Vitamins and our body

Adequate amounts of vitamins and minerals are essential to good health.

Vitamins and minerals are essential to good health. The best way to get them is from food — but there are specific situations where a supplement genuinely earns its place.

There's a reason the word "essential" so often sits in front of "vitamins." Vitamins and minerals keep the body running the way it's meant to, and the body cannot make most of them on its own — it has to get them from outside. (There are a few exceptions: the body makes vitamin D from sunlight, produces some vitamin K and biotin with the help of gut bacteria, and can make niacin from the amino acid tryptophan.) For everything else, the source is what you eat.

Thirteen vitamins do a remarkable range of jobs: helping the body fight infection, turning food into energy, supporting growth, and clearing waste. Think of them as building blocks the body assembles into the enzymes and hormones that quietly manage heart rate, blood pressure, blood sugar, and countless other processes.

When vitamins run short

Deficiencies often cause no obvious symptoms at first, which is what makes them easy to miss. Over time, though, they take a toll. Too little vitamin D can weaken bones. Too little vitamin C brings on fatigue, weakness, aching, and bleeding gums. Severe, prolonged deficiencies can be dangerous and, left untreated, even life-threatening.

Most people who eat a reasonably varied diet get what they need. If you're genuinely concerned you might be short of something, the reliable way to find out is a blood test — a doctor can check and advise, rather than guessing.

Fat-soluble and water-soluble vitamins

Vitamins fall into two groups, based on how the body handles them, and the practical difference is worth knowing.

Fat-soluble vitamins — A, D, E, and K — are absorbed in the small intestine, and the process works best when some dietary fat is present in the same meal. Once absorbed, the body can store them, mainly in the liver and body fat, keeping a reserve for when they're needed:

• Vitamin A is the vision vitamin, helping the eyes adjust to dim light and distinguish colour. It also supports tissue growth and helps the immune system fight infection.
• Vitamin D lets the body absorb calcium and helps regulate calcium and phosphorus in the blood, which is why it matters so much for bones.
• Vitamin E is an antioxidant that helps protect cells, including red blood cells, from damage.
• Vitamin K is needed to make several of the proteins involved in blood clotting, and plays a role in bone health too.

Water-soluble vitamins — the B vitamins (including biotin, once known as vitamin H), and vitamin C — are not stored to any real degree. The body uses what it needs and passes the rest out in urine, which means they need topping up regularly through the diet. The B vitamins help release energy from food and are needed to process proteins and fats; vitamin C supports the immune system and acts as an antioxidant.

How much is enough?

Recommended amounts vary from person to person, depending on age and stage of life. Children, teenagers, adults, and older people all have different needs, men and women differ, and pregnancy changes the picture again. A useful way to think about it is fuel: give the body the right kind, in the right amount, and it runs well; the wrong kind, or too little, and performance slips over time.

Food first

For most people, the best source of vitamins is not a bottle — it's the plate. A varied diet with plenty of vegetables, fruit, whole grains, and good protein delivers vitamins alongside fibre, minerals, and other compounds that work together in ways a tablet can't reproduce. Many everyday foods are also fortified, cereals and orange juice among them.

It's worth being clear-eyed about what a routine multivitamin does and doesn't do. For generally healthy adults who already eat reasonably well, the evidence that a daily multivitamin improves health is weak. In 2022 the US Preventive Services Task Force found insufficient evidence that multivitamins prevent heart disease or cancer in healthy adults, and a 2024 analysis by the US National Cancer Institute that followed nearly 400,000 adults for more than two decades found no link between daily multivitamin use and living longer. None of this means vitamins don't matter — they're essential — only that, for a well-nourished person, a general multivitamin adds little that food isn't already providing.

And more is not better. With some water-soluble vitamins, very high doses can cause harm — too much vitamin B6 over time can damage nerves, large amounts of niacin can affect the liver, and excess vitamin C can upset the stomach and contribute to kidney stones. Fat-soluble vitamins, which the body stores, carry more risk still at high intakes. Vitamin A is the one to watch in pregnancy: too much can cause birth defects, so anyone who is or may become pregnant should be careful with high-dose vitamin A supplements and check with their doctor. The reassuring flip side is that it's very hard to overdo vitamins through food alone.

When a supplement genuinely helps

Supplements come into their own in specific situations, where they can make a real difference:

• Pregnancy. Anyone who is pregnant or planning to be is advised to take folic acid, which sharply lowers the risk of certain birth defects. Prenatal supplements are a clear, well-established case.
• Vitamin B12 for those who eat little animal food, or little food overall. B12 comes almost entirely from animal sources, so vegans and many vegetarians benefit from a supplement. So too can people who are simply eating much less than they used to — including the growing number using appetite-reducing weight-loss injections, where a sharply smaller intake can open up gaps in B12 and other nutrients. Doctors increasingly monitor for this, and a supplement may be recommended.
• Older adults. The body absorbs B12 less efficiently with age, and many older people are low in vitamin D, so both are commonly recommended.
• Diagnosed deficiencies. If a blood test shows you're short of iron, vitamin D, or anything else, a targeted supplement is exactly the right tool — guided by your doctor rather than guesswork.

The common thread is that supplements work best aimed at a real need, not taken as blanket insurance. If you're unsure whether you fall into one of these groups, or you take medication that might interact with a supplement, a quick conversation with your doctor or a registered dietitian is the sensible first step.

This article is general information, not medical advice.