Can supplements like L-glutamine that affect GABA (Gamma-Aminobutyric Acid) mask vitamin deficiencies in a patient with a history of Small Intestine Bacterial Overgrowth (SIBO) and malabsorption, who is taking Ativan (lorazepam) and has a potential vitamin E deficiency?

L-Glutamine and GABA-Affecting Supplements Do Not Mask Vitamin Deficiencies in SIBO

L-glutamine and other GABA-affecting supplements do not mask vitamin deficiencies—they simply fail to address the underlying malabsorption problem caused by SIBO. The vitamin deficiencies in your case stem from bacterial overgrowth causing bile salt deconjugation and impaired fat-soluble vitamin absorption, not from any masking effect of supplements 1.

Why Supplements Don't Mask Deficiencies in SIBO

The core issue is malabsorption, not symptom masking. In SIBO, bacterial overgrowth deconjugates bile salts, leading to steatorrhea and subsequent malabsorption of fat-soluble vitamins (A, D, E, K) 1. L-glutamine affects GABA neurotransmission and may provide symptomatic relief for anxiety or gut symptoms, but it does nothing to improve vitamin absorption or hide laboratory evidence of deficiency 2.

• Vitamin E deficiency is particularly concerning in your case because it's the fat-soluble vitamin most likely to cause cardiac abnormalities (QT prolongation) in SIBO-related malabsorption 3.
• Laboratory testing will still reveal low serum levels of deficient vitamins regardless of L-glutamine use 3, 1.
• The combination of lorazepam (Ativan) and potential vitamin E deficiency creates additional risk, as both can affect neurological function 3.

The Real Problem: SIBO-Induced Malabsorption

Your SIBO history is the primary driver of vitamin deficiencies, not supplement interactions. The pathophysiology is straightforward:

• Bacterial overgrowth in stagnant bowel loops causes bile salt deconjugation and pancreatic enzyme degradation 1.
• This results in steatorrhea and malnutrition, specifically affecting fat-soluble vitamins 1.
• Vitamin E deficiency manifests as peripheral neuropathy, ataxia, ophthalmoplegia, and myopathy 1.
• Vitamin A deficiency causes night blindness and xerophthalmia 4, 1.
• Vitamin D deficiency increases fracture risk 4, 1.
• Vitamin K deficiency causes bleeding disorders with prolonged PT/INR 1.

Diagnostic Approach for Your Situation

Immediate testing is warranted given your SIBO history and potential vitamin E deficiency:

1. Confirm current SIBO status through hydrogen and methane breath testing (more accurate than hydrogen-only testing) 4, 1, 5.
2. Check complete fat-soluble vitamin panel including serum alpha-tocopherol (vitamin E), retinol (vitamin A), 25-hydroxyvitamin D, vitamin K1, and PIVKA-II 3, 1.
3. Evaluate for steatorrhea and weight loss despite adequate caloric intake 1.
4. Obtain EKG if vitamin E deficiency is confirmed, as it can cause cardiac conduction abnormalities 3.

Treatment Algorithm

The treatment sequence must address SIBO first, then supplement appropriately:

Step 1: Eradicate SIBO

• Rifaximin 550 mg twice daily for 1-2 weeks is the most effective treatment with 60-80% efficacy 5.
• Alternative antibiotics include doxycycline, ciprofloxacin, or amoxicillin-clavulanic acid if rifaximin fails 5.
• Treating SIBO is essential before supplementation to restore normal absorption 1.

Step 2: Initiate Vitamin Supplementation

Use water-miscible forms for improved absorption in malabsorption states 4, 1:

• Vitamin E: 100 IU daily (start immediately if deficiency confirmed) 4, 3.
• Vitamin A: 10,000 IU daily (adjust based on blood results to avoid toxicity) 4, 1.
• Vitamin D: 3,000 IU daily (titrate to maintain 25-hydroxyvitamin D >75 nmol/L) 4, 1.
• Vitamin K: 300 μg daily 4.

Step 3: Monitor Response

• Recheck vitamin levels every 6 months and adjust dosing based on laboratory results 4, 3, 1.
• Monitor for SIBO recurrence, which occurs in up to 14% of patients without surgical history 5.

Critical Pitfalls to Avoid

Several common mistakes can worsen your situation:

• Do not use bile acid sequestrants (cholestyramine, colesevelam) without careful consideration—they can cause vitamin D deficiency in 20% of patients and rarely cause significant vitamin A, E, and K deficiency 4, 1.
• Avoid assuming L-glutamine is masking deficiencies—chronic high-dose glutamine supplementation (>40 g/day) has its own side effects including altered amino acid transport and abnormal aminoacidemia, but it doesn't hide vitamin deficiencies 2.
• Don't restart proton pump inhibitors after SIBO treatment unless absolutely necessary, as gastric acid suppression is a well-established SIBO risk factor 5.
• Recognize that normal B12 levels don't exclude deficiency in SIBO—bacterial consumption can cause B12 malabsorption even with normal serum levels, requiring methylmalonic acid and homocysteine testing 1, 5.

Regarding Your Ativan Use

Lorazepam doesn't interact with vitamin absorption, but the combination of benzodiazepine use and potential vitamin E deficiency (which causes neurological symptoms) requires careful monitoring 3. If you're experiencing neurological symptoms, distinguishing between benzodiazepine effects and vitamin E deficiency is essential through proper laboratory testing 3, 1.

Bottom Line

Stop worrying about L-glutamine masking deficiencies and focus on treating the SIBO and directly measuring vitamin levels. The malabsorption from SIBO is your primary problem, and laboratory testing will reveal true deficiency states regardless of any supplements you're taking 3, 1. Treat the SIBO with rifaximin, supplement with water-miscible fat-soluble vitamins, and monitor levels every 6 months 4, 3, 1, 5.