Climate Change and Its Impact on Silymarin Supply

Walk into any health food store, and you'll likely find a bottle labeled "milk thistle extract" tucked between the multivitamins and herbal supplements. Inside that bottle, there's a compound that's been trusted for centuries: silymarin. Derived from the seeds of the milk thistle plant ( Silybum marianum ), silymarin is celebrated for its remarkable ability to support liver health—a fact backed by modern research and generations of traditional use. But here's the thing: this unassuming plant, and the valuable extract it produces, is facing an invisible threat: climate change.

For decades, milk thistle has thrived in specific pockets of the world, from the sun-drenched hills of the Mediterranean to the rolling fields of California and the temperate plains of Australia. Farmers in these regions have honed their craft, planting seeds in well-drained soil, relying on predictable seasons, and harvesting when the spiky purple flowers give way to the nutrient-rich seeds. But in recent years, the rules of the game have changed. Winters are warmer, summers are drier (or deluged with unexpected rain), and extreme weather events—droughts, heatwaves, even late frosts—are becoming the norm rather than the exception. And for a plant as particular about its growing conditions as milk thistle, these shifts aren't just inconvenient; they're existential.

In this article, we'll dive into the delicate relationship between milk thistle, silymarin, and the changing climate. We'll meet the farmers on the front lines, explore how rising temperatures and erratic weather are altering harvests, and unpack what this means for the millions who rely on milk thistle extract for their health. We'll also look at the innovative ways farmers, researchers, and milk thistle extract suppliers are fighting back to keep this natural healer accessible. Because when the plants that power our wellness are at risk, the stakes couldn't be higher.

Before we talk about threats, let's get to know the star of the show: the milk thistle plant. If you've ever seen it growing wild, you'd probably remember it—the stem is thick and sturdy, the leaves are broad and spiky with white marbled veins (hence the "milk" in its name), and the flower heads are a vibrant purple, protected by sharp bracts that deter grazers. But it's the seeds, hidden inside those flowers, that hold the treasure: silymarin, a complex of flavonolignans (including silybin, silydianin, and silychristin) that give milk thistle extract its powerful properties.

Milk thistle isn't a diva, but it does have preferences. It loves full sun, well-drained soil (clay-heavy soil can rot its roots), and a climate with distinct seasons: cool, wet winters to kickstart growth, followed by warm, dry summers to encourage flowering and seed production. In the Mediterranean, where it's native, this climate is practically tailor-made. The region's mild winters (average temperatures around 10–15°C) and hot, dry summers (25–30°C) allow the plant to grow tall, flower profusely, and set seed without stress. It's no wonder countries like Italy, Greece, and Spain have long been top producers of milk thistle seeds.

But milk thistle is also adaptable—up to a point. Over time, farmers in other regions, including parts of the United States (California, Oregon), Australia (South Australia, Victoria), and even parts of China, have successfully cultivated it by mimicking these conditions. In California's Central Valley, for example, farmers plant in fall, letting the seeds germinate with winter rains, then rely on the dry summer heat to ripen the seeds by late July. It's a system that worked for decades. But as the planet warms, those "reliable" seasons are becoming unpredictable.

To understand why climate change is hitting milk thistle so hard, let's start with the basics: what does this plant need to thrive? Think of it as a Goldilocks scenario—everything has to be "just right."

• Temperature: Milk thistle seeds germinate best in cool soil (around 10–15°C). Once established, the plants can handle heat, but prolonged temperatures above 35°C during flowering can cause the flowers to ｄｒｏｐ, reducing seed set. Frost is also a problem—late spring frosts can kill young shoots, while early fall frosts can damage ripening seeds.
• Water: The plant needs consistent moisture during the early growth stage (winter and spring) but hates "wet feet"—waterlogged soil leads to root rot. In summer, it prefers dry conditions; too much rain during seed ripening can cause mold or mildew on the seeds.
• Soil: Well-drained, sandy or loamy soil with a neutral pH (6.0–7.5) is ideal. Poor drainage or overly acidic soil stunts growth.

Now, let's overlay climate change onto this picture. According to the Intergovernmental Panel on Climate Change (IPCC), global average temperatures have risen by 1.1°C since the late 19th century, and each decade is warmer than the last. For milk thistle-growing regions, this isn't just a numbers game—it's a daily reality.

Case Study: The Mediterranean's Warming Winters

Take Tuscany, Italy—a region famous for its rolling hills, olive groves, and, yes, milk thistle fields. For generations, farmers here counted on cool, wet winters to soften the soil and trigger seed germination. But in the past 15 years, winters have gotten noticeably warmer. Average January temperatures in Florence, for example, have risen from 5°C in the 1980s to 7°C today. That might not sound like much, but for milk thistle seeds, which need a period of cold stratification (exposure to cold temperatures) to break dormancy, those extra degrees are a problem.

"We used to plant in November, and the seeds would lie dormant through December and January, then sprout when the rains came in February," says Marco, a fifth-generation milk thistle farmer in Pistoia, Tuscany. "Now, if we plant in November, the seeds might germinate too early—like in December—because the soil is warm enough. Then, if we get a late frost in January, those young plants die. We've had to shift planting to December or even January, but then we risk not getting enough rain to help them grow. It's a guessing game now."

And it's not just germination. Warmer winters also mean fewer frosts, which sounds like a good thing—until you consider pests. In the past, cold winters kept populations of aphids, thrips, and caterpillars in check. Now, with milder winters, these pests survive year-round, feeding on milk thistle leaves and stems. Marco has had to increase pesticide use, which not only adds cost but also risks harming beneficial insects and reducing the "organic" status many buyers seek.

California's Drought and Deluge: A Double Whammy

Across the Atlantic, in California's Central Valley—another major milk thistle producer—the problem isn't just heat; it's water, or the lack (and occasional excess) of it. California has always had droughts, but the "megadrought" of 2012–2016, followed by another severe drought in 2020–2023, has pushed farmers to the brink.

"Milk thistle is drought-tolerant once it's established, but the young plants need water to get going," explains Maria, who grows milk thistle on 200 acres outside Fresno. "In the past, we relied on winter rains to water the crop. But in the dry years, we had to irrigate—using groundwater, which is already depleted. That drove up our costs, and even then, the plants were stressed. Stressed plants don't produce as many seeds, and the seeds they do produce have lower silymarin content."

Then, when the rains finally came—like the atmospheric rivers that hit California in 2023—it was too much of a good thing. "We had fields flooded overnight," Maria recalls. "Milk thistle roots can't handle standing water. The plants turned yellow, wilted, and rotted. We lost 30% of our crop that year. And the worst part? We didn't see it coming. The weather models didn't predict that level of rain."

The result? Smaller harvests, lower-quality seeds (with less silymarin), and higher costs for farmers. And when farmers struggle, the ripple effects reach everyone down the supply chain—including the milk thistle extract supplier who buys the seeds, the manufacturer who processes them into extract, and ultimately, the consumer who pays more for supplements.

So, what happens when milk thistle harvests shrink or the seeds are lower quality? Let's follow the journey of a milk thistle seed from Marco's field in Tuscany to a supplement bottle on a store shelf.

First, the seeds are harvested, dried, and sold to a processor, who extracts silymarin using solvents like ethanol or water. The extract is then tested for purity (ideally 70–80% silymarin content) and sold to manufacturers, who use it in capsules, tablets, or liquid supplements. Finally, these products reach retailers and, eventually, consumers.

When harvests are small, processors have to compete for limited seeds, driving up prices. In 2022, for example, a severe drought in Spain (another top milk thistle producer) reduced the country's harvest by 40%. As a result, the price of milk thistle seeds spiked by 35% in just six months, according to data from the International Herbal Trade Association. Processors, in turn, passed those costs on to manufacturers, who then raised prices for supplements. A quick check of online retailers shows that a bottle of milk thistle extract that cost $15 in 2019 now averages $22–$25—a 47% increase in four years.

But it's not just about price. Lower-quality seeds—those grown under stress, with less silymarin—mean manufacturers have to use more extract to achieve the same potency. "We used to get seeds with 18–20% silymarin content," says Elena, a quality control manager at a major supplement manufacturer in Germany. "Now, it's not uncommon to see seeds with 12–15% silymarin. That means instead of using 500mg of extract per capsule to get 140mg of silymarin, we need 700mg. That's more extract, more cost, and bigger capsules—all of which frustrate consumers."

Some manufacturers are cutting corners, using lower-potency extract or blending milk thistle with cheaper herbs to keep prices down. But this erodes trust in the product. "Consumers buy milk thistle for its silymarin content," Elena adds. "If they don't get the dose they expect, they won't buy it again. And for us, reputation is everything."

Then there's the issue of supply chain reliability. In the past, milk thistle extract suppliers could count on steady deliveries from regions like the Mediterranean and California. Now, with harvests unpredictable, suppliers are scrambling to source from multiple regions, increasing logistics costs and the risk of delays. "Last year, we ordered a shipment from Australia, but a heatwave there destroyed the crop," says Raj, who runs a supplement company in Canada. "We had to switch to a supplier in China at the last minute, but their extract was lower quality. We had to delay production, and some customers canceled orders. It was a nightmare."

It's not all doom and gloom, though. Farmers, researchers, and suppliers are rolling up their sleeves and finding innovative ways to help milk thistle survive—and even thrive—in a changing climate.

1. Developing Climate-Resilient Varieties

Plant breeders are working to develop milk thistle varieties that can handle higher temperatures, drought, and pests. At the University of Padua in Italy, researchers have spent the past decade cross-breeding wild milk thistle plants from drought-prone regions (like Morocco) with domesticated varieties. The result? A new strain called "Silybum 2.0" that can tolerate temperatures up to 40°C and requires 30% less water than traditional varieties.

"We tested it in Tuscany last year, and it yielded 20% more than the local variety, even during the summer heatwave," says Dr. Lucia Rossi, who leads the breeding program. "The silymarin content was also higher—around 22%—because the plant wasn't stressed. We're now working with farmers to scale up planting."

2. Precision Agriculture and Irrigation

In California, farmers like Maria are turning to technology to optimize water use. She's installed soil moisture sensors that send real-time data to her phone, telling her exactly when and how much to water. "Before, I watered on a schedule—every 10 days. Now, the sensors tell me if the soil is dry 6 inches down, so I only water when needed. I've cut water use by 25% and seen yields improve by 15%," she says.

Other farmers are using drip irrigation instead of flood irrigation, which delivers water directly to the roots, reducing waste. Some are even experimenting with shade cloths to protect plants during heatwaves, though this adds cost. "It's an investment, but it's better than losing the entire crop," Maria adds.

3. Diversifying Growing Regions

Milk thistle extract suppliers are also looking beyond traditional regions. Canada, for example, wasn't a major milk thistle producer 10 years ago, but its cooler climate and reliable rainfall are now attracting farmers. "We started growing milk thistle in Alberta five years ago," says James, a farmer in Calgary. "The summers are cooler here—around 20–25°C—and we get enough rain. So far, yields are steady, and the silymarin content is high. We're working with suppliers in the U.S. and Europe to become a go-to source."

Similarly, parts of southern Chile and New Zealand are emerging as "climate refuges" for milk thistle, with conditions that mimic the Mediterranean's traditional climate.

4. Organic and Regenerative Farming

To combat pests without synthetic chemicals, some farmers are adopting regenerative farming practices, like crop rotation (planting milk thistle after legumes to improve soil health) and intercropping (growing companion plants like marigolds, which repel aphids). "We've stopped using pesticides entirely," says Sofia, a farmer in Greece who grows organic milk thistle. "Instead, we plant clover between the rows to attract ladybugs, which eat aphids. The soil is healthier, the plants are stronger, and we get a premium price for organic seeds. It's harder work, but it's sustainable."

Climate change is a global problem, and there's no quick fix. But the resilience of farmers, researchers, and suppliers gives reason for optimism. As we've seen, innovations in breeding, technology, and farming practices are helping milk thistle adapt. But there's also a role for consumers to play.

By choosing high-quality, sustainably sourced milk thistle extract—even if it costs a little more—consumers can support farmers who are investing in climate-resilient practices. Look for certifications like "organic," "regenerative," or "sustainably grown," and don't be afraid to ask manufacturers where their raw materials come from. A reputable milk thistle extract supplier should be transparent about sourcing and testing.

It's also important to remember that silymarin isn't just a supplement ingredient—it's a lifeline for millions. For people with liver conditions, those recovering from alcohol or drug use, or anyone looking to support their body's natural detox processes, milk thistle extract is more than a "nice-to-have"—it's essential. Protecting its supply means protecting their health.

As Marco, the Tuscan farmer, puts it: "My grandfather grew milk thistle because it helped people. My father did the same. I want to pass this farm on to my son, and I want him to be able to grow milk thistle too. Climate change is tough, but we're not giving up. This plant has helped people for centuries, and we're going to make sure it keeps doing that—no matter what the weather throws at us."

In the end, the story of silymarin and climate change is a story of adaptation, innovation, and the deep connection between human health and the health of our planet. By working together—farmers, scientists, suppliers, and consumers—we can ensure that this natural healer continues to thrive, even in a changing world.