A Gastroenterologist’s 8 Essential Supplements for Gut Health–and How to Use Them Correctly

Feb 5, 2026 - 11:03 Updated: Feb 4, 2026 - 13:42

A Gastroenterologist’s 8 Essential Supplements for Gut Health–and How to Use Them Correctly

You’re not eating enough fiber, so you start a prebiotic. You feel bloated, so you add a probiotic. Your energy is dragging, so you pick up vitamin D. Before you know it, you’re swallowing a handful of pills you’re not even sure are working—and honestly, your gut still feels off.

Gastroenterologist Dr. Will Bulsiewicz said that such a scattershot approach is why many people see little benefit from supplements—and that a personalized plan is the way to go.

“Gut health should be a daily priority for literally everyone, and supplements are a part of that package,” he told The Epoch Times. “I wouldn’t argue it’s the number one thing, but strong, strategic supplementation is an opportunity to improve our health starting today.”

Supplements can be potent. The right one at the right time, taken correctly alongside a healthy diet and lifestyle, can help improve gut motility and bowel movements, strengthen the immune system, optimize sleep, and lower inflammation. Supplements can also be weak or inappropriate, amounting to little more than expensive urine.

The Foundation: 8 Evidence-Based Supplements

Bulsiewicz, who details his supplement protocol in his latest book “Plant Powered Plus,” recommends eight specific evidence-based, foundational supplements for his patients. Not everyone needs all eight, and some may benefit from others not on this list. Ideally, he said, you’d want to formulate your plan with a health care provider who can determine what your body is lacking and monitor whether the supplements improve your health.

Prebiotics: Feed Your Gut Microbes

Prebiotic fiber supplements feed your gut microbial community, and the benefits extend beyond improved digestion to an increase in satiety hormones, better calcium and magnesium absorption, and enhanced cognitive function.

However, increasing fiber, whether through supplements or diet, can cause uncomfortable abdominal symptoms such as bloating, gas, and pain. It’s best to resolve constipation before starting prebiotics and then begin with a low dose of 1 to 2 grams or less, especially if you have small intestinal bacterial overgrowth, Bulsiewicz said.

“I’m a big believer in prebiotic fiber supplements. You'll never be able to convince me otherwise, because I’ve witnessed it in my own life and in thousands of patients,” he said.

Dietitian Cassie Madsen, who works mostly with patients with irritable bowel syndrome (IBS), told The Epoch Times that 60 percent or more of her clients end up taking a fiber supplement—usually psyllium or a brand containing guar beans, which are gentler on the gut.

Bulsiewicz recommends the same, as well as acacia fiber and galacto-oligosaccharides. He said to consider brands that include a variety of fibers, which will feed a more diverse microbiome, which research links to better health.

Probiotics: Target Your Specific Problem

Probiotics are good microbes, found abundantly in fermented foods, but they don’t always stick around in the gut for long. General probiotics marketed like multivitamins are the wrong approach, Bulsiewicz said.

It’s best to use probiotic supplements in a targeted way, he said. For instance, certain strains are effective for specific conditions:

Saccharomyces cerevisiae for IBS with bloating
Saccharomyces boulardii for antibiotic-associated diarrhea
Lactobacillus rhamnosus GG for acute diarrhea
Bifidobacterium lactis DN-173010 for constipation
Escherichia coli 1917 for ulcerative colitis that’s in remission

“Start with the outcome, the thing you want to fix, and determine what probiotic has a human clinical trial that can help you with that,” Bulsiewicz said, adding that taking the same dose as stated in the trial is important and may not match what’s on a product label.

Madsen consults a clinical probiotic guide—a rating of probiotics that have been validated by clinical trials—before recommending a probiotic or to see if a client is using probiotics appropriately.

Vitamin D and Omega-3s: Test First, Then Supplement

Both vitamin D and omega-3 fatty acids, which help strengthen the gut barrier and immune system, can be part of your strategic supplementation plan, depending on deficiencies that can be measured through blood tests.

Those with inflammatory conditions should aim for higher levels, Bulsiewicz said. For vitamin D, that would be 40 to 60 ng/mL. For omega-3 index results, the high end is 10 to 12 percent of EPA and DHA fatty acids.

If you don’t have access to lab testing, Bulsiewicz said he would recommend a maintenance dose of both, on the assumption that most people are deficient and that there’s a low risk in taking them. For vitamin D, that’s 1,000 to 2,000 IU per day; for omega-3, 500 milligrams per day of combined DPA and DHA.

Research has shown that vitamin D supplementation can help prevent relapses of inflammatory bowel disease. Omega-3 supplements—found to enhance the gut ecosystem similar to prebiotics—increase short-chain fatty acids, chemical messengers made when microbes feed on fiber that play a role in health and disease prevention.

Melatonin, Magnesium, and Zinc: The Sleep-Gut Connection

Bulsiewicz lumps melatonin, magnesium, and zinc together for regulating the circadian rhythm, noting that sleep affects gut and overall health.

Research supports melatonin use to improve IBS, acid reflux, and ulcerative colitis. Zinc contributes to melatonin production, and magnesium helps improve sleep and lower anxiety, both of which are important because chronic stress can negatively impact the gut.

Most of us don’t have adequate zinc and magnesium intake, Bulsiewicz added, and levels can be tested. There is no target baseline or test for melatonin, so it’s best to start supplementing with a low dose of 0.5 milligram taken about an hour before bed.

Several forms of magnesium and zinc can be chosen based on symptoms such as constipation, depression, anxiety, fatigue, and mental clarity. Madsen recommends magnesium citrate or magnesium oxide for those who are chronically constipated, taken with fiber in the evening. “It can prime their body to have bowel movement in the morning,” she said.

Curcumin: Anti-Inflammatory Without the Side Effects

Curcumin has anti-inflammatory properties. Not only is it a better option than nonsteroidal anti-inflammatory drugs such as ibuprofen that can damage the stomach, intestines, and kidneys, but it can also promote the growth of beneficial bacteria, Bulsiewicz said. Curcumin can also lower systemic inflammation and suppress the growth of microbes that degrade the gut barrier.

He noted that curcumin is better absorbed when taken with black pepper or healthy fats, such as your morning omega-3 supplement. If your inflammation is worse at night, it might be better to take it before bed, he said.

There is no testing for curcumin. Bulsiewicz recommends 500 to 1,000 milligrams daily for general health and up to 2,000 milligrams taken in two to three doses over a day, with medical supervision, for acute inflammation.

Mistakes That Undermine Your Supplements

Taking the right supplement is only half the battle. There are several common mistakes people make with supplements that sabotage results.

Misunderstanding the Label

Choosing the right supplement brands can be daunting. Products often include marketing language on the front of packaging that may be false claims or not match the dosing, Bulsiewicz said.

“You’re basically being marketed to as you walk down the aisles just like in the supermarket,” he said.

Bulsiewicz started his own supplement company because of industry issues with quality, efficacy, and safety, but he said that shopping for the best supplements is a skill that can be learned.

Ignore the front-of-package claims and instead look for logos from companies such as NSF International and U.S. Pharmacopeia that verify product label accuracy and check for contaminants.

Then, verify the dosing to see if it matches what you need based on your individual labs or product clinical trial. Avoid any with artificial colors or flavors, preservatives, or other additives, which can be damaging to the gut, he said.

Starting Too Many at Once

Each supplement should have a meaningful effect on your health, he said. The best way to gauge how it makes you feel is to try only one at a time.

“In the vast majority of cases, you should feel the difference. In order to really achieve that, initiation should be done in isolation because then you know what it’s doing.”

Giving Up Too Soon

Just as clinical trials measure a supplement’s effect from a starting and ending point, you need to use the supplement long enough to determine if it’s working.

Many probiotics need at least four weeks to work, Madsen noted.

Ignoring Timing

Taking supplements at random times throughout the day misses a crucial opportunity.

Human genes flip on and off throughout the day, and microbe levels in the gut also rise and fall at different times, too, Bulsiewicz said. “We were designed with a 24-hour schedule in mind. Our body is not the same at all times.”

Aligning with the body’s timeline by delivering hormones and nutrients when our body most needs them is an easy way to more effectively influence digestion, sleep, and overall health, he said. Melatonin, magnesium, and zinc should be taken in the evening; all others can be taken in the morning. Create consistency by taking supplements at the same time you brush your teeth.

Overdoing It

Some supplements might not be effective or needed. Madsen reviews supplements with new clients, who are often taking several for unknown reasons. “We usually pick a few that they can come off of. I do take kind of a minimalist approach,” she said.

“Sometimes there are other health care providers involved that recommended them, so I usually tell them to discuss whether it’s worth continuing with your doctor, because supplements are expensive, and there is potential for harm,” she added.

More isn’t always better, Bulsiewicz added, particularly when it comes to taking higher dosing. Follow evidence-based dosing and have regular laboratory blood work done, which can be monitored by your doctor, who should be able to detect problems, he said.

Supplement injuries are less common than injuries due to medication, Bulsiewicz said. “The amount of injury that occurs due to medications on a yearly basis—it’s terrifying—but that said, there are some people who do get hurt by supplements, and so we need to be smart and cautious.” You can check online for supplements that interact with prescriptions and over-the-counter medications.

Part of a Bigger Plan

Ideally, advice on gut health supplements would come from or be managed by a physician, Bulsiewicz said, noting that when he meets with patients, each plan is tailor-made. In any event, he said you should discuss any additions or changes to your supplements with your doctor.

He also suggests a comprehensive lifestyle approach to accompany supplement use, including foods to add and avoid, stress and emotion management, and light exposure.

Every strategy points back to one foundational element to human health—the microbiome, Bulsiewicz said. Not only does the microbiome offer a snapshot of how someone has been living their life, it profoundly affects physiology through metabolism, hormone production, cognition, and mood.

“It makes sense to orient that through the microbiome, because it has such a powerful impact on what I’m trying to accomplish,” he said. “I think of it as command central for our health.”