The evidence file
Two plants. Four decades of research. One honest page.
You have probably been let down by a supplement before. So instead of asking you to trust us, this page shows you the actual studies behind citrus bergamot and olive leaf — the doses, the sample sizes, the results, and the places where the research still falls short.
Start here
Your skepticism is the correct starting position
Most of the metabolic supplement aisle does very little. That is not cynicism — it is the predictable result of how the category is built.
Cassia cinnamon is cheap, widely available, and has thin human evidence behind it at supplement doses. Proprietary blends let a brand list five impressive ingredients while disclosing only a single combined total, so the expensive ones can appear in amounts too small to do anything. And a great deal of what gets sold as science is a rodent study or a test-tube result dressed up as a clinical finding.
If you have already tried cinnamon capsules or fish oil and seen nothing change, the reasonable conclusion is not that your body is unusual. It is that you were probably given too little of something that did not have much behind it in the first place.
So the useful question is not whether a supplement sounds scientific. It is three plain things: what was actually tested, at what dose, and in how many people. That is what the rest of this page answers.
The ledger
How strong is the evidence, ingredient by ingredient
Not every ingredient in a formula deserves the same confidence. Rather than describe all of them as "clinically studied," here is our own reading of the human evidence — including where it is weak.
Citrus Bergamot
Lipids & cholesterol
Multiple randomised, placebo-controlled human trials plus a 14-trial meta-analysis, all pointing the same direction. The strongest leg the formula stands on.
Olive Leaf
Blood pressure
A 232-person controlled trial and a 12-trial meta-analysis show a real but modest effect, concentrated in people whose readings are already elevated.
Citrus Bergamot
Glucose metabolism
Glucose improvements show up in several bergamot trials, but as a secondary finding rather than a primary endpoint. Promising, not settled.
Olive Leaf
Blood sugar
The pooled analysis found no significant effect on HbA1c, insulin or insulin resistance. We include olive leaf for circulation, not for glucose — and we are not going to pretend otherwise.
Mechanism
Why this particular citrus, and no other
Bergamot is not simply a fruit with a nice smell. It carries two flavonoid compounds that are close to unique in the plant world — and their shape is the whole story.
Two molecules shaped like a key
Bergamot peel contains brutieridin and melitidin — flavonoid glycosides carrying a 3-hydroxy-3-methylglutaryl group. That HMG fragment is the same chemical motif the body uses in its own cholesterol pathway, which is why researchers describe these compounds as statin-like in structure. They were first isolated and characterised in 2009.
Less made in the liver
HMG-CoA reductase is the enzyme that governs how much cholesterol the liver produces. Cell work published in Nutrients found that bergamot extract reduced HMG-CoA reductase levels in liver cells and raised AMP-kinase activity. Notably, the same study found the compounds did not block the enzyme directly — the effect appears to work by turning the enzyme down rather than jamming it.
Less absorbed in the gut
In intestinal cells, brutieridin reduced cholesterol uptake and lowered levels of NPC1L1, the transporter that ferries dietary cholesterol across the gut wall. Two different points of action, which is why the researchers concluded bergamot's activity is distinct from how statins work.
Olive leaf covers the vessels
Oleuropein, the principal phenolic in olive leaf, is associated with reduced angiotensin activity — part of the system that governs vessel tone. It is a different pathway from bergamot's, which is why the two are in the same softgel rather than competing for the same job.
The trials
The four studies worth actually reading
Every source is linked in full at the bottom of this page. Read them yourself — that is rather the point.
Meta-analysis · 14 trials
Bergamot and lipid profiles
Published in Phytotherapy Research, 2022. The largest pooled look at bergamot supplementation and blood lipids to date.
- Design
- Systematic review and meta-analysis
- Trials
- 14 randomised controlled trials
- Measure
- Weighted mean difference in serum lipids
All results reached statistical significance at p<0.001.
RCT · double-blind · placebo
Four months, 64 participants
Spina and colleagues, Foods, 2024. Adults with elevated cholesterol, randomised and blinded.
- Design
- Double-blind, placebo-controlled
- Participants
- 64 adults with hypercholesterolaemia
- Duration
- 4 months
- Dose
- 150 mg/day standardized flavonoids
No liver or kidney abnormalities were recorded over the four months.
RCT · active-controlled
Olive leaf, head to head
Susalit and colleagues, Phytomedicine, 2011. Compared against a prescription blood pressure medication rather than a sugar pill.
- Design
- Double-blind, active-controlled
- Participants
- 232 adults with stage-1 hypertension
- Duration
- 8 weeks
- Dose
- 500 mg twice daily
The difference between groups was not statistically significant. Triglycerides also fell in the olive leaf group.
Meta-analysis · 12 trials
Olive leaf across 819 people
Diabetology & Metabolic Syndrome, 2022. A broader and more conservative read than any single trial.
- Design
- Systematic review and meta-analysis
- Participants
- 819 across 12 randomised trials
- Measure
- Cardiovascular risk markers
No significant change in HbA1c, insulin or insulin resistance.
The other half
What this research does not show
Any brand can quote its best study. Here are the limitations we would want to know about if we were the one reading — and they are the reason we describe this as support rather than treatment.
- No heart attack or stroke dataBergamot has been measured against blood markers, not against cardiovascular events. Nobody has run a trial large or long enough to say whether it changes what happens to people over decades. The Cleveland Clinic has said as much publicly.
- A great deal of it comes from one groupMuch of the bergamot literature traces back to researchers connected to the University of Catanzaro in Calabria. The findings have held up across separate trials, but concentration in one group is a genuine limitation, and independent replication would strengthen the picture considerably.
- The percentages come from a lower doseThe −8.8% and −11.5% figures come from a trial using 150 mg per day of standardized flavonoids. Our softgel carries 500 mg of standardized extract with 190 mg of polyphenols. A higher dose is not automatically better evidenced, and we are not going to imply the numbers scale up.
- The trials are shortThirty days to six months, in most cases. What that tells you about five years of daily use is genuinely unknown.
- Olive leaf did not move glucoseIn the pooled analysis, there was no significant effect on blood sugar markers. Olive leaf earns its place in this formula on circulation, not on glucose.
- A combination trial came back negativeOne randomised trial in people with prediabetes tested a combination including bergamot and olive leaf and found no glucose effect. We would rather you heard that from us.
- This is not a statin replacementThe mechanism is statin-adjacent in structure. That is a fact about chemistry, not a claim about clinical equivalence, and it is not a reason to stop a prescription. If you are on one, that conversation belongs with your doctor.
Dose transparency
Research is worthless if the dose is hidden
Under US labelling rules, a brand may group several ingredients into a "proprietary blend" and disclose only the combined total. The ingredients are listed in descending order by weight, but no individual amount appears. A blend can be almost entirely one cheap ingredient with traces of the ones named on the front.
A typical proprietary blend
One number, five ingredients
- 850 mg Metabolic Support Blend
- Cinnamon bark extract
- Chromium
- Bitter melon
- Banaba leaf
- Alpha lipoic acid
You cannot tell whether the fifth ingredient is 200 mg or 2 mg. That is the feature, not the flaw.
Metabella
Every number on the front
- 500 mg Standardized citrus bergamot
- 190 mg Bergamot polyphenols per serving
- 1 Softgel a day, taken with breakfast
Standardized means each batch is measured for polyphenol content rather than assumed. It is the difference between a weight of plant material and a known quantity of the compounds the research was run on.
What to expect
This builds. It does not switch on.
In the trials above, measurable change was recorded at the four-week mark at the earliest, and more often at eight to twelve weeks. Anyone promising you a first-week transformation is selling something other than bergamot.
Week 1–2
Nothing dramatic, and that is normal
One softgel with breakfast. The only thing that matters in this stretch is that the habit sticks — the research is built on daily use, not occasional use.
Week 3–4
The earliest point anything was measured
The shortest trials in the literature ran thirty days. If you are the sort of person who wants a baseline to compare against, this is a sensible moment to have had one taken.
Week 5–8
Where most of the trial data sits
The olive leaf blood pressure trial ran eight weeks. Several bergamot trials report their primary results in this window.
Month 3–6
The four-month trial's territory
The 2024 placebo-controlled trial ran four months. Our ninety-day guarantee is set deliberately long enough to cover a fair trial of your own.
Safety
Read this part before you order
Most people over fifty are taking something else. Bergamot and olive leaf are well tolerated in the trials — the most commonly reported effects are mild digestive upset and heartburn — but they are biologically active, and that cuts both ways.
Speak to your doctor before starting if you take any of the following
- Statins. Bergamot acts on the same cholesterol pathway. One trial found the effects were additive, which is interesting research and a reason for medical supervision rather than self-experimentation.
- Blood pressure medication. Olive leaf has an additive effect on blood pressure. Two things pulling in the same direction can pull further than intended.
- Metformin or insulin. Monitoring makes sense where anything else may influence glucose.
- Blood thinners. Worth raising with whoever manages your prescription.
Citrus compounds can interact with the CYP450 enzyme system, the same route behind the familiar grapefruit warning on certain medications. Refined oral bergamot extracts generally have the photosensitising compounds removed, but if you take a medication carrying a grapefruit caution, ask.
You have read the evidence. Including the gaps.
500 mg of standardized Calabrian bergamot with 190 mg of polyphenols, plus standardized olive leaf. One softgel, once a day, both numbers printed on the front of the pouch.
90-day money-back guarantee · Easy returns
References
Every source, linked
Citrus bergamot
- Spina A. et al. Citrus bergamia extract, randomised controlled trial. Foods 2024. pmc.ncbi.nlm.nih.gov/articles/PMC11641072
- Effect of bergamot supplementation on lipid profiles: systematic review and meta-analysis of 14 RCTs. Phytotherapy Research 2022;36(12):4409–4424. onlinelibrary.wiley.com/doi/10.1002/ptr.7647
- Defining the cholesterol lowering mechanism of bergamot extract in HepG2 and Caco-2 cells. Nutrients 2021;13(9):3156. ncbi.nlm.nih.gov/pmc/articles/PMC8469228
- Di Donna L. et al. Statin-like principles of bergamot fruit: isolation of 3-hydroxymethylglutaryl flavonoid glycosides. Journal of Natural Products 2009.
- Gliozzi M. et al. Bergamot polyphenolic fraction with rosuvastatin. International Journal of Cardiology 2013. internationaljournalofcardiology.com
- Musolino V. et al. BPF and the lipid transfer protein system. Lipids in Health and Disease 2019. ncbi.nlm.nih.gov/pmc/articles/PMC6525455
- Cleveland Clinic. Why bergamot won't lower your cholesterol. health.clevelandclinic.org
Olive leaf and oleuropein
- Susalit E. et al. Olive leaf extract compared with captopril, n=232. Phytomedicine 2011. pubmed.ncbi.nlm.nih.gov/21036583
- Effects of olive leaf extract on cardiovascular risk factors: meta-analysis of 12 RCTs, n=819. Diabetology & Metabolic Syndrome 2022. ncbi.nlm.nih.gov/pmc/articles/PMC9585795
- Lockyer S. et al. Phenolic-rich olive leaf extract, randomised crossover trial. European Journal of Nutrition 2017;56:1421–1432. pmc.ncbi.nlm.nih.gov/articles/PMC5486627
- Olive leaf extract and cardiometabolic profile in prehypertension and hypertension: systematic review. PeerJ 2021;9:e11173. ncbi.nlm.nih.gov/pmc/articles/PMC8035902
Population context
- Carroll M.D. et al. Total and HDL cholesterol in adults. NCHS Data Brief No. 515, 2024. cdc.gov/nchs/data/databriefs/db515.pdf
- Fryar C.D. et al. Hypertension prevalence in adults. NCHS Data Brief No. 511, 2024. cdc.gov/nchs/products/databriefs/db511.htm
- CDC National Diabetes Statistics Report. cdc.gov/diabetes/php/data-research
Safety and interactions
- Pharmacy Times. The grapefruit drug interaction. pharmacytimes.com