Should You Take Supplements? A Science-Based Guide to When and Why
- Katrin Peo
- Jul 26
- 6 min read
Updated: Sep 14
At the beginning of this year, I completed a micronutrients and vitamins/minerals course led by a biologist and nutritional therapist. Over five weeks, we explored the science behind vitamins, minerals, and omega-3 fats — and how supplementation can support different stages of life, when needed.
One message came through clearly:
Supplements are meant to supplement, not replace, a healthy balanced diet.
In this article, I want to help you make better informed, balanced decisions about supplements — when they can be helpful, how to identify quality, and how to avoid the risks of overuse or misinformation.
🥦 Start With Food, Not Pills
A varied, nutrient-rich diet is the foundation of good health. Whole foods contain not just isolated vitamins and minerals but also:
Phytonutrients and antioxidants
Fibre and enzymes
Nutrient synergies that pills can never replicate
For example, the vitamin C in a red pepper is accompanied by flavonoids that enhance its absorption. The iron in lentils comes with fibre and plant polyphenols that also support gut health.
👉 If you’d like to learn more about how to get essential vitamins and minerals from food sources, you can download my free PDFs here.
But modern life — with stress, consuming too many processed foods, drinking excessive alcohol, digestive issues, certain medications, and age-related changes — can sometimes lead to nutrient shortfalls, even with a decent diet. That’s where targeted supplementation could become useful — and necessary in some cases.
⚠️ The Supplement Industry Is Not Well-Regulated
Most people assume their supplements are safe and effective. Unfortunately, the reality is more complicated.
In many countries — including the United States and those in the European Union — dietary supplements are not subject to the same rigorous regulations as pharmaceutical drugs.
Unlike prescription medications, supplements:
❌ Do not require pre-market approval for safety, effectiveness, or quality
❌ Are not required to prove their health claims, unless they're classified as novel foods or make disease treatment claims
❌ Often lack standardised dosing across brands
❌ Can be brought to market without clinical trials
In the United States, supplements are regulated under the Dietary Supplement Health and Education Act (DSHEA) of 1994. This law classifies supplements as a category of food, not medicine. As a result, manufacturers do not need to demonstrate safety or efficacy to the FDA before selling a product. The FDA can only act after a product is on the market, and only if it’s shown to be harmful or misleading.
In the European Union, there is more oversight on nutrient levels and labelling, but enforcement varies between member states. For example:
Ingredients must be on the EU’s approved list (unless applying for novel food status),
Maximum permitted levels for vitamins and minerals are not harmonised across the EU, meaning dosages differ widely by country,
Herbal supplements are even less standardised, and many are sold as food supplements without therapeutic evidence or quality control.
This lack of consistent regulation has real consequences. A 2015 study in JAMA found that over 2/3 of supplements previously recalled by the FDA still contained banned or dangerous substances, such as anabolic steroids, unapproved stimulants, or sibutramine (a weight-loss drug withdrawn from the market for safety concerns).
In short: regulatory bodies don't verify the quality or contents of supplements before they're sold. It's up us as the consumers to check for third-party testing, read ingredient labels carefully, and avoid misleading health claims.
You must be your own advocate when it comes to supplements — because no one else is checking before they reach the shelf.
✅ How to Choose a Supplement
Look for products that are third-party tested (typically also stated on the company's website) to ensure they contain what the label claims — and nothing harmful.
Check for any of these certifications, verifications on the product labels:
GMP certified (ensures supplements are produced in facilities that meet strict safety, hygiene and quality standards)
NSF Certified for Sport- helps athletes, coaches, dieticians, consumers make safer decisions when choosing supplements
HACCP certified
Informed-Sport / Informed-Choice
Read Labdoor or ConsumerLab.com evaluations.
Also:
Choose brands that clearly state dosages and forms (e.g., methyl folate vs folic acid)
Avoid proprietary blends that don’t disclose individual amounts
Be wary of high doses unless specifically prescribed by your doctor
✅ Toxicity: Yes, You Can Overdo It
Especially with fat-soluble vitamins (A, D, E, K) and certain minerals (like selenium or iron), it’s possible to exceed safe upper intake levels without realising it — especially if you take multiple supplements, protein powders, or fortified foods during the day and for periods of time.
I’ve created downloadable resources showing upper safe limits (ULs) for vitamins and minerals (for some of them they are not known, which makes the risk of overdosing more risky):
👉 Download them for vitamins here and for minerals here.
(Information in the downloadables is retrieved from the Health Development Institute in Estonia and Agriculture and Food Board).
Always consult with your doctor, before starting to take supplements, especially if you are on prescribed medications.
🧪 Personalised Testing: A Smarter Way to Supplement
Rather than guessing what your body needs, consult your doctor and consider micronutrient testing— especially for nutrients like:
Vitamin D
Ferritin (iron storage)
B12
Magnesium
Omega-3 index
Your family doctor might not be able to order you the blood tests depending on the country. But in Estonia, for example, Synlab offers individual and bundled blood tests to assess nutritional status and you can order the tests yourself. This is a great first step before starting or adjusting a supplement regimen. Laboratory doctor or your family doctor can help to explain you your test results.
🧬 What Supplements Might Be Needed — and When?
Your supplement needs shift with age, life stage, health conditions, diet and also where you live. Here’s a simplified guide (considering you are consuming first and foremost a healthy balanced diet):
Note: Always talk to a healthcare provider before starting new supplements, especially if you take medications or have chronic conditions.
Magnesium supplementation could be beneficial for diabetics, alcoholics, people with high stress, people with sleep challenges, women in perimenopause and menopause. Learn more about the magnesium here.
Selenium may be necessary as a supplement for those who eat little fish, eggs, Brazil nuts, offal, dairy. 75-90 mcg is the recommended daily amount.
Omega-3 fatty acids (DHA and EPA) is recommended to be taken as a supplement if fatty fish—such as salmon, herring, mackerel, sardines, and anchovies—are consumed less than 2–3 times per week. Trout and tuna are also good sources of omega-3s, although they generally contain lower amounts compared to the fish listed above.
Plant-based foods like chia seeds, walnuts, hemp seeds, flaxseeds, and rapeseed (canola) oil provide ALA (alpha-linolenic acid), the plant form of omega-3. ALA is essential for health in its own right and contributes to heart and metabolic health. However, the body must convert ALA into EPA and DHA to meet all omega-3 needs, and this conversion is limited: only about 5–10% of ALA is converted to EPA, and just 0.5–1% to DHA.
Therefore, for vegans and vegetarians, it’s especially important to supplement with omega-3—preferably from algae-based sources that directly provide DHA and EPA.
C-vitamin and zinc could be beneficial for a short period of time, when there are viruses spreading around you and to support immune function and can be beneficial to athletes to lower the chances of getting cold and viruses. But important with C-vitamin is that our bodies can absorb only around 200mg at a time, so taking high doses of C-vitamin supplement could tax the kidneys and cause diarrhoea.
🌞 Vitamin D: The Most Common Deficiency
Vitamin D deserves special mention — especially for people living in northern climates like Estonia. It plays a role in:
Bone health
Immune regulation
Mood balance
Chronic disease prevention
A vitamin D blood test will show your current status. While 1000–2000 IU/day is safe for most to supplement, some people may need more during a short period of time to correct their severe deficiency. Talk to your doctor or laboratory doctor after the blood test to understand whether and how much should you supplement.
Final Thoughts: Be an Informed Supplement Taker
Supplements aren’t inherently good or bad — they’re just tools to supplement a healthy diet. But like any tool, you need to use them correctly, safely, and intentionally.
Before you supplement, ask:
Am I getting enough of this nutrient from food?
Do I actually need this based on my age, health, or lab tests?
Is the product from a trusted, certified source?
Am I staying within safe intake limits?
Supplements are helpful only when they’re the right kind, in the right dose, for the right person.
Start with food first. Supplement when needed. And always stay curious, cautious, and informed.
If you want to understand whether your diet is balanced, if you are looking to improve your nutrition, don't hesitate to reach out to me for personal nutrition counselling at info@katrinpeo.com.
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