Zinc and Resveratrol in FitSpresso: Supporting Ingredients Explained
Zinc and resveratrol are the two smallest dosed ingredients in FitSpresso. Neither has good evidence for weight loss, but both come with interactions worth knowing.
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Zinc: 11 mg per serving
| Form | Zinc gluconate |
|---|---|
| Amount in FitSpresso | 11 mg (100% DV) |
| Adult RDA | Men 11 mg, women 8 mg |
| Upper limit | 40 mg/day from food and supplements |
| Evidence for weight | Weak |
| Interactions | Quinolone and tetracycline antibiotics, penicillamine, thiazide diuretics |
Zinc is an essential mineral involved in immunity, wound healing and hundreds of enzymes. FitSpresso’s 11 mg matches the Daily Value. There is no good evidence that extra zinc causes weight loss in people who are not deficient, so its role here is nutritional support.
Zinc safety
The NIH upper limit for adults is 40 mg a day from all sources. Many multivitamins contain zinc too, so add up your total. NIH notes excess zinc can cause nausea, dizziness, headaches, stomach upset and loss of appetite; 50 mg or more a day over weeks can impair copper absorption, lower HDL cholesterol and reduce immune function.
Zinc interactions
- Quinolone and tetracycline antibiotics: zinc reduces absorption of both. NIH advises taking the antibiotic at least 2 hours before or 4 to 6 hours after zinc.
- Penicillamine: separate doses by at least 1 hour.
- Thiazide diuretics increase zinc loss in urine.
Resveratrol: 40 mg per serving
| Source | Polygonum cuspidatum (Japanese knotweed) root extract |
|---|---|
| Amount in FitSpresso | 40 mg |
| Doses in human trials | Roughly 10–1,000 mg/day in metabolic studies |
| Evidence for weight | Weak (no human body-weight outcomes reported by LPI) |
| Interactions | Anticoagulants, antiplatelets, NSAIDs; CYP3A4 drugs |
Resveratrol is a polyphenol found in grapes, peanuts and berries; most US supplements use Japanese knotweed root. It is absorbed reasonably well but rapidly metabolised, so little unchanged resveratrol reaches the blood.
What the research shows
The Linus Pauling Institute summarises improved insulin sensitivity in obese animals and some short-term benefits in people with type 2 diabetes (for example 1,000 mg a day for 45 days). In overweight or obese people without metabolic disease, studies found little or no metabolic benefit, and there is no evidence it reduces diabetes risk in people with impaired glucose tolerance.
Resveratrol safety and interactions
- GI effects (nausea, abdominal pain, diarrhoea) were seen at doses above 1,000 mg a day, far above FitSpresso’s 40 mg.
- It inhibits platelet aggregation in the lab and could theoretically raise bleeding risk with warfarin, heparin, clopidogrel, aspirin or ibuprofen.
- It inhibits CYP3A4, which could raise levels of drugs such as some statins, calcium channel blockers, amiodarone, cyclosporine and tacrolimus.
- Safety in pregnancy and breastfeeding has not been established; women with oestrogen-sensitive cancers should avoid resveratrol supplements.
Bottom line
Neither zinc nor resveratrol is a reason to buy FitSpresso. Zinc is a sensible daily amount if you are not already taking it elsewhere; resveratrol is a low dose with mainly theoretical benefits but real interaction cautions. See drug interactions.