Questions
Short answers to the supplement questions people ask most. Each answer names its evidence grade (A to D) and how many people were studied, and every claim links to the study behind it. How we grade.
Can any supplement slow early puberty?
No supplement has good evidence that it slows early puberty. Herbal formulas lowered puberty hormones in 9 small trials with 650 children, but the formulas varied and the evidence is weak (grade C). Low vitamin D goes along with early puberty, yet giving it has not been shown to delay puberty. Lavender and tea tree oil skin products are tied to early breast growth in case reports. Treatment decisions belong with a pediatric endocrinologist.
Last reviewed
Can supplements lower eye pressure?
Not reliably. Fish oil capsules lowered eye pressure slightly in 105 adults whose pressure was already normal (grade C), and black currant extract lowered it in two small studies. A 2026 review of supplement studies in glaucoma found no clear change in pressure after 6 months. Prescription eye drops lower pressure in 114 trials (grade A) and reduce the chance of glaucoma damage. Caffeine can raise eye pressure for about an hour.
Last reviewed
Do any supplements help cannabis withdrawal?
Not clearly. NAC (N-acetylcysteine), the most tested supplement, was judged on clean urine tests rather than on how withdrawal felt, and only one of three trials, 610 people in all, found a benefit. Grade B for no clear benefit. Counseling that pairs cognitive behavioral therapy with motivational enhancement has better support. Symptoms usually peak in the first week. With thoughts of self-harm, get help now.
Last reviewed
Do any supplements help toenail fungus?
No vitamin or other supplement taken by mouth has a controlled trial showing it clears toenail fungus, and biotin was studied for brittle nails, not infection. The one supplement-type product tested is 100% tea tree oil painted on the nail: in a trial of 117 people it showed no clear difference from a clotrimazole antifungal solution (grade C). Prescription antifungal tablets work far better. Never swallow tea tree oil.
Last reviewed
Do any vitamins help type 1 diabetes?
No vitamin replaces insulin or has been shown to change the course of type 1 diabetes. Vitamin D, the most studied, gave mixed, low-certainty results in a 2025 review of 12 small trials, with no change in HbA1c, the long-term blood sugar measure (grade C). Vitamin B3 did not stop diabetes in 552 people with a high-risk family history, and active vitamin D did not protect insulin-making cells. Any glucose-lowering supplement can change insulin needs.
Last reviewed
Do oral nutrition supplements help malnutrition?
Yes, modestly, for older adults and hospital patients. Protein-and-calorie drinks (sip feeds, not pills) added about 2% to body weight across 42 trials of older people at risk (grade A), and deaths fell in trials of 2,461 people who were already undernourished. In 2,088 hospital patients, a dietitian-planned nutrition program lowered deaths at 30 days from 10% to 7%. For frail older people at home, the evidence is weak. Severe weight loss needs a clinician first.
Last reviewed
Do supplements help aromatase inhibitor joint pain?
No supplement has clearly helped. In the largest trial, omega-3 eased aromatase inhibitor joint pain no more than a placebo oil in 249 women, though pain fell by half in both groups, and vitamin D trials mostly found no clear benefit. Grade B. Exercise and acupuncture have better trial support. Keep taking your aromatase inhibitor unless your oncologist changes it, and tell your cancer team about any supplement.
Last reviewed
Do supplements help people with HIV?
No supplement replaces antiretroviral therapy (ART), the daily HIV medicine. The multivitamin benefits come from people not taking ART: comparing 538 pregnant women in Tanzania, daily B, C and E vitamins slowed progression to AIDS (grade B). In 3,418 adults starting ART, high-dose multivitamins added nothing and raised a liver enzyme. St John's wort and garlic supplements cut blood levels of some HIV drugs in volunteers. Check every supplement with your HIV clinician.
Last reviewed
Do supplements improve sperm count?
Probably not much. In the largest trial, folic acid plus zinc taken for 6 months by 2,370 men did not raise sperm counts or live births, and a 7-ingredient antioxidant pill did no better than placebo in 174 men with poor semen tests. Smaller CoQ10 trials look more hopeful, but that evidence is weak. Grade B. A urologist visit to look for treatable causes comes first.
Last reviewed
Does CoQ10 help mitochondrial disease?
Not clearly. CoQ10 is widely offered for mitochondrial disease, but the best trial, 60 days at a high dose in 30 adults, only slightly changed lactate and oxygen use during exercise, with no gain in strength. Grade C. For Kearns-Sayre syndrome there are only case reports. Specialists still suggest trying it, but as an add-on to heart checks, supervised exercise and specialist care, not a replacement.
Last reviewed
Does diosmin help varicose veins?
A little, for swelling and aching, but not for the veins themselves. In a Cochrane review, vein-toning pills that include diosmin probably reduced lower-leg swelling slightly (13 trials, 1,245 people) but made little or no difference to quality of life. Grade B. The trials tracked symptoms and swelling, not whether varicose veins shrank. Diosmin can raise blood levels of some medicines, and a vein specialist can close the faulty vein.
Last reviewed
Does fish oil help dry eye?
Probably not much. In the largest and best trial, 535 people with moderate to severe dry eye took 3,000 mg of fish oil a day or an olive oil placebo for a year, and their symptoms improved by about the same amount (grade B for no clear benefit). Pooled smaller trials suggest a small, uncertain gain at most. High doses of fish oil raise the risk of an irregular heartbeat.
Last reviewed
Does ginger help motion sickness?
Maybe a little, but the evidence is thin and mixed. In 80 naval cadets at sea, 1 g of powdered ginger root cut vomiting and cold sweats compared with a placebo, yet in a lab trial of 28 volunteers ginger gave no protection while a scopolamine pill did (grade C). Antihistamines and scopolamine have stronger evidence. Ginger can upset the stomach and cause heartburn.
Last reviewed
Does NAC help schizophrenia or schizoaffective disorder?
Maybe a little, and only as an add-on. In the trials, people with schizophrenia kept taking their antipsychotic and added NAC (N-acetylcysteine). Some trials lasting 6 months or longer found negative symptoms (loss of motivation and of emotional expression) eased slightly, but a 2024 review of 8 trials with 594 people found no clear difference on any symptom score. Grade B, mixed. Never stop or change an antipsychotic on your own.
Last reviewed
Does selenium help Hashimoto's?
Not in a way you would feel. Selenium lowers thyroid antibody levels a little, but in the largest trial, 412 adults with Hashimoto's on levothyroxine took 200 mcg a day or a placebo for a year, and quality of life improved equally in both groups, with no change in their thyroid medicine dose (grade B). More is not better: the adult upper limit is 400 mcg a day.
Last reviewed
Does vitamin C help sepsis?
No. In 18 hospital trials with 3,364 patients, vitamin C given by IV drip did not lower deaths from sepsis (grade A), and in the largest trial, 872 adults in intensive care had more death or lasting organ failure with it than with a placebo. No trial has tested vitamin C pills as a sepsis treatment. Sepsis is an emergency: call 911 and get hospital care fast.
Last reviewed
Has toothache plant been studied for heart health?
Not in people. As of 7 November 2026, PubMed lists no human study of toothache plant (Acmella oleracea, also called Spilanthes) for heart disease, heart rhythm or blood pressure. That work is in lab dishes and rats only (grade D). The closest human trial gave a spilanthol extract by mouth to 279 men with high blood fats: cholesterol fell, but so did protective HDL cholesterol. No interaction studies with heart medicines were found.
Last reviewed
What supplements help ALS?
No supplement has been shown to slow ALS (amyotrophic lateral sclerosis). Creatine made no difference to survival or decline in 3 trials with 386 people (grade A), and vitamin E and CoQ10 trials were also negative. Ultra-high-dose methylcobalamin, a vitamin B12, slowed decline over 16 weeks in 130 people with early ALS, but as a shot into the muscle twice a week, so B12 pills remain untested. Use supplements only alongside care from an ALS clinic.
Last reviewed
Which supplements help basketball performance?
Caffeine has the best evidence in basketball players, and its gains are small. Pooled crossover trials found slightly faster sprints and higher jumps but no better shooting or dribbling, and in one trial of 20 experienced players it also made sleep worse after the game. Grade B. Creatine, beta-alanine and baking soda have only a few small basketball trials. Teens should ask a clinician before using any of them.
Last reviewed
Which supplements help bone density?
None adds much. Calcium raises bone density by about 1 to 2% in the first year and no further, and vitamin D on its own barely changes it; in 25,871 generally healthy adults aged 50 or older, vitamin D did not lower fractures. Grade A. Very high vitamin D doses even lowered wrist bone density in one trial. Supervised strength and impact training, enough food calcium and protein, and osteoporosis medicines when needed do more.
Last reviewed