Beta Carotene is No Substitute for Vitamin A
Beta Carotene is No Substitute for Vitamin A
Those who are familiar with my writings know that I am a big proponent of vitamin A, and I have written considerably on the subject, including material disproving a lot of bad science about vitamin A. (Vitamin A Blog Part One, Part Two, Part Three)
Because vitamin A is critical for a number of essential functions in the body, including helping to build and maintain the mucous membranes (Blog), supporting vision, and working to detoxify chemicals from the body, it is important that we all consume a good amount of it, either from our diet or in supplement form.
From the diet, vitamin A is mostly found in the livers of fish and mammals, something not a lot of us in the West consume anymore. Thus, for most people a supplement is necessary, usually derived from fish liver oil, or synthesized (which in the case of vitamin A is fine, but not in the case of beta carotene, as we shall see).
New studies, to be explored below, have confirmed what I have long believed, that beta carotene is no substitute for vitamin A. This information is of particular importance to vegans and strict vegetarians.
I’m sure you all know what beta carotene is: an antioxidant pigment, found mostly in yellow and orange fruits and vegetables (e.g. carrots, sweet potatoes). Studies have indicated that consuming four or more servings of beta carotene rich foods lead to a lower risk of developing heart disease and cancer.
Beta carotene is also known as “pro-vitamin A”, given that the body will convert some into vitamin A, if one is deficient. This idea leaves many people believing that if they consume lots of beta carotene-rich foods, their vitamin A needs will be fulfilled. This I have debated as no one knows exactly how much conversion occurs, and certain health conditions (e.g. thyroid malfunction), and nutritional deficiencies, can inhibit the conversion of beta carotene into vitamin A.
The studies we are about to examine started with the premise that people who have high blood levels of beta carotene generally have lower levels of LDL (“bad”) cholesterol. This type of cholesterol is associated with ischemic heart disease, the most common cause of death worldwide.
Since the biological processes that link beta carotene to lower blood cholesterol levels are poorly understood, scientists set out to determine the molecular mechanisms involved.
So, we eat some food rich in beta carotene, along with some fat which is essential for fully absorbing many carotenoids (including lycopene). Once digested, the beta carotene uses the enzyme β-carotene 15,15′-monooxygenase (BCMO1 or BCO1 gene), in order to convert the beta-carotene into vitamin A.
It has already been determined that “genetic variants in the BCO1 gene cause varying amounts of the enzyme to be produced and cause a large difference in the amount of vitamin A produced from dietary beta-carotene. The BCO1 enzyme is active in the intestines, liver, and mucosal epithelium (e.g. lining of the lungs). As a result, the conversion of beta-carotene to vitamin A occurs in all of those locations.” (Source)
The irony here is that vitamin A is required for maintaining the mucosal epithelium, which in turn is responsible for converting beta carotene into vitamin A. So, low amounts of vitamin A in the diet will inhibit us creating vitamin A from the beta carotene we ingest.
On the other hand, high amounts of vitamin A in the diet (or from supplements) will create a feedback loop whereby the production of the BCO1 enzyme decreases, thereby decreasing the amount of beta carotene that is converted into vitamin A.
That beta carotene which is not needed to be turned into vitamin A, is then free to serve its function as a free radical scavenger. This is why better multivitamin products (such as our NutriPods) will mix vitamin A with beta carotene: by fulfilling the body’s requirements for vitamin A, all the beta carotene can then work fully as an antioxidant.
This BCO1 enzyme makes vitamin A from beta carotene, and the vitamin A goes on to reduce the amount of LDL cholesterol produced in the liver. However, in order to gain the full benefits of beta carotene for cardiovascular health we need to have a fully functioning form of this enzyme. And, these studies revealed that up to 50% of people may have a less active form of this enzyme, thus putting them at a genetic disadvantage when it comes to making vitamin A from fruits and vegetables.
Cholesterol in Mice and Humans
In the first study, researchers “compared the effects of a beta carotene-rich diet in one group of regular mice and another group of mice without the gene for making BCO1”.
After 10 days on the diet, it was determined that the mice without the ability to produce the BCO1 enzyme had more beta carotene in their blood and higher cholesterol levels, than the normal mice.
Next, the researchers looked at humans. They analyzed DNA and blood samples from 475 healthy young adults (aged 18–25), along with questioning them about their diet.
After factoring in the amount of beta carotene and vitamin A in the diet of the participants, the researchers discovered those with a more active form of the BCO1 gene had significantly lower LDL cholesterol levels.
While those who have an active form of the BCO1 gene may have only around a 9% reduction in LDL cholesterol (compared to those without the functioning version) “this decrease may be clinically meaningful if maintained through adulthood”.
Also finding that total cholesterol was higher in those who do not produce much vitamin A, the scientists wanted to know what kind of long term effect on heart disease risk this would have in the long run. However, according to the lead author of the study, “To know if that observation has an effect in the long run, we would have to wait 70 years to see if they develop [cardiovascular disease].”
In order to further explore the effect of the BCO1 enzyme on the risk of atherosclerosis (build up of arterial plaque), without waiting 70 years, the research team conducted another study. This time with two types of mice made genetically prone to develop atherosclerosis, and again, one group of mice had a working version of the gene for making the BCO1 enzyme, and the other did not.
The results of this test showed that the mice with an active version of the BCO1 enzyme had reduced total cholesterol levels and “developed less severe atherosclerosis than the mice without the enzyme”. “We observed that in mice with high levels of vitamin A, the secretion of lipids [cholesterol] into the bloodstream slows down.” (Source)
This result was attributed to the effect of vitamin A on the livers of the test animals, since cholesterol is produced in the liver. Therefore, it makes sense for those wrestling with high cholesterol to make sure they are getting a good amount of vitamin A into their bodies.
(What is a good amount? Well, as I’ve discussed elsewhere, a serving of cow liver provides around 40 to 50,000 IU of vitamin A, so I consider that to be a reasonable weekly intake of vitamin A in supplement form. However, that is a maintenance dose, and one may need to take a higher dose initially if they feel they are deficient. More on the subject can be found in this blog: How 3 Nutrients Can Heal Most Ailments.)
My primary reason for discussing this information is not because of a lowering of total cholesterol and LDL levels, but because of the many critical functions that vitamin A serves, and the widespread deficiency of vitamin A in the modern diet. Not to mention the importance of getting this information to vegans, and those who rely on fruits and vegetables for their vitamin A intake. According to the lead author of the two studies referred to, people “may need to get more vitamin A directly from animal sources, such as dairy, milk, oily fish, or cheese, for example”.
But what is the vegan, or those who can’t stand the idea of eating liver, to do? For those who are not vegan there are natural sourced vitamin A supplements available. For those who are vegan, fortunately synthetic vitamin A works just fine. But (and it’s a big but), synthetic beta carotene is not okay. “Studies in smokers have unexpectedly reported increased lung tumor rates after high, long-term, beta-carotene supplementation.” (Source)
Thus, you will often hear doctors and pharmacists tell people to avoid beta carotene in supplements. However, the fact is these studies were all based on people consuming synthetic beta carotene supplements. This danger does not hold true for beta carotene from food, nor from natural source beta carotene supplements. Beta carotene from natural sources also has the advantage of containing the full family of carotenoids, including alpha carotene which is a far more powerful antioxidant than the beta form.
But, natural beta carotene is quite expensive, so nine times out of ten any multivitamin product you see will be using synthetic beta carotene, and have little or no actual vitamin A (as the companies are still paying attention to the bad science on vitamin A implying that it is dangerous). If a product does not specify that the beta carotene is from a natural source, or if it only lists it as “beta carotene” and nothing else, then you can be pretty sure it is synthetic.
It is this very subject that led me to work for NutriStart, as many years ago when their first product was their only product, namely NutriPods, I was asked how the formula might be improved. I immediately pointed out that the synthetic beta carotene should be replaced with a natural source beta carotene. The owner, ever seeking to improve his product, did so as soon as possible, and later invited me to join him in developing further products.