What are the health effects and typical therapeutic doses of raspberry ketones, green tea extract, guarana, maca, ginseng and capsicum individually?
Executive summary
A cluster of popular supplement ingredients—raspberry ketones, green tea extract, guarana, maca, ginseng and capsicum—each carries plausible biological effects but widely varying quality of evidence and dosing guidance: some have human trial data and rough therapeutic ranges (green tea, ginseng, maca, capsicum topical), while others lack reliable human-dose studies and show concerning safety signals at supplement doses (raspberry ketone, concentrated green tea extract) [1] [2] [3] [4] [5].
1. Raspberry ketone — the aroma compound with weak human evidence and uncertain dosing
Raspberry ketone is an aromatic phenolic compound studied in cells and rodents for antioxidant, anti‑inflammatory and anti‑obesity signals, but human data are lacking and appropriate supplement dosing is unknown; studies warn that many commercial supplements deliver far higher amounts than those naturally present in fruit and that intakes reported on supplements range roughly 100–1,400 mg/day, raising safety concerns including possible cardiovascular and drug interaction signals (warfarin, blood pressure effects) [6] [7] [1] [8]. Animal models suggest effects at very high exposures but regulators and reviews (including OPSS and scientific reviews) call for more toxicology and clinical trials before recommending any therapeutic dose in people [9] [10].
2. Green tea extract — antioxidant benefits, modest metabolic effects, and a liver‑safety caveat
Green tea extract concentrates catechins (notably EGCG) and caffeine; randomized trials and meta‑analyses report modest benefits for weight management, cardiovascular markers and cognitive alertness, typically at relatively high catechin doses—clinical effects often noted around 400–500 mg EGCG per day (extracts are often ~50% EGCG)—but concentrated catechin preparations have been associated with dose‑dependent hepatotoxicity in some trials and case reports, so safety and variability between products matter [11] [2] [12]. Traditional brewed tea is generally safe, but taking extracts standardized to deliver several hundred mg EGCG/day requires caution and medical supervision [13] [2].
3. Guarana — a caffeine‑rich stimulatory extract with dose limits driven by total caffeine
Guarana’s primary active is caffeine (plus theophylline/theobromine and polyphenols); effects—energy, alertness, modest cognitive boosts—track with caffeine dose rather than a unique “guarana magic” (acute cognitive benefits usually appear at ~1–3 mg/kg caffeine; extract dosing in studies varies) [14] [15]. Safety guidance is therefore tied to caffeine limits: many agencies cite ~400 mg caffeine/day as a practical upper bound for most adults, whereas guarana extracts have been associated with side effects at ~250–300 mg/day and reviews report extract doses from about 75–1,200 mg/day in studies—individual tolerance and combined caffeine sources must be considered [16] [17] [18].
4. Maca — traditional food‑medicine with modest human trial doses (grams, not milligrams)
Maca (Lepidium meyenii) shows preliminary human benefits for libido, menopausal symptoms and energy; most clinical trials use root powder in the gram range—commonly 1.5–3 g/day (some studies up to 3.5 g) for weeks to months—with generally good short‑term tolerability but limited long‑term safety data and cautions for hormone‑sensitive conditions and thyroid disease [3] [19] [20]. Systematic reviews stress heterogeneous preparations and the need for standardized extracts before firm therapeutic claims [21].
5. Ginseng — adaptogen with a clearer dosing window but variable formulations
Panax ginseng has the strongest clinical footprint among these herbs: standardized extracts showing cognitive, fatigue and some sexual‑function benefits are often dosed as 200–400 mg/day of extract, while traditional herbal preparations use 1–3 g of dried root daily; some trials for cancer‑related fatigue and other endpoints used 1,000–3,000 mg/day depending on species and formulation (Panax versus American) [4] [22] [23]. Safety appears acceptable at common supplement doses, but herb–drug interactions (e.g., warfarin, CYP3A4 substrates) and variability in ginsenoside content require clinical oversight [23] [24].
6. Capsicum/capsaicin — topical analgesia and modest metabolic signals; dose depends on route
Capsaicin is well established as the active in capsicum: topical creams (commonly 0.025–0.075% capsaicin) are evidence‑based for neuropathic pain, while oral/capsule studies probe modest metabolic and appetite effects and are variable; whole‑food chili intake studies tolerate dozens of grams of chili daily in short studies (e.g., ~30 g/day) but supplement concentrations and systemic effects vary, and capsicum can irritate GI tract and interact with some drugs and bleeding risk—topical and dietary uses have different safety profiles [5] [25] [26]. Clinical trials of capsicum‑containing weight‑loss combinations show small adjunct benefits when combined with diet [26].