Is your protein powder secretly sabotaging your gut health? Most brands prioritise taste and shelf-life over your metabolic well-being. Learn the 5 red-flag ingredients to avoid and how to read a supplement label like a clinical nutritionist.
6 min read
Walk down the supplement aisle or browse protein powders online and you’ll see the phrase “clean ingredients” or “natural ingredients” everywhere. But what does that actually mean, and how do you know if a protein powder is actually what it's claiming to be?
For many people, protein powder is a daily staple. You can put it in almost everything- smoothies, oats, baking, used as a meal replacement or as a quick shake after gym. When something is consumed regularly, the quality of its ingredients is of the utmost importance, since you’re consuming it in larger amounts. Let’s break down what’s commonly added to protein powders, why some ingredients may not be ideal for gut or metabolic health, and how to read labels with confidence.
Most protein powders start with a solid base, usually whey or plant protein. Where they differ is in what’s added to improve taste, texture, shelf life, and cost.
Many mainstream protein powders include:
● Artificial sweeteners (maltodextrin, aspartame, sucralose for example)
● Added sugars
● Gums and thickeners
● Anti-caking agents
● Synthetic flavours
While these ingredients are technically “approved for use,” approval does not automatically mean optimal for your health, particularly when consumed daily over long periods. It’s also important to note that none of the below ingredients are dangerous and consuming them every now and then is fine, what we are referring to here is regular everyday use and how understanding what you’re consuming may lead to better choices.
1. Artificial sweeteners (e.g. sucralose 955, Ace-K 950 or aspartame 951)
Sucralose is one of the most common sweeteners used in protein powders. While it’s calorie-free, research suggests it may:
● Alter gut microbiota composition and may increase gut permeability in some individuals (Mohamed B Abou-Donia et al., 2009)
● Trigger bloating, gas or loose stools (Mendoza-Martínez et al., 2022)
● Impact insulin and glucose responses in susceptible people (Romo-Romo et al., 2025)
● May cause systemic inflammation (Raoul et al., 2025)
For clients with gut symptoms, chronic inflammatory or autoimmune conditions such as Rheumatoid arthritis or thyroid autoimmune conditions (Hashimoto’s/Graves), hormone imbalances, or insulin resistance, this is often one of the first ingredients I ask them to avoid in their diet.
2. Added sugars and fillers
Dextrose is a rapidly absorbed sugar added to improve taste. Its downsides include:
● Sharp blood sugar spikes (good for short bursts of energy, but may not last your whole training session before a crash!)
● Increased insulin demand
● Reduced satiety, meaning more ghrelin (hunger hormone) released
● No real nutritional benefit
In a product marketed as a health supplement, added sugars are really not necessary and if you need an energy hit pre-workout, or glucose recovery post-training, there are much better options.
3. Some emulsifiers and gums
● Certain emulsifiers may disrupt the gut barrier and cause “leaky gut”, such as Carrangeenan (E407) (Kimilu et al., 2024)
● Some gums can ferment rapidly in the gut, causing bloating (Borsani et al., 2021)
● Soy-based emulsifiers may not suit those with sensitivities
● Other emulsifiers, such as a Sunflower lecithin, offer a more natural alternative. Sunflower lecithin is non-GMO, allergen-free and derived from sunflower seeds via cold-pressing.
Not all emulsifiers and gums are harmful, but the type and quantity matter if you are consuming your protein powder daily.
Example 1 - A Common well-known supermarket “high protein” protein powder targeted at people for “bulking” and rapid muscle growth
Ingredients include: Whey protein concentrate, whole milk powder, skim milk powder, emulsifiers (soy & sunflower lecithin), cocoa, dextrose, guar gum, enzyme (papain), sucralose.
Key notes:
● Added sugar (dextrose)
● Artificial sweetener (sucralose)
● Multiple dairy fillers beyond protein isolate
● Soy-based emulsifiers
While it delivers protein, it also delivers unnecessary ingredients that may negatively impact gut health and blood sugar regulation for some people.
Example 2 - Another common protein powder brand at the supermarket who sell a number of protein products in the health aisle.
Ingredients include: Protein blend, cocoa, flavours, dextrose, salt, silicon dioxide, soy lecithin, sucralose, acidity regulator, digestive enzyme blend.
Key issues:
● Added sugar and artificial sweetener combination
● “Flavours” can contain 100 ingredients on their own and they are not specific on whether this is from a natural plant, animal, or synthetic origin
● Anti-caking agent (silicon dioxide)
● Heavy processing and multiple additives
Side note: Digestive enzymes don’t necessarily “cancel out” the effects of ultra-processed ingredients.
A cleaner protein powder focuses on:
● A high percentage of quality protein
● Minimal ingredients
● Natural sweeteners (if any) such as monk fruit and stevia
● Gentle emulsifiers
● Ingredients that serve a functional purpose, not just taste or texture
Ingredients: Whey protein isolate (90%), cocoa powder, organic inulin, natural flavours, sunflower lecithin, vegetable gum, organic steviol glycosides.
Why this stands out:
● No artificial sweeteners
● No added sugars
● High protein concentration
● Prebiotic fibre included intentionally
● Minimal, transparent ingredient list
Ingredients: Yellow pea protein, faba bean protein, organic pumpkin protein (78% protein), natural cocoa, natural flavours, organic coconut MCT powder, Himalayan pink salt, digestive enzymes, monk fruit, organic stevia, thaumatin, Bacillus coagulans.
Why this works well:
● Diverse plant protein sources for gut bacteria
● Natural sweeteners only
● Added MCTs for energy and satiety
● Probiotic support
● Designed with digestion in mind
When choosing a protein powder, ask yourself:
● Can I recognise and pronounce most of the ingredients?
● Is there added sugar or artificial sweeteners?
● Are the additives there for health or just for taste and shelf life?
● Would I be comfortable consuming this daily?
Shorter ingredient lists aren’t always better, but purposeful ingredient lists are.
● More than 12-ish ingredients, alongside ingredients where you aren’t sure what they are!
● Artificial sweeteners or numbers (Aspartame, Ace-K, Sucralose)
● Multiple fillers (Dextrose, maltodextrin, glucose solids, rice syrup solids, corn syrup solids, fructose, cane sugar, carboxymethyl cellulose, locust bean gum)
● “Proprietary blend” or similar words without a breakdown of what that actually means
● Low protein content <75%
● Around 80–90% protein content
● Transparent ingredient list and wholefoods
● Natural sweeteners (such as stevia or monk fruit, or unsweetened)
● Minimal gums and gentle emulsifiers such as sunflower lecithin or acacia gum
● Functional extras with purpose, such as digestive enzymes for reducing bloating
“Clean ingredients” doesn’t necessarily mean healthy. Protein powders don’t need to be packed with fillers, artificial sweeteners, or sugars to taste good or be effective. When brands prioritise ingredient quality, digestion, and transparency, the difference is noticeable, not just on the label, but in how your body responds. If protein powder is part of your regular routine, choosing one with clean, functional ingredients is a small change that can make a meaningful impact over time.
By Georgina Waugh
Clinical Nutritionist (BHSc Nut Med.)
Is plant-based protein as effective as whey?
Can I use these protein powders if I have a sensitive stomach?
What is the best way to use "clean" protein powders?
Are natural sweeteners like Stevia and Monk Fruit safe for daily use?
Why does "clean" protein usually cost more?
Blog post
Give your customers a summary of your blog post
IMPORTANT INFORMATION: all content provided here is of a general nature only and is not a substitute for individualised professional medical advice, diagnosis or treatment and reliance should not be placed on it. For personalised medical or nutrition advice, please make an appointment with your doctor, dietitian or qualified healthcare professional.
References
