Kicking off the new year by cleansing your body with a detox diet? A dietitian unpacks the science behind these fads

Detox diets are often touted as a way to cleanse the body after the excess food and drinks that come with the holidays. These diets promise quick results and can particularly entice people around the new year, when there tends to be a renewed focus on health and lifestyle habits.

There are a few different types of detox diets: fasting, juice cleanses, eating only certain foods, using dietary commercial detox supplements or “cleansing” the colon with enemas or laxatives.

Most of these diets have a few things in common: They are short-term and aim to eliminate allegedly toxic substances from the body. Typically, these diets include a period of fasting followed by an extremely restrictive diet for a number of days.

As a registered dietitian, I have seen clients attempt detox diets and experience a slew of negative side effects, including developing a negative relationship with food.

Research shows that there is little evidence to support the use of detox diets and that they are not needed anyway. The body is well-equipped to eliminate unwanted substances on its own, without expensive and potentially harmful supplements sold by the nutrition and wellness industry.

About toxins

What are toxins – and how do they get into the body in the first place?

Internal toxins include natural byproducts created by the body during metabolism, such as lactic acid, urea and waste from the gut microbes.

External toxic exposures enter the body through eating, drinking, breathing or penetration of the skin. These can come in the form of air pollutants, food or water contaminated with chemicals or heavy metals, household products such as laundry detergent and even beauty products like facial cleansers, body wash and makeup.

The body’s built-in detoxification system includes the liver and kidneys, with assistance from the lungs, lymphatic system, digestive tract and skin. Briefly, the liver breaks down harmful substances, which are then filtered out through the kidneys. The digestive tract also expels them through bowel movements.

But our bodies aren’t always functioning optimally. That’s why a proper diet and improved lifestyle behaviors, such as increased exercise and sleep, may have a significant – and positive – impact on the body’s detoxification system.

Having a diverse microbiome and an abundance of healthy gut bacteria also helps to rid the body of harmful substances. Fermented foods such as kefir, sauerkraut and cultured dairy products can benefit gut health. These foods contain probiotics, which are the beneficial bacteria that live in your gut.

Another category, called prebiotic foods, are also beneficial for gut health. They provide nutrition and energy for the healthy probiotics in the gut and are high in fiber. Examples of prebiotic foods are whole grains and fruits and vegetables, particularly bananas, greens, onions and garlic.

The potential harms of detox diets

Through glossy and pervasive advertising, detox diets perpetuate a quick-fix mindset about weight and body image rather than promote lifestyle changes that are sustainable for a lifetime.

Although proponents claim that detox diets and juice cleanses lead to weight loss, improved liver function and overall better health, research shows they have little to no effect. What’s more, they can lead to side effects, including headaches, fatigue, weakness, fainting and irritability. However, studies show there is some evidence that certain foods and spices, such as coriander, may enhance the body’s natural detoxification pathways.

According to the Academy of Nutrition and Dietetics, other foods that may give the body’s own detox system a boost include cruciferous vegetables like broccoli and Brussels sprouts, berries, artichokes, garlic, onions, leeks and green tea. Eating adequate amounts of lean protein may also benefit the body’s natural system by maintaining adequate levels of glutathione, the body’s master detoxification enzyme, or catalyst. Glutathione is an enzyme produced by the liver that is involved in numerous processes within the body including building and repairing tissues, assisting in the natural detoxification process and improving immune system function.

A handful of clinical studies have shown increased liver detoxification with a commercial detox diet or supplements, but these studies have flawed methodologies and small sample sizes and are often done on animals. In addition, supplements are not regulated by the U.S. Food and Drug Administration as food and drugs are. They can be put on the shelf without full evaluation of ingredients or proven efficacy, except in rare cases in which supplements are tested by a third party.

In fact, some commercial supplements have raised so many health and safety issues that the FDA and the Federal Trade Commission have taken legal action against the companies that make them to remove their products from the market.

Some detox diets and programs can have serious side effects, particularly those including laxatives or enemas, or those that restrict intake of solid foods. These approaches can lead to dehydration, nutrient deficiencies and electrolyte imbalances.

In addition, diets that severely restrict certain foods or food groups usually don’t lead to lasting weight loss.

Instead, these types of diets often put the body into “starvation mode.” That means that rather than burning calories, your body holds on to them to use as energy.

Doing that repeatedly over a long period can lead to a chronic decrease in metabolism, which means that the number of calories you burn at rest may slowly decrease over time. This can make it more difficult to lose weight and balance blood sugar. It can also leave people more susceptible to chronic metabolic conditions such as cardiovascular disease and diabetes.

A healthy lifestyle, without the detox diet

Focusing on sustainable lifestyle shifts can make a huge difference – and unlike a detox diet, actually work.

Number one, eat a balanced diet. Aim to eat mostly whole grains, lean protein choices, fruits and vegetables of many colors, low-fat dairy, nuts and seeds. This way, you’re getting a variety of nutrients, antioxidants and a good amount of fiber.

Number two, hydrate. For women, the recommended daily water intake by the Academy of Nutrition and Dietetics is 11½ cups; for males, it’s 15½ cups. However, you get about 20% of that total from food, which leaves nine cups for women and 13 cups for men as the daily recommended water intake. This is comparable to 4½ 16-ounce water bottles for women and 6½ 16-ounce water bottles for men.

Lastly, move your body in a way that you enjoy. The more you enjoy being active, the more likely it will become a routine. Aim for at least 150 minutes, or 2½ hours of moderate-intensity physical activity every week.

Focusing on these types of long-term, sustainable healthy habits is the key to weight loss and overall health and wellness.