I flunked cleansing. I failed at the most basic of cleanse “prescriptions” – drinking warm water with fresh lemon every morning.

As a dietitian, I was curious whether I’d find lemon water a more pleasant or invigorating start to my day than my usual cold tap water and hot coffee. But after trying it for a week, the only result I could detect was my development of a healthy dislike for tepid water with a squeeze of citric acid.

Perhaps it was just me. Portland-based yoga teacher Alice Riccardi enjoys lemon water regularly. “About one day a week, I have nothing but lemon water,” she said. “It helps my body come back to baseline and sort of resets my body.”

Judging from the plethora of positive reviews and blog articles touting the supposed benefits of the lemon water ritual (Liver detoxification! Clear skin! Metabolism boosting!), Riccardi has plenty of company.

Cleanses have become ubiquitous, and they are often pricey. A three-day supply – 18 (16-ounce) bottles – of one juice brand sold online costs a whopping $144 plus $53.79 (!!) shipping and is made from nothing magical – just organic fruit and vegetable juices.

A Harmful Organism Cleanse Kit from another online retailer costs $74.95 and makes laughably overheated claims: “If you’ve been exposed to raw vegetables, undercooked meat, or even have a pet, there’s a chance you’ve been invaded by harmful organisms.”

You can find made-to-order cleansing beverages at your local juice bar, cleanse kits for specific body parts (liver and colon typically) as well as specific conditions (such as the Candida cleanse). You can order a variety of juice-based concoctions online and have them shipped to your doorstep, or you can consult one of the many books on the subject and whip up a cleansing beverage at home.

I get their appeal. The urge to start fresh is strong. In the spring, it seems like a chance to wake up winter-weary palates, shake off last season’s dietary excesses and renew our commitment to healthful eating. Then, there’s the marketing hype – cleanses will “flush out” our systems, give our gastrointestinal tracts a rest from digesting our food, purge poisons and lead to weight loss.

But are cleanses really necessary?

The short answer, according to the traditional medical establishment, is no. The body has its own, highly effective methods of filtering and removing toxins. Every day the digestive system, liver, lungs, skin and kidneys are working to remove toxins that our bodies themselves create, or that we encounter from alcohol, foods and medicines.

Without these organs and systems in place, we would die. And if for some reason a person did retain wastes and toxins to the point where he or she needed to be “unclogged” or otherwise cleaned out (as is the goal of most cleanses), that person would need prompt medical attention – not a cup of cleansing tea or juice.

The nebulous nature of cleanses means that, aside from pounds lost, none of these purported effects can be measured scientifically. Do our digestive systems really need to “rest” and for how long? And exactly which toxins are removed?

It’s that kind of vague health talk as well as promises of big benefits – often weight loss – that attract consumers, explains Maine Medical Center outpatient clinical dietitian Jessica Bouchard. “Detoxes and cleanses are a temporary fix, usually only lasting about a week or two,” she said, “and they do not teach or form healthy lifestyle changes.”

Yes, pounds may be lost, but that’s not surprising given that some cleanses provide fewer than 1,000 calories per day. “Patients of mine who have completed detox diets or cleanses do tend to lose weight rapidly,” Bouchard continued. “However, many find themselves gaining that weight back shortly after resuming their regular diets.”

Rebound weight gain isn’t the only potential downside, Bouchard said. People who continuously try cleanses can be at increased risk for nutritional deficiencies due to severely restricting intake and eliminating entire food groups, Bouchard said.

“Cleanses can potentially be dangerous to some people, such as those with diabetes, pregnant women and those with certain GI disorders,” said registered dietitian Dave Seddon, president of the Maine Academy of Nutrition and Dietetics. He lists a series of potential and unpleasant side effects: irregular bowels, headaches, moodiness.

Are we even sure what’s in them? Many claim to be made of mixtures of herbs (which can interact negatively with other medications), and the U.S. Food and Drug Administration has on occasion taken action against companies selling cleanse products containing illegal ingredients. Others – some liver cleanses – contain such items as milk thistle, which has no clinically proven benefits, according to the National Institutes of Health. Still others list vague “proprietary blends” of ingredients.

The word “detox” has a real medical meaning – the removal of drugs or poisons from the body. But these days, the term is often used casually for selling programs and products to promote weight loss and a “clean” lifestyle. Very often, commercial detox diets and cleanses are extreme, physically unnecessary and potentially hard on the body.

So if you really want to cleanse yourself, what should you do?

“For healthy living and weight loss, I encourage my patients to concentrate on gradual healthy changes that can be sustained in the long run,” Bouchard said.

Cleaning up your regular diet – eating more whole foods and cutting way back on highly processed foods – will go a long way toward giving your body the nutrients it needs to do its digesting and filtering jobs efficiently. What does that mean exactly?

“A varied diet that focuses heavily on fruits, vegetables, some whole grains, quality protein and plenty of water,” Seddon advises. Plain water is fine by the way; warm lemon water is not required.

Kitty Broihier has been a registered, licensed dietitian for over 25 years. She holds a master’s degree in nutrition communications from Boston University and runs her consulting company, NutriComm Inc., from South Portland.