What's the Deal with Nightshades and Lupus? 🍅

2 days ago

5 min read

"Eliminate nightshades — it fixed everything!" If you've spent any time in an autoimmune support group online, you've probably seen this comment at least once. And for some people, it might be true. But just like everything else you read on the internet, it doesn't apply to everyone — and the science is more nuanced than most posts let on. Let's break it down.

First: What Actually Is a Nightshade?

Nightshades are plants from the Solanaceae family — which, fun fact, also includes the "deadly nightshade" (belladonna) you've probably heard of in poison-mystery plots. Most nightshades we eat are perfectly safe; a small handful of relatives in the family are not.

Common nightshades (the ones you're most likely eating regularly are bolded):

Ashwagandha
Bell peppers / sweet peppers (any color — red, yellow, orange, green; the color just reflects ripeness, not a different plant)
Bush tomato
Cape gooseberry / ground cherries (not the same as regular cherries)
Cocona
Eggplant
Garden huckleberry (not the same as regular huckleberries)
Goji berries / wolfberry
Hot peppers (chili peppers, jalapeños, habaneros, and chili-based spices like red pepper and cayenne)
Kutjera, naranjillas, pepinos (melon pear), tamarillos, tomatillos
Paprika, pimentos
Potatoes — there are hundreds of nightshade potato varieties, most commonly the white potato. (Sweet potatoes and purple potatoes are not nightshades — different plant family entirely.)
Tomatoes
Tobacco — obviously not a food, but worth flagging: smoking is linked to worse lupus outcomes independent of nightshades (more on that below)

Can you find the nightshades in the picture below?

⚠️ Watch your spice cabinet — many spice blends sneak in paprika, chili powder, or cayenne.

Common mix-ups — these are NOT nightshades, even though some internet lists claim otherwise:

Artichokes, blueberries, huckleberries, okra, sweet potatoes
Peppercorns (black, white, green, red, pink) — these come from a flowering vine, not a nightshade. They're sometimes excluded on the Autoimmune Protocol (AIP) anyway, since AIP also eliminates seed- and berry-based spices as a category.

Why Do People Eliminate Them? The Actual Science

Three compounds in nightshades get most of the attention:

1. Lectins — proteins that help the plant defend its seeds from being eaten. They resist digestion and can bind to cells lining your intestine. Some research suggests lectins may worsen intestinal permeability ("leaky gut") in people already genetically prone to autoimmune conditions like rheumatoid arthritis — but this hasn't been studied specifically in nightshade lectins in humans. Most of the strongest leaky-gut evidence for nightshades comes from rodent studies (not people!) - glycoalkaloids and lectins are thought to increase risk for certain autoimmune diseases, although studies haven't specifically looked at those from nightshades, and rodent studies have shown a relationship between potato glycoalkaloids and increased intestinal permeability, though this hasn't been studied in humans. It's an area that needs greater research, but may be worth doing a trial of eliminating in your diet and see how you feel! (1, 2)

2. Saponins (specifically glycoalkaloids) — a plant compound that can act as an immune adjuvant, meaning it can rev up immune activity. That's generally not what you want if your immune system is already overactive, as it is in lupus. But saponins also can act as a potent anti-inflammatory agent. (4, 5, 6)

3. Capsaicin — the compound that makes chili peppers hot. It's a known irritant to mucous membranes, which is why it can bother some people's digestive tracts more than others.

The leaky gut connection is still debated. It's a popular theory, but it's genuinely unsettled science — human data is limited, and some researchers think leaky gut may be a symptom of autoimmune disease rather than a root cause of it whether leaky gut is actually the cause of autoimmune and other health issues, or a symptom, is highly debated. (1, 2)

The Other Side of the Coin

Here's something most "eliminate nightshades" posts leave out: some research actually points the other direction.

A 2016 pilot study using NHANES III data found that people with lupus who had higher blood levels of lycopene (an antioxidant abundant in tomatoes) had a mortality rate of just 5.3%, compared to 33.3% in those with lower lycopene levels — a striking difference, though the researchers were clear this needs to be confirmed in larger studies before we draw firm conclusions the mortality rate was significantly lower in the higher lycopene level group (5.3%) than in the lower level group (33.3%), and higher serum lycopene has a protective effect on mortality in SLE, though further studies with a larger sample size are needed to confirm these primary results. (source)
On the flip side, a separate large survey found that dietary intake of antioxidants like lycopene didn't change someone's risk of developing SLE in the first place dietary intake of antioxidant nutrients, including lycopene and other carotenoids, from foods and supplements does not change the risk of developing SLE in women — which tells us these two questions (does it help once you have lupus vs. does it prevent lupus) have different answers, and nightshades aren't a simple "good" or "bad." Cambridge Core

Real Talk: Should You Eliminate Nightshades?

Nightshades aren't nutritionally empty — they bring real value to the table, including fiber, vitamin C, and vitamin A. So this isn't about fear — it's about paying attention to your own body.

If you notice gas, bloating, fatigue, joint pain, or a flare-up of your usual lupus symptoms after eating nightshades, that's worth paying attention to. It may mean you're sensitive to them right now — not necessarily forever. Food tolerance can shift as your inflammation levels change over time.

One important note that's not about nightshades but is worth flagging while we're on the topic of things that interfere with your treatment: smoking has been shown in multiple studies to significantly reduce the effectiveness of hydroxychloroquine (Plaquenil), one of the most common lupus medications tobacco smoking significantly reduced the therapeutic effectiveness of hydroxychloroquine in cutaneous lesions, with a pooled odds ratio of 0.53. If you smoke and are on hydroxychloroquine, that's a conversation worth having with your rheumatologist. PubMed

If You Do Want to Try an Elimination

You don't have to give up flavor entirely. A few swaps that keep meals satisfying:

Sweet potato in place of white potato
"No-mato" sauce (nightshade-free tomato sauce alternative) for pasta night
Pesto instead of red sauce
Fresh herbs, ginger, wasabi, or turmeric to replace some of the heat/flavor that chili-based spices bring

Bottom Line

The research on nightshades and lupus is genuinely mixed — some mechanisms could make things worse for a sensitive few, while other evidence suggests nightshades (tomatoes especially) may actually be protective for some people with lupus. There's no universal answer here, which is exactly why a personalized approach matters more than a blanket rule you saw in a Facebook group.

If tracking this on your own feels overwhelming, that's what I'm here for.

Reach out to learn more about my 1:1 nutrition counseling packages or my group coaching programs.

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