Can these popular diets do more harm than good?

These days, the terms “gluten-free” and “lactose-intolerant” are household words. Diets that restrict or eliminate gluten and lactose are common eating patterns. Reflecting this trend, global demand for gluten-free products is skyrocketing—with a projected market value of $5.6 billion-$8.3 billion between 2020-2025, according to Statista, a leading market and consumer data firm.  

Demand for lactose-free dairy products is an even more dramatic story—by 2017, the global market value for these products reached $10.6 billion, and is expected to increase to about $17.8 billion by 2027.

Many people have sound medical reasons for following gluten-and lactose-free diets. However, studies suggest that for those without a medical diagnosis, following these diets might do more harm than good.  

Here’s what the latest research says about these two popular eating patterns.

Celiac disease and gluten intolerance

Gluten is a protein found in grains like wheat, barley, and rye, which means it’s present in bread, pasta, crackers, cereal, cookies, and much more. Eating gluten can cause adverse symptoms in people with celiac disease or gluten-intolerance, but research indicates that these conditions only affect a small number of people. 

Celiac disease is an immune-mediated enteropathy, which affects just 1% of Americans, according to a literature review published in the Journal of Nutrition and Metabolism. When people with celiac disease ingest gluten, inflammation occurs in the intestines, which can result in symptoms like diarrhea, steatorrhea, weight loss, and growth failure. Some can experience symptoms unrelated to the digestive tract, like anemia, ataxia, loss of bone density, or symptoms similar to inflammatory bowel disease.

By contrast, gluten intolerance, also known as nonceliac gluten sensitivity (NCGS), affects 6% of Americans and produces similar symptoms, but its pathology is poorly understood and is the subject of debate.    

According to the Journal of Nutrition and Metabolism review, studies found that a high percentage of patients suspected to have NCGS “did not have symptoms in response to gluten ingestion when they were not able to distinguish between foods with or without gluten.” This led them to hypothesize that in some patients, the symptoms suffered after ingesting gluten may be due to: “(a) psychological anticipation of intolerance (nocebo effect), (b) the possibility that NCGS may be a transient disorder, or (c) the methods used in the gluten challenge procedure.” 

Despite the low prevalence of celiac disease and gluten intolerance, an estimated 25% of Americans follow a gluten-free diet, and roughly two-thirds of Americans believe that the diet could improve their mental and physical health.

But following a gluten-free diet can lead to nutritional deficiencies of macronutrients and micronutrients, noted the authors of the review. Many gluten-free foods, compared with similar wheat-based foods, have lower levels of calcium, iron, magnesium, zinc, vitamin B12, folate, and vitamin D, as well as significantly reduced fiber. Additionally, a gluten-free diet can increase exposure to arsenic, and result in meals that are higher in hydrogenated and saturated fatty acids and have a higher glycemic index. 

Adding to possible confusion, some people have wheat allergies, but these are also extremely rare in adults, and result in slightly different symptoms, including itchy eyes, hives, and anaphylaxis.

Here’s the takeaway: A gluten-free diet is a far unhealthier choice than a regular diet for those who do not have medical reasons for adhering to it.  

Lactose intolerance

Unlike gluten, lactose intolerance is relatively common. Roughly two-thirds of the world’s population is lactose-intolerant, but it’s least prevalent in Northern and Central Europe, where rates can be as low as 4%-10% of the population.

In the past, lactose intolerance was considered a disorder, but it is now considered normal, as most people lose the ability to digest lactose after infancy. It’s hypothesized that this is because early hunter-gatherers had no milk in their diet, so the enzyme lactase (which is used to digest lactose) served no purpose. 

However, following the advent of agriculture and the domestication of animals, certain European populations developed a number of genetic mutations over several thousands of years, which has left them able to digest lactose into adulthood.

The condition, which can result in symptoms like bloating, diarrhea, nausea, abdominal pain, and vomiting, is a result of lactose malabsorption, which means the small intestine produces low levels of lactase. In these cases, undigested lactose passes through into the colon, where it’s broken down by bacteria, creating fluid and gas.

This differs from milk allergies, which are the result of the immune system identifying certain milk proteins like casein and whey. This triggers the production of immunoglobulin E antibodies, which signal the immune system to release chemicals like histamine, resulting in allergic symptoms. This can include hives, wheezing, itching, swelling of the tongue or throat, and vomiting. 

Of course, lactose intolerance or a milk allergy are very good reasons to opt for a lactose-free diet. But that doesn’t mean that cutting out dairy won’t impact your health. 

According to health experts, cutting dairy from your diet can lead to nutrient deficiencies, including lower levels of calcium and vitamin D intake. Dairy products are also a major dietary source of choline, phosphorus, calcium, riboflavin and vitamins B12 and A. 

Calcium deficiencies can lead to osteoporosis, a condition characterized by weaker and more breakable bones. Vitamin D, too, is important for bone mineralization, which can help lower risks of fractures. According to a review published in Nutrients, studies have shown that lactose-intolerant individuals often have a low calcium intake, even if taking supplements, which ultimately leads to poor bone health. The authors also noted that dairy-free diets are associated with a number of other adverse health outcomes, including higher blood pressure and a higher risk of developing diabetes.