Chlorogenic acid (CGA) is a polyphenol antioxidant naturally concentrated in unroasted (green) coffee beans, and also found in many fruits, vegetables, and herbs. It's the compound largely responsible for many of the health benefits associated with coffee consumption — especially since roasting destroys a large portion of it. As a standalone supplement, it's most commonly delivered through standardized green coffee bean extract.

CGA slows the absorption of carbohydrates from the gut by inhibiting an enzyme called glucose-6-phosphatase, which helps keep blood sugar steadier after meals. It also activates AMPK, a cellular energy sensor that encourages the body to burn fat and improves insulin sensitivity. On top of that, it acts as a potent antioxidant that helps protect blood vessels and reduce low-grade inflammation — both linked to metabolic and cardiovascular health.

Green coffee bean extract is the most studied supplemental form, standardized to a known percentage of CGA. Isolated CGA capsules are available for those who want to avoid any residual caffeine. Food sources like coffee, apples, and blueberries deliver CGA alongside other beneficial plant compounds, making them a complementary dietary approach.

• High blood sugar and prediabetes
• Weight loss and obesity
• High blood pressure
• Insulin resistance
• Metabolic syndrome
• High cholesterol and triglycerides
• Oxidative stress and inflammation
• Cognitive decline and brain health
• Liver health and fatty liver
• Gut microbiome imbalance

• Type 2 diabetes — consistent prospective cohort evidence links higher dietary CGA intake with meaningfully reduced risk of developing type 2 diabetes
• Cardiovascular disease — higher coffee polyphenol consumption, driven largely by CGA, is associated with lower rates of heart disease in large population studies
• Non-alcoholic fatty liver disease progression — early clinical evidence suggests CGA may slow or prevent worsening liver fat accumulation

• Green (unroasted) coffee beans — The richest known source of CGA by far — containing up to 10% CGA by dry weight. Roasting destroys 50–95% of the CGA, which is why green coffee extract is used for supplementation rather than regular brewed coffee.
• Brewed coffee (light roast) — Still a significant dietary source — a standard cup provides 70–350 mg of chlorogenic acids depending on roast level and brew method. Light roasts retain significantly more CGA than dark roasts.
• Apples (with skin) — One of the best fruit sources of CGA, concentrated mainly in the skin. A medium apple with skin provides roughly 50–100 mg of chlorogenic acid and related polyphenols.
• Blueberries — A good source of CGA and closely related hydroxycinnamic acids. Also delivers anthocyanins, which work synergistically with CGA on blood sugar and antioxidant pathways.
• Potatoes (especially purple and red varieties) — Surprisingly rich in CGA — particularly in the skin and when consumed cooked but cooled (which also raises resistant starch). Purple and red-fleshed potatoes have the highest concentrations.

• Mild digestive discomfort or loose stools at higher doses
• Headache or jitteriness if using caffeinated green coffee extract
• Insomnia or disrupted sleep if taken late in the day (caffeine-containing products)
• Increased heart rate in caffeine-sensitive individuals
• Potential blood sugar drops if combined with diabetes medications without dose adjustment
• Mild nausea on an empty stomach

• Recommended daily: 200–400 mg of chlorogenic acid per day from standardized green coffee extract (45–50% CGA) or isolated CGA. Most clinical studies have used 200–400 mg/day split into one or two doses. Some blood pressure studies used up to 140 mg of pure CGA twice daily.
• Best time of day: Before meals, ideally 30 minutes before the largest carbohydrate-containing meal of the day, to maximize blood sugar-blunting effects.
• With or without food: Best taken shortly before eating a meal. Avoid taking on a completely empty stomach to reduce risk of nausea. If using caffeinated green coffee extract, avoid afternoon or evening doses to protect sleep.
• Time to effect: Blood sugar: 2–4 weeks. Blood pressure: 4–8 weeks. Weight management: 8–12 weeks of consistent use.
• How long to take it: Can be used continuously as part of a metabolic health strategy. If using for weight loss, most studies ran 8–12 weeks. No established need to cycle; long-term safety data at standard doses is reassuring. Reassess every 3 months based on goals and response.