Drug & supplement interaction

Fermented Milk + Natalizumab

Natalizumab brand name: Tysabri.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Fermented Milk has a moderate interaction with Natalizumab. Theoretically, fermented milk might decrease the effects of immunosuppressants.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Fermented Milk and Natalizumab

Here is the interaction we found between these two, with the evidence behind it.

Moderate

IMMUNOSUPPRESSANTS

Why this applies to Natalizumab

Natalizumab falls under IMMUNOSUPPRESSANTS — the group Fermented Milk interacts with.

Theoretically, fermented milk might decrease the effects of immunosuppressants.
Clinical research suggests that fermented milk has immunostimulant effects.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist with Tysabri (natalizumab): it works by calming part of your immune system to keep MS flares in check. Fermented milk, like yogurt or kefir, may have a mild immune-stimulating effect from its live probiotic cultures. In theory, nudging the immune system the other way could slightly work against what natalizumab is trying to do, which might mean less protection from relapses.

I want to be honest about how thin this evidence is. This is a theoretical concern based on how things behave in the lab, not proven in people taking this medication. Everyday food amounts of fermented milk are very unlikely to cause a problem. If you're eating a lot of probiotic foods or taking concentrated probiotic supplements, just mention it to your neurologist or pharmacist so they can keep an eye on things.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Turchet, P., Laurenzano, M., Auboiron, S., and Antoine, J. M. Effect of fermented milk containing the probiotic Lactobacillus casei DN-114001 on winter infections in free-living elderly subjects: a randomised, controlled pilot study. J Nutr Health Aging 2
  2. Fukushima, Y., Miyaguchi, S., Yamano, T., Kaburagi, T., Iino, H., Ushida, K., and Sato, K. Improvement of nutritional status and incidence of infection in hospitalised, enterally fed elderly by feeding of fermented milk containing probiotic Lactobacillus
  3. Cobo Sanz, J. M., Mateos, J. A., and Munoz Conejo A. [Effect of Lactobacillus casei on the incidence of infectious conditions in children]. Nutr Hosp 2006;21(4):547-551.
  4. Tormo Carnicer R., Infante Pina D., Rosello Mayans E., and Bartolome Comas R. [Intake of fermented milk containing Lactobacillus casei DN-114 001 and its effect on gut flora]. An Pediatr (Barc) 2006;65(5):448-453.
  5. Rio, M. E., Zago Beatriz L., Garcia, H., and Winter, L. [The nutritional status change the effectiveness of a dietary supplement of lactic bacteria on the emerging of respiratory tract diseases in children]. Arch Latinoam Nutr 2002;52(1):29-34.

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Fermented Milk Also Interacts With Other Medications

Fermented Milk has 473 moderate known drug interactions in our database — the Natalizumab one above is one of them. If you take anything else, check it against the full list below.

Moderate 473 No known interaction 2,357 (incl. Natalizumab)
Taking anything else?

Check Another of Your Medications Against Fermented Milk

Covers the 2,830 medications we’ve checked against Fermented Milk. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Natalizumab

This page covers Fermented Milk only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Natalizumab page lists 70 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Active Hexose Correlated Compound (ahcc) (moderate), Alfalfa (moderate), American Ginseng (moderate) and Andrographis (moderate).

By severity: 1 major · 59 moderate · 10 minor.

From our pharmacist’s overview on the Natalizumab page

“Natalizumab (Tysabri) works by quieting an overactive immune system in multiple sclerosis and Crohn's disease, and that is exactly why this list of 70 supplements deserves real care rather than a shrug. Fifty-three of them, ashwagandha among the familiar names, are believed to stimulate immune function, which could work directly agains…”

Reviewed by 2 · Jul 18, 2026

Open the Natalizumab interaction page

How much people look this up

Where Fermented Milk and Natalizumab Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Fermented Milk
Top half

#482 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Natalizumab
Steady interest

#1,778 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Fermented Milk

What is Fermented Milk?

  • Digestive health
  • Supporting gut bacteria (probiotics)
  • Lactose-related digestive discomfort
  • General nutrition (protein, calcium)
  • Immune support
  • Diarrhea prevention

Fermented milk is a food made by culturing milk with helpful bacteria or yeast, and it provides protein, calcium, and probiotics. It is generally safe for most people and may help digestion and gut health, though benefits depend on the product and strains used. People with milk allergy or weakened immune systems should be cautious.

Read the full Fermented Milk monograph & all interactions
Medication

About Natalizumab Injection

What Is Natalizumab Injection Used For?

Brand name: Tysabri

Tysabri is approved for adults with relapsing forms of multiple sclerosis — including clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease. It is used as a solo therapy (monotherapy) for MS, not combined with other disease-modifying drugs.

Tysabri is also approved to induce and maintain remission in adults with moderately to severely active Crohn's disease when standard treatments and TNF-alpha inhibitors have not worked or cannot be tolerated. In Crohn's disease, it must not be combined with immunosuppressants or TNF-alpha inhibitors.

See full Natalizumab Injection drug information
Keep checking

Other Drugs & Fermented Milk

Browse every other medication we’ve checked against Fermented Milk — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
473Moderate
0Minor
2,356No known interaction
473 Moderate 2,356 No interaction
Moderate

473 interactions

Showing 60 of 473 moderate interactions — see all 473 on the Fermented Milk page.

No interaction 2,356 drugs checked — show the list

We also checked Fermented Milk against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,356 medications checked with no known interaction — see the full Fermented Milk list.

See the full Fermented Milk interactions page
See every supplement checked against Natalizumab, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Fermented Milk monograph › Uses, safety, and every drug interaction in one place Natalizumab supplement interactions › Every supplement checked against Natalizumab, ranked by severity Natalizumab Injection drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Fermented Milk and Natalizumab Together: Common Questions

Can you take Fermented Milk with Natalizumab?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Fermented Milk and Natalizumab interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Natalizumab and Fermented Milk?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.