Gut reset: what actually helps your gut health, and what to skip

A gut reset usually means a short plan, often three to seven days, that promises to “reboot” digestion or the gut microbiome: the trillions of bacteria and other microbes that live in your intestines. The microbiome science is real and moving fast, but it is still young. There is no test that tells you whether your microbiome is “good,” and no single plan that fits everyone.

“Gut reset” has no medical definition and no studied protocol, and we found no clinical trials showing that a 3-day reset durably changes the gut. A 2014 study in Nature did show that gut microbes respond within days to a sharp change in diet. But a fast change is not a lasting one: what counts is what you eat most of the time.

So this guide uses “reset” in one sense only: restarting everyday habits. It is education, and it does not replace a medical evaluation or individualized advice from a licensed dietitian.

None of these is a promise. They are the habits with the best support so far:

• Fiber. According to the NIH’s NIDDK, adults should get 22 to 34 grams of fiber a day, depending on age and sex. Those are the goals in the Dietary Guidelines for Americans, 2020-2025, which also report that more than 90% of women and 97% of men fall short. Fiber comes from legumes, whole grains, fruits, vegetables and nuts.
• A variety of plants. In the American Gut Project, a citizen-science study with more than 10,000 volunteers, people who ate more than 30 types of plants a week had differences in their gut bacteria, including more fiber-fermenting bacteria, compared with people who ate 10 or fewer. It is an observational study: it shows a link, not a cause.
• Fermented foods. In a Stanford trial (Wastyk and colleagues, Cell, 2021), 36 healthy adults spent 10 weeks on a diet high in fermented foods (yogurt, kefir, kimchi, other fermented vegetables and kombucha) or a diet high in fiber. In the fermented-food group, microbiome diversity rose and 19 inflammatory proteins in the blood fell; in the fiber group, diversity stayed stable over that time. It is a small study in healthy people, and it does not show that fermented foods prevent or treat any disease.
• Water. The NIDDK explains that water and other liquids help fiber work better. How much you need depends on your size, health, activity level and climate.
• Movement and sleep. The NIDDK notes that, for people with irritable bowel syndrome, research suggests that more physical activity, less stress and enough sleep may help symptoms. Whether they change a healthy person’s microbiome is not yet clear.

Probiotics are live microorganisms taken with the aim of a health benefit. According to the NIH’s NCCIH, different types of probiotics may have different effects, and in most instances we still don’t know which probiotics are helpful and which are not. A result shown for one strain does not carry over to another.

The American Gastroenterological Association (AGA) reviewed the evidence in 2020 and suggests specific probiotics in only three settings: to prevent *C. difficile* infection in people taking antibiotics, in preterm, low-birthweight infants, and for pouchitis. Since then, in 2023, the FDA warned that premature infants given probiotics are at risk of serious, potentially fatal infections; a probiotic for a premature baby is a decision for the neonatal team only. For irritable bowel syndrome, Crohn’s disease and ulcerative colitis the AGA found the evidence insufficient, and it recommends against probiotics for children with acute infectious gastroenteritis.

In healthy people probiotics have a long history of apparently safe use, but the NCCIH warns that the risk of harmful effects is greater in people with severe illnesses or weakened immune systems. If that is you, or you are thinking of giving them to a baby, ask your doctor first. We don’t sell or recommend products here.

• Colon cleanses and detox teas: there is no good evidence they remove toxins; your liver and kidneys already do that. The NIH’s NCCIH adds that colon cleansing can have side effects, some of them serious, especially in people with a history of gastrointestinal disease, colon surgery, kidney disease or heart disease, and that the laxatives in these programs can cause diarrhea and dehydration.
• “Leaky gut” as a diagnosis. Intestinal permeability is real and studied: Harvard Health explains that it is increased in conditions such as celiac disease and Crohn’s disease. What is not established is that it causes diseases outside the digestive tract; there are not yet clinical studies in humans showing that cause and effect.
• IgG “food sensitivity” tests. The American Academy of Allergy, Asthma & Immunology (AAAAI) advises against them: IgG antibodies to a food are a normal response to having eaten it. See which tests are worth it in functional medicine labs.
• Cutting out whole food groups without a medical reason. It can leave you with less fiber and less variety, the opposite of what you are after. See also functional nutrition and intermittent fasting.

The habits in this guide are for people who feel generally well. Don’t try to manage these symptoms with a diet, teas or probiotics; see a doctor if you have:

• Blood in your stool, or black, tarry stools. According to the NIDDK, these are signs of bleeding in the digestive tract. With lightheadedness, fainting, trouble catching your breath or vomiting blood, call 911.
• Weight loss you can’t explain. The CDC lists it, with blood in the stool and a change in bowel habits, among the possible symptoms of colorectal cancer; it also has many other causes, which is why it needs an evaluation.
• Diarrhea that lasts. The NIDDK advises adults to get care for diarrhea lasting more than 2 days, or with a high fever or six or more loose stools in a day.
• Severe belly pain, or pain that keeps getting worse.
• A change in your bowel habits that stays, especially if you are 45 or older. The US Preventive Services Task Force (USPSTF) recommends colorectal cancer screening starting at age 45 for adults without symptoms; if you have symptoms, don’t wait for screening.

If your symptoms sound more like a condition, read about IBS, constipation or stomach pain.

If you are in Puerto Rico, you can book an online visit with Dr. Diana Nieves Castro, a general practice physician licensed in Puerto Rico. We evaluate, diagnose and treat; if needed, we give you a lab order for a lab near you. Video visits are only for people who are physically in Puerto Rico, and they are not for emergencies. Everywhere else, see your own doctor.

If you are wondering what meals and a typical day look like, read what to expect at the retreat.