The bananas-only diet isn't as healthy as you think it is. Here's why

The bananas-only diet is a fad diet that focuses on eating one food — unsurprisingly, this food is bananas. With this diet, you're allowed to eat as many bananas as you want, as well as maybe some milk. You might lose weight, but your entire body will be starved of nutrients found in other foods, and, as it turns out, this is not that great for you. 

This mono-diet seems to have gotten its start in the late 1920s with Dr. Sidney Haas, who believed that bananas cured celiac disease (via HPPR). When children were diagnosed with celiac disease they were admitted to inpatient care at the hospital where they would eat bananas, milk, cottage cheese, vegetables, and meat. Approximately 30 percent of them died, while survivors were allowed to go home after six months.  

We now know that celiac disease is an autoimmune disorder where there is an immune reaction to gluten, a protein found in wheat, rye, and barley. Eating gluten with celiac disease damages the lining of the small intestine, preventing it from absorbing some nutrients, causing an array of uncomfortable and distressing symptoms (via Mayo Clinic). 

Eating only bananas restricts your diet

According to Harvard Health, bananas are a good source of potassium, vitamin C, vitamin B6, manganese, fiber, and magnesium. One medium-sized banana has about 0 grams of fat, 110 calories, 450 milligrams of potassium, 15 grams of sugar, one gram of protein, three grams of fiber, and 28 grams of carbohydrates. 

A 2015 study published in PLOS Medicine found that increasing certain fruits in the diet (apples, bananas, pears, and berries) did result in less weight gain. This study followed 133,468 people over the course of 24 years — however, these people did not restrict themselves to eating just bananas. 

That said, while you might lose weight while eating a bananas-only diet, these types of fad diets are impossible to maintain (via LiveStrong). You cannot survive on a mono-diet for the rest of your life. You will lose weight too quickly, suffer from malnutrition, and you will probably gain it all back when you go back to your regular diet. Healthy weight loss is losing one to two pounds per week (via USDA Nutrition).

Dangers of eating only bananas

Bananas are good for you one at a time, but eating too many can be bad for some people — for example, anyone taking beta-blockers, those with allergies related to bananas, and anyone with migraines.

Beta-blockers are often prescribed for high blood pressure and cardiovascular disease. The Laborers' Health and Safety Fund of North America warns that beta-blockers contain potassium and consuming too much can lead to kidney failure and erratic heart rhythm. Anyone taking a beta-blocker should limit their intake of bananas, papayas, avocado, kale, and tomatoes — all foods high in potassium. 

Also, anyone who has an allergic reaction to bananas should avoid eating them (via Anaphylaxis Campaign). Some symptoms can include itchiness in the mouth and throat, swelling of the skin, narrowing of the throat, wheezing, and even collapsing. The severe side of this is known as anaphylaxis and can be life-threatening.

Eating too many bananas may trigger migraines in some people, according to a 2018 study published in the Journal of Pain Research. The study included 684 people with past migraine and tension-type headaches. Several foods were listed as triggers for these people, and bananas were one of them.