In the world of supplementation and nutrition, few compounds have been as misunderstood—and yet as fundamental—as vitamin A. For years, its use has been surrounded by fear, misinformation, and confusion, largely due to poorly designed studies and the misuse of its active forms. But when we understand its physiological function and origins clearly, the perspective changes. What was once feared becomes a powerful tool for health.
Where Does Vitamin A Come From—and Why Does It Matter?
Vitamin A is available in two main forms: provitamin A (carotenoids) found in plant-based foods, and preformed vitamin A (retinyl esters) found in animal-based sources. Fruits and vegetables like papaya, spinach, and sweet potato are rich in carotenoids. However, there’s a catch: the conversion of these compounds into active vitamin A depends on numerous factors. Not everyone converts carotenoids into usable vitamin A efficiently. Genetics, stomach acidity, intestinal health, dietary fat content, and food preparation methods all drastically influence this process.
The primary site for this conversion is the intestinal mucosa. And this highlights why gut health is key. A person with dysbiosis, poor bile acid production, or intestinal inflammation may struggle to activate vitamin A—even if they consume plenty of carotenoids. This is critical to understand when aiming to prevent or reverse deficiency, especially in the context of immunity.
Vitamin A and Immune Response: It’s Not Just About Defense
When we think about the immune system, we often focus on its ability to attack pathogens. But there’s another equally important side to that coin: tolerance. That is, the immune system’s ability to recognize self and avoid overreacting. This is where vitamin A plays a central role.
This nutrient not only strengthens the body’s ability to fight infections like measles, pneumonia, or diarrhea, but it also helps restore immune balance after an inflammatory response. Its key function is to promote an immune system that can defend itself without becoming self-destructive. This is particularly relevant in autoimmune diseases, where the regulation between inflammatory (Th17) and regulatory (Treg) cells is disrupted.
Vitamin A, through its influence in the cell nucleus, helps maintain the population of regulatory T cells, which are essential for preserving immune tolerance. This action reduces the likelihood of chronic inflammation leading to autoimmune disorders. And while this process involves genes, receptors, and complex proteins like Foxp3, the main point is this: without sufficient vitamin A, immune balance breaks down.
Nutrition and Vitamin A: Who’s Really Providing It?
Few foods offer meaningful amounts of preformed, bioavailable vitamin A. Liver is, by far, the most potent and reliable source. Some fish contain modest amounts, followed by butter, eggs, and cheese—but in much smaller quantities. This means that for many people, achieving optimal vitamin A levels through modern diets is a challenge, especially when organ meats and animal fats are avoided.
To make things worse, vitamin A is rapidly depleted in times of stress, illness, viral infections like COVID-19, or chronic inflammation. In other words, you need more vitamin A exactly when your body is least likely to have it.
A Brief Historical Perspective—and Persistent Misunderstandings
Since the early 20th century, vitamin A has been recognized for its anti-infective properties. During World War II, it was added to foods to prevent respiratory and gastrointestinal diseases. However, over time, its reputation suffered due to studies using excessive doses—often in animals—and the pharmaceutical use of synthetic derivatives like isotretinoin (Accutane).
These medications, used to treat acne, rely on a less active form of vitamin A administered in pharmacological doses, which can cause serious side effects. But we must distinguish between a drug and an essential nutrient. Natural, bioactive vitamin A functions within the body in a regulated, controlled manner and has not been shown to be toxic when used responsibly.
IgA, the Microbiome, and Gut Immunity
Vitamin A regulates the production of IgA, the body’s main mucosal antibody. Along with intestinal mucus and antimicrobial peptides, IgA forms the first line of defense for epithelial cells. It not only prevents pathogenic bacteria from attaching to the gut lining but also stabilizes the microbiome by supporting the growth of beneficial species.
This is critical, considering that 70–80% of our immune system resides in the gut—and that vitamin A’s active form (retinoic acid) is produced right within intestinal epithelial cells. A vitamin A deficiency can therefore compromise microbiome integrity, immune defense, and the delicate balance of immune tolerance.
What the Evidence Says
Recent studies have shown that vitamin A deficiency is associated with significant microbiome disruption, intestinal inflammation, and decreased levels of butyrate-producing bacteria—a key component of gut barrier health. An overgrowth of opportunistic bacteria has been observed in individuals with persistent diarrhea, asthma, Crohn’s disease, and autism.
In Crohn’s patients, up to 21% were found to have low vitamin A levels. Among children with autism, the deficiency was even more pronounced. And in cases of asthma or intestinal transplant rejection, low vitamin A levels were linked to greater risk and poorer outcomes.
Vitamin A and D: The Forgotten Partnership
Vitamin D has become the focus of many health trends in recent years, but vitamin A is rarely part of the conversation. Interestingly, they often work together. Studies show that as much as 70–80% of the gene expression induced by vitamin D depends on the presence of vitamin A. We also know that high doses of one can deplete the other, and this imbalance can be corrected by restoring both.
Conclusion
Vitamin A is not a fad, a quick fix, or a supplement to take lightly. It is an essential regulator of immune function, gut health, immune tolerance, and microbiome stability. The fear surrounding its use has been driven by misinformation—but the evidence is clear: when used wisely, it becomes a powerful tool to restore health from the gut outward.
If you want to learn more about how vitamin A can impact your health, explore the protocols available on this platform or consider scheduling a consultation. True recovery starts with information that works—and a strategy that respects how the body really functions.
