Ingredient profile
Green Tea and Oolong in Cardio Slim Tea: Small Effects, Real Cautions
Green tea and oolong both come from the Camellia sinensis plant. In 24 trials, green tea lowered blood pressure by only about 1 point (Xu 2020 - Green tea BP meta-analysis), and a Cochrane review found almost no weight loss outside Japan (Cochrane - Green tea and weight loss). Oolong's weight data come from one study without a control group (He 2009 - Oolong tea and weight). The sales page calls the green tea decaf, but oolong has caffeine.
Written by the Cardio Slim Tea reading deskUpdated
The basics
How are green tea and oolong different?
They come from the same plant, processed in different ways. Green tea leaves are heated soon after picking. Oolong leaves are partly oxidized first, which darkens them and changes the taste.
Both are named on the Cardio Slim Tea brand graphic. The sales page describes the green tea as decaffeinated. It says nothing like that about the oolong, which naturally holds caffeine.
| Name on the sales page | Green Tea (decaffeinated) |
|---|---|
| What it is | Camellia sinensis leaf |
| Where it is named | On the brand graphic |
| Amount in the tea | Not printed |
| Amount used in research | 208-1,344 mg catechins a day in BP trials |
| Strength of evidence | About 1 point on blood pressure |
| Marketed use | Catechins; sold for metabolism |
| Main caution | High doses lower nadolol levels; extracts (not tea) linked to rare liver injury. |
| Name on the sales page | Oolong |
|---|---|
| What it is | Camellia sinensis, partly oxidized |
| Where it is named | On the brand graphic |
| Amount in the tea | Not printed |
| Amount used in research | 8 g a day in one uncontrolled 6-week study |
| Strength of evidence | Weak: no controlled weight trial |
| Marketed use | Sold for weight and metabolism |
| Main caution | Contains caffeine (amount not published); watch if caffeine-sensitive. |
Blood pressure
Does green tea help blood pressure?
Only slightly. A review of 24 randomized trials with 1,697 adults found readings about 1.2/1.2 mmHg lower than in comparison groups (Xu 2020 - Green tea BP meta-analysis).
Those trials lasted 3 to 16 weeks. They used 208-1,344 mg of catechins a day, the main plant compounds in green tea. The authors want larger, longer trials before green tea is advised for high blood pressure.
That is far smaller than the hibiscus results, which averaged about 7 points (Ellis 2021 - Hibiscus BP meta-analysis). See the hibiscus profile for that research.
Weight
Do green tea and oolong help with weight loss?
The evidence says very little. Green tea has been tested well, and the result was close to zero. Oolong has only weak data.
| Study | What was tested | What it found |
|---|---|---|
| Cochrane review (Cochrane - Green tea and weight loss) | Green tea in 18 studies, 1,945 people | Outside Japan, 0.04 kg difference: not clinically important; no help keeping weight off |
| Oolong study (He 2009 - Oolong tea and weight) | 8 g of oolong a day for 6 weeks, 102 adults | About two-thirds lost more than 1 kg, but there was no control group |
| Energy-use review (Hursel 2011 - Tea catechins and energy use) | Catechins plus caffeine vs placebo | About 4.7% more energy used, roughly 100 kcal a day, almost the same as caffeine alone |
The last row matters for the "metabolism" claim on the pouch. Much of the effect tracks with caffeine, not with tea compounds. Decaf green tea would lose most of it.
The oolong study used 8 g of tea a day. A whole day of Cardio Slim Tea is about 2 g, for all 14 ingredients together. That is our math from a 60 g pouch sold as a month. The NIH says there is little evidence that weight-loss supplements work (NIH ODS - Weight-loss supplements). Read more in does tea help weight loss?
Caffeine
How much caffeine is in Cardio Slim Tea?
The amount is not published. The sales page lists the green tea as decaffeinated, but oolong is a regular tea leaf with natural caffeine.
For scale, a 12 oz cup of regular green tea has about 37 mg, and black tea about 71 mg (FDA - Caffeine: how much is too much). We found no verified figure for oolong. The FDA says 400 mg a day is not generally linked to harm in most healthy adults.
- Decaf does not mean zero: decaf coffee still has 2-15 mg per 8 oz (FDA - Caffeine: how much is too much)
- The oolong share of the blend is unknown, so the caffeine is too
- If caffeine keeps you up or makes your heart race, brew it earlier in the day
The sales page also says the tea has "no stimulants." Caffeine is a stimulant, so that line does not fit an oolong blend well.
Safety
Can green tea hurt your liver?
Brewed tea is not the concern. The liver injury reports involve concentrated green tea extract pills, not cups of tea (LiverTox - Green Tea).
A known, rare risk
LiverTox rates green tea extract a well-established cause of liver injury, with more than 100 cases. Cases often involved 0.8-1.9 g of extract a day, and symptoms usually began 1-6 months in (LiverTox - Green Tea).
Not the same thing
The reports are tied to extracts, not to tea brewed from leaves (NCCIH - Green Tea). Cardio Slim Tea is sold as tea in a pouch, not as an extract pill.
Warning signs of liver trouble include dark urine, yellow skin or eyes, and unusual tiredness. Stop any supplement and call your doctor if they appear.
Cardio Slim Tea: from $49 a pouch60 g herbal tea · 2, 3 or 6 pouches · 60-day money-back guarantee
See packsMedicines
Does green tea interact with blood pressure pills?
With at least one, yes. In a small study, 700 mL of green tea a day for 14 days cut blood levels of nadolol, a beta-blocker, by about 85% (Misaka 2014 - Green tea and nadolol).
If you take nadolol or any heart medicine, ask your pharmacist before adding tea. Keep taking prescribed medicine, and never stop it because of a tea (AHA - Types of BP medications).
Fair view
What are the strengths and weak spots of these two teas?
They are familiar, gentle drinks with modest research. The trouble is the gap between that research and the pouch claims.
Strengths
- Green tea is listed as decaf on the sales page
- Brewed tea is a low-calorie habit that can replace sweet drinks
- Small but measured blood pressure effect for green tea (Xu 2020 - Green tea BP meta-analysis)
Weak spots
- Almost no weight effect in good trials (Cochrane - Green tea and weight loss)
- Oolong caffeine amount not published
- Green tea can lower nadolol levels
For every possible reaction across the blend, see Cardio Slim Tea side effects.
More ingredients
Which ingredient comes next?
Ginger and lemongrass add warmth and citrus flavor to the blend. Ginger has some blood pressure data, but only at larger doses.
FAQ
Green tea and oolong questions people ask
Is the green tea in Cardio Slim Tea decaffeinated?
The sales page says it is. We cannot verify that from the pouch, and decaf tea still holds a little caffeine. The blend also contains oolong, which is not called decaf. No caffeine amount is published for the tea as a whole.
Does oolong tea help you lose weight?
The evidence is weak. One 6-week study of 102 adults drinking 8 g of oolong a day reported that about two-thirds lost more than 1 kg, but it had no control group. Without a comparison group, the tea cannot be credited for the change.
Does green tea speed up metabolism?
Slightly, and mostly because of caffeine. Catechins plus caffeine raised daily energy use by about 4.7%, roughly 100 calories. Caffeine alone did almost the same. Decaf green tea would likely have far less effect.
Is green tea bad for your liver?
Brewed green tea is generally not linked to liver injury. The reported cases involve concentrated green tea extract pills, often 0.8-1.9 g a day. Watch for dark urine, yellow skin or eyes, or unusual tiredness. If they appear, stop the supplement and call your doctor.
How much caffeine does oolong tea have?
We found no verified figure for oolong in our sources. For comparison, the FDA lists about 37 mg in a 12 oz cup of green tea and about 71 mg in black tea. Cardio Slim Tea does not publish its oolong amount, so its caffeine is unknown.
Can I drink green tea if I take a beta-blocker?
Ask your pharmacist first. In one study, 700 mL of green tea daily for two weeks cut nadolol levels by about 85%. It also weakened the drug's effect on blood pressure. Other beta-blockers were not tested there, so a professional should check your list.
How many cups of green tea a day is safe?
There is no single number for everyone. Most healthy adults can have up to 400 mg of caffeine a day from all sources. If you use Cardio Slim Tea, follow the directions printed on your pouch rather than adding extra cups of other teas.
Who wrote this
Written and reviewed by
Pages built from the pouch, the brand graphic, the sales page and linked NIH, FDA, FTC and peer-reviewed sources.
Last updated . Read our editorial standards and how we check reviews. This website is run by an authorized U.S. retailer, not by the manufacturer. We earn money when you buy through our order links.
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