Are nightshade vegetables bad for you?

Lately, guests at the Pritikin Center have been asking: “Are nightshade vegetables like potatoes, tomatoes, and peppers - and beans and whole grains - bad for you?"

Say, what?! Many of the healthiest populations around the world eat the most beans, whole grains, and vegetables, including nightshade vegetables. But unfortunately, a few self-professed “experts” in nutrition are now decrying these foods as the biggest danger in the American diet. Get the facts. And get past the nonsense.

Are nightshade vegetables bad for you?

Nightshade vegetables include tomatoes, potatoes, eggplant, peppers, pimentos, and many berries. They belong to a group of plants that contains more than 2,500 species. Are they bad for you? Get the evidence-based truth.

Are nightshade vegetables bad for you?

Some diet “experts” have recently been sounding alarms about chemicals found in nightshade vegetables, whole grains, and beans (legumes), for example, pinto and garbanzo beans. The apparently dangerous chemicals are lectins.

What are lectins?

Lectins are proteins found in most plants. Essentially, they serve as defenders of the plant. They’re part of a whole group of compounds naturally found in plants that fend off invaders.

Beans are a Nightshade Vegetable, but are among the healthiest foods on earth.

There’s nothing to fear from nightshade vegetables and other lectin-containing foods like beans. In fact, these foods are eaten regularly, often daily, by the healthiest, longest-living populations worldwide.

Adult acne? Weight gain?

But according to a few diet book authors, lectins threaten human survival (never mind that lectins have been on earth since plants have been on earth).

Lectins, these authors insist, incite a form of chemical warfare in our bodies that leads to everything from arthritis, digestive problems, adult acne, high cholesterol, and brain muddiness to weight gain.

Deactivated via cooking

While it’s true that some lectins, especially those found in uncooked or undercooked beans, can cause some gastrointestinal problems, “it’s a problem easily avoided with cooking,” points out Jay Kenney, PhD, RD, FACN, nutrition research specialist and educator at the Pritikin Longevity Center in Miami. Pritikin has been teaching heart-healthy living since 1975.

“Lectins get denatured by cooking. Soaking dry, raw beans such as black beans overnight and throwing away the water and then boiling them for 10 to 15 minutes deactivates all the lectins found in beans that can cause GI problems.”

No good science

Moreover, there is nothing – that’s right, nothing – in major medical journals to support any claims that lectins are dietary public enemy #1.

Longevity zones

In fact, the vast body of research published over the last several decades indicates the exact opposite. The healthiest and longest-living people – those living in “Blue Zone” areas like Okinawa, Costa Rica’s Nicoya Peninsula, and Loma Linda, California, home of many Seventh Day Adventists – typically get about two-thirds of their calories from whole grains, beans, and starchy vegetables.

Thin (not fat) zones

“Even more puzzling is any claim that high-lectin foods promote obesity. There is no doubt that obesity is far less common in Blue Zone areas despite the fact that people in all these long-living populations have a much higher intake of lectin-rich plant foods than the average American,” notes Dr. Kenney.

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Don't let quack nutritionists scare you away from beans. Beans are super healthy. Want to Live to 100? Eat More Beans!

Recently, too, data from the PURE Study,1 which examined the health and diets of 18 populations around the globe, found that people who consumed more beans and other lectin-containing whole plant foods were healthier than those eating a diet far lower in lectins.

In fact, the PURE Study data suggest that eating more raw fruits and vegetables (which contain more lectins than cooked vegetables and fruits) was healthier than cooked.

Whole grains

In addition to beans, other foods that contain a lot of lectins include whole grains such as barley, corn, brown rice, and whole wheat, especially wheat germ.

Nightshade vegetables and Lectins are everywhere. They should be part of your healthy diet.

If you’re eating a plant-based diet, you’re eating lots of lectins. That’s fine! In fact, a plant-based diet, one that’s full of whole foods like nightshade vegetables – and all vegetables – is an incredibly healthy diet.

Minimal GI problems

Wheat germ is consumed raw or lightly roasted. Its lectins remain intact. And certainly, many vegetables are consumed raw. But even in fairly large amounts, they appear to cause only minimal GI problems, and often in people who are not accustomed to eating them.

Lectins everywhere

“Overall, the lectins found in zucchini, carrots, rhubarb, beets, mushrooms, asparagus, turnips, cucumbers, pumpkin, sweet peppers, and radishes, whether cooked or consumed raw, do not appear to cause significant GI problems,” assures Dr. Kenney.

“Citrus fruits such as oranges, lemons, and grapefruit, and berries, including blackberries, raspberries, and strawberries, and many other fruits like pomegranate, grapes, cherries, quinces, apples, watermelon, banana, papaya, plums, and currants are also sources of dietary lectins.”

Lectins are also found in nuts and seeds such as walnuts, hazelnuts, peanuts, sunflower seeds, and sesame seeds. Other sources of dietary lectins are chocolate, coffee, and some spices, including caraway, nutmeg, peppermint, marjoram and garlic.

Benefits of lectins

Some of these lectins can escape being denatured, and some do appear to get absorbed. Interestingly, there is evidence that lectins found in wheat and other whole grains might improve GI health and possibly help reduce the risk of some cancers if consumed regularly.2 That’s right, just as lectins fend off a plant’s invaders, they might do the same for us.

Bottom Line |
Are nightshade vegetables bad for you?
Are beans and whole grains bad for you?

Eating a lot of uncooked or undercooked beans may cause transient GI problems.

But who eats uncooked beans?

What’s more, any GI problems from excessive lectin intake would likely lead to weight loss, not weight gain.

“There is no evidence I am aware of that supports any claims that dietary lectins are bad for you, or that they somehow promote obesity,” sums up Kimberly Gomer, MS, RD, Director of Nutrition at the Pritikin Longevity Center.

“The preponderance of credible scientific evidence suggests that eating a diet high in lectin-containing whole plant foods, including nightshade vegetables, is far more likely to promote a leaner body, better health, and longevity than the weight gain and other maladies recent diet book authors have claimed.”

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