Vitamin Toxicity

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vitamin toxicity

Vitamins mean “Vital Amines’; in other words, “supporters for our survival”. It is what we have been taught about vitamins in our biology class. Since centuries ago, vitamins have been believed to be beneficial for the human body facilitating the function of the organs to work in an optimal condition. So, it might seem unreasonable when you see the title “Vitamin Toxicity”. How could such vital elements be toxic to our bodies? When might they occur? What kinds of vitamins are prone to overdose? How could I avoid vitamin toxicity? The following article will cover all the questions that come to your mind. Let’s see how “too much of a good thing” can be harmful to us. 

What are vitamins? 

Vitamins are essential ingredients that help our body function in optimal conditions. Vitamin D can be synthesized by our body from sunlight while our gut bacteria can produce Vitamin K.  

Vitamin C, Vitamin E, Vitamin A, and B-Vitamins are not able to be produced from our bodies which are necessary to be supplied via dietary sources or taken as vitamin supplements. 

A vitamin-rich diet includes fruits, green leafy vegetables, milk and dairy products, meats and oily fish. 

Can vitamins be toxic to our body?

Generally, there are two forms of Vitamins, “Water Soluble” and “Fat Soluble”. The former like Vitamin C and B Vitamins are less likely to be toxic since they are excreted largely in urine and stored only in a limited amount while the latter like Vitamin A, D, E, and K can are stored in a variable amounts by our body favoring for toxicity to some extent.  

Let me make it clear, “A NORMAL balanced diet cannot generally lead to vitamin toxicity regardless of how the food you have eaten is rich in vitamins” which means your body can handle pretty well with the vitamins in your diet. However, when taken in excess and extreme amounts, they can be harmful to some extent; the following are some effects of toxicity of respective vitamins. 

What happens when you have taken vitamins in excess and extreme amounts? 

Vitamin A  

Why does it occur? 

Since the body lacks the mechanism to destroy excess vitamin A, when it is taken in an excess amount as supplements, as some form of medication (e.g. retinol -to treat acne), or as diet (e.g. carrot), it can lead to overloading of vitamin A (a condition called Hypervitaminosis A) in your body. Its symptoms include drowsiness, irritability, nausea, vomiting, abdominal pain, and increase skin pigmentation (which is generally harmless except for cosmetic purposes) 

Your skin might turn yellow 

A condition called hypercarotenemia results from over-consumption of vitamin A precursors (particularly carrots) which causes yellow discoloration of the skin although it has no dangerous consequences apart from cosmetic reasons.   

It can be toxic for your fetus 

It is important to note that Vitamin A can be teratogenic when taken more than 1000 IU/day during pregnancy, particularly in the first trimester so is Isotretinoin (Accutane), a drug used for the treatment of severe forms of acne. 

Hypervitaminosis-A Epidemic 

Although extremely rare, vitamin A toxicity can result from the diet. A well-known event of vitamin toxicity is the “hypervitaminosis-A epidemic” that occurred in the Arctic during the 20th century. The Inuit people who lived in the region relied heavily on the consumption of polar bear liver without knowing it contains high levels of vitamin A. Over time, they developed headaches, dizziness, nausea, vomiting, joint pain, blurred vision, coma and some even died. 

That event enlightened them about the potential dangers of consuming high levels of vitamin A and led to recommendations for limiting the consumption of polar bear liver and other animal sources of vitamin A. 

Vitamin D  

Why does it occur? 

Its toxicity occurs mainly from taking excessive Vitamin D supplements rather than sun exposure or diet. 

Vitamin D toxicity is more common in people with kidney (glomerular) disease, some lymphoma and some congenital disorders of metabolism. However, most cases of vitamin D toxicity result from over-supplement, misunderstanding of prescription, and prescription errors. 

Hypervitaminosis D and Vitamin D Toxification 

An excess of vitamin D in the body can be described in two terms. Hypervitaminosis D is defined as blood vitamin D levels over 100 ng/mL, while vitamin D intoxication is defined as serum levels over 150 ng/mL. 

“An excess of vitamin D leads to hypercalcemia.” 

Since vitamin D helps to produce calcium in your body, its excess will lead to increased calcium in your blood, leading to headache, abdominal discomfort, thirst, dehydration, and altered mental status. 

A case study from the National Institute of Health reported that an old man with a history of dementia who was given 50000 IU of daily vitamin D for 6 months presented with multiple symptoms of the aforementioned symptoms of hypercalcemia. 

In addition, increased calcium in blood and urine can also result in Calcium stones in the urinary tract.  

Have your Vitamin D Level “Checked” 

So, it is noteworthy that although vitamin D deficiency is common in the general public, especially in the elderly population, its toxicity should not be underestimated.  

So, the best way to consider whether you should take supplements or not is to consult with a healthcare professional for a blood vitamin D level check.  

Vitamin E  

Why does it occur? 

When it is taken in excess amounts, its toxicity mainly results from interaction with some enzyme from our body which might interfere with blood clotting. 

 It rarely occurs in healthy individuals but should be considered in patients who are taking warfarin1 since both of them can act synergistically to interfere with blood clotting resulting in an increased bleeding tendency. 

Risk of Prostate Cancer and Heart Disease 

On top of that, a study conducted on 35000 men in the US and Canada suggested that taking vitamin E as supplements can slightly increase the risk of prostate cancer and heart failure. However, more studies and stronger shreds of evidence are expected to confirm and validate such long-term complications. 

Acute Vitamin E Toxicity 

Regarding acute toxicity of vitamin E, Fatigue and weakness are possible in patients taking moderately high doses (800 IU/day) and gastrointestinal disturbances like nausea and vomiting can be seen in patients taking very high doses (~2500 IU/day). 

Vitamin K 

Toxic doses for vitamin K are not established since its toxicity is rare. However, patients taking warfarin should be careful since Vitamin K can interfere with the action of warfarin1.  

Vitamin C 

Although it is rare and less serious, its symptoms include bloating, abdominal discomfort, nausea and diarrhea since it is osmotically active and draws water from the gut.  

There are also a few case scenarios of chronic vitamin C toxicity which results in the formation of kidney stones.   

B Vitamins 

Generally, Vitamins B1, B2, B3, B6, and B12 are not toxic to the human body even when taken as daily supplements. However, people with liver disease are prone to vitamin B3 toxicity, and those with kidney disease the vitamin B6 toxicity. 

Not prone to be toxic but can be allergic 

Although rarely presented as toxicity, B Vitamins, particularly Vitamin B1 can cause an allergic reaction in some people which presents with varying symptoms from a minor rash to severe wheezing.  

Too much Nerve-enhancer can be toxic to “Nerves” 

It is also worth noting that Vitamin B6 which is commonly used as a supplement for nerves and neurons, can have adverse effects on the nerves when it is taken for a long time with 300-500 mg/day, especially with poor kidney function. 

1Warfarin – a medication used for thinning of the blood given in patients with blood hyper-clotting diseases like deep vein thrombosis and pulmonary embolism as well as in patients with abnormal heart rhythm to prevent stroke. 

Can I get vitamin toxicity if I take daily multivitamin supplements?  

No, most OTC multivitamin supplements in the market are within the recommended daily allowance which means your body can handle the amount you have taken as supplements on a once or twice daily basis. 

How Can I Avoid Vitamin Toxicity?

Do not take Multiple Multivitamins 

But, it is noteworthy that you should not take multiple forms and brands of multivitamins on a daily basis which might cause more harm than benefits. To make it clear, one form or brand of Multivitamins on a recommended daily dose is enough for your body. 

Consult for a Tailored and Focused Supplement  

It is also a wise idea to consult with a healthcare professional who could provide you with a tailored and focused supplement of vitamins regarding your symptoms of vitamin deficiency which can also avoid unnecessary adverse effects of vitamin toxicity.    

So, what are the general “safe” recommended doses? 

If you have liver or kidney diseases, you should consult with your doctor before taking OTC Multivitamins since the storage and excretion of vitamins largely depends on these organs. As long as you do not have any medical problems, the following are regarded as recommended doses for vitamin supplements. 

Table reference: 

Take-home message 

“Being too much” is not good for any occasion, as in “Vitamin Supplements”. It is a good habit to have concerns about your health and take vitamin supplements to function your body in optimal condition. That being said, a better habit is to always consider acquiring vitamins from diet and taking vitamin supplements in the correct amount in order to get rid of these unnecessary effects of vitamin toxicity. 

I think you will be interested in this article, Do Vitamins Work? Check this out if you want to know how different vitamins and supplements benefit us or not.

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Dr Tun Min is s GP working in NHS UK and writing articles about supplements and vitamins based on personal clinical experience and clinical research.

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