different vitamin A nutrients.
These sub-nutrients can be segregated into two main groups: Retinoids and Carotenoids. You’ll want to familiarize with these two foreign-sounding words, because I will be referring to them regularly throughout this article.
Say them with me…
Good. Now let’s quickly look at the distinctions between these two subgroups of vitamin A.
Retinoids are vitamin A nutrients that are found in animal foods, while carotenoids are vitamin A nutrients that are found in plant-based sources.
Again, retinoids are vitamin A nutrients that come from animals. Carotenoids are the vitamin A nutrients that come from plants.
Retinoids and carotenoids each provide the body with unique health benefits. However, the body can actually convert carotenoid forms of vitamin A into retinoid forms.
In general, plant-based sources of carotenoid vitamin A contain a much greater amount of vitamin A nutrients than the animal-based retinoid versions (we’ll talk more about this a little later).
This is enough to give you a basic high level understanding of vitamin A.
But for those reading this who are like me and wish to nerd it out, I’m obliged to explain that the carotenoid group of vitamin A nutrients actually contains two sub-groups of carotenoids: carotenes and xanthophylls.
Below is a table that lists every retinoid version of vitamin A, along with every carotenoid version broken out into the carotene and xanthophylls sub-groups:
At this point, I don’t feel it’s necessary for me to delve into any more detail regarding the subsets of carotenes and xanthophylls. However, I wanted you to know that they do exist because I may briefly refer to them throughout the remainder of this article.
Now that you have a basic overview of vitamin A under your belt, it’s time to look at the benefits of providing our bodies with sufficient amounts of vitamin A.
As I mentioned earlier, the retinoid (from animals) and carotenoid (from plants) versions of vitamin A provide unique health benefits, so I will address them individually.
Benefits of Vitamin A Retinoids
When discussing the benefits of vitamin A retinoids it’s important to note that the bodies of healthy individuals can convert carotenoids into retinoid forms. Since they can be converted into retinoid forms of vitamin A, carotenoids inherently possess the ability to provide all the benefits that are credited to retinoids.
However, it doesn’t work the other way around, as retinoid forms of vitamin A cannot be converted into carotenoid forms of vitamin A.
To kickoff the benefits of vitamin A retinoids, let’s look at a familiar example of this carotenoid-to-retinoid conversion in action.
Retinoid Vitamin A Supports Vision Health
Many of us were taught as kids that carrots are great for our eyes because they contain vitamin A. This is actually a misnomer. Well, sort of.
It’s true that carrots support vision health. And it’s true that vitamin A is responsible for this.
But, the vitamin A carrots provide is of the plant-based carotenoid variety, which provides no known benefit for vision health. It is the conversion of the carotenoids in carrots into retinoid vitamin A that is responsible for carrots being given such esteemed eye-health status.
There may be a litany of yet unknown ways that vitamin A supports the eyes. What is currently known, however, indicates that vitamin A enhances visual acuity by increasing the ability of the rod cells within the retina to detect light, as follows:
The human retina contains four kinds of photopigments that store vitamin A compounds. One of these pigments, called rhodopsin, is located in the rod cells of the retina. Rhodopsin allows the rod cells to detect small amounts of light, and, thus, plays a fundamental role in the adaptation of the eye to low-light conditions and night vision.
Retinal, a retinoid form of vitamin A, aids in the synthesis of rhodopsin, and in the series of chemical reactions that causes visual excitation, which is triggered by light striking the rod cells.1
This is how vitamin A promotes eye health (as we know it today). By using retinoid vitamin A to make the rod cells more sensitive to photons, we are able to see better at night and under low-lighted conditions.
Who knows? Maybe if one pounded back enough carrots they would eventually build up enough rhodopsin that they’d develop an organic form of night vision.
Either way, I’d bet our kids would eat carrots like Skittles if they believed there was even a remote possibility of it being true.
Even though carrots provide carotenoid vitamin A nutrients, the body is able to convert them into retinoids (like retinal). And this is how carrots, containing carotenoid vitamin A, provide us with the retinal our eyes need to function optimally.
Retinoid Vitamin A Fights Cancer
As I previously reported on the Craig Leonard Fitness Natural News site, a recent study was published in the International Journal of Oncology that provides new evidence for the healing properties associated with retinoid forms of vitamin A.
The study was performed by Sandra V. Fernandez, Ph.D., Assistant Research Professor of Medical Oncology at Thomas Jefferson University, and colleagues, where they used a model of breast cancer progression composed of four types of cells, each one representing a different stage of breast cancer: normal, pre-cancerous, cancerous and fully aggressive.
When the researchers exposed the four breast cell types to different concentrations of retinoic acid – a retinoid form of vitamin A – they noticed a strong change in the pre-cancerous cells.
Not only did the pre-cancerous cells begin to look more like normal cells in terms of their shape, they also changed their genetic signature back to normal.
Unfortunately, the retinoic acid seemingly had little or no effect on the cells that had advanced beyond being pre-cancerous.
Nevertheless, this effect that retinoic acid had on pre-cancerous cells in this study holds a lot of promise for vitamin A being a powerful nutrient in the fight against cancer, particularly as a preventative agent.2
Retinoid Vitamin A May Promote Skin Health and Prevent Infertility
I say that retinoid vitamin A may promote skin health and prevent infertility because, as wikipedia points out, the science surrounding vitamin A and skin health is still shrouded in uncertainty and is mostly inconclusive.
As it pertains to preventing infertility, the cited study published on the same wikipedia page was performed on rats, not humans. While there’s some degree of mammalian biological similarities between rats and humans, far too many studies have shown inconsistencies between the way rat biology reacts to certain conditions when compared to humans.
Still, there is promise that the retinoid form of vitamin A may one day be shown to help teenagers with acne, prevent wrinkles as we age, and maintain our ability to grow a family by preventing infertility.
The latter could prove to be a lifesaver for many, as the Mayo Clinic estimates that 15% of all couples are struggling with infertility.3
So far we’ve seen how vitamin A – in its retinoid forms – can enhance our ability to see, keep us cancer free, and may even hold promise in terms of enhancing our skin health and preventing infertility.
Studies are still being conducted to verify all the ways retinoids may benefit humans. However, it’s believed that vitamin A retinoids may play a role in the prevention and/or treatment of:
- Atopic Dermatitis
- Cystic Fibrosis
- Dry Eyes
- Impotence (Lack of Sperm Production)
- Inflammaotory Bowel Disease
- Ear Infections
- Poor vision
- Premature Delivery
- Thyroid disorders
- Varicose veins
- Viral infections 1
Benefits of Vitamin A Carotenoids
Before we consider the benefits of carotenoid vitamin A sources, I want to remind you that carotenoid sources of vitamin A hold the potential to provide all of the benefits already covered by being converted to retinoid versions, making carotenoids what I’d consider to be the preferred source of vitamin A.
Beta Carotene Linked To Improved Cognitive Function
A randomized trial of beta carotene supplementation and cognitive function was conducted by Harvard Medical School to determine if supplementing with beta carotene had any impact on preserving cognitive ability in its male participants.
It’s established science that oxidative stress is a contributor to cognitive decline (and the aging process in general). Therefore, it would logically follow that providing the body with increased antioxidants to fight this oxidative stress would serve to offset this undesirable effect.
The aforementioned study confirmed this hypothesis as a sample set of more than 4,000 participants supplementing with beta carotene for a mean duration of 18 years had cognition markers that were “significantly higher” than those in the placebo group.7
Interestingly, it appears that the ability of beta carotene to preserve brain function is proportional to the number of years it’s supplied to the body in adequate quantities.
Study participants that supplemented with beta carotene for a mean duration of 1 year received no discernible cognitive benefit from doing so.
If anything, this points to the importance of being consistent with eating nutrient dense foods. The benefits of eating a healthful diet will only compound as time goes by.
Alpha Carotene Stymies Cancer and Gives Heart Disease a Beat Down
In a 2011 study conducted by researchers from the Centers for Disease Control and Prevention, and published in the Archives of Internal Medicine, people with the highest blood levels of alpha carotene were 39 percent less likely to die over the course of the 18-year study than those with the lowest levels.
When talking about death, a 39% improvement is a big deal!
Specifically, the greatest effect was seen through lowered death rates from heart disease and cancer. Also of particular note is that alpha-carotene-rich foods appeared to protect against lung cancer better than any other vegetables did.2
Carotenes Support Immune Function
Carotenes support immune function by stimulating the production of white blood cells.
As we are taught in middle school, white blood cells are a critical immune system component that help determine overall immune system strength. In fact, our ability to fight off potentially harmful pathogens is directly tied to our body’s ability to efficiently produce white blood cells.
White blood cells attack and eliminate harmful bacteria, viruses, cancer cells, and yeast inside the body.
Carotenes also improve the communication between cells which results in fewer cell mutations, again pointing to the cancer-preventing benefit of vitamin A.8
There are a number of other benefits that are thought to be derived from carotenes, though science has yet to definitively substantiate them. Here’s a list of other potential benefits that are believed to have some veracity within the naturopathic and/or conventional medicine communities:
- Improves asthma symptoms
- Slows age related macular degeneration (AMD)
- Helps to overcome substance addiction, including alcoholism
- Fights depression
- Prevents cataracts
- Promotes healthy blood pressure levels
- Slows the onset of Parkinson’s disease symptoms
- Improves the pain caused by rheumatoid arthritis 9
The benefits of vitamin A I’ve covered so far ought to be enough to convince you of how important vitamin A is in our quest to live with optimal health.
But, just to make sure, let’s quickly cover what can happen if you don’t get enough vitamin A and become vitamin A deficient.
Symptoms of Vitamin A Deficiency
In case it isn’t obvious, I want to make clear that having a vitamin A deficiency will preclude you from gaining any of the benefits linked to vitamin A I discussed above (cancer prevention, enhanced vision health, preserved cognitive function, bolstered immunity and reduced risk of heart disease).
More than that, though, being deficient in vitamin A can also lead to the onset of a number of undesirable conditions, including the possibility of death.
Young children appear to be especially vulnerable to the fatal consequences of being vitamin A deficient.
According to this Science Direct report, vitamin A deficiency is responsible for as many 600,000 deaths every year among the world’s children under the age of five by making them susceptible to extreme health complications arising out of what are typically common childhood illnesses and infections.5
The risk of death from being vitamin A deficient is most prevalent in children within third world countries and among other food-deprived populations. Nevertheless, it certainly exposes the important role this crucial vitamin plays in keeping us alive and healthy.
Vitamin A Deficiency Causes Ocular Degeneration and Blindness
Apart from the risk of death, children who do not ingest enough vitamin A also run the risk of ocular degeneration and blindness.
Vitamin A deficiency is one of the top causes of preventable blindness in children. As the World Health Organization reports, an estimated 250,000 to 500,000 vitamin A-deficient children become blind every year, with half of them dying within 12 months of losing their sight.5
Those that are fortunate enough not to become blind still run the risk of severe visual impairment, especially under low-lighting, as the retina’s rod cells are unable to efficiently detect light as their rhodopsin levels wane.
In fact, the inability to see clearly in dim lighting is one of the earliest signs of vitamin A deficiency.
These conditions – as scary as they are – may only just be a small sample of the total scope of how vitamin A deficiency is detrimental to humans. The effects of this condition are still being studied and future research is, unfortunately, likely to uncover additional cause for concern.
If you desire to dig deeper into the full impact vitamin A deficiency is having on the world, this World Heath Organization report on global vitamin A deficiency is one of the best places to start.
The most important point to take away from all this is that vitamin A, along with the rest of the vitamins I’ll be covering, is a nutrient that is absolutely essential for optimizing one’s health.
And just because you aren’t deficient to the point of becoming blind doesn’t mean you aren’t suffering from a lesser deficiency that, while not causing blindness, is still placing you at exponentially greater risk of developing cancer, heart disease, cataracts or some other debilitating condition.
But how can we be certain that we’re ingesting enough vitamin A so as not to become deficient?
Let’s find out…
Best Dietary Sources of Vitamin A
Before giving you a complete breakdown of the most concentrated sources of vitamin A, I want to give you an idea of what to shoot for as a minimum daily intake of this essential vitamin.
It is suggested that adult men provide their bodies with 900 mcg RAE of vitamin A per day. Adult women should strive for at least 700 mcg RAE. (I will explain the “RAE” denotation in just a moment.)
These values are different for pregnant and nursing mothers with suggested daily vitamin A intakes of 770 mcg RAE and 1,300 mcg RAE, respectively.6
As you will see below, I have taken the time to put together a list of the most concentrated sources of vitamin A. This list will make clear that with a little thought and planning it isn’t at all difficult to provide your body with a sufficient amount of vitamin A.
In fact, if you’re being intentional about eating a healthy diet consisting of nutrient-dense foods you won’t have to worry that you’re not getting adequate amounts of vitamin A – or any other vitamin, for that matter.
By the way, it is possible to consume so much vitamin A that it will induce an effect that is known as vitamin A toxicity.
However, everything I have read on vitamin A toxicity leads me to conclude that as long as you aren’t taking in hefty amounts of vitamin A in supplement form, or eating the livers of seals, polar bears or walruses (which are extremely high in vitamin A), your chances of experiencing vitamin A toxicity is virtually zero.
In the table of vitamin A sources below you’re going to see each food’s vitamin A content listed in RAE. RAE stands for retinol activity equivalents, which describes the estimated total amount of retinoid vitamin A that a food provides after the carotenoid-to-retinoid conversion has taken place within the body.
Because the body converts carotenoids into retinoids, accounting for the total retinoid equivalent is the widely recognized standard unit of measurement for vitamin A.
To give you an idea of how this number is calculated, 1 mcg of retinol is considered equivalent to 12 mcg of beta carotene or 24 mcg of alpha carotene.6
So the true mcg measurement of vitamin A nutrition provided by carotenoids is actually greater than what is shown in RAE units. That said, RAE is the standard, so that’s how I’ve decided to show the vitamin A content in the table below.
RAE (in mcg)
|Sweet Potatoes||1 Medium||180.0||1,921.80|
|Mustard Greens||1 Cup||36.4||865.90|
|Collard Greens||1 Cup||62.7||722.00|
|Beet Greens||1 Cup||38.9||551.09|
|Turnip Greens||1 Cup||28.8||549.00|
|Swiss Chard||1 Cup||35.0||535.85|
|Winter Squash||1 Cup||75.8||535.36|
|Romaine Lettuce||2 Cups||16.0||409.37|
|Bok Choy||1 Cup||20.4||361.16|
|Bell Peppers||1 Cup||28.5||144.03|
|Sea Vegetables||1 TBSP||10.8||81.05|
|Chili Peppers||2 TSP||15.2||80.05|
|Brussels Sprouts||1 Cup||56.2||60.45|
|Cow’s Milk||4 Oz.||74.4||56.12|
|Green Beans||1 Cup||43.8||43.75|
Where Are All The Processed Foods With Vitamin A In Them?
My astute readers will have noticed that there isn’t a single processed food listed in the table above. As you might have guessed, this will be a consistent theme as we continue through this series of looking at the foods that provide us with the most health-promoting nutrition.
Processed foods are not designed for sustaining life and promoting optimal health. They’re designed to addict consumers, minimize production costs and maximize profits – the health of their consumers be damned in the process.
It’s estimated that these nutritionally bankrupt processed foods are responsible for 70% of the calories in the diet of the typical American.10
The toxic ingredients and lack of essential nutrients in processed foods are directly responsible for the widespread epidemic of disease and obesity in this country.
With hardly any nutritive substance to their credit, and also being packed with calories from refined fats and sugars, the massive consumption of processed foods have led to Americans gorging themselves on toxic calories – well in excess of their daily energy expenditure – while still being starved of the nutrition they need to fend off disease.
Is it any wonder then that we see the combination of obesity, cancer and heart disease running rampant in this country? It makes perfect sense to me – and so does the solution:
Stop filling our bodies with toxins and starving them of the nutrition they need to function as intended. And then start providing them with the nutrients they require to look their best on the outside, while becoming impervious to disease on the inside.
The key to optimal health is nutrition – and vitamin A is just one part of the equation. I will be covering nearly the entire panoply of essential vitamins and minerals as I continue through this series devoted to educating you on what you need to know in order to feed your body so you can look and feel your best.
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