Hyaluronic Acid Supplement: Benefits, Dosage and Does It Work?
Do hyaluronic acid supplements work? Clinical trial results for skin hydration, the best dosage, side effects, and oral vs topical HA.
“Antioxidant” might be the most overused word on supplement labels. It’s printed on everything from vitamin C to green powders, usually with a promise to fight free radicals, slow aging and protect your cells. The science is more interesting, and more surprising. Some antioxidant supplements have useful, targeted evidence. Others did nothing in huge trials. And a few, taken in high doses, actually caused harm.
This guide explains what antioxidants really do, which antioxidant supplements are worth considering, which ones to avoid, and why the smartest approach is to support your body’s own antioxidant system rather than flood it.
Every cell in your body produces reactive oxygen species (often called free radicals) as a by-product of making energy. In small amounts they’re useful signals. They help your immune system fight infection and tell your muscles to adapt to exercise. Problems start when production outpaces your defenses. That imbalance, called oxidative stress, can damage fats, proteins and DNA, and it’s linked with aging and many chronic diseases.
Your body’s main defense isn’t vitamins from outside. It’s an internal network of antioxidant enzymes and molecules, led by glutathione, which your cells make from three amino acids: cysteine, glycine and glutamate. Minerals such as selenium, zinc, copper and manganese are essential parts of these enzymes. Dietary antioxidants like vitamin C and plant polyphenols play a supporting role. For more on how this connects to energy, see signs of mitochondrial dysfunction.
It depends heavily on which antioxidant and how much. The early theory was simple: if free radicals cause damage, taking lots of antioxidants should prevent disease. Large trials in the 1990s and 2000s tested this directly, and the results were sobering:
The lesson isn’t that all antioxidants are useless. It’s that megadoses of single antioxidant vitamins don’t work the way the theory predicted, and oxidative signals are sometimes useful. Newer research has shifted toward supplements that support your body’s own antioxidant system or that have specific, measurable effects. That’s where the more promising evidence sits.
NAC supplies cysteine, usually the scarcest building block for glutathione. It’s been used in hospitals for decades as the antidote to acetaminophen (Tylenol) overdose, precisely because it restores glutathione in the liver. In a meta-analysis of 13 trials in people with chronic bronchitis and COPD, NAC reduced flare-ups by about 25%, with 600 mg a day for milder cases and 1,200 mg or more for diagnosed COPD (Cazzola et al., 2015).
Glycine matters too. In older adults, whose glutathione levels tend to be low, supplementing both cysteine and glycine raised glutathione by about 95% and lowered markers of oxidative damage to levels seen in younger people (Sekhar et al., 2011).
For years, experts assumed oral glutathione was simply digested before it could help. A six-month randomized trial challenged that: 1,000 mg a day raised glutathione by 30 to 35% in blood cells and plasma, and by 260% in cheek cells, with levels falling back within a month of stopping (Richie et al., 2015). Glutathione tends to cost more than NAC, and NAC has the longer track record, so many people start with NAC. For a detailed comparison, see NAC vs glutathione.
Alpha-lipoic acid (ALA) is unusual because it works in both watery and fatty parts of cells, and it helps recycle other antioxidants such as vitamins C and E and glutathione. Its best clinical evidence is in diabetic nerve damage: in the SYDNEY 2 trial, 600 mg a day for five weeks halved burning, stabbing and numbness symptoms compared with a one-third improvement on placebo (Ziegler et al., 2006). Higher doses mainly added nausea. ALA can lower blood sugar, so check with your doctor if you take diabetes medication. Read more in alpha-lipoic acid benefits and side effects.
A 2023 GRADE-assessed meta-analysis of randomized trials found that turmeric or curcumin supplements lowered inflammatory markers including CRP, TNF-α and IL-6. They also raised total antioxidant capacity and reduced malondialdehyde, a marker of oxidative damage (Dehzad et al., 2023). Curcumin is poorly absorbed on its own, so look for formulas designed for absorption, such as those combined with black pepper extract.
Quercetin is the most common flavonoid in the diet, found in onions, apples and capers. A meta-analysis of seven randomized trials found it lowered blood pressure by about 3 mm Hg, with larger effects at 500 mg a day or more (Serban et al., 2016).
Resveratrol, famous from red wine, reduced the inflammatory markers TNF-α and hs-CRP in a meta-analysis of 17 trials (Koushki et al., 2018). It’s quickly broken down by the body, so very little reaches the bloodstream unchanged (Walle et al., 2004), and its long-term benefits in people are still being studied. Our guide to how resveratrol and quercetin work together goes deeper.
Vitamin C is essential and helps regenerate other antioxidants. Most people can meet their needs from food. The recommended intake is 75 mg a day for women and 90 mg for men. In the Cochrane review, vitamin C supplements neither raised nor lowered mortality. There is one caution: in a large Swedish study, men taking regular vitamin C supplements had about twice the risk of kidney stones (Thomas et al., 2013). Moderate doses are sensible, and megadoses are hard to justify.
Your antioxidant enzymes can’t work without minerals. Glutathione peroxidase needs selenium, and superoxide dismutase needs zinc, copper and manganese. A modest trace mineral supplement can cover gaps, but more isn’t better. Selenium, for example, becomes harmful above 400 mcg a day.
| Supplement | What it does | Studied dose | Evidence |
|---|---|---|---|
| NAC | Builds glutathione; fewer COPD flare-ups | 600–1,200 mg/day | Strong (meta-analysis) |
| Glutathione | Raises body glutathione stores | 250–1,000 mg/day | Moderate (6-month RCT) |
| Alpha-lipoic acid | Recycles antioxidants; eases diabetic nerve symptoms | 600 mg/day | Moderate (RCTs) |
| Curcumin | Lowers inflammatory and oxidative markers | Varies by formula | Moderate (meta-analysis) |
| Quercetin | Modestly lowers blood pressure | 500+ mg/day | Moderate (meta-analysis) |
| Resveratrol | Lowers some inflammatory markers | Varies | Early to moderate |
| Vitamin C | Essential antioxidant | 75–90 mg/day from food | No benefit from megadoses |
| Beta-carotene, vitamin E | — | High doses | Possible harm; avoid megadoses |
Here’s the striking contrast. While antioxidant pills largely failed to prevent disease, people who eat more fruit and vegetables consistently do better. A meta-analysis of 95 studies found that eating up to 800 g a day (about 10 portions) was linked to lower risk of heart disease, stroke, cancer and early death (Aune et al., 2017). Whole foods deliver thousands of compounds in natural amounts, alongside fiber.
Regular exercise and good sleep also strengthen your natural antioxidant defenses over time, even though a single workout briefly increases oxidative stress.
The Holitro Antioxidant Pack focuses on the ingredients with the more promising evidence in this guide: NAC to support glutathione, Alpha Lipoic Acid, Quercetin, Resveratrol, Vitamin C and Trace Minerals, in one daily tear-away pouch. It contains no high-dose beta-carotene or vitamin E. Thirty pouches arrive each month.
Want to add turmeric or omega-3s? Use the Custom Pack Builder. Taking medication, pregnant, or managing a health condition? Please check with your doctor or pharmacist first.
There isn’t a single best one, but NAC is a strong starting point because it helps your body make its own master antioxidant, glutathione, and has decades of clinical use. Alpha-lipoic acid and curcumin also have good evidence for specific benefits.
High-dose antioxidant vitamins like beta-carotene and vitamin E didn’t prevent disease in large trials and may have caused harm. Supplements that support glutathione, along with some plant compounds, show more promising, targeted benefits. Fruit and vegetables have the most consistent evidence of all.
Yes, at high doses. Beta-carotene increased lung cancer risk in smokers, vitamin E increased prostate cancer risk in men, and megadoses of vitamin C are linked to kidney stones. Antioxidants can also interact with medications and cancer treatments.
For long-term health, yes. Diets rich in fruit and vegetables are consistently linked to lower rates of heart disease, cancer and early death, while isolated antioxidant pills haven’t matched those results. Supplements can complement a good diet but can’t replace it.
The same evidence applies to women. NAC, ALA, curcumin and polyphenols like quercetin are reasonable options. Women who are pregnant, breastfeeding or trying to conceive should check with their doctor before taking anything beyond a prenatal vitamin.
Most can be taken with a meal, which helps absorption of fat-soluble compounds like curcumin and resveratrol. If you exercise regularly, consider taking them away from your workouts rather than right before or after.
Vitamin C also matters for your skin, because your body needs it to make collagen. See our guide to the best supplements for skin hydration.
The best antioxidant strategy isn’t to swallow as many antioxidants as possible. It’s to support the system your body already runs. Eat plenty of colorful plants, move regularly and sleep well. If you supplement, favor ingredients that support glutathione, like NAC and glycine, and compounds with targeted evidence, like alpha-lipoic acid, curcumin and quercetin. Skip megadoses of beta-carotene and vitamin E. For immune-specific options, see our guide to supplements for cold and flu season.
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