Liver is an excellent source of many nutrients. A couple of weeks ago I discussed how it is an excellent food source of methylation nutrients, especially B vitamins. Today I want to explore what liver is often better known for, and that is its Vitamin A content.
A single serving of liver provides us with more than 100% of our recommended daily allowance (RDA) of vitamin A. In fact, it provides us with about 10 days worth of vitamin A.
What does Vitamin A do for us?
Vitamin A has a key function in our immunity. In fact, vitamin A deficiency is now classified as an acquired immune deficiency disorder where deficiency greatly increases susceptibility to infections.
With the seasons changing, the children back at school, and colds and flu on the horizon, now is the time to optimize our immune system to reduce infections. Fall may be the perfect time to start incorporating liver into our regular diet to support your immunity and avoid those nasty winter colds, and flu.
Vitamin A’s immune function has profound effects on the mucosal tissue. Mucosal tissue includes the tissues lining the whole of the gastrointestinal system and also the nasal passages and into the lungs. This means that Vitamin A is protective of those areas, so it protects against pathogens that affect our nasal/lung system as well as GI pathogens.
Types of Vitamin A
There are two types of vitamin A – retinoids from animals and carotenoids from plants. Take a look at my previous post on sweet potatoes and carotenoids to find out more about these two types.
How much vitamin A is there in liver?
As I mentioned, we get more than 100% of our RDA from a serving of liver. In fact, one 4 ounce serving of liver provides more than 30,000 IU of Vitamin A.
The RDA for Vitamin A is 3,000IU for men and 2,300IU for women. This means that eating liver once every 10-14 days can provide us with good levels of vitamin A.
In comparison, other foods that provide 100% or more of vitamin A as carotenoids are sweet potatoes ( ~ 28,000 IU), frozen spinach (~11,000IU), then raw carrots (~9,000IU).
The big difference between getting vitamin A from liver and vegetable sources is that the liver provides vitamin A as a retinoid and the vegetables supply it as carotenoids. Eating vegetable sources only means the body has to convert the carotenoids into retinoids. However, many people cannot make this conversion efficiently, especially women. This can lead to someone being deficient in vitamin A, but having high levels of carotenoids.
In fact, in a recent study in England, as many as 50% of women studied were unable to efficiently convert carotenoids into vitamin A. Thus including animal sources is beneficial.
Measuring your vitamin A levels will help you see if you can convert carotenoids and whether you are deficient.
Vitamin A and vaccines
In addition to Vitamin A helping prevent infections, there is also a lot of research on the use of vitamin A prior to vaccinations. In fact, the World Health Organization recommends a single dose of 200,000IU vitamin A prior to some vaccinations (e.g. measles or MMR vaccine). That is a very large dose but is seen to protect against the pneumonia and diarrhea often associated with vaccination.
These findings may be of interest to you if you are at high risk for influenza. Maybe you are considering getting the flu vaccine? If so, think about having some food sources of vitamin A, like liver, before your vaccination. Maybe add a sweet potato and spinach too? Improving your immunity through your diet may help with the vaccine. Talk to your doctor or healthcare practitioner about it when you discuss vaccinations.
What about the studies which cautioned us about Vitamin A?
There have indeed been some unfavorable studies regarding vitamin A. However, these studies were using synthetic forms of carotenoids at high doses, not food sources and not retinoid vitamin A. One such study showed a higher incidence of lung cancer in smokers who consumed high doses of synthetic beta-carotene (ie not food sources).
Also, remember that vitamin A works in tandem with vitamin D and K2. We want to make sure we balance the level of all three, for optimal function.
Liver as a source of Vitamin A
So we can see that including liver in our diet can provide us with good vitamin A levels, which can support our immune system. This may lead to less infections and/or reduced severity of infections. I recently gave you a recipe for lemon and sage calves liver. This Friday I’ll include a chicken liver pate recipe for you to try. Let’s avoid infections this winter and stay healthy by incorporating liver into our diet and lifestyle.
But remember – we don’t want excessive intake either so don’t eat liver every day (!). And check how much you are getting in your multivitamin. Is it in the form of a carotenoid or retinoid?