Fact or Snake Oil? A Physician’s Guide to Supplements

By Patrick Mullen, M.D. — Co-Founder & Medical Director, Precision Health

Open almost any health-conscious kitchen in Sarasota, and you will find the same thing: a supplement graveyard. Half a bottle of turmeric. A greens powder from last spring. Something with “longevity” on the label that a podcast host recommended. A magnesium, a different magnesium, and a multivitamin that contains both of them again.

Every one of those bottles was bought for a good reason. Almost none of them came with a way to find out whether it worked.

That is the real problem with supplements, and it is not the one people usually argue about. The question is rarely “are supplements good or bad?” Some are useful, a few are excellent, and many are a waste of money. The better question is: what is this supposed to change, and how will we know if it did?

Why the supplement aisle is so loud

Supplements occupy an unusual place in American health care. Under the federal law that governs them, a supplement does not need FDA approval for safety or effectiveness before it goes on sale. The manufacturer is responsible for both, and the FDA generally steps in only after a problem shows up. A prescription drug, by contrast, has to prove it works before anyone can sell it.

Combine that with a feed that rewards confidence over accuracy, and you get the environment we all live in now: a subscription box built from a two-minute quiz, a discount code in every video, and a product that exists before anyone has looked at your data.

That last part is the tell. If someone knows what they want to sell you before they know your numbers, you are being marketed to, not treated.

Where supplements actually fit

We think about this as an order of operations, and we hold to it with every member.

• Lifestyle first. Nutrition, movement, sleep, and stress management remain the most powerful interventions available, and nobody profits from selling them to you. No capsule outruns five hours of sleep.
• Targeted supplementation second. Tied to a specific number you have measured, at the dose that number calls for, and re-checked to confirm it moved.
• Medical intervention third, used deliberately and only where the data calls for it.

Supplements are the fine-tuning on a solid foundation. They are not the foundation.

Fact or snake oil: five claims we hear every week

On the first episode of our podcast, “It Depends,” we ran a quick round called “Fact or Snake Oil.” This is the written version of the claims that come up most often in the exam room. Each gets one of three verdicts: fact, snake oil, or the most honest answer in medicine: it depends.

1. “A multivitamin or a greens powder makes up for a poor diet.” Verdict: Snake oil

Large randomized trials of multivitamins in healthy adults, including the Physicians’ Health Study II and the more recent COSMOS trials, have found benefits that are small, specific, or inconsistent — nothing close to what the marketing implies. Whole food carries fiber, thousands of interconnected compounds, and a structure that a capsule or powder cannot reproduce. If your diet needs work, the fix is on your plate. A supplement can fill a gap your labs have actually shown; it cannot replace the meal.

2. “Everyone should take 10,000 IU of vitamin D.” Verdict: It depends

Vitamin D behaves more like a hormone than a vitamin, and correcting a true deficiency matters for bone, muscle, and immune health. But the large VITAL trial found that giving vitamin D to a general adult population, most of whom were not deficient, did not lower rates of cancer or cardiovascular disease. More is not automatically better, either: too much can push calcium to unsafe levels. Living in Florida helps, but plenty of people here still run low. For most people, our goal is a level of 40 to 60 ng/mL, with levels up to 75 ng/mL supporting bone mineral density. The answer is a blood test, a dose that matches the result, and a recheck, especially if your sun exposure changes during the year.

3. “Detox and liver-cleanse blends flush out toxins.” Verdict: Snake oil

Your liver and kidneys are the detox system. They run around the clock; they are very good at it, and they work for free. There is little evidence that a commercial cleanse improves them, and some herbal blends carry their own risks to the liver. The best (and cheapest) plan is prevention: reduce toxic exposures so the liver and kidneys do not have to do any additional work. Some people have reduced activity in phase 1 or phase 2 detoxification pathways, and targeted agents like NAC or sulfur-containing compounds can help compensate for those gaps. If you are worried about a specific exposure, that is a reason to test for it, not to buy a tea.

4. “Fish oil is fish oil.” Verdict: It depends

Omega-3 fatty acids are among the few supplements with substantial evidence supporting them, which is exactly why the details matter. What counts is not what is on the label but what ends up in your cells. The Omega-3 Index measures the proportion of EPA and DHA in your red blood cell membranes; a level above 8% is associated with lower cardiovascular risk, and a level below 4% with higher risk. Some people reach the target on about 1,000 mg a day of EPA/DHA. Others need several times that dose. Quality varies, too: fish oil can oxidize on the shelf or contain mercury from accumulation in the ocean. So we measure, dose to the result, and measure again.

5. “More antioxidants are always better.” Verdict: Snake oil

This one surprises people. In a well-known study, healthy adults who took high doses of vitamin C and vitamin E around their workouts lost some of the metabolic benefits that exercise would otherwise have produced. Part of the stress of training is the signal that makes you adapt; flood it out, and you blunt the result. High-dose antioxidants can help prevent and support recovery from viral infections. Antioxidants have a place, at the right dose and the right time. Mega-dosing them because “more is better” is not that. Know the dose and know the reason.

The U-shaped curve

Notice what the “it depends” answers have in common. For most nutrients, the relationship between dose and benefit is not a line that keeps rising. It is a U: too little causes problems, a middle range is where you want to be, and too much causes problems of its own. Fat-soluble vitamins (A, D, E, and K) accumulate in the body rather than being washed out.

Stacking products makes this worse. Two or three “complete” formulas plus a few single ingredients can quietly double or triple a dose without anyone noticing, because nobody is adding up the labels. The fix is not a better product. It is a measurement.

Five questions to ask before you buy any supplement

1. What number is this supposed to change? If nobody can name one, it is a hope, not a plan.
2. Has that number been measured in me? A deficiency you have not tested for is a guess.
3. How will I know it worked? If there is no plan to re-test, there is no way to tell.
4. Has the product been independently verified? Look for third-party testing (USP, cGMP, and NSF marks are common examples) so you know the label matches the capsule.
5. Who profits from the recommendation? Follow the incentive. Advice from someone who earns a commission on the sale deserves a second opinion.

How we do it instead

Our answer to all of this is the Precision Personalized Supplement Program. It starts from the opposite end: data first, product second.

• Test. We start with the Genova NutrEval, a functional assessment of how your body actually uses vitamins, minerals, antioxidants, amino acids, and fatty acids, with more than 125 biomarkers. You stop your current supplements for three days beforehand so we can see your real baseline, not the one your bottles are propping up. Compare that to static genetic tests on the market that do not account for diet, or to survey-based sales tools.
• Formulate. Your physician builds one compounded formula from the results: a base of multivitamin and minerals, vitamin D3 with K2 dosed to your level, fish oil, methylated B vitamins and antioxidants, typically four to six capsules a day. Targeted packs for heart, metabolism, bone, joints, vision, or cognition are added only when your risk profile calls for them.
• Review. At your comprehensive exam, you see every ingredient, the capsule count, and the price, and you decide what to include. Nothing is ordered unless you choose to go ahead.
• Make, verify, re-test. Each formula is compounded in a NSF/GMP-certified, U.S.-based facility and third-party tested before it ships. When follow-up labs show a change, your physician updates the formula.

For most people, that means fewer pills, not more. One member came to us taking 19 different supplements a day and described it as “managing a pharmacy.” After testing, his physician consolidated what his labs supported into a single formula of 9 total capsules containing just the essentials. Three months later, his vitamin D, B12, and Omega-3 Index were retested, and all were within the optimal range: neither too high nor too low. Half the daily pills, lower cost, and the same results.

The bottom line

Some supplements earn their place. A few are among the most useful tools we have. But the value never comes from the bottle alone. It comes from knowing what you need, taking the right amount, and checking that it worked.

If you aren’t measuring the deficiency, you aren’t practicing medicine. You’re practicing expensive guesswork.

Bring us your supplement list

Members: ask for a supplement review at your next visit, or message us through Spruce. Not yet a member? Book a discovery call and bring your current list. We will tell you what we would keep, what we would test, and honestly whether we are the right fit.

Book a Discovery Call

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SELECTED REFERENCES

U.S. Food and Drug Administration. Questions and Answers on Dietary Supplements.
Gaziano JM, et al. JAMA. 2012 (Physicians’ Health Study II, cancer).
Sesso HD, et al. JAMA. 2012 (Physicians’ Health Study II, cardiovascular disease).
Baker LD, et al. Alzheimers Dement. 2022 (COSMOS-Mind).
Manson JE, et al. N Engl J Med. 2019 (VITAL).
Harris WS, von Schacky C. Prev Med. 2004 (Omega-3 Index).
Ristow M, et al. PNAS. 2009 (antioxidants and exercise).

Educational content only. Individual recommendations depend on your history and a full clinical evaluation. Supplements are not medications and are not intended to diagnose, treat, cure, or prevent disease. Results vary. Nothing here is a substitute for a conversation with your physician.