Can You Overdose on Vitamins and Multivitamins?


Most people take some kind of vitamin or multivitamin tablet daily to boost their health and plug any gaps in their dietary nutrition.  Sometimes, when we are feeling run down or it is flu season, we may be tempted to take a few extra.  After all, you can’t have too much of a good thing, can you?  If one tablet is good for you then, surely 3 tablets will be three times as good?  But then the worry is that you could be overdosing.  So can you overdose on vitamin or multivitamin tablets?  The short answer is yes but it’s unlikely and depends on a number of factors.  So let’s look at this in more detail.  For a start, what actually is a vitamin?

What Are Vitamins and Minerals?


It can be confusing to know how to classify vitamins.  They usually come in the form of tablets or capsules and are sold next to medicines so some think they are drugs.  Others think that a multivitamin can give them more energy.  Both these beliefs are incorrect.

Vitamins are organic substances, that is they come from plants or animals and they contain carbon.  Minerals are inorganic substances, that is they that come from the ground and water and are absorbed by plants or consumed by humans and animals.

What Are Macronutrients And Micronutrients?

The food we eat is divided into macronutrients and micronutrients. The things we need to eat in large quantities are the macronutrients and these build and maintain our tissues, such as our skin and muscles, and give us energy to function. Carbohydrates, fats, dietary fibre, water and proteins are classed as macronutrients.  Vitamins and minerals are micronutrients because we only need very small amounts of them. They react with our bodies to keep everything working properly.  Some of the things micronutrients do are improve the immune system, stimulate growth and development, and aid cells and organs do their jobs.

Think about your body as being a bit like a car.  The macronutrients are like petrol.  Petrol is essential to provide the energy to move the engine and macronutrients do the same job for our bodies.  Micronutrients are like engine oil.  Without enough oil in your engine none of the moving parts will function properly and eventually it will breakdown.  In the same way micronutrients are vital for all the different systems in your body to function and without adequate amounts of them we will end up with serious health problems and eventually die.  However, in the same way as putting too much oil in an engine will cause problems, so will taking too many micronutrients.

What Are The Essential Vitamins and Minerals?

There are certain vitamins and minerals that scientists have discovered are vital for the human body to operate correctly.  These are called ‘essential’ vitamins and minerals as we can’t manage without them.  There are thirteen essential vitamins and sixteen essential minerals. Most multivitamins contain all of these in the correct amounts or you can choose to take them individually.

The thirteen essential vitamins are vitamins A, C, D, E, K, and the B vitamins, B6, B12, biotin, folate, niacin, pantothenic acid, riboflavin, and thiamine.  The minerals are divided between macrominerals and microminerals.  The microminerals are only needed in tiny amounts. The macrominerals are calcium, chloride, magnesium, phosphorus, potassium, sodium, and sulphur.  The microminerals are iron, zinc, iodine, chromium, copper, fluoride, molybdenum, manganese, and selenium. To give you some idea, the recommended daily amount for a man of vitamin C is 90 mg, of calcium it is 1000 mg and of iron it is 8 mg.

How Are Vitamins Absorbed?

Vitamins are absorbed by the body in three ways.  Vitamin D is synthesised by your skin from sunlight.  Water soluble vitamins can dissolve in water and so are easily absorbed into your bloodstream. Your body can’t really store water soluble vitamins so any extra passes out of your body in urine.  This means you have to consume these vitamins every day. Vitamin C and all the B vitamins are water soluble. Fat soluble vitamins are not absorbed as easily and they are stored in your liver and fat cells.  The good side of this is they don’t have to be taken every day but the bad side is that it is easy for them to build to toxic levels.  The fat soluble vitamins are vitamins A, D, E, K. Minerals are not so easily classified into water or fat soluble but generally speaking most of them are stored by the body in some form.

How Can You Overdose On Vitamins and Multivitamins?

The obvious answer is, of course, by taking too many!  You may think that it is safe to take as many of the water soluble vitamins as you like since any excess is flushed out of your body.  This is what normally happens.  However, if you take very large amounts of even the water soluble vitamins it can be too much for your body to handle and it will store the vitamins instead, leading to ongoing problems.  Think of it like alcohol.  If you have a small amount of alcohol your body can process it through your liver and flush it out of your body. On the other hand, if you have a large amount your body can’t cope and you will end up with a hangover.

Another danger is that you can unintentionally overdose on your vitamins and minerals.  Some kinds of food can be fortified with a number of different vitamins and minerals.  Cereals are a common example of this.  Some countries add things like iodine to their water.  It’s a good idea to double check the ingredients and quantities of anything that says it is fortified.

Lastly, the recommended amounts of vitamins and minerals are based on an average man.  If you are smaller than average you may need less.  If you are female you need to find guidelines for your gender. Drinking anything containing alcohol, tannins and caffeine affects how your body uses nutrients. Also if you are having digestive problem it can affect how fast or slow your body absorbs nutrients.

However, if you are sensible and don’t go to extremes, vitamins and minerals, usually in the form of a multivitamin, are a safe and sensible supplement to your diet.

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