The Truth About Fasts and Cleanses

Companies and influencers promote countless ways to clear your body of unwanted substances, from fasting and special diets to herbal teas, juice cleanses and colonics. But are these cleanses effective? Is fasting safe? Most medical experts agree that cleanses aren’t necessary and can even be harmful. Here’s what you need to know. 

Your Body Detoxifies Itself

Your liver, digestive tract and kidneys are your body’s main detox systems, and your lungs and skin play a role, too. These parts of your body process the substances you take in and remove the substances you don’t need.

Thomas Hopkins, M.D., an internist with Sutter, says our bodies are extremely effective at their jobs and don’t need much assistance.

“Nothing you can do externally can outperform what the body already does,” Hopkins says. However, he notes that you can slow down the body’s effectiveness through bad habits and poor food choices.

What the Research Says

Erica Lewis, M.S., R.D., a dietitian with Sutter, says no studies have found any benefit to external efforts to detoxify the body.

“Many of these product promotions are really scams,” Lewis says. “Even herbs or herbal teas with claims of detoxification can be a waste of money. Spend that money on organic produce and healthy grains instead.”

Cleanses Can Be Harmful

Many doctors agree that colonics, physically flushing the colon with water, are not only unnecessary, but can be dangerous. Colonics may upset the balance of helpful bacteria that live inside the colon, and there’s a remote but real chance they could perforate the wall of the colon.

Many medical experts agree that a one-day fast can feel great. But for fasting safety, don’t overdo it. Fasting for more than three days can be harmful, especially if you have other medical conditions, such as diabetes, heart disease or a history of an eating disorder.

“A fast longer than a day or two can deplete vitamins, minerals and electrolytes,” Hopkins says. “Fasts can actually deplete the liver of proteins needed to deal with potentially carcinogenic substances.”

Be especially careful about fasting and medications, since fasting may change how effective medications are and whether they cause side effects. What about fasting vs. GLP-1s? If you’re taking a GLP-1, talk to your doctor about fasting to make sure you’re getting the nutrients you need.

Benefits of Intermittent Fasting

Intermittent fasting is a schedule where you only eat during a portion of the day, and your body goes 12 hours or more without food. For example, on an intermittent fasting schedule, you might only eat between 7:00 a.m. and 7:00 p.m. This pattern of eating doesn’t change the total number of calories you consume each day, but it shortens the timeframe when you eat these calories.

Intermittent fasting has been shown to curb sugar cravings, reduce overeating and improve gut function, and it may protect against various types of cancer. It may also improve concentration and memory and boost energy levels.

Plus, it may help drive blood sugar and insulin levels down, possibly reducing your risk of weight gain, diabetes and heart disease. Intermittent fasting also increases the release of human growth hormone, which regulates your metabolism and preserves muscle mass while burning fat.

Of course, not everyone gets the same results. Talk with your doctor before making any major dietary changes. Intermittent fasting may not be right for you if you take certain medications or have chronic conditions. Women who are pregnant or breastfeeding and people with significant nutrient deficiencies who need to eat every few hours should not fast for long periods of time.

Healthy Ways to Cleanse Your Body

Many Americans eat a diet high in fat and ultra-processed foods, which can slow down the digestive tract and cause bloating, fatigue and irregular bowel habits. Lewis says the cure is a healthy diet focused on fiber, fruits and vegetables, and regular exercise to stimulate the body’s own processes.

Hopkins says water is also crucial in cleansing the body. “Water helps you increase your body’s own natural methods of detoxification,” he says. “One of the best things you can do is to provide your body with a consistent, adequate intake of water.”

Antioxidant foods are another natural way to support the body’s functions. Fruits and vegetables get high praise, as well as nuts and seeds — walnuts, almonds and flax seeds in particular — which also contain beneficial omega-3 oils.

Eliminate Toxins

Caffeine, alcohol in all forms, processed foods and too much salt and sugar can upset your body’s natural functioning. In large amounts, they’re toxins, and they force your body to work harder to process and eliminate them.

Hopkins recommends these natural ways to lower toxins:

• Choose fresh, natural products instead of ultra-processed foods.
• If you drink alcohol, limit it to no more than one drink a day for women or two drinks a day for men.
• Restrict caffeine to the amount that causes no side effects for you — no jitters, sleeplessness or heartburn.

Your Long-Term Cleansing Plan

A short-term change cannot provide long-term health benefits. From a fad diet to a cleanse day at a spa, the results will fade. You need a sustainable approach to health for the long term.

Along with eating plenty of healthy foods, drinking water and reducing potentially toxic food habits, Hopkins suggests that you:

• Exercise regularly and learn how to get the most out of your workout.
• Find healthy ways to reduce stress.
• Get enough sleep. Review this checklist for a better night’s sleep.

Get Inspired

Lewis says it’s possible that a short, well-supported fast or cleanse can be the boost some of us need to change our dietary habits — like a kickoff for better health.

“Many people who do a short juice fast do feel clear-headed and begin some weight loss that inspires them to continue healthy eating,” Lewis says.

But beware of extending the fast too long, as it can send your body a signal of food deprivation. This could make you hold on to more of the calories you consume, slowing your metabolism and making weight loss more difficult.