One of the worst foods for your smoothie Bananas Dr. Rick Cohen, M.D.

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Skip Bananas in ChocoBerry and Polyphenol-Rich Smoothies: How to Make a Better Smoothie

By Dr. Rick Cohen • Updated September 24, 2025

Certain ingredients blunt the very compounds you’re trying to get from a smoothie. When polyphenol-rich foods are blended with ingredients that contain high polyphenol oxidase (PPO), flavan-3-ols and related flavanols are degraded before you ever absorb them. The most common offender in home smoothies is the banana.

Why bananas can sabotage a flavanol smoothie

High-PPO foods drive an enzymatic reaction that oxidizes flavanols. A controlled, single-blinded, cross-over study showed that pairing flavan-3-ols with a banana-based drink led to an 84% lower peak plasma level versus capsules, and markedly lower than a low-PPO berry smoothie. The effect persisted even when contact was prevented until ingestion, consistent with post-ingestion PPO activity. See the study summary and full paper here: Impact of polyphenol oxidase on the bioavailability of flavan-3-ols.

Bananas are widely used for texture and sweetness, but their PPO activity makes them a poor match when the goal is maximizing cocoa, berry, or green-veg flavanols. Additional background on PPO in banana pulp and enzyme behavior is covered in: Yang et al., 2000 and Sojo et al., 2008.

What to do instead (keep the benefits, keep the taste)

Build the smoothie around low-PPO, high-flavanol ingredients. Mixed berries, dark cocoa, and ChocoBerry-style blends preserve the signal. If you need creaminess, use avocado or chilled cooked oats instead of banana. If you want sweetness, use a small date or a measured amount of maple syrup or honey added separately rather than a high-PPO fruit base.

Acidic conditions and antioxidant co-factors can help limit PPO activity during prep. A squeeze of lemon or lime and vitamin-C-rich ingredients are common culinary strategies referenced in PPO control literature. Heat can inactivate PPO, but that defeats the purpose of a raw smoothie; favor ingredient choice and pH instead. See reviews on PPO control: Moon et al., 2020, Queiroz et al., 2008.

A better smoothie blueprint (ChocoBerry without the PPO hit)

Start with cold water or unsweetened nut milk. Add a flavanol source such as cocoa and berries or your preferred berry-cocoa blend. Add structure and creaminess from avocado or cooked-then-chilled oats. Add protein as needed. Finish with a squeeze of lemon. Do not include banana when flavanols are the priority. If you want banana for calories or potassium, have it as a separate snack at a different time window rather than inside the flavanol smoothie.

If you use a functional blend, keep the intent intact. For a ready option, see ChocoBerry Blast™.

Other high- and low-PPO notes you asked about

Besides banana, high PPO activity has been reported in certain leaves and pome fruits. The study noted beet leaves and pome fruits among higher-PPO items and confirmed (-)-epicatechin can be used as a substrate by these enzymes. When building flavanol-forward drinks, keep these categories separate from the main blend if your aim is maximal absorption. For general lists of flavonoid-rich foods and context: WebMD overview, market reference.

FAQs

Can I blend banana and still get some benefit? Yes, but expect a reduced flavanol signal based on human data. If the goal is cocoa or berry flavanol absorption, skip banana in that drink.

Can I “fix” a banana smoothie with lemon? Lowering pH and adding ascorbate can limit browning in foods, but the human crossover data still showed reduced bioavailability with banana. Best practice is to avoid high-PPO co-ingestion when targeting flavanols.

What about whole-fruit smoothies for kids or general nutrition? If the priority is overall fruit intake, banana can be fine. If the priority is flavanol bioavailability for cardiometabolic or cognitive targets, use low-PPO builds and keep banana separate.