Beyond Vitamin C: Building Strong Immunity With Vitamin A

Often when we talk about nutrition to build a healthy immune system we are told what to take out of our diets—sugars, fried foods, processed foods, etc. And often we are told to get more vitamin C; many of my new patients list daily vitamin C as a part of their self-prescribed supplement regimen. However, there is an extremely important and often misunderstood vitamin to remember when you seek to build a stronger immune system: Vitamin A.   And most of you are not getting enough to support optimal immune function! Think that carrot or yam is a good source? Read on to find out what are good sources and how vitamin A can protect against some serious infectious diseases.

What is Vitamin A:

The term Vitamin A actually refers to a group of compounds called retinoids; you may be familiar with the words retinol, retinal and retinoic acid in relationship to eye and skin health. Many people confuse beta-carotene, the nutrient found in carrots and other vegetables, with Vitamin A.   Please note that beta-carotene and other carotenoids are not actually vitamin A. I see this mistake made by nutritionists, food/health bloggers and doctors all the time. Some carotenoids, but only about 10% of those synthesized by plants, are pro-vitamin A compounds capable of being converted by your body into vitamin A ¹. The conversion rate depends on several factors including the type of fruit or vegetable the pro-vitamin A comes in, whether or not the meal contains fat, the health of your thyroid and gut, and even your BMI and possibly your genetic make-up. Charts that show RAE (retinoic acid equivalents) for fruits and vegetables are showing the amount available if 100% of the pro-vitamin A were converted, not the amount you are actually converting. Preformed vitamin A can only be obtained dietarily from animal sources.

Vitamin A is a fat soluble vitamin which means that it is stored by your body in adipose (fat) tissue and in your liver. Because your body can store them, fat soluble vitamins do not necessarily need to be eaten every day (although, as you will see below, I recommend that you do). Another feature of fat soluble vitamins is that they are heat stable and not destroyed by cooking. Water soluble vitamins, like vitamin C, are destroyed by heat and not stored so efficiently. Because it is fat soluble, vitamin A is better absorbed by your body when eaten with fat.

What does vitamin A do in your body?

Vitamin A has a plethora of uses in the human body, including cell differentiation (this is how cells become specialized to perform certain tasks in your body), production of red blood cells, vision, the healthy development of embryos, and regulating the expression of many genes including growth hormone (important for growth and development in children and repair and anti-aging as you get older). The role I am focusing on today is the role Vitamin A plays in your immune system. It is such a powerful regulator of the immune system that the Linus Pauling Institute calls vitamin A the anti-infective vitamin.

This anti-infective vitamin is important for the optimal functioning of both your innate and adaptive immune systems. Here are some highlights of what is does:

• White blood cells (WBCs), the cells of our immune system, need vitamin A for development and differentiation (becoming specialized WBCs for specific tasks).
• As part of its role in the innate immune system, vitamin A is essential to creating strong mucosal linings and skin; both skin and mucosa ² (think the tissue lining your gut, lungs and urinary tract) provide barriers that act as your body’s first line of defense against disease. The mucosa lining your gut is home to about 80% of your immune system—helping to keep this lining healthy with adequate vitamin A is very important!
• Vitamin A deficiency diminishes the function of Neutrophils, macrophages and natural killer cells, all of which are specialized WBCs involved in our innate immune response ³.
• Vitamin A is essential in activating T cells and increasing the number of them circulating in your body ⁴.  T cells are part of your adaptive immune system and they play a large role in regulating immune response.
• B cells, another WBC in your adaptive immune system, also need vitamin A to do their job, part of which is producing antibodies.  Studies show that animals suffering from vitamin A depletion show little or no production of antibodies after administration of vaccines ⁵.

Vitamin A is really an All Star anti-infective active against viral, bacterial and protozoan infections. It has been shown to reduce mortality and morbidity in many serious infectious disease, including malaria and measles ^{6 7}.  Many of the studies confirming this have been done in developing nations where malnutrition is common and there are few quality dietary sources of vitamin A.  But, there is evidence of the vitamin’s importance in developed nations as well.  High dose vitamin A therapy administered in hospitals shortens stays and the need for intensive care for children infected with measles ⁸.  Additionally, even slight vitamin A deficiency, which is likely common in the US,  contributes to an increase in illnesses causing respiratory issues and diarrhea.  Vitamin A may also boost immune response in the elderly and in persons who have undergone surgery⁹, both populations being more susceptible to serious complications for infections.

Classic diseases of vitamin A deficiency, like xerophthalmia and blindness, are rarely seen in the United States and other developed countries. Subclinical deficiencies, however, are common, and optimizing your vitamin A intake is part of creating a truly healthy, robust immune system.

Sources of vitamin A and how to optimize intake:

As mentioned above, vitamin A is not abundant in fruits and vegetables; only pro-vitamin A can be found in them as a percentage of overall carotene content. Instead, we must look to animal foods for vitamin A. Some of the richest sources of vitamin A are cod liver oil, shellfish, egg yolks, liver and dairy products from cows that have been grass-fed and raised in pastures. The animals from which the liver, eggs, and dairy products come must have a good source of vitamin A and/or pro-vitamin A in their diets in order to be good sources of vitamin A for us. When the animals are pasture-raised on green pastures, the grass and insects provide these nutrients.

For your body to best absorb and make use of vitamin A, it is important that you cultivate eating habits that support good digestion and absorption and that you have adequate supportive nutrients, including zinc and vitamin D in your diet. Zinc is needed to form the transport vesicles that carry vitamin A across the lining of your gut and into your body ¹⁰.  Once inside your body, zinc is again needed to carry and utilize it.   Vitamin D is another fat-soluble vitamin, one you have probably heard a lot about. Vitamin A and D work together to support your immune system and to influence the transcription of your genes  ^{11 12}. Cod Liver oil is a great source of these two nutrients, not only because they are delivered together in a favorable ratio but because the oil helps these two fat-soluble vitamins be more easily absorbed.

Vitamin A in food vs. Supplements:

In general, I am a big fan of getting nutrients in their whole foods form rather than from a supplement. There are some exceptions to this, particularly when treating specific disease states. When vitamins and minerals are found in whole, natural foods they are combined with other nutrients that work synergistically with them to increase absorption and function. We know the names and identity of many vitamins and phytonutrients but new nutrients from real foods are being discovered all the time. When we isolate a single vitamin or nutrient we may be missing out on other important nutrients that nature routinely pairs with it. Isolating it this way can lead to nutrient imbalances in your body.

With vitamin A, and fat-soluble vitamins in general, it is possible to get too much and reach a level of toxicity in the body. This is because the body will store these vitamins, unlike the water-soluble vitamins. Symptoms of vitamin A toxicity include headache, nausea, dry and itchy skin, and pain or discomfort in the area of your liver. Supplementing with vitamin A is much more likely to cause toxicity than eating vitamin A-rich foods. I will use very high doses of vitamin A to treat acute and chronic viral infections and sometimes lower doses in vegetarians and vegans who are not getting enough in their diet. High-dose vitamin A should be taken under the supervision of a knowledgeable practitioner.   Toxicity is of particular concern in fetuses (although also a necessary nutrient for development!); women who are pregnant or desiring to get pregnant should take precautions in supplementing vitamin A.

Vitamin A Immune Prescription (the take-home message):

I recommend that most people increase their vitamin A intake through whole foods in order to optimize the function of their immune system.   Even though fat-soluble vitamins can be stored, you should have a regular source of vitamin A in your diet. Here are some suggestions on how to make sure you are getting enough:

• Have butter or ghee made from the milk of pasture-raised cows every day.  Organic Valley Pasture Raised Butter in the green foil is a good choice.
• If you tolerate dairy, eat organic, full-fat yogurt made from grass-fed cows or homemade yogurt, preferably from raw milk,  several times each week.
• Enjoy liver at least several times each month or liver pills daily.  Liver can be sautéed with onions, ground and mixed into hamburger or meatloaf or made into a pate.
• Eat eggs from chickens raised in pastures.  Remember, the yolk is what contains vitamin A.  An omelet with caviar or shrimp provides an extra dose of vitamin A.
• When eating beta-carotene-rich fruits and vegetables, eat them with some fat.  The fat will cause an increase in bile production from the gall bladder and therefore increase absorption and conversion of the carotene into vitamin A.
• Remember to make sure you are getting adequate sources of vitamin D and zinc to increase your body’s ability to utilize vitamin A

If you’ve recently been sick, it is a good idea to increase your intake of vitamin  A as it becomes depleted after infections, making you more vulnerable to getting sick again quickly.  Breastfeeding mothers may also want to consider increasing their intake of vitamin A-rich foods as their stores will be shared with their babies, providing a boost to the infant’s immune system.

1. Linus Pauling Institute: Vitamin A http://lpi.oregonstate.edu/infocenter/vitamins/vitaminA/
2. Vitamin A, infection, and immune function http://www.ncbi.nlm.nih.gov/pubmed/11375434
3. Vitamin A, infection, and immune function http://www.ncbi.nlm.nih.gov/pubmed/11375434
4. Linus Pauling Institue: Vitamin A http://lpi.oregonstate.edu/infocenter/vitamins/vitaminA/
5. Antibody production in vitamin A-depleted rats is impaired after immunization with bacterial polysaccharide or protein antigens. http://www.ncbi.nlm.nih.gov/pubmed/2110538
6. Vitamin A as an Immunomodulating Agent http://www.ncbi.nlm.nih.gov/pubmed/8354037
7. Impact of vitamin A with zinc supplementation on malaria morbidity in Ghana http://www.nutritionj.com/content/12/1/131
8. Routine high dose vitamin A therapy for children hospitalized with measles http://www.ncbi.nlm.nih.gov/pubmed/8133555
9. Vitamin A as an immunomodulating agent http://www.ncbi.nlm.nih.gov/pubmed/8354037
10. Interactions between zinc and vitamin A: an update http://www.ncbi.nlm.nih.gov/pubmed/9701158
11. Nutritional adjuncts to the fat-soluble vitamins http://www.westonaprice.org/health-topics/abcs-of-nutrition/nutritional-adjuncts-to-the-fat-soluble-vitamins/
12. Linus Pauling Institute: Vitamin A http://lpi.oregonstate.edu/infocenter/vitamins/vitaminA/