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Gut Health
Wellav8 Standard — 4.4/5

Thorne FiberMend

“Feed the bacteria you actually want.”

$35–45supplement

Most fiber supplements are psyllium husk that bloats you and does nothing for your microbiome. FiberMend uses a blend of five research-backed prebiotic fibers that selectively feed beneficial bacteria — especially the butyrate producers that maintain your gut lining. Dissolves completely in water with no grit or taste.

Our assessment

Purity5/5
Efficacy4/5
Sourcing4/5
Value4/5
Transparency5/5

Purity & verification

Verification & Testing

NSF Certified for Sport
Third-party tested
GMP certified
Heavy metals free
No proprietary blends
COA available
View Certificate of Analysis →
Gluten-freeSoy-freeDairy-free

Why we chose it

Five prebiotic fiber sources (not just psyllium)

Selectively feeds butyrate-producing bacteria

Dissolves completely — no grit, no taste, no bloating

Thorne's standard third-party testing and NSF certification

Key ingredients

Partially hydrolyzed guar gumAcacia fiberFlaxseed powderGlucomannanPrune powder

The science

Short-chain fatty acids (SCFAs) — especially butyrate — are the primary fuel for colonocytes (gut lining cells). Prebiotic fibers like partially hydrolyzed guar gum and acacia fiber selectively increase butyrate production. Studies show prebiotic supplementation improves gut barrier integrity, reduces systemic inflammation markers (CRP), and increases microbiome diversity.

Evidence

From the sources we read every week for our concierge recommendations.

  • Mary Claire Haver

    “ Fiber GDX | The 'Pause Life – The 'Pause Life by Dr. Mary Claire Haver”

    Insoluble + soluble blend includes 7g of fiber to support gut microbiome, digestive regularity, energy, and already healthy blood sugar levels. 1 scoop daily | 30-day supply. Choose Your Flavor UnflavoredUnflavoredUnflavoredVariant sold out or unavailableOrangeOrangeOrangeVariant sold out or unavailable Modify or cancel anytime Subscription Details Save 10% on all subscription orders. 30-day satisfaction guarantee policy Pause,skip, or cancel anytime-just log into your account Subscribe & Save Save 10% Regular price$40 Regular price$40Sale price$36.00 USD Unit price/ per Select frequency Every 4 Weeks Every Month Every 6 Weeks Every 2 Months Every 3 Months One-time purchase Regular price$40.00 USD Regular price$40.00 USDSale price$36.00 USD Unit price/ per Add to bag Coming Soon Email when available Minimum quantity allowed is 0. Max quantity allowed is 0 The product can be bought in quantity increments of 0. Pay using HSA/FSA with flexSelect Flex at checkout to pay for your HSA/FSA eligible items About Fiber GDX is a combination of whole grains that civilizations have thrived on for millennia. It contains well-researched, high-quality ingredients to create a fiber formula with both soluble and insoluble fibers. They work together to support digestive regularity, making it a valuable addition to any balanced diet. When your digestive system is running smoothly, it can support an increase in energy and already healthy blood sugar levels. Our Fiber GDX products are free of gluten ingredients and third-party tested for confirmation! Read more about fiber in the 'Pause Blog The Power of Fiber. For additional product information and tips, visit our Help Center. Help Center Creatine Additional information on our Third Party Testing FREE shipping on orders $99+, OR any weighted vest order. $8 flat shipping under $99. Orders fulfilled within 2 business days, or 3 during holidays/high volume. Ingredients Psyllium Husk Buckwheat Millet Quinoa Amaranth Chia Seed Powder Apple Fiber Powder Citrus Pectin Powder (no grapefruit) Guar Gum (legumes) Citric Acid Natural Flavor (Orange) - Fiber GDX Orange Stevia Leaf Extract - Fiber GDX Orange Monk Fruit Extract - Fiber GDX Orange Benefits Supports:

    read the source →
  • Examine.com

    “The effect of dietary fiber on constipation - Study Summary”

    This meta-analysis of 16 randomized controlled trials examined the effect of fiber supplementation on constipation. The trials included 1,251 participants with chronic, idiopathic constipation (i.e., constipation that couldn’t be easily attributed to something). The types of fiber used were polydextrose (2 trials), psyllium (4 trials), inulin-type fructans (5 trials), galactooligosaccharide (2 trials), pectin (1 trial), wheat bran (1 trial), and unspecified (1 trial). Fiber was provided in dosages ranging from 4 to 40 grams per day. The trials lasted 2 to 8 weeks. The outcomes examined were constipation symptom improvement, symptom severity, stool characteristics (frequency, consistency, weight), gastrointestinal symptoms, quality of life, laxative use, and adverse events. These findings were based on participant self-report via various questionnaires. Subgroup analyses were performed to examine the effect of different fiber types, dosages, and durations of treatment, among other variables. The results The number of participants experiencing an improvement in symptoms was greater in participants receiving fiber compared to placebo. This benefit was seen in trials using psyllium (3 trials) and pectin (1 trial) and with fiber dosages over 10 grams per day (9 trials). Fiber supplementation led to a large increase in stool frequency and a small improvement in stool consistency. Fiber supplementation led to a small decrease in the severity of straining. Medium reductions in straining were seen with doses of at least 10 grams per day of fiber or psyllium specifically. Fiber supplementation using inulin-type fructans and wheat bran led to a large increase in flatulence. Supplementation with pectin decreased bloating. Neither wheat bran nor inulin-type fructans appeared to decrease bloating. Note The assessed studies frequently had potential issues that were identified by the investigators. Of the 16 trials, half were considered at high risk of deviation from the intended intervention (i.e., the study participants may have not adhered well to the study protocol). The investigators also reported some concerns about the randomization process in 13 trials. Some trials sparked other concerns, including potentially missing outcome data. Ultimately, none of the trials were considered at low risk of bias in all domains assessed. The big picture The results of this meta-analysis indicate that fiber supplementation can be beneficial for chronic constipation. Two specific types of fiber that appeared beneficial were psyllium and pectin. However, in addition to the potential study quality limitations discussed above, there were also only a limited number of studies for these fiber types. Pectin appeared to improve symptom response rates and bloating based on a single trial with 80 people. There was slightly more research using psyllium, but not much: 3 trials with 275 participants suggested an improved symptom response rate and 2 trials with 223 participants suggested reduced straining.

    read the source →

How to use

Mix 1 scoop (6g) into water, smoothie, or any beverage daily. Start with half a scoop for the first week to avoid gas. Increase to 2 scoops once tolerated for optimal prebiotic effect.

Who it's for

Anyone eating a standard diet (which means you're probably getting 10–15g fiber when you need 25–35g). Especially helpful alongside a probiotic — prebiotics make probiotics work better.

Get Thorne FiberMend

Affiliate link. We earn a small commission — it's how we keep Wellav8 free. We'd recommend this regardless.

Related topics

Gut HealthInflammation

This product supports these goals.

Gut Health
Reduce Inflammation
Foundational Nutrition

Wellav8 may earn a commission from products linked on this page. All products are independently selected based on our five-point standard. No brand pays for placement. These statements have not been evaluated by the FDA. These products are not intended to diagnose, treat, cure, or prevent any disease.