Do You Need Supplements? How to Decide With Evidence

Most people walk into a supplement aisle, or scroll a supplement site, with a reasonable goal: more energy, better sleep, a stronger immune system, some insurance against getting sick. Then they walk out with a bag of bottles and no clear way to know if any of it is doing anything. If that is you, you are not being foolish. The industry is built to make everything look necessary. The honest answer is that most people who eat a reasonably varied diet do not need most supplements, and a smaller number of supplements are genuinely worth taking for the right person at the right time. The whole game is telling those two groups apart.

This post walks through how we think about that decision at NoMi Beach Health: how to figure out what you actually need, which supplements have real evidence behind them, why the quality and regulation questions matter more than most people realize, and when it is worth bringing a clinician into it.

Start by testing, not guessing

The single most useful shift you can make is to stop treating supplements as a guessing game and start treating them like any other medical decision. You would not take a blood pressure medication because a podcast host felt great on it. The same logic applies here.

A basic blood panel can tell you a lot. It can show whether you are low in vitamin D, iron, or vitamin B12, which are three of the most common and most correctable gaps. Your diet, your symptoms, your age, and your medical history fill in the rest of the picture. Someone who is exhausted and has heavy periods is a very different case from someone who is exhausted and sleeps five hours a night, even if both are reaching for the same iron pill.

When you test first, one of two useful things happens. Either you find a real deficiency and now you have a specific reason to supplement and a way to recheck later, or your levels come back normal and you have just saved yourself money and a shelf full of bottles. Both outcomes are wins. What you want to avoid is the third path, where you take something indefinitely with no baseline, no target, and no way to know if it ever helped.

What the evidence actually supports

Here is the part that surprises people. For healthy adults, the evidence that routine supplements prevent the big things -- heart disease, cancer -- is weak. The U.S. Preventive Services Task Force reviewed this carefully and concluded there is not enough evidence to recommend multivitamins for preventing cardiovascular disease or cancer, and it recommended against beta-carotene and vitamin E for that purpose because the harms outweighed the benefits (https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/vitamin-supplementation-to-prevent-cvd-and-cancer-preventive-medication). The large VITAL trial similarly found that vitamin D did not lower the overall rate of cancer or major cardiovascular events in the general population it studied (https://pubmed.ncbi.nlm.nih.gov/30415629/).

That does not mean supplements are useless. It means their real value shows up in narrower, more specific situations. A few examples where the evidence is genuinely strong:

• Folic acid in pregnancy. For anyone who could become pregnant, a daily folic acid supplement before and during early pregnancy meaningfully lowers the risk of neural tube defects. This carries the Task Force's highest recommendation grade (https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/folic-acid-for-the-prevention-of-neural-tube-defects-preventive-medication).
• Vitamin D for people who are actually low. Certain groups run low more often, including older adults, people with darker skin, people with little sun exposure, and people with conditions that limit fat absorption (https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/). Correcting a documented deficiency is reasonable; dosing everyone regardless of level is not.
• B12 for those who cannot absorb or eat enough of it. People on strict plant-based diets, many older adults, and anyone on long-term acid-reducing medication are at higher risk of B12 deficiency, which is worth catching because it can cause fatigue and nerve problems (https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/).
• Iron for diagnosed iron deficiency. Iron is genuinely helpful when testing confirms you are low, which is common with heavy menstrual bleeding, pregnancy, or certain gut conditions (https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/). It is also one of the easier supplements to overdo, which is exactly why testing matters.

Notice the pattern. The strong cases are about correcting a specific, measurable gap or covering a defined life stage. They are not about a general promise of more energy or a longer life.

The regulation gap most people miss

There is a structural fact about supplements that changes how you should read every label. In the United States, the FDA does not approve supplements for safety or effectiveness before they go on sale. Manufacturers are responsible for making sure their own products are safe and their claims are truthful, and the FDA generally can only step in after a product is already on the market (https://www.fda.gov/food/dietary-supplements/information-consumers-using-dietary-supplements).

That is the opposite of how prescription and over-the-counter drugs work, where a company has to show a product is safe and effective before anyone can buy it. So when a bottle says it "supports immune health," that phrasing is doing careful legal work. It is not the same as a proven claim that the product treats or prevents anything.

The practical consequences are real. Independent testing has repeatedly found products that contain more, less, or something other than what the label says. This is why, when a supplement does make sense, we point people toward brands that carry third-party verification such as USP or NSF, which at least confirms that what is in the bottle matches the label. It does not make the supplement effective, but it removes one large source of risk.

More is not safer

A quiet assumption drives a lot of over-supplementing: if a little is good, more must be better, and worst case it just passes through. That is not how the body works. Fat-soluble vitamins like A, D, E, and K can build up. Minerals like iron can be toxic in excess. And supplements are not risk-free at a population level either. One national study estimated that adverse events tied to dietary supplements lead to roughly 23,000 emergency department visits in the U.S. each year (https://www.nejm.org/doi/full/10.1056/NEJMsa1504267).

Interactions are the other underappreciated risk. St. John's wort is the classic example: it can reduce the effectiveness of a long list of medications, including some antidepressants, birth control pills, and blood thinners (https://www.nccih.nih.gov/health/st-johns-wort). Many other herbal and dietary products interact with prescription drugs in ways that are easy to miss unless someone is looking at your full list (https://www.nccih.nih.gov/health/providers/digest/herb-drug-interactions). This is why "it is natural" is not the same as "it is safe with everything else you take."

When to bring in a clinician

You do not need a professional to take a sensible daily approach to food and sleep. But a few situations are worth a real conversation. If you are pregnant or planning to be, on prescription medications, managing a chronic condition, taking more than a couple of supplements, or simply spending real money without knowing if any of it works, that is the moment to get a second set of eyes on it.

A useful exercise: gather every bottle you currently take, put them on the table, and for each one answer two questions. Why did I start this, and how would I know if it is helping? If you cannot answer both for a given product, that is not a reason to feel bad. It is just a signal that the item is a candidate for testing, tapering, or letting go.

Our approach in functional medicine is deliberately unglamorous. We test where testing helps, we keep the supplements that have a clear reason behind them, and we stop the ones that do not. The goal is not a longer list. It is a shorter, smarter one that fits your actual biology and your budget.

The bottom line

Supplements are neither magic nor scam. They are tools, and like any tool they are useful in the right hands for the right job and pointless or harmful in the wrong ones. If you eat a varied diet and your labs look good, you probably need far less than the internet suggests. If testing shows a real gap, or you are in a life stage like pregnancy, the right supplement can matter a great deal. The way to tell which situation you are in is to measure, not to guess.

If you want help sorting your shelf into "keep," "test," and "let go," we are glad to do exactly that. You can book a functional medicine visit with us, or call NoMi Beach Health at (786) 744-5152. Dr. Jezwah Harris will review your history, your labs, and what you are already taking, and give you a straight answer about what is worth keeping and what you can put down. For more on how we weigh evidence in this space, browse the rest of our blog.