THE FOOD · INVESTIGATION
Vitamins:
do we actually
need to think
about them
this much?
I went down the vitamin rabbit hole.
And there is a lot down there.
Thirteen vitamins. Multiple forms. Reference values. Upper limits. Deficiencies. Supplements. Fortified foods. Fat-soluble vitamins. Water-soluble vitamins.
And, somehow, we managed to get all the way from vitamin A to vitamin K without using every letter in between.
At some point, I had a table open in front of me with numbers for every vitamin and a growing collection of tabs explaining what each one supposedly does.
And then I had to stop and ask myself:
Because knowing that vitamin B6 has a recommended intake of a certain number of milligrams doesn't necessarily make me better at eating.
And knowing that vitamin D matters for calcium absorption doesn't tell me whether I need a supplement.
And knowing that vitamin C is found in kiwis and peppers doesn't mean I need to start calculating how much vitamin C I ate today.
So I went looking for something more useful than a list of vitamins and their recommended daily amounts.
What even is
a vitamin?
Vitamins are micronutrients: substances your body needs in relatively small amounts to keep all sorts of biological processes running.
They aren't fuel. They don't give you energy in the way carbohydrates, fat and protein do.
Instead, vitamins tend to help your body use other things, build things, protect things and keep chemical reactions moving.
And there are 13 of them that we consider essential to humans.
They are very different molecules doing very different jobs. Vitamin C has little in common chemically with vitamin D. Vitamin A behaves differently from vitamin B12. Some can be stored in the body for relatively long periods, while others are not stored to the same extent.
So the word vitamin doesn't describe one particular kind of molecule.
And the 13 vitamins ended up in that category largely because we discovered, one by one, that our bodies needed them.
Which brings us to the next question:
Let's investigate.
So why are
there 13 of them?
If vitamins are just a category, the obvious question is: why these 13?
The answer isn't that your body has a specific “vitamin system” containing exactly 13 slots.
The 13 vitamins are simply a collection of different organic compounds that we have established humans need in small amounts to stay healthy.
And they are very different from one another.
Vitamin C is a small water-soluble molecule. Vitamin D is made from a cholesterol-related molecule and can actually be produced by your skin when it is exposed to UVB light. Vitamin B12 is a large, complex molecule containing cobalt. Vitamin K is involved in blood clotting. Vitamin A is important for vision, among many other things.
Calling all of these things “vitamins” can therefore be a little misleading.
of molecules.
They're more like a collection of essential tools that happen to share one important characteristic: your body needs them, but generally can't make enough of them itself.
And even within the vitamin family, there are smaller families.
The B vitamins are a good example.
There isn't actually a single molecule called “vitamin B”. There are eight different B vitamins, each with its own structure and functions.
They ended up sharing the letter B because of how the history of vitamin discovery unfolded, not because they are all versions of the same thing.
And yes, this is also why you don't see vitamin F, G, H, or I on the shelf next to vitamin C.
The naming history is messy. Some substances were initially thought to be vitamins and later turned out not to meet the definition. Others were reclassified or discovered to be different forms of compounds we already knew.
Vitamin K is one of the survivors of that rather chaotic history. The letter comes from the German word Koagulation, referring to blood clotting.
ONE CLASSIFICATION ACTUALLY MATTERS
Not all vitamins
behave the same way.
Fat-soluble
These can be stored in the body's tissues, particularly the liver and body fat.
Water-soluble
These generally aren't stored in the body to the same extent, although there are important exceptions — vitamin B12, for example, can be stored in substantial amounts.
Why does this distinction matter?
Because how your body handles a vitamin affects what happens when you get too little — but also what happens when you get a lot.
A vitamin that can accumulate in the body has a different story from one that is more readily lost.
This is one reason why the sentence “it's just a vitamin” doesn't really tell us much.
But that doesn't mean more is better.
So what happens
when you don't
get enough?
Vitamins are needed in tiny amounts, but “tiny” doesn't mean optional.
Your body can compensate for a lot of things for a while. It can use stored nutrients, change how efficiently it uses them, and prioritise some biological processes over others.
But eventually, if a vitamin is missing for long enough, something starts to go wrong.
And because different vitamins are involved in different processes, vitamin deficiency doesn't look the same for every vitamin.
Can affect vision and immune function.
Can interfere with collagen production and, in severe cases, eventually lead to scurvy.
Can impair calcium and bone metabolism.
Can affect blood cells and the nervous system.
Can interfere with normal blood clotting.
So there isn't really one thing called “vitamin deficiency”.
And this is where I think the vitamin conversation can become unnecessarily confusing.
Because reading about all of these consequences can make it sound like we're constantly one missed vegetable away from disaster.
We're not.
NUMBERS ARE USEFUL
But they're not
a daily exam.
Reference values are useful. They give us an idea of how much of a nutrient people generally need to avoid inadequate intake and maintain normal function.
But they aren't a daily exam.
If you eat slightly less vitamin C than your reference value one day, your body doesn't suddenly send you an emergency notification.
Your nutritional status is influenced by your intake over time, your body's stores, absorption, physiology and individual circumstances.
And the consequences of inadequate intake usually develop over time rather than appearing because you missed a target on Tuesday.
vitamin C
Not a number you have to hit with mathematical precision.This distinction matters because nutrition numbers can create a strange illusion of precision.
You might see: 95 mg vitamin C and start thinking: Ok. I need exactly 95 mg.
But biology rarely works like that.
Reference values are tools for understanding nutritional needs at the population level. They are not instructions telling every individual exactly what to eat every single day.
And they become particularly important in situations where nutritional needs or risks change.
Pregnancy is one example. So are certain medical conditions, malabsorption problems, restrictive diets, and other circumstances that can make deficiency more likely.
For most healthy people eating a reasonably varied diet, the question usually isn't:
“How do I make sure I hit all 13 vitamin targets every single day?”It's a much simpler one:
“Am I regularly eating a variety of foods that give my body the nutrients it needs?”That question is considerably easier to live with.
MEET THE 13
Okay, so what are these
13 vitamins actually doing?
This is where the list finally becomes useful.
I don't think you need to memorise every vitamin, its chemical name, its reference value and every food that contains it. I certainly wasn't going to.
Instead, I wanted to know something much simpler:
So let's meet them.
VITAMIN A
More than just carrots.
Vitamin A is involved in vision, immune function, reproduction, growth and the maintenance of tissues such as skin and the lining of organs.
But there is an important distinction here.
When we talk about vitamin A in food, we're actually talking about several related compounds.
Preformed vitamin A, mainly retinoids, is found in animal foods such as liver, dairy products and eggs.
Then there are provitamin A carotenoids, which are found in plants. Some carotenoids can be converted by the body into vitamin A.
This is where carrots became so closely associated with vitamin A.
Carrots are rich in beta-carotene, a carotenoid that gives them their characteristic orange colour.
But carrots aren't the only place you'll find these compounds. Orange and yellow fruits and vegetables can contain them, as can leafy green vegetables.
And leafy greens give us a fun example of how colour can be misleading.
They contain carotenoids too — you just don't necessarily see them because they're sitting underneath a much stronger green pigment: chlorophyll.
That distinction is small, but it matters.
B VITAMINS
One family.
Eight different jobs.
The B vitamins are probably the easiest group to misunderstand.
There isn't one vitamin B.
There are eight: B1, B2, B3, B5, B6, B7, B9 and B12.
And although they share a letter, they aren't interchangeable.
Many of them are involved in the enormous network of chemical reactions that keeps your cells running — particularly reactions involved in energy metabolism.
But each has its own functions.
Helps enzymes involved in energy metabolism and is important for normal nerve and heart function.
Forms part of molecules that help enzymes carry out oxidation-reduction reactions.
Is used to make NAD and NADP, molecules involved in hundreds of metabolic reactions.
Is a component of coenzyme A, which is central to the metabolism of carbohydrates, fats and proteins.
Is involved in amino-acid metabolism, neurotransmitter synthesis and many other reactions.
Acts as a cofactor for enzymes involved in processes including fatty-acid synthesis and metabolism.
Is essential for DNA synthesis and cell division. This is particularly important during periods of rapid cell growth, including pregnancy.
Is involved in DNA synthesis, red blood cell formation and normal nervous-system function.
Eight slightly different jobs.
And suddenly “take your B vitamins” sounds a lot less informative.
VITAMIN C
The collagen connection.
Vitamin C has quite a few jobs, but one of the most interesting is its role in collagen synthesis.
Collagen is a structural protein found throughout the body — in skin, blood vessels, bones, cartilage and connective tissue.
Vitamin C is needed for enzymes that modify collagen so that it can form its normal structure.
It also contributes to normal immune function and is involved in other metabolic processes, including the synthesis of L-carnitine.
And yes, citrus fruits are a source.
But oranges don't have a monopoly on vitamin C.
Kiwis, berries, peppers, broccoli and many other fruits and vegetables can provide it too.
VITAMIN D
The slightly unusual one.
Vitamin D is where the vitamin story gets interesting.
make vitamin D itself.
When UVB radiation reaches your skin, it triggers a series of chemical reactions that ultimately produce vitamin D3.
That doesn't mean sunlight is a universal prescription for getting enough vitamin D.
How much vitamin D your skin produces depends on factors such as latitude, season, time of day, skin pigmentation, clothing and sunscreen use.
UV exposure also comes with its own risks.
Vitamin D is important for calcium and phosphate metabolism and therefore for maintaining normal bones. It also has roles in other tissues and physiological processes.
Dietary sources include fatty fish, egg yolks and some fortified foods.
And because getting enough from sunlight and food isn't equally easy for everyone — particularly at northern latitudes and during winter — vitamin D is one of the vitamins where supplementation can sometimes make sense depending on the individual context.
VITAMIN E
The antioxidant.
Vitamin E is actually a family of compounds, with alpha-tocopherol being the form used when discussing human requirements.
One of its main roles is as an antioxidant.
In simple terms, it helps protect cell components from oxidative damage.
Vitamin E is found particularly in foods such as nuts, seeds and vegetable oils, as well as some vegetables.
Severe deficiency is rare in healthy people and is usually associated with particular medical circumstances affecting fat absorption or metabolism.
Sometimes the important question isn't “How can I get more?”
It's:
VITAMIN K
The clotting vitamin.
Vitamin K is best known for its role in normal blood clotting.
It is also involved in proteins that help maintain bone and vascular health.
There are several forms of vitamin K.
Vitamin K1, or phylloquinone, is the main form found in plants. Leafy green vegetables are particularly rich sources.
And there is a neat reason for that.
Vitamin K1 is involved in photosynthesis, so plants — especially green ones — naturally contain it.
Vitamin K2, or the menaquinones, is a group of related compounds found in some fermented foods and animal products.
Despite its important functions, vitamin K deficiency is uncommon in healthy adults and is more often associated with problems such as malabsorption or certain medications.
But needing something and constantly worrying about getting more of it are two very different things.
THE QUESTION I ACTUALLY CAME FOR
Okay, but do I actually
need supplements?
So we've established that vitamins are essential. There are 13 of them. They all do different things. And getting too little of some of them can genuinely cause problems.
Which brings us to the question that probably sent most of us looking for this information in the first place:
But biology is
more complicated.
This is where I think nutrition advice gets particularly confusing.
Because the logic seems almost impossible to argue with:
Except that isn't quite how biology works.
Your body needs vitamins within a certain range. Getting too little can be a problem. But once you've got enough, adding more doesn't automatically give you an extra health benefit.
THE FUEL-TANK ANALOGY
It's a little like filling up your car.
If the tank is nearly empty, adding fuel is very useful. Once the tank is full, pouring another five litres onto the roof doesn't make the car run better.
SO I WENT LOOKING
But aren't supplements
supposed to make us healthier?
This is where I went looking for something more useful than supplement advertisements.
Researchers have actually spent a lot of time asking whether giving generally healthy adults extra vitamins and minerals prevents things like cardiovascular disease, cancer or death.
The answer isn't a simple yes.
A large evidence review for the U.S. Preventive Services Task Force found little or no overall benefit from most vitamin and mineral supplements for preventing cardiovascular disease, cancer or death in healthy adults without known deficiencies.
There are exceptions and uncertainties, and the evidence differs between individual supplements and outcomes.
The Nordic Nutrition Recommendations come to a similar practical conclusion: in healthy people eating a varied diet that covers their energy needs, prolonged supplement use generally hasn't been associated with reduced chronic-disease risk or other health benefits.
“vitamin supplements don't work.”
That's much too broad.
A supplement can be extremely useful when someone actually needs the nutrient.
So when do
supplements
actually make sense?
There are plenty of situations where getting enough of a vitamin through food isn't necessarily straightforward.
Pregnancy
Certain medical conditions
Problems with nutrient absorption
Particular medications
Restrictive diets
Life stages or circumstances affecting nutrient needs
And sometimes the issue is simply that a particular nutrient is difficult to obtain in sufficient amounts from food under certain circumstances.
The Nordic recommendations, for example, identify specific situations where supplementation can be appropriate, including vitamin D in certain groups and folic acid for people planning pregnancy.
They also note that people following restrictive diets may need particular supplements — vitamin B12 is a clear example when foods of animal origin are excluded.
The useful question isn't:
“Should humans take vitamins?”It's:
“Does this particular person have a reason to take this particular nutrient?”That's a much better question.
THE MULTIVITAMIN
Ah, the nutritional
insurance policy.
The little tablet that promises to cover all your bases just in case.
I understand the appeal.
You don't have to think about whether you got enough B12. Or vitamin C. Or folate. Or whatever vitamin you happened to read about last week.
and move on.
But if your diet already provides what you need, there's no obvious reason to assume that adding a multivitamin will make you healthier.
That doesn't mean multivitamins are inherently dangerous or that nobody should take one.
It means the evidence doesn't support the much bigger promise that more vitamins automatically equal better health.
And there is another reason not to think of supplements as completely harmless.
They're concentrated.
It's much easier to consume a large dose of a nutrient in a tablet than it is through ordinary food.
Some vitamins can accumulate in the body, and excessive intake of certain nutrients can cause harm.
The Swedish Food Agency therefore advises against unnecessarily high doses and notes that most people can get the vitamins and minerals they need from ordinary food.
BACK TO WHERE WE STARTED
Remember that table
I was obsessing over?
All those numbers looked incredibly important when I first collected them.
But after digging into what they actually mean, I don't think they're telling us:
you need to hit every day.”
They're telling us something much more useful:
Not a homework assignment.
SO, WHAT DID I ACTUALLY LEARN?
Not every tired day
is a deficiency.
I started this article with thirteen vitamins, a spreadsheet full of numbers and a slightly uncomfortable feeling that I was supposed to somehow keep track of all of them.
After going down the rabbit hole, I don't think that's the point.
Yes, vitamins matter.
They are involved in hundreds of processes that keep us alive and functioning. Deficiencies are real, and in some situations they can have serious consequences.
But that doesn't mean healthy eating requires us to know the exact amount of every vitamin we ate today.
It doesn't mean every tired day is a vitamin deficiency.
And it definitely doesn't mean that taking more vitamins automatically makes us healthier.
Eat a variety of foods.
Pay attention to circumstances that can increase the risk of deficiency.
Use supplements when there is a reason for them.
Not because variety is a magical nutrition rule, but because different foods bring different nutrients to the table.
Fruits and vegetables. Grains and legumes. Nuts and seeds. Dairy or alternatives. Eggs, fish, meat or other sources of protein. Whatever combination makes sense for you.
And then there are the situations where food alone might not be enough — pregnancy, certain medical conditions, restrictive diets, deficiencies, particular medications, or simply a nutrient that is difficult to get enough of in a particular circumstance.
That's where supplements can become useful.
Not as a shortcut to being healthier.
Not as a replacement for food.
And not because we should be frightened of missing something.
AND MAYBE THAT'S THE PART I WAS LOOKING FOR
Understanding gives us
better questions to ask.
I don't think the lesson of vitamins is that we should know more numbers.
I think it's that what those numbers actually mean is far more useful than memorising them.
“Am I getting enough of all 13 vitamins?”
becomes“Am I eating a reasonably varied diet?”
“Is there something about my diet or circumstances that puts me at risk of deficiency?”
“Do I actually have a reason to take this supplement?”
And if the answer to those questions is no?
and get on with our lives.
Because nutrition is supposed to exist within our lives.
Not become another thing we have to constantly get right.
I'm still learning, obviously.
I went into this expecting to come out with a perfect list of what I should eat.
Instead, I came out thinking that I probably need to worry about vitamins a little less — and understand them a little better.
And honestly, I'll take that.
Don't obsess over nourishing perfectly.
READ THE EVIDENCE
Sources
- Nordic Nutrition Recommendations 2023. Nordic Council of Ministers.
- U.S. Preventive Services Task Force. Vitamin, Mineral, and Multivitamin Supplementation to Prevent Cardiovascular Disease and Cancer.
- Livsmedelsverket — Swedish Food Agency. Information and recommendations concerning vitamins, minerals and dietary supplements.
- National Institutes of Health, Office of Dietary Supplements. Fact sheets for individual vitamins and minerals.