Vitamin A: The Companion To Vitamin D

By Alan Inglis, MD

Scientists who study nutrition know that Vitamin D and Vitamin A together are essential for a healthy immune system.

One the one hand, Vitamin D helps us defeat disease-causing viruses and bacteria. On the other hand, Vitamin A helps helps our respiratory tracts protect us by strengthening its delicate mucosal surfaces. Together these two companion nutrients form a disease fighting team you can harness to help fight colds and the flu.

You may wonder exactly how vitamin A works.  I know I did before I decided many years ago to study nutrition and its impact on human health.

Bear with me now, because I need to get a little “scientific” on you:

IgA is an immune system protein in your respiratory tract -- your sinuses, bronchial tubes and lungs.  And that’s where it helps protect you and me against the viruses and bacteria that trigger colds and the flu.

Here’s the exact Vitamin A -- IgA connection:


  • Vitamin A supports IgA.

  • In turn, IgA is an immune system protein that fights disease causing viruses and bacteria in respiratory tract.

So where do you get Vitamin A? You need to understand that your body cannot make its own. You have to get Vitamin A from the food you eat or from supplements.

Now you and I are always being told that we can get all the nutrients we need from food. And that’s usually true. When it comes to vitamin A, however, many of us may come up short. Especially when we are being threatened by a cold or the flu. That’s because our diets have changed. We eat fewer fresh veggies and pastured dairy and meat, so we get it from our fortified our foods.

Many folks simply do not tolerate fortified milk, wheat and cereals. And if you don’t eat organ meats and are a poor converter of carotene, you may not have enough vitamin A in your body.

I always ask my patients if they like chicken livers or lambs kidneys. They usually shake their heads politely, smile and say “no”. Then I remember the times I brought home chicken livers, for example. Just like my mother used to. I’m afraid I usually ended up feeding them to our dogs. Oh well!

You may have heard of carotenoids. There are over 600 of them and they give vegetables their colors. About fifty are turned into the active form of vitamin A.

Major carotenoids include beta-carotene, alpha-carotene, lycopene and lutein. When I say “active form” I mean the so-called retinoid form of vitamin A that actually does the real work when it comes to fighting infection. The richest sources of the active form of vitamin A are organ meats, foods most of just don’t much of these days, as I mentioned above.

Science shows us you can have a big problem if you think you get all the vitamin A your body needs just from fruits and vegetables. That’s because the conversion of carotenoids to vitamin A is flawed. A study from Newcastle University in England showed up to 50% of women studied were unable to efficiently convert carotenoids into the active form of vitamin A (retinoid form).

The lead researcher for this important study, Dr. George Lietz, told Science News, “What our research shows is that many women are simply not getting enough of this vital nutrient because their bodies are not able to convert the beta-carotene."

There’s more to the story. Research in American Journal of Clinical Nutrition (2000) found no evidence of benefit on vitamin A status from the increased consumption of dark-green or yellow vegetables. I also think the following is really important to keep in mind:  The Council for Responsible Nutrition considers supplements of up to 10,000 IU daily of the  active form of   vitamin  A (retinoid form) to be generally safe.

We have been very careful about how we designed Dr. Schnuffie’s Cold and Flu Remedy. For all the reasons I have given you, we have included higher doses of both Vitamin D and the active retinoid form of Vitamin A.

And please also remember, it’s all about balance. Having too much or too little of either Vitamin A or Vitamin D interferes with the other’s ability to do its job. And important jobs they are!

Sarah W