Dietary supplements: who needs them and what to look for when buying
Should you take vitamins or not? Almost everyone who cares about their health asks this question. According to EFSA, the vitamin D requirement for healthy adults is 15 mcg per day, but many people do not get enough. Some supplements do close that gap, while others provide no benefit. At the same time, store shelves are packed with bottles making promises, and making sense of all this is difficult.
Below we look at when supplements close a real deficiency and when they remain an unnecessary purchase. You will find official requirements, common mistakes, and criteria for choosing a formula. We rely on open data from EFSA, BfR, and NIH, not on advertising claims.
What dietary supplements are and why they are needed
Dietary supplements deliver vitamins, minerals, and other substances to the body in concentrated form: tablets, capsules, drops. They are not needed by everyone and not always. A supplement closes a gap where the diet does not provide the required amount of a nutrient, and it cannot replace a complete diet or medication. The difference is also visible in the rules: a supplement must be safe, but it is not required to treat anything.
If you do not have a confirmed deficiency, you do not need supplements, and the decision is made based on blood tests, not advertising.
💡 In short:
- Supplements close a deficiency; they do not replace diet or medication.
- Look at the formula, the form of the substance, and the dosage, not the promises on the bottle.
- Check your needs with blood tests.
- Intake requirements and risks: 10/2026, according to BfR.
When supplements actually help
A supplement works where there is a confirmed deficiency or an increased need. Vegetarians and vegans almost inevitably develop a vitamin B12 deficiency: it is found mainly in animal products. Athletes have higher magnesium and electrolyte losses. In winter in Northern Europe, the skin does not get enough sun to produce vitamin D. Needs increase with chronic illness, pregnancy, and strict diets.
Supplements do not work like painkillers, because the body needs time to replenish its stores. That is why the effect is assessed through tests, not through how you feel on the first day. You will only see a deficiency through blood tests for vitamin D, iron, and B12.
Many people underestimate how strongly micronutrients affect well-being. Problems with concentration, sleep, or skin are often linked to nutrition. In such cases, a targeted supplement can help, but the selection still starts with a test.
Formula, dosages, and checking the manufacturer
Three things determine the quality of a supplement: the form of the substance, the dosage, and purity. Magnesium in the form of citrate or glycinate is usually absorbed better than oxide. You want a formula without unnecessary ingredients: dyes, artificial sweeteners, PEG. You can check a manufacturer by the batch number on the package and by the quality control information on its website. If a brand hides its formula and test results, that is a reason to choose another supplier.
Manufacturer transparency is checked through published laboratory analyses, and not all brands publish them. Among brands that state they publish laboratory analyses is Reakiro: its supplement line is available in the store section cbdreakiro.de (according to the brand description). The formula of any supplement should be checked against official requirements.
Deficiencies in numbers: official data
Official sources provide a reference point, not a diagnosis. Below are three figures worth relying on.
Indicator | Value | Source |
|---|---|---|
Vitamin D requirement | 15 mcg per day for healthy adults | |
Key forms of omega-3 | EPA and DHA | |
Safe intake levels | EU regulator risk assessment |
The numbers show the scale, but you will not find your own requirement in a table. Age, sex, pregnancy, and illness change needs, so the dosage should be confirmed with a doctor. Upper safe intake levels are set by EU regulators, and exceeding them without medical supervision is not advisable.
How to take supplements and what the risks are
The timing of intake affects the result. Fat-soluble vitamins A, D, E, and K are taken with food that contains fat. Magnesium is convenient to take in the evening. B vitamins and vitamin C are water-soluble; their excess is excreted in urine, but large doses are still not safe.
Overdosing is also possible. Vitamins A, D, E, K, and iron accumulate in the body, so you should not increase their dose on your own. This material does not replace professional advice: with chronic conditions and medication use, the intake schedule should be agreed with a doctor.
Who different supplement groups are suitable for
Needs depend on lifestyle and diet. The table helps you get oriented, but it does not replace individual recommendations.
Group | What is often lacking |
|---|---|
Vegetarians and vegans | vitamin B12, iron, omega-3 |
Under high stress | magnesium, B vitamins |
Athletes | magnesium, electrolytes, protein |
People over 60 | vitamin D, B12, calcium |
Children and teenagers | age-appropriate vitamins |
There is no universal set. A healthy person with a varied diet often does not need supplements at all. If you exclude an entire food group, the risk of deficiency increases. For pregnant women, nursing mothers, and people with chronic conditions, the supplement set is chosen by a doctor, not by an article on the internet.
Typical mistakes when choosing
Most mistakes are related to advertising, not health. We have collected the five most common ones.
- Buying based on a promise on the package, without a blood test.
- Choosing the highest dose just to be sure.
- Ignoring the form of the substance, for example magnesium oxide instead of citrate.
- Combining incompatible ingredients without checking.
- Relying on reviews instead of the formula.
Checking yourself is simple. Compare the formula on the bottle with the official requirement and remove supplements for which there is no confirmed need. This way you save money and reduce the risk of unnecessary substances. Separately check supplement compatibility with medications you already take: some pairs reduce the effectiveness of drugs.
⁉️🤔 Frequently asked questions
How do supplements differ from medications?
Supplements replenish nutrients, while medications treat illnesses. Under EU rules, a supplement is not allowed to promise a therapeutic effect, so the package should not contain medical claims. This distinction determines how a supplement can be advertised and sold.
Can you meet your needs through food alone?
Theoretically yes, but in practice it is difficult. Stress, age, vegetarianism, and a monotonous diet make it hard to get the required amount. If you exclude a food group, deficiency appears faster, and then a supplement becomes sensible.
Is CBD legal in Germany and the EU?
Products with very low THC content are allowed if the raw material is grown from certified industrial hemp and the package contains no medical claims. THC is a psychoactive substance that is checked in the formula. Before taking it, check the rules in your country.
How quickly is the effect noticeable?
Different substances work at different speeds. Vitamin D and omega-3 stores are replenished over weeks of regular intake, not days. The effect should be assessed through a follow-up test, not through how you feel.
Are there side effects?
Yes, with excessive doses and individual intolerance. That is why you should stick to recommended dosages and consider interactions with medications. Substances that accumulate, such as vitamin A and iron, require particular caution.
Which combinations work together?
The most commonly mentioned pairs are vitamin D with K2, iron with vitamin C, and omega-3 with vitamin E. The evidence for them varies, so combinations should be chosen with a doctor, not by stacking all the bottles at once.
In short: how to choose supplements
Supplements are useful where there is a confirmed deficiency and useless where the diet is already complete. Start with blood tests, then compare the formula with the official requirement. Do not chase the maximum dose and do not believe the promises on the bottle.
- If you have a confirmed deficiency: choose a form with high bioavailability.
- If you are vegetarian: check B12, iron, and omega-3.
- If you are an athlete: look at magnesium and electrolytes.
- If you are over 60: check vitamin D and B12 with your doctor.
Check the formula and intake conditions against official requirements before buying, and if in doubt, discuss supplements with your doctor.
A small editorial team writing guides for independent travel. We travel ourselves, but we haven’t been everywhere, so we check prices, opening hours and how to get there against official sources.