Can your diet be too clean?

Cutting entire food groups is certainly en vogue, but it might do more dietary harm than good.

Elimination diets can serve an important purpose for those prone to food allergies. They can also help you kick off a short-term cleanse. But cutting categories of food—be it gluten, dairy, sugar, corn, or soy—in a quest for better health or a leaner physique may actually be counterproductive.

“Cutting food groups has become a popular dietary tactic because it sounds simple and it’s easy to visualize. Plus it’s a clear-cut rule, which is appealing,” says Precision Nutrition coach Brian St. Pierre, MS, RD, CSCS. “People can’t always visualize the idea of moderation, but eliminating a food group like dairy is easily visually represented. There goes milk, ice cream, butter, cheese, and cream in your coffee.”

It also works quickly to lean the body out. “It forces a calorie reduction that causes weight loss. Anytime you make drastic changes to your intake, you see rapid results,” says St. Pierre. The caveat: This limited way of eating is not necessarily sustainable long-term—unless you have a true intolerance.

For example with gluten, celiac disease in North America is estimated at about 1% of the population and gluten sensitivities at about 10%. In those cases, you’re better off eliminating it. Though even gluten, it turns out, has its benefits. It’s been shown to act as an angiotensin-converting enzyme (ACE) inhibitor, like many blood pressure drugs, is rich in glutamine, an important amino acid, and wheat itself contains pre-biotic fructans, which may improve GI health, notes St. Pierre.

By that same token, careful consideration should be given before you drop everything. Here, St. Pierre offers up reasons to re-think eliminating food groups at will:

your body may thrive on the food you cut

Starchier potatoes and grains help you produce calming, feel-good brain chemicals like serotonin that can help offset stress. Cutting carbs can also put you at risk for insulin resistance. “Incidences of insulin resistance sometimes go up when these types of carbs are cut from the diet,” says St. Pierre.

you could lose your metabolic flexibility

Never had a lactose intolerance? You may develop one. “Lactase persistence is the adaptation that allows us to consume dairy beyond being breastfed and if you give up dairy for an extended period of time, it’s possible your body will stop making lactase or your production of it will diminish. A more varied diet makes you more metabolically flexible,” say St. Pierre.

you may miss out on nutrients

Cut dairy, a rich source of calcium, and you need to up your intake of calcium-rich foods (leafy greens, nuts, and fortified nut milks) or risk becoming deficient. Eliminate meat and you lose protein plus vitamin B6, iron and zinc. Since those can be harder to find in the plant kingdom, you need enough good sources to compensate.

you risk going off the rails

The backlash of the elimination trend is a binge, restrict, binge cycle. “Sugar is a good example. If you’re overly restrictive and don’t have any sweets for an extended period of time you can feel deprived and then when you’re presented with something forbidden, say cookies, you eat the entire box instead of just one,” says St. Pierre.

you might nix foods that are actually ok for you

Limiting GMO corn and soy is a good thing. But if you really enjoy corn and soy and feel great when you eat them, they may be ok as a small part of your diet. If possible, of course, choose organic.