Why Juice 'Cleanses' Don't Deliver

4 reasons why that "cleanse" won't cut it

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Even before the hangovers have cleared on New Year's Day, throngs of diet-related resolutions will officially take effect. And for a growing number of Americans, these will include some form of a so-called "detox diet" or "cleanse."

Tamara Duker Freuman
Tamara Duker Freuman
The most common versions of these diets generally involve juicing—either complete liquid juice fasts, or spartan, juice-based diet plans that allow some solid foods free from sugar, meat, gluten, or a number of other purported "toxins." Many include a regimen of proprietary (read: expensive) supplements. Some of the more popular commercial juicing programs can cost upwards of $60 per day. Let me repeat that: $60 per day. For juice.

As you may have guessed, I'm not a fan of these regimens. That's because I believe cleanse marketers overstate their products' health benefits, relying on a combination of pseudo-science and a flawed understanding of basic human physiology to sell them. I think that a short-term juice fast is neither likely to be harmful nor beneficial in an otherwise healthy, non-diabetic, well-nourished person.

One will almost certainly lose weight on a juice-only program, which I understand is a primary reason many people undertake these regimens. But beyond a kick-start for weight loss, so-called "detox" regimens or "cleanses" don't deliver on their key promises–of which there are often many. Here's why:

1. Juicing programs don't actually "detox" anything. Marketers of cleanses throw around the vague term "toxin," without providing any specifics as to which toxins their regimen is purported to remove. To be sure, we all encounter a host of toxins in our modern lives: environmental ones like mercury, pesticides, and BPA; and food-borne ones like pesticides, PCBs, aflatoxin from peanut butter, and heterocyclic amines (HCAs) from charred meat. Our bodies even create toxins as metabolic byproducts of foods we eat, like nitrosamines from processed-meat preservatives or ammonia from protein (of both plant and animal origin). But I've yet to see a shred of scientific evidence to indicate that any ingredient in these juices—including lemons, herbs, green veggies, or cayenne pepper—has demonstrated any clinical utility in neutralizing or eliminating such toxins from the body at all, let alone doing so more effectively than the body's own "detox organs" in the setting of a reasonably healthy, solid-food diet.

2. Juice cleanses don't generally support optimal function of the body's built-in "detox organs"—namely, the liver, the intestines, and the kidneys. Together, these organs process toxic substances like alcohol and drugs into safe byproducts, neutralize and excrete the toxic ammonia that results from normal protein metabolism, prevent harmful carcinogens from being absorbed into the bloodstream, and remove heavy metals from the body. But to enable the intestines to trap carcinogens in the stool and escort them out, you need a steady flow of fiber. To support the liver's ability to maintain an abundant supply of the mega-potent detoxifier called glutathione, you'll want to feed it lots of sulfur-containing cruciferous vegetables like broccoli, cabbage, and cauliflower. To prevent damage to the delicate blood-filtering mechanisms in the kidneys, you'll want to make sure your blood sugar levels stay low. In general, this type of dietary support for the body's detox organs is not optimally achieved through a juice-only diet.

3. A healthy gut does not function better when it is "rested." In fact, the opposite is true. Some cleanse marketers claim that juicing is beneficial because it allows the gut to rest from the work of digesting complex, solid foods. This "gut rest," they falsely assert, makes the body better able to absorb the nutrients in the juice. In fact, our intestines function best when provided with a predictable stream of nutrient-dense, fiber-containing foods.

The intestinal cells themselves require nourishment from protein (of which juice has none); they especially love glutamine, an amino acid. And the beneficial bacteria that live in the gut require nourishment from a variety of plant-based fibers (of which juice also has none). When resident gut bacteria metabolize fiber, they release substances called short-chain fatty acids (SFCAs), which stimulate the cells of the intestines to replicate; strengthen the junctions between cells so that foreign matter like bacteria, chemicals, or food cannot leak through the gut barrier into the bloodstream; and modify the pH level of the intestine in a manner that may help protect against colon cancer.

The intestines do their best work when they are working regularly. Indeed, in extreme cases of "gut rest"—such as that which occurs during starvation or severe food restriction among people with anorexia—it is very common for the nerves and muscles of the colon to stop functioning normally. This results in a severe and often irreversible form of constipation. Use it or lose it!

4. Detox regimens don't necessarily eliminate (or even reduce) exposure to dietary toxins. Gluten is only "toxic" if you have a wheat allergy or celiac disease. Organic (hormone-free) dairy is not an inherent toxin, either. Eliminating these foods in a cleanse program isn't likely to lower your toxin burden by much, if at all. And if your sole source of energy comes from fruit and vegetable juice, do remember that these contain pesticide residues—often in quite substantial amounts. (Incidentally, recent research suggests choosing organic versions should reduce that load by about 30 percent on average; alas, most popular juice cleanses do not use organic produce for their products.)

While I am by no means suggesting that it is prudent for anyone to reduce fruit and vegetable intake, I am trying to make a point here about dietary variety. A varied diet consisting of minimally-processed, nutrient-dense foods from a variety of sources may be a better strategy than a juice-only regimen to reduce risks associated with the unavoidable toxins we encounter as eaters on present-day Planet Earth. If these foods are also organic and sustainably raised, that's all the better.

So what if you're ready to make a break from your processed, energy-sapping diet? What if you want to adopt a cleaner way of eating year-round—not just for a week or two at a time? What if you'd like to shed some weight, feel energized, and limit your exposure to actual, bona-fide environmental toxins? What if you don't have $60 per day to shell out for fresh-squeezed snake oil? Stay tuned for my column next week, where I'll share some thoughts on my common-sense approach to clean eating!

Hungry for more? Write to eatandrun@usnews.com with your questions, concerns, and feedback.

Tamara Duker Freuman, MS, RD, CDN, is a NYC-based registered dietitian whose clinical practice specializes in digestive disorders, Celiac Disease, and food intolerances. Her personal blog, www.tamaraduker.com, focuses on healthy eating and gluten-free living.