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Vitamin A is a nutrient that has gotten a seriously bad rap over the years, with most people (dietitians/nutritionists included!) under the false impression that vitamin A is dangerous, and that we need to be careful we don’t get too much.
In my practice as a nutritionist, I find that many, if not most of my clients aren’t getting enough vitamin A in their diets, and that increasing their vitamin A intake through food and/or supplementation can have a big impact on optimizing their health.
While most people commonly equate vitamin A with good vision, the role of vitamin A in the body extends well beyond your eyes. In addition to vision, vitamin A is essential for optimal immune function, skin cell turnover, reproduction and cellular communication.
Perhaps the most impressive function of vitamin A is its role in supporting cell differentiation and growth, ensuring proper development and maintenance of all our vital organs.
And you may be Vitamin A deficient even if you eat plenty of carrots!
Most people associate vitamin A with orange plant foods like carrots, sweet potato, pumpkin and squash. But, many people are surprised to learn that these plants actually don’t technically contain any ready-to-use vitamin A.
Instead, these foods are rich in carotenoids like beta-carotene that must be converted into vitamin A by the body. Many animal foods on the other hand contain preformed vitamin A (retinol) that can be used directly by the body.
Vitamin A deficiency is not addressed too often in the US, because it’s commonly thought that a diet filled with colorful veggies adequately provides everyone with adequate levels of Vitamin A. But the adequate conversion of carotenoids to Vitamin A should not be assumed.
Even nutritional labels are guilty of this, calculating that 1 mg of beta carotene yields 1667 IUs of vitamin A in the body. But, this level of conversion is not guaranteed, and may not even be accurate based on genetic differences in our ability to make the conversion.
Recent studies have been confirming that the conversion of carotenoids into vitamin A is lower than we originally thought. The Food and Nutrition Board recently reduced its conversion rate of beta carotene to vitamin A by 50% and there is speculation that this standard conversion rate may continue to be lowered as more studies are performed.
Other papers report that absorption rate of carotenoids is as low as 3% even in optimal conditions, while the absorption of preformed vitamin A from animal products is 70-90%.
Research has also shown that some people are much better at converting carotenoids to vitamin A compared to others. Many individual factors affect if you are a good or bad converter and why you may be more prone to a deficiency.
What are the symptoms of Vitamin A deficiency?
While severe vitamin A deficiency can lead to complete blindness and even death, most people in developed countries aren’t at risk for this level of deficiency. However, mild deficiency can cause a variety of troublesome symptoms, including:
- Night blindness and trouble seeing in dim lighting
- Other eye disorders like Keratomalacia, Bitot spots, corneal perforation and eye dryness
- Dry skin and hair
- Pruritus (itchy sensations)
- Broken or chipped fingernails
- Decreased immunity and infections
- Follicular hyperkeratosis (excessive keratin formation in hair follicles) i.e. “chicken skin” or keratosis pilaris
- Hormonal imbalances
Are you at risk for vitamin A deficiency?
Wondering if you have poor conversion and need more pre-formed vitamin A in your diet to meet your needs? Here are the big factors to consider:
1. Genetic Factors
There are two genetic variations (SNPs), R267S and A379V, that could reduce an individual’s ability to make this conversion by impacting the enzyme needed to convert beta carotene to retinol. These genes are actually quite common, with one UK study reporting that 47% of their sample population had at least one of these genes.
Individuals with these genes cannot rely solely on plant foods for their vitamin A and must consume animal foods high in preformed vitamin A to adequately meet their needs
2. Gut imbalances and Inflammation
The majority of conversion of carotenoids to vitamin A occurs in the intestines, so if gut disturbances are present the conversion will be reduced. Gut inflammation will also impact absorption of carotenoids. Even absorption of preformed vitamin A will be effected if the gut inflamed.
Most gut inflammation is rooted in microbiota imbalances in the intestines, so in order to ensure optimal vitamin A absorption and synthesis, you may need to rebalance and repair your gut.
Some of the more common causes of gut inflammation and/or impaired absorption of vitamin A are: parasitic infection, food allergies such as gluten intolerance or celiac disease, fat malabsorption, hydrochloric acid insufficiency (often caused by H.pylori infection), Clostridium difficile infection, or small intestine bacterial overgrowth (SIBO).
3. Liver Dysfunction
After the intestines, the liver is the most important site of vitamin A synthesis. So it’s no surprise that studies have shown that individuals with liver problems don’t efficiently convert beta carotene to vitamin A.
With nonalcoholic fatty liver disease on the rise, primarily related to related to insulin resistance and metabolic syndrome, it is important for individuals with liver problems to consume foods rich in preformed vitamin A.
4. Food Preparation
Since vitamin A is a fat soluble vitamin, eating both carotenoids and preformed vitamin A with fat will help absorption and utilization in the body. That means people on a very low fat diet may struggle to absorb adequate vitamin A from their food.
Cooking carotenoid rich foods also helps increase the bioavailability and absorption in the body. Sauteing vegetables in butter or olive oil could be the best cooking method for improving carotenoid absorption.
Additionally, certain plant fibers, especially pectin, can actually hinder carotenoid absorption. Foods high in pectin include apples, peaches, oranges, blackberries, grapes, grapefruit and apricots.
5. Bile Production and Flow
Bile is released in the small intestine in response to fat intake and serves as an emulsifier to aid in fat digestion. Bile also serves a lesser known, yet very important, function of activating the enzyme that converts carotenoids into vitamin A.
If bile flow isn’t optimal, the conversion rate will be reduced. Gut imbalances, low fat diets, gall bladder removal and liver dysfunction can all negatively affect bile flow and impair the conversion of dietary carotenoids.
Low thyroid hormone production is fairly common, with the American Thyroid Association estimating that 1 in 8 women will develop a thyroid disorder at some point in their lifetime.
Thyroid hormone helps activate the liver to convert carotenoids into vitamin A. This means low thyroid hormone equals less conversion. Thyroid hormone also is important in removing cholesterol from the bloodstream to be used to make the bile needed to activate the conversion enzyme (as discussed above).
In the presence of low thyroid hormone, cholesterol remains high in the blood and bile synthesis suffers, leading to lower vitamin A production by the liver. This leads to a vicious cycle, as vitamin A deficiency is known to exacerbate hypothyroidism.
7. Vitamin D Excess
Too-high levels of vitamin D are something I see frequently in my work with clients. And while vitamin D and vitamin A have a synergistic and protective effect on our health, too much of one will disrupt the binding of the other to its receptor sites.
This means high doses of vitamin D can actually cause symptoms of vitamin A deficiency. If your vitamin D levels are above 60 ng/mL, you should NOT be supplementing with extra D3.
And if you are supplementing with vitamin D, consider adding vitamins A and K2 simultaneously (I like this product). And check out this article for more guidelines on vitamin D supplementation in general.
8. Alcohol Consumption
Alcohol intake has a big impact on vitamin A status because alcohol dehydrogenase—the enzyme that converts retinol to retinaldehyde, which is then oxidized to retinoic acid— is greatly used up by processing alcohol, leaving less to form usable vitamin A.
While most of you reading this blog probably aren’t struggling with alcoholism, that doesn’t mean that you’re in the clear. Being 29 (at the time of this writing) myself, I understand the social pressures to drink in excess when out with peers.
Even one or two nights per week of heavier drinking is enough to impact your vitamin A conversion. (Guidelines for high vs. low risk drinking can be found here.)
9. Zinc Deficiency
Vitamin A and zinc interact in a significant number of ways to support health, and inadequate zinc intake can lead to symptoms of vitamin A deficiency. Zinc is a component of retinol-binding protein (RBP), a protein that transports vitamin A in the blood.
Lower levels of zinc cause reductions in both liver and serum RBP. Zinc deficiency is associated with decreased release of vitamin A from the liver, and zinc supplementation has been shown to significantly increase the vitamin A levels in the blood.
Zinc deficiency is one of the more common deficiencies found in vegetarians, but other at-risk populations include people with gut disorders and those on low calorie diets.
10. Constant Dieting and/or Undereating
This one may seem obvious to some of you, but you might be surprised how easy it is to be chronically undereating on a whole-foods diet. Many popular diet plans are known to be micronutrient deficient, and very low fat diets are especially problematic when it comes to vitamin A intake, absorption, and conversion.
That doesn’t mean low-carb diets are off the hook either; a very low carbohydrate intake often suppresses thyroid activity, which, as mentioned previously, reduces the conversion of beta carotene to vitamin A.
While a low fat diet is more problematic than a low carb diet when it comes to vitamin A, if you’re constantly in a calorie deficit, you can pretty much guarantee you’ll be lacking in a variety of micronutrients.
And even the most “balanced” diets might leave you at risk for a nutrient deficiency like vitamin A or zinc (which affects vitamin A status).
Best sources of Vitamin A
As you just learned, a high intake of beta carotene isn’t enough to provide most people with the vitamin A they need for optimal health. That’s why I recommend to all my clients that they get some source of pre-formed vitamin A in their diet or supplement routine.
Animal products like dairy, eggs, meat and fish are going to provide the highest dietary sources of vitamin A. Liver and other organ meats are especially high in vitamin A. Just 3oz of beef liver has about 300% of the RDA for vitamin A.
So, all you need is a couple ounces of liver a week to meet your Vitamin A requirements. While liver isn’t necessarily the tastiest of foods, it can be easy to sneak into dishes if you are not a fan.
If you dislike liver, check out this blog post for sneaky recipes that can provide you with liver’s many benefits while hiding the taste.
If my clients can’t (or won’t) eat liver and egg yolks, I suggest they supplement with some pre-formed vitamin A on a regular basis. 5,000-10,000 IU per day is plenty for most people, and I like using these vitamin A drops which gives more control over the dosage.
Relying on carotenoids to reach your vitamin A needs is not a good idea for most people, especially if you have genetic and other individual factors that could hinder the conversion.
These factors include gut health, dietary restrictions, and chronic diseases like hypothyroidism, metabolic syndrome, and alcoholism.
Eating a diet rich in animal sources of preformed vitamin A is the best way to ensure that you are providing your body with all your body’s vitamin A needs. Taking a supplement is a good plan B if there’s any reason you can’t (or won’t) eat foods like liver or egg yolks.
So, how do YOU get pre-formed vitamin A in your diet? Tell me in the comments below!