The 21 Supplements That Actually Work

People ask me about supplements every single day. In my office. At dinner. In my DMs.

“Doc, what do I take for my migraines?” “Doc, my stomach is a mess.” “Doc, I’m on a statin and my legs ache.”

So here is my answer, once, in one place, supplement by supplement: what it is for, how much to take, how to take it, what form to buy, and when to stay away.

I have spent more than twenty years practicing cardiology at UCLA. I have watched patients waste thousands of dollars on bottles that do nothing, and I have watched others get real relief from a single, well-chosen one. The difference is always the same.

Correct a deficiency or target a defined mechanism. Do not stack twenty bottles and call it a protocol.

I rank everything on three shelves:

• WORKS: Backed by human trials. Use it when your problem matches.

• WORTH A TRIAL: Evidence is mixed. Reasonable if the problem is real and the downside is small. If nothing changes in 8 to 12 weeks, stop.

• STORY, NOT A TREATMENT: The mechanism sounds beautiful. The human data does not support the claim on the label.

One rule above all: none of this replaces a diagnosis. Ulcers, arrhythmias, low blood pressure, thyroid disease, and anything involving the liver need a clinician, not a shopping cart.

Let’s go.

1. Vitamin D3 — WORKS (if you are low)

What it is for: Immune balance, autoimmune disease, bone and deep muscle pain, low back and hip pain, and winter or deficiency-related low mood.

What the evidence says: The VITAL trial gave adults over 50 about 2,000 IU a day for roughly five years and found 22% fewer new autoimmune diseases. Low vitamin D is also linked to worse activity in rheumatoid arthritis, lupus, and multiple sclerosis. Deep bone pain and low back pain often track a low level and improve when it is corrected. Depression data is real but smaller, mostly in people who start deficient.

What it does not do: It does not treat cancer or AIDS. Anyone who says it does is selling something.

Dose: Test your 25(OH)D level first. Guidelines say at least 30 ng/mL. Many clinicians focused on immunity aim for 40 to 60. Typical repletion is 1,000 to 2,000 IU daily, more if you are clearly low. Retest in 8 to 12 weeks.

How to take it: With a meal that contains fat.

Buy: D3 (cholecalciferol), not D2. Look for third-party testing.

Caution: Do not chase levels above 50 ng/mL on your own if you have high calcium, kidney stones, or granulomatous disease.

2. Magnesium Glycinate — WORKS (migraine, sleep, blood pressure)

What it is for: Migraine prevention, falling asleep faster, and a modest drop in blood pressure.

What the evidence says: Migraine prevention is the strongest non-deficiency use. About 400 to 600 mg of elemental magnesium daily cut attack frequency by roughly 40% in the better trials, and headache societies rate it as probably effective. Sleep trials show people fall asleep about 15 to 17 minutes faster. Blood pressure falls about 2 mmHg on average, more if you are deficient or already on medication. Blood sugar effects are modest and mostly in people with diabetes or low magnesium.

What it does not do: It does not reliably stop ordinary night cramps (Cochrane reviewed it and walked away). It does not “prevent clotting.” It does not treat arrhythmias, and high-dose magnesium can worsen rhythm problems in the wrong person.

Dose: Start with 200 to 400 mg elemental magnesium in the evening. For migraine, work up to 400 to 600 mg as your gut allows, and give it a full 12 weeks before you judge it.

Buy: Glycinate or citrate, not oxide. Glycinate is not proven better for migraine than citrate. It is simply gentler on the gut, and the glycine may help sleep. Check that the label states elemental magnesium per serving.

Caution: Unsafe if your kidneys do not clear it. If you have a heart rhythm disorder, ask your cardiologist first.

3. Betaine Hydrochloride — WORTH A TRIAL (narrow use)

What it is for: Indigestion and a heavy, “protein just sits” feeling when stomach acid is truly low.

The logic: Aging, long-term acid blockers, and autoimmune gastritis can leave the stomach under-acid. Protein sits, the valve at the top of the stomach misbehaves, and iron, B12, and zinc absorb poorly. The trial evidence that capsules fix this is thin.

Dose: Start with one capsule mid-meal with protein. Stop if you feel any burning.

Caution: Do not use it if you have an active ulcer, erosive gastritis, or take NSAIDs. Never use it to “close the valve” while an ulcer is untreated. If you have chronic heartburn, get it evaluated first.

4. Zinc Carnosine — WORKS (ulcers and gastritis)

What it is for: Gastric ulcers, gastritis, and as an adjunct around H. pylori treatment. It is also supported for oral mucositis.

What the evidence says: This is the stomach supplement with real human data. In Japan it is used for gastric ulcers. In a controlled trial of 258 people with confirmed ulcers, 150 mg a day matched or beat a known mucosal protectant on symptoms and endoscopic healing at 8 weeks.

Dose: About 75 mg twice daily (or 37.5 to 75 mg twice daily of the branded form) for 8 weeks.

How to take it: With or after meals, alongside proper medical care.

Buy: Zinc carnosine, often sold under the name PepZin GI.

Caution: It supports H. pylori treatment. It does not replace eradication therapy.

5. Selenium — WORKS (Hashimoto’s)

What it is for: Autoimmune thyroiditis.

What the evidence says: Several trials used 200 mcg a day of selenomethionine and saw lower thyroid antibodies and, in some, better well-being. It is not an AIDS treatment.

Dose: 200 mcg daily. Do not exceed that without a reason. Brazil nuts are an unreliable source because their selenium content varies wildly.

Buy: Selenomethionine.

Caution: Keep your thyroid labs monitored. More is not better; selenium toxicity is real.

6. Thiamine (Vitamin B1) — WORKS (when you are deficient)

What it is for: Nervous tension, restless legs, and the “wired and worried” feeling, but only when a deficiency or high demand is behind it.

The logic: Alcohol use, high-carbohydrate diets, bariatric surgery, and refeeding states burn through B1. Correcting a real deficit restores energy metabolism in nerve tissue. It is not a general anti-anxiety drug.

Dose: Commonly 50 to 100 mg daily in a B-complex or standalone. Ask your doctor about higher doses if you have a known deficiency.

Who benefits most: Heavy drinkers, post-bariatric patients, and people on very high-carb diets.

7. Benfotiamine — WORTH A TRIAL (diabetic nerve pain)

What it is for: Symptoms of diabetic peripheral neuropathy: burning, tingling, pain.

What the evidence says: This is the fat-soluble form of B1 with higher tissue levels. Short trials at about 300 to 600 mg a day improved symptom scores. Longer trials on objective nerve function are weaker, so use it for symptom relief, not as proof the nerve is being rebuilt.

Dose: 300 to 600 mg daily, split into two doses.

Safety: Well tolerated.

8. Molecular Iodine — WORTH A TRIAL (fibrocystic breast pain, with a clinician)

What it is for: Cyclical, fibrocystic breast pain.

What the evidence says: The Ghent program (Canadian Journal of Surgery, 1993) found molecular iodine outperformed iodide, with roughly 65 to 74% showing subjective and objective improvement and fewer thyroid effects than iodide forms.

Dose: The studied doses sit in the low-milligram range, far above the 150 mcg that prevents goiter. That is exactly why this is not a casual supplement. Do not self-dose. Work with a clinician.

Caution: Excess iodine can trigger hyperthyroidism or worsen autoimmune thyroid disease. Be especially careful with nodules or Hashimoto’s.

Also worth knowing: Vitamin E (tocopherol, about 400 IU) has small trials for cyclic breast pain as well.

9. Coenzyme Q10 — WORTH A TRIAL (statin muscle aches)

What it is for: Muscle aches on a statin.

What the evidence says: Statins lower blood CoQ10. That part is solid. Whether that drop causes your ache is not. A 2025 pooled analysis found a small reduction in pain intensity. A 2020 analysis found none. Major lipid guidelines do not recommend it routinely. My honest view: a fair personal trial is reasonable.

Dose: 100 to 200 mg of ubiquinol or ubiquinone daily, with food, for 8 to 12 weeks. If nothing changes, stop.

Buy: Softgels in an oil base for absorption.

Caution: Never drop your statin on your own. Call me or your doctor first.

10. TUDCA — MEDICAL CONVERSATION

What it is: A real bile acid, not a nootropic. It is used medically for certain cholestatic conditions.

What the evidence says: The neurological claims (ALS and others) come from early or mixed trials and are not a reason to self-prescribe.

Dose: Research doses are typically 250 to 500 mg with meals. If you have sluggish bile, fat intolerance, or a diagnosed cholestatic problem, this belongs in a conversation with your physician.

11. NAC (N-Acetylcysteine) — MIXED

What it is for: The proven uses are acetaminophen overdose (given in a hospital), and mucus in COPD and cystic fibrosis. In non-acetaminophen acute liver failure, pooled data suggests better transplant-free survival.

What it does not do well: Everyday “liver detox” and fatty liver enzyme changes. A recent controlled trial in fatty liver found no meaningful change.

Dose: Studies outside overdose often use 600 mg twice daily.

Caution: Can upset the stomach. Interacts with nitroglycerin, so tell your cardiologist.

12. Mastic Gum — WORTH A TRIAL (as an add-on for H. pylori)

What it is for: Supporting H. pylori treatment.

What the evidence says: A pilot study found eradication in roughly 30 to 38% with mastic alone, far below antibiotics. The useful version is as an add-on to standard therapy, never a substitute.

Dose: Trials ranged from 350 mg three times daily up to about 1 g three times daily for 14 days.

13. Potassium — FOOD FIRST

The old “4,700 mg a day” figure is outdated. Current U.S. adequate intakes are about 3,400 mg for men and 2,600 mg for women. The WHO recommends at least 3,500 mg for blood pressure.

What works: Food (beans, potatoes, leafy greens, yogurt, bananas) and potassium-enriched salt substitutes, which showed benefit in trials, especially in salt-sensitive people. Capsules are legally tiny and do very little.

Caution: Skip potassium products entirely if you have kidney disease or take ACE inhibitors, ARBs, or potassium-sparing diuretics. As a cardiologist, I will not budge on this one.

14. Iron — ONLY TO A LAB RESULT

What it is for: Low iron causes fatigue and can contribute to low blood pressure and restless legs.

The rule: Test ferritin first. Pills cause constipation and iron overload if you do not need them. Food is the default: red meat, shellfish, and legumes paired with vitamin C. Supplement only to a lab result and only under guidance.

15. Vitamin C — WORKS (for the basics)

What it is for: Collagen synthesis and bleeding gums when your intake is poor.

Dose: 200 to 500 mg with meals is enough for most people. Megadoses mostly become expensive urine and, in some people, kidney stones.

16. Tocotrienols — INTERESTING, NOT PROVEN

What they are: A vitamin E family with stronger lab data than alpha-tocopherol on fibrosis pathways, liver fat in animals, and arterial markers.

The honest truth: Human outcome data for chest pain, infertility, and established fibrosis is not strong enough to call them a treatment. If you take vitamin E, a mixed tocotrienol/tocopherol product is the more interesting form.

Caution: Do not stack high-dose vitamin E on top of blood thinners.

17. Probiotics — STRAIN-SPECIFIC OR NOTHING

“A probiotic” is not a thing. Strains matter. Probiotics are useful after antibiotics and in some IBS. Diet soda is not a reason to take one. If you want a gut effect, name the strain and the condition you are treating, or you are buying a random organism.

18. Biotin — ONLY IF DEFICIENT

What it is for: Hair, nails, and skin, but only when you are deficient, which is uncommon.

The warning almost nobody gives: Biotin interferes with lab tests, including thyroid tests and troponin, the marker we use to diagnose a heart attack. Stop it several days before any bloodwork and tell the ER if you are taking it.

19. Melatonin — USE LOW

What it is for: Shifting circadian timing: jet lag and delayed sleep phase.

Dose: 0.3 to 1 mg, taken at the same time each night. Higher doses of 3 to 5 mg are sedating for some and groggy for others. It is not a sleeping pill you escalate forever. “More until it works” is the wrong approach.

20. Clove Oil — A TEMPORARY TOOTH FIX

What it is for: Eugenol numbs a painful tooth or gum for a night.

How to use it: A dab on the area while you wait to see a dentist.

What it does not do: Treat the infection or the crack. See a dentist.

21. Manganese and Calcium Lactate — SKIP

Using manganese for tics and Tourette’s, or calcium lactate for chronic cough, is anecdote, not evidence. Excess manganese causes a Parkinson-like syndrome in exposed workers. Do not supplement manganese for Tourette’s.

How to Buy Well

Supplements are loosely regulated, so quality is on you:

• Look for third-party testing seals: USP Verified, NSF Certified, or ConsumerLab-tested.

• Match the exact form I listed: magnesium glycinate or citrate, zinc carnosine, selenomethionine, D3, ubiquinol or ubiquinone in softgel, molecular iodine.

• Buy from brands with a testing track record, and check the label for elemental amounts and the exact dose.

The Bottom Line

Pick one problem. Match one tool. Run it long enough to judge.

If two supplements are in play, they should solve two different problems. A shelf of twenty is not a protocol. It is a bet that you will not notice which one did nothing.

Test before you guess. Change one thing at a time. Give it 8 to 12 weeks. And tell your doctor everything you take, especially if you are on blood thinners or heart medication, or have kidney disease.

If this helped, send it to the person in your life who keeps buying bottles. And tell me in the comments: what are you taking, and what is it for?

Blessings.

Afshine Ash Emrani, M.D., F.A.C.C.
Assistant Clinical Professor, UCLA
David Geffen School of Medicine

Join Our new website

Castle-Connolly Nationwide Top Doctor (Since 2008)
Los Angeles Magazine Super Doctors (every year since 2013)
LA Style Magazine Top 100 Doctors in America (2024)

Subscribe to mynewsletter: substack.com/@afshineemrani
Explore my books: Amazon Author Profile