Vitamins are one of those things everyone knows they need but few people truly understand. We hear “take your vitamins” from childhood, see them plastered across cereal boxes and juice cartons, and vaguely accept they’re important.

But what do they actually do? Why does the body need 13 of them? And if a balanced diet covers most needs, why are vitamin supplements a multi-billion euro industry?

The short answer: most people eating a reasonably varied diet are fine. But there are a few common gaps that affect millions of people, and understanding which vitamins matter most can save both money and worry.

What Vitamins Actually Do

Vitamins are organic compounds the body needs in small amounts but can’t produce enough of on its own. They don’t provide energy like carbs, protein, or fat. Instead, they enable the processes that keep the body running.

They help convert food into usable energy. They support the immune system. They assist in building and repairing tissue. They protect cells from damage. Without them, these processes slow down or stop entirely.

Vitamins fall into two groups based on how the body stores them, and this distinction matters for supplementation.

Fat-Soluble Vitamins: A, D, E, K

These dissolve in fat and get stored in body tissue. Because they accumulate, you don’t need them every single day. But this also means it’s possible to take too much through supplements, which can become toxic.

Vitamin A

What it does: Supports vision, immune function, skin health, and cell growth.

Where to get it: Liver, fish, eggs, and orange vegetables like carrots and sweet potatoes (as beta-carotene), plus leafy greens.

Supplement it? Rarely necessary. Most people get enough through food. High-dose supplements can actually be harmful, particularly during pregnancy.

Vitamin D

What it does: Helps the body absorb calcium, supports bone strength, plays a role in immune function and mood regulation.

Where to get it: Sunlight is the primary source. Small amounts come from fatty fish, egg yolks, and fortified foods.

Supplement it? This is the big one. In northern Europe, where sunlight is limited for months of the year, deficiency is extremely common. Fatigue, low mood, frequent illness, and bone pain can all be signs. A blood test confirms it, but many health authorities now recommend supplementation as a general precaution during autumn and winter.

A combined D3 and K2 supplement is often the smartest choice, since K2 helps direct calcium where the body needs it. This UK-made option provides a full year’s supply for around £10.

Vitamin E

What it does: Acts as an antioxidant, protecting cells from damage. Also supports immune function.

Where to get it: Nuts, seeds, vegetable oils, and leafy greens.

Supplement it? Almost never necessary. Deficiency is rare, and food sources are widely available.

Vitamin K

What it does: Essential for blood clotting and bone health.

Where to get it: Leafy greens (K1) and fermented foods like natto and certain cheeses (K2).

Supplement it? Deficiency is uncommon. K2 is gaining attention in research for bone and cardiovascular health, but evidence is still developing.

Water-Soluble Vitamins: B-Complex and C

These dissolve in water and aren’t stored in the body in significant amounts. You need them regularly, ideally daily. The upside is that toxicity risk from supplements is much lower because the body excretes what it doesn’t use.

The B Vitamins

There are eight B vitamins and they work as a team, primarily helping convert food into energy. Here’s what each one does and where to find it:

B1 (Thiamine): Energy metabolism and nerve function. Found in whole grains, pork, and legumes.

B2 (Riboflavin): Energy production and cell growth. Found in dairy, eggs, lean meats, and leafy greens.

B3 (Niacin): DNA repair and cholesterol metabolism. Found in meat, fish, whole grains, and peanuts.

B5 (Pantothenic Acid): Hormone production and energy metabolism. Found in nearly all foods. Deficiency is extremely rare.

B6 (Pyridoxine): Amino acid metabolism and neurotransmitter production. Found in poultry, fish, potatoes, and bananas.

B7 (Biotin): Fat and carbohydrate metabolism, hair and nail health. Found in eggs, nuts, seeds, and sweet potatoes.

B9 (Folate): DNA synthesis and cell division. Found in leafy greens, legumes, and fortified grains. Critical before and during pregnancy to prevent neural tube defects.

B12 (Cobalamin): Red blood cell formation, nerve function, and DNA synthesis. Found exclusively in animal products: meat, fish, dairy, and eggs.

The crucial one: B12 deserves special attention. It’s only found in animal foods, which means anyone on a vegan diet must supplement. Absorption also decreases with age, so people over 50 may need supplements regardless of diet.

Methylcobalamin is the most bioavailable form of B12 for most people. This BetterYou Vitamin B12 provides the recommended daily dose in an easy-to-swallow format.

Vitamin C

What it does: Supports collagen production, acts as an antioxidant, boosts iron absorption, and contributes to immune function.

Where to get it: Citrus fruits, berries, peppers, broccoli, and tomatoes.

Supplement it? Most people get more than enough from food. The idea that megadoses of vitamin C prevent colds is not well supported by research. Very high doses (above 1000mg) can cause digestive issues without providing additional benefit.

Which Vitamins Most People Should Actually Think About

Out of all 13 vitamins, three account for the vast majority of real-world deficiencies:

Vitamin D. Especially in northern Europe. Limited sunlight, indoor lifestyles, and darker skin tones all increase risk. Supplementing through autumn and winter is recommended by many European health authorities.

B12. Essential for vegans. Worth checking for vegetarians and anyone over 50.

Folate. Critical for women who are pregnant or planning to become pregnant. Supplementation is standard medical advice in this case.

For most other vitamins, a diet that includes vegetables, fruits, whole grains, protein sources, and some dairy or alternatives will cover the bases.

Food vs. Supplements: Why Food Usually Wins

Nutrients from whole foods come with built-in advantages that isolated supplements can’t replicate.

An orange doesn’t just deliver vitamin C. It also provides fibre, flavonoids, and other compounds that work together to enhance absorption and health benefits. A vitamin C pill gives you ascorbic acid and nothing else.

This concept, called nutrient synergy, is why nutrition scientists consistently recommend food as the primary source. Supplements fill genuine gaps. They don’t replace the complexity of whole foods.

The practical takeaway: eat a varied, colourful diet first. Supplement only where a real gap exists.

The Bottom Line

The body needs 13 vitamins, and a varied diet covers most of them without any extra effort. The exceptions that affect the most people are vitamin D (especially in northern climates), B12 (for vegans and older adults), and folate (for pregnancy).

Before spending money on vitamin supplements, consider whether your diet already provides what you need. If you’re unsure, a blood test is more useful than guessing. And if you do supplement, stick to the specific vitamins you actually need rather than buying a shelf full of bottles.