Nightshades—Nourishment or Nemesis?

Nightshade vegetables—namely potatoes, eggplant, tomatoes and peppers—have long been the subject of persistent, nasty rumors concerning their effect on our health. Given that nightshades include a roster of veggies that many of us eat on a daily basis, I felt it was time to shed some light on this ‘dark’ but important topic.

What Are Nightshades?

Nightshades are a botanical family of plants, technically called Solanaceae, which share certain common characteristics such as flower shape and seed arrangement. The term ‘nightshade’ was coined since many of these plants prefer to grow in shady areas or often flower at night.

There are 3000 species of nightshades. Included in this large family of plants are very commonly consumed vegetables like potatoes, tomatoes, eggplants and peppers as well as non-food plants like tobacco.

Sliced red, yellow and green peppers on white background

Why Do They Get Such a Bad Rap?

Nightshades have a bad reputation; the mere mention of this sinister-sounding name raises questions and causes confusion. Part of this stems from the fact that most nightshades are inedible and toxic to humans; the best-known of these is the belladonna (or ‘deadly nightshade’) immortalized in the play Macbeth as a fatal poison.

With such terrifying ‘family members’ many just assume that the more common nightshades (like the humble potato) are ‘guilty by association’. To make matters worse, nightshade vegetables have long been linked to a variety of health complaints—from arthritis to migraine headaches.

Why Nightshades Are Good for You

But this bad reputation is unfair. For starters, nightshade vegetables—as nutritious whole food plants—are brimming over with great positive health benefits. Tomatoes and peppers are amazing sources of phytochemicals that can potentially lower the risk of certain types of cancer. Potatoes, whose benefits we have discussed at great length in our recent article Potatoes: Man’s Best Friend, Not Worst Enemy, are high in vitamin C, B6 and potassium while eggplant is an excellent source of Vitamin K. And all of these nightshades are rich in fiber.

Let’s Clarify the Misconceptions

Nonetheless, nightshades continue to be blamed for a variety of ills from toxicity to their supposed contribution to osteoporosis, arthritis and migraines.

Let’s examine these nightshade misconceptions one by one.

Nightshades increase arthritic pain as well as migraines

There is no scientific evidence that nightshade vegetables worsen arthritis pain (or migraines). However some people do have food sensitivities. If you start to ache every time you eat tomatoes, then maybe tomatoes are a contributing factor. Try eliminating nightshades from your diet for 2-3 weeks and see if you feel a change. If you notice an improvement, it may be that one of these foods is a problem for your system. To test, reintroduce a single nightshade food and you will quickly notice whether or not your symptoms return again.

In terms of arthritic and joint pain, there very well may be other culprits and you need to do the following:

  1. Remove processed foods, white flour, sugar and all oils from your diet.
  2. Eat the colors of the rainbow, particularly green leafy vegetables and all types of berries which are rich in phytochemicals.
  3. Be active and keep your weight down. If you suffer from osteoarthritis (the most common form of arthritis) you will want to keep your weight down since excess pounds stress joints. Studies show that for every 1-pound loss in body weight, there is a 4-pound reduction in knee joint stress and an accumulated reduction in knee load of more than 4800 pounds per mile walked.

Nightshades contribute to osteoporosis

Certain people argue that nightshades are high in oxalic acid which inhibits the absorption of calcium, weakens bones and leads to osteoporosis. This is simply not true; nightshades are not high in oxalic acid. In fact, it is quite the opposite. And as I wrote before, high intakes of sodium, protein, and caffeine play primary roles in calcium loss and possible increased risk of osteoporosis.

Nightshades are toxic

Many people argue that nightshade vegetables contain a toxic alkaloid compound called solanine (a compound which is a defense mechanisms that protects some nightshade plants from natural threats like insects). Eggplant, peppers and tomatoes (even the green ones!) do not produce solanine and are therefore perfectly safe to eat.Cherry tomatoes with green basil leaves on white background

Solanine may develop in potatoes; green spots on potatoes (raw or cooked) or new sprouts on the outside of the potato are telltale signs that there is a high alkaloid content. If you notice sprouting or a green color on your potato it is therefore best to avoid them.

Millions of nightshade vegetables (including potatoes!) are consumed daily without incident. This is a clear sign that they are safe to eat. The bottom line is that if you’ve been enjoying potatoes, eggplants, tomatoes and peppers without any ill effects, you can continue eating them. If you have noticed muscle or joint pain, heartburn or sleeplessness after eating these foods (cooked plain without added oils), you may have food sensitivity to them. If this is the case, consider removing the nightshade vegetables from your diet for 2-3 weeks to see if this does make a difference.

At the end of the day, despite the vicious rumors, nightshades are brimming over with nutrients and vitamins, which are excellent for your health and for most people, should be welcomed warmly into their plant-based lifestyle.