I know that we are surrounded by information, and many people are experiencing ‘information fatigue’ (ie. exhausted by the sheer amount of information coming at them, and often conflicting, too).
I try to keep this in mind when sharing information, because I don’t want to just be another person adding to the noise and clamour.
But as I’ve delved more into this subject of beef liver and whether it could be contributing to chronic toxicity of nutrients (namely copper and Vitamin A), I’ve felt more and more compelled to speak on this.
In this post I am going to address concerns about Vitamin A toxicity, in regards to beef liver, but I also will be referencing the use of cod liver oil (some people take both liver and cod liver oil simultaneously) along with an otherwise high-retinol diet.
Please note, I haven’t been able to fit all information I’ve uncovered into this one post, but I’ve tried to cover some of the main points (in no particular order).
First, The Basics:
Vitamin A is considered an essential, fat-soluble nutrient, that helps with eyesight (retinoid is derived from the word ‘retina’), immune function, fertility, skin health, and more.
A deficiency of Vitamin A causes night blindness (leading to total blindness, if not addressed), prone to acute infections, acne, keratosis pilaris, dry skin, dry eyes, goiter, and more.
Ironically, symptoms of too much Vitamin A can also mimic deficiency symptoms.
Vitamin A: Why The Source Matters
You may see me referring to Vitamin A as ‘retinol’, so I wanted to quickly clarify. Vitamin A comes in ‘preformed Vitamin A’ and ‘pro-Vitamin A’. It is important that we distinguish the difference between these two types, because they come from different food sources, and are absorbed differently (and therefore, the toxicity threshold is very different)
Preformed Vitamin A, is retinol, and is found in animal foods, such as liver, eggs, dairy. The body converts this to retinal, and then oxidised to retinoic acid. The absorption rate of preformed Vitamin A is very high – about 70% - 90% of it gets absorbed in the GI tract.
Pro-Vitamin A (beta-carotene), however, is found in plant foods like orange and green vegetables, and because it requires an extra conversion step, before it becomes retinol, then retinal and then retinoic acid, its absorption rates are much lower (only about 20% - 50% is absorbed).
In developed countries (which will apply to most of us reading this email), about 75% of Vitamin A intake is preformed Vitamin A, not only from animal foods, but also from supplements, skincare/sunscreen and fortified foods.
In the developing world, however, the situation is inverted, with 75% of Vitamin A intake coming from pro-Vitamin A plant foods, which are really just precursors to Vitamin A.
The stark difference in intake is probably why some researchers maintain that the developing world is more at risk of Vitamin A deficiency (and why supplementation programs exist in many third-world countries), while the developed world is more at risk of chronic toxicity, due to high intake of preformed Vitamin A.
In addition, preformed Vitamin A is highly absorbed AND it is excreted slowly, which increases the risk of toxicity, which can gradually build up over a period of months or years, depending on intake.
This situation is referred to as Hypervitaminosis A (or Vitamin A toxicity).
Because pro-Vitamin A (plant food sources) requires an extra conversion step, the body is more protected from overdose.
If Vitamin A intake is high, the conversion rate becomes less efficient, which helps the body maintain homeostasis. Therefore, overdose from beta-carotene is highly unlikely (but not impossible), while overdose from preformed Vitamin A is much more likely, because the body has less ability to regulate its intake.
The current Recommended Daily Allowance is 700ug for adult women and 900ug for adult men. The allowable upper limit is 3000ug (micrograms) per day for adults.
If an adult woman takes 1 teaspoon of cod liver oil per day (1350ug per day), she is immediately getting almost double the RDA, without taking into account anything else she may be eating in the diet.
If an adult woman then also eats 100g of beef liver per week (or equivalent in dessicated liver capsules), she is getting a further 5070ug of Vitamin A per week, or 724ug per day.
So, with beef liver and cod liver oil alone, she is already getting 3x the RDA, without factoring anything else in her diet.
Other food sources of preformed Vitamin A include:
Eggs: 80ug each
Whole milk (unfortified): 110ug per cup
Skim milk (fortified): 134ug per cup
Butter: 95ug per tablespoon
Cooked mackerel: 252ug per 100g
Liverwurst sausage: 8300ug per 100g
Cheddar cheese: 140ug per 50g
Bluefin tuna: 750ug per 100g
Fortified cereal: 430ug per 50g
Remember these are only ‘preformed Vitamin A’ sources. What about plant foods?
Scientists have now come up with a measurement known as Retinol Activity Equivalents (RAE), that accounts for the differing absorption amount of plant foods (this will still differ somewhat between individuals, though, but let's go with it, to get the general idea).
The Retinol Activity Equivalent of:
One medium-sized raw carrot = 835ug
One whole sweet potato, baked = 1403ug
½ cup raw cantaloupe = 135ug
One whole mango = 112ug
Let’s add up how much someone on a typical ‘prometabolic’ diet might be ingesting on a daily basis, with or without beef liver and cod liver oil.
Let’s say they eat at breakfast: Two eggs with 100g of cottage cheese, one tablespoon of butter on sourdough bread with one cup of whole milk. This adds up to approximately 400ug
A raw carrot salad, mid morning = 835ug
For lunch, half a sweet potato with fish = 952ug
Mid Afternoon snack: Nectarine with 50g cheddar cheese = 160ug
Dinner: One cup of mashed pumpkin with chicken thigh = 493ug
So, without any beef liver or cod liver oil, this person has ingested approximately 2840ug per day (very close to the upper limit of 3000ug per day).
If they ALSO take approximately 100g beef liver per week (this equates to 725ug per day), and one teaspoon of cod liver oil per day (1350ug per day), their total intake is approximately 4915ug.
This is well above the upper limit of 3000ug per day.
As you can see, it wouldn’t be overly difficult for someone eating a pro-metabolic or ‘animal-based’ diet (or indeed, even a Standard American Diet, if eating fortified foods) to meet the Recommended Daily amount, without cod liver oil or beef liver.
How much do we actually need, and is it the same as our ancestors?
One thing that strikes me, as I consider the foods richest in Vitamin A...is that nearly all of them were traditionally available only in summer.
Before refrigeration, dairy was a summer-time food, following spring calving season.
Many orange or red-coloured vegetables, and leafy greens, were typically available only in warmer months.
Modern hens have been bred to lay eggs virtually year-round, but once upon a time, eggs were mainly available during the warmer months
So, Vitamin A-rich foods were typically most available during the season when our Vitamin A needs were higher, due to sunlight exposure.
Beef liver, might have typically been eaten during the colder months, since many families slaughtered their animals as Winter approached (born and fattened in Spring, grew over Summer and Autumn, and then slaughtered before the food/pasture shortages of Winter). The meat could also keep for longer, during the colder months.
Perhaps, the beef liver (or livers from other animals) acted as a ‘top-up’ of nutrients, during the Winter months when other Vitamin A-rich foods would typically be scarce?
Which brings me to the question: do we modern humans, living a mostly indoors, sedentary lifestyle, even require year-round supply of Vitamin A-rich foods?
Vitamin A helps protect both skin and eyes from UV radiation. Therefore, a more outdoor lifestyle, like our ancestors lived, may require higher amounts of Vitamin A food intake. (Another way of putting it, is to say that sunlight exposure helped protect them from Vitamin A overload...)
But on the other hand, this means a more indoor lifestyle requires less Vitamin A...
Another circumstance that temporarily increases Vitamin A requirements significantly, is acute infections. Since today’s children have far fewer infections than children of previous generations, their Vitamin A stores don’t get depleted on a semi-regular basis, like children from a few generations ago.
In fact, the hygiene hypothesis considers that children in developed countries are ‘too clean’. The lack of challenge to their immune system in the early years, causes immune issues and allergies, and potentially creates auto-immune conditions.
Honestly, I don’t have the answers here, but it seems logical to me that we may, in fact, need less Vitamin A than our ancestors did. The fact that we now eat it, supplement it, use it on our skin, year-round, could potentially be problematic?
(Something else quite interesting I discovered about cod, and the oil made from their livers, was that in northern climates, cod were typically fished at the end of Winter, when nutrient stores in the liver had been depleted.
Could this mean that cod liver oil traditionally had less Vitamin A than modern forms of cod liver oil?)
Vitamin A and The Thyroid
There is a carrier protein that transports thyroxine (thyroid hormone) around the body. The carrier protein is called Transthyretin.
It is named this way because it is a TRANSporter of THYroxin and RETINol.
In other words, it transports both thyroid hormone AND retinol.
I do wonder...if retinol levels are high, does it displace thyroid hormone?
It turns out that in the 1940’s, high doses of Vitamin A were used to treat hyperthyroidism. Researchers at the time, also experimented on normal rats and found that high doses of Vitamin A lowered metabolism (by 10%), and decreased the size of the thyroid (by 35%)
Recent rat studies (published in 2022) also showed similar findings. In rats, high doses of Vitamin A caused hypothyroidism, an increase in insulin resistance, and over time, Type 2 diabetes.
There is a cancer treatment called bexarotene (a type of carotenoid – precurser to retinol), that has been shown to cause hypothyroidism in those undergoing treatment with it. (Of 27 patients, 19 became hypothyroid).
Interestingly enough, the Merck Manual lists one of the side effects of Vitamin A toxicity, as thinning of the eyebrows. Many people know by now that thinning eyebrows (especially the outer third) can be a sign of sluggish thyroid.
Also note that people given accutane (a type of retinoid medication) for acne were found to have lowered thyroid function, decreased thyroid hormone levels, and decreased size of thyroid gland, when compared with controls who did not take accutane.
Vitamin A and asthma
An interesting research article I came across, theorized that some forms of asthma are caused by ‘retinoid intoxication’. They surmise that the lack of acute infections in childhood (which deplete Vitamin A) cause a build-up of Vitamin A in the lung, which later manifests as asthma. You can read that article here: (PDF) Could bronchial asthma be an endogenous, pulmonary expression of retinoid intoxication? (researchgate.net)
In looking around for more info, I found another very large and very interesting study undertaken in Norway. Over 61,000 children took part, and researchers were looking at Vitamin A and Vitamin D intake of the mother, during pregnancy, and the risk of asthma when the child was 7yrs old.
Interestingly, they found that asthma increased according to maternal intake of Vitamin A. Conversely, higher intake of Vitamin D (which offsets Vitamin A) had the opposite effect (correlated to lower risk of asthma).
Their conclusion was that maternal Vitamin A intake of 2.5x higher than recommended, was linked to asthma in the child. (Many people who eat a pro-metabolic or WAPF-style diet, or take cod liver oil/beef liver are getting more than this amount.)
In saying that, another study (albeit, much smaller) of preformed Vitamin A intake during childhood found that higher intake of preformed Vitamin A (but not carotenoids) was associated with better lung function.
So! The jury is still out on this one. What we do know however, is that some retinol is both synthesized and stored by the alveoli of the lung, so Vitamin A deficiency or excess, could potentially negatively affect the lungs.
Vitamin A Overload Is More Common Than Vitamin A Deficiency?
Blood retinol levels are not always an accurate indicator of Vitamin A status. There have been cases of hypervitaminosis A, but normal blood levels. (I also read that blood tests for Vitamin A must be immediately wrapped in foil, to avoid being affected by light exposure. Not sure if this is widely known, but if not, then Vitamin A blood testing is potentially inaccurate on a grand scale)
The only real way to assess Vitamin A overload, is to take a liver biopsy. This is expensive, invasive and painful, and therefore we don’t have data from a population level. One study, however, aimed to investigate Vitamin A content in liver of 27 cadavers (bodies of deceased people).
Of the 27 people, 22% were found to be vitamin-A deficient, while 33% where found to have hypervitaminosis A (excess Vitamin A)
Now, this is only a small sample size, however, in this small sample of ordinary, everyday people, eating an ordinary diet, there were more people with Vitamin A overload, than there were with deficiency. Chances are, these people were not eating beef liver, or taking cod liver oil, either!
Vitamin A & The Skin
Accutane medication, as well as retinol-containing skincare are touted as being anti-acne. What actually happens is the retinol shrinks the sebaceous glands (and subsequent oil production) by 90%.
Viola! Acne ‘cured’. But is it really...or have we just destroyed the sebaceous glands, and can no longer produce sebum (hence why dry skin is a side-effect of accutane)???
Because there are retinoid receptors in the skin, both deficiency and excess of Vitamin A can cause skin problems. Unfortunately, they look strikingly similar, making it hard to gauge whether one is dealing with an excess or a deficiency (this is where a detailed personal history of exposures and dietary habits comes in handy).
These skin conditions include dry skin, peeling skin, itching, cracking in the corners of the mouth, yellowing of the skin, sensitivity to sunlight.
Vitamin A & Weight Gain/Metabolic Conditions
It turns out that, like copper, too much or too little of Vitamin A also causes metabolic dysfunction and unwanted weight gain.
In animal studies, excessive amounts of Vitamin A causes carb intolerance (a rather common complaint in the wellness world, at the moment), accumulation of liver fat, dysregulation of blood sugar, and elevated cholesterol levels.
Vitamin A & Bone Health
Numerous studies have suggested that high intake of preformed Vitamin A (via supplements, food fortification, or animal products) causes loss of calcium from the bones, followed by weakening of the bones.
It seems that more than 2000ug per day, is linked to hip fractures.
Is it true we cannot overdose on food sources?
A claim I have seen made by some, is that we cannot overdose on food sources of Vitamin A.
While it’s true that we are less likely to overdose on food sources (than, say, massive doses of Accutane, or supplements), it is false to say we cannot overdose from food sources.
There are numerous cases of poisonings published in medical journals, from food sources, such as eating liver. Some even resulted in death.
One of these cases was a 3yo boy who suffered chronic Hypervitaminosis A which was, sadly, not picked up soon enough and subsequently passed away from kidney failure and sepsis.
His younger brother later began to exhibit the same symptoms (high calcium in the blood, bone pain, swelling of the skull, leading to headaches and nausea, fluid build-up in the abdomen, enlarged spleen, swollen liver). Doctors eventually realized he was suffering hypervitaminosis A and implemented a low-Vitamin A diet.
Although this prevented him suffering the same fate as his older brother, it was a very long (3+ years) and difficult recovery, interspersed by periods of extreme hypervitaminosis signs. (Perhaps this happened each time the overloaded liver released retinol into the bloodstream?)
While both children had taken multi-vitamins at different times during their childhood, researchers felt that their regular diet of chicken liver, 2-3 times per week, may have been the ‘tipping point’.
Strangely enough, an older sister, and both parents, were also eating the same diet, and seemed to show no ill effects. Which just goes to show that there are individual (genetic, or otherwise) variations to how much Vitamin A we can tolerate. Whether their childhood history of antibiotic use for ear infections played any role (or whether the ear infections were in fact, a symptom of Vitamin A toxicity already
underway) remains to be answered.
Other cases of toxicity have been documented after eating beef liver, seal liver, or fish liver.
A strange phenomenon amongst the Inuit people, known as ‘Polar Hysteria’ is thought by some researchers to be caused by chronic vitamin A toxicity, from eating seal livers.
It’s been a few years since I read Weston Price’s book, so I can’t recall if he acknowledges this, or warned about the dangers of too much Vitamin A/liver intake(?)
What’s interesting is that the symptoms of ‘polar hysteria’ are quite similar to some of the symptoms listed as potential side effects of Accutane medication – including mania, hallucinations, suicide ideation, etc.
Polar mania seemed to affect women more than men – I do not know if this was because women have smaller livers than men, and could therefore, experience intoxication sooner, or if they followed the practice of giving the organ meats to the women of child-bearing age.
Historians believe infanticide was fairly common amongst Eskimo peoples (some estimates as high as 60% of babies, particularly female babies, were left to die). This practice of infanticide likely prevents us from knowing how prevalent birth defects were among these people (side-effect of Vitamin A toxicity during pregnancy).
Phew!
All this was a lot to take in! If you’re still here, well done! As I said, this is not the entirety of the research I’ve covered in the last 10 days or so, but I hope it gives a decent overview.
In my next post I’m going to share my conclusions and my personal approach, moving forward.