8+ Reasons to Avoid Plant Sterols (Side Effects & Risks)
Written By Ana Aleksic, MSc Pharm

8+ Reasons to Avoid Plant Sterols (Side Effects & Risks)

Phytosterols are the seemingly healthy cholesterol of the plant kingdom—a wolf in sheep’s clothing. Our body tries to get rid of them, but guidelines keep on recommending plant sterols supplementation in people with high cholesterol despite a lack of evidence. What does the latest research reveal about their toxicity and side effects?

Disclaimer: This post is for informational purposes only. Please consult your doctor about your health-related concerns and medications before taking any supplements.

Plant Sterols: Health Food or Dangerous Supplement?

Experts Warn About Plant Sterols Risks Based on the Latest Research

Phytosterols or plant sterols are the cholesterol of the plant kingdom. Whereas cholesterol is only found in animal foods, plant sterols are found in everything else—plants, mushrooms, algae, and even seafood.

What most people know about plant sterols is an example of science and professional guidelines gone bad. 

These experimental plant fats are often recommended as a “safe” health supplement or fortified food ingredient to people with high cholesterol. Yet, most international guidelines on plant sterols were put in place without valid scientific evidence. 

For example, the FDA allows health claims that foods with added plant sterol/stanol esters may reduce the risk of coronary heart disease and lower blood total and LDL cholesterol levels. 

Meanwhile, research published in 2020 warns that plant sterols seem to do more harm than good (Makhmudova et al., 2021; Helgadottir et al., 2020).

Does this come as a surprise? Well, once you realize that doctors learn nothing about plant sterols in med school—not so much. 

Skeptical? Check out this podcast and this youtube video where the greatest experts on plant sterols in the world admit just that and caution about the dangers of mass food fortification with plant sterols.

If the leading doctors in the field are struggling, how on earth is the average person expected to keep up with the research?

Don’t worry, we’ve got you covered! This article sums up dozens of the latest scientific studies to help you understand what a handful of plant sterols experts have been passionately discussing behind the scenes. 

If you’re an impatient reader, here’s the bottom line: avoid supplements and foods with added plant sterols altogether, eat a healthy and balanced wholesome diet, and consider adding a probiotic like L. Reuteri NCIMB 30242 to your daily regimen

Why Are We Eating More Plant Sterols than Ever?

Unlike cholesterol, we don’t produce plant sterols—we only get them through diet. That’s why phytosterols are also called xenosterols, meaning foreign sterols (xenos—stranger). We’re exposed to over 50 types of plant sterols in our diet. Plant sterols are found in most plant foods (like fruits, vegetables, nuts, and seeds), mushrooms, algae, and seafood. 

Here’s the catch: natural, whole foods contain relatively small quantities of plants that most humans can process without issues. Since plant sterols don’t play a role in our body, our physiology is adapted to getting rid of them as efficiently as possible (Makhmudova et al., 2021). 

Of the phytosterols we eat, we only absorb about 5% or so in the gut. Our liver then gets rid of most of the absorbed plant sterols. As a net result, we retain less than 0.5% of the total plant sterols we take in through food (Weingärtner et al., 2015). 

Phytosterols compete with cholesterol for absorption. Theoretically, the more plant sterols we eat, the less cholesterol we will absorb. Since high cholesterol is known to be a risk factor for heart disease, anything that may help reduce cholesterol levels in the whole population is usually seen as beneficial. 

This led to the massive fortification of foods with plant sterols since the 2000s. A bunch of foods like margarine, dairy, juice, spreads, salad dressing, soy, and others now have extremely high amounts of added plant sterols. 

In addition, vegetable oils contain high levels of plant sterols and they’re used in many processed foods. These include refined corn, sunflower, soybean, and palm oil (Klingberg et al., 2008; Yang et al., 2019).

Humans are now eating more plant sterols than ever before!

Are “Heart Healthy” Products with Plant Sterols a Scam?

Foods fortified with plant sterols are marketed as “heart-healthy.” They were supposed to reduce your cholesterol blood levels and, subsequently, your risk of having a heart attack. However, no proper human studies support these claims. No studies have explored the long-term safety of mass fortification with plant sterols either.

In one double-blind, randomized, placebo-controlled study on healthy volunteers, eating margarine with plant sterols didn’t affect cholesterol blood levels. It only increased plant sterol blood levels and markers of cholesterol production in the body (Weingärtner et al., 2017). 

Recent research cautions that plant sterols may build up in blood vessels, cause damage, and directly increase the risk of atherosclerosis (Makhmudova et al., 2021; Helgadottir et al., 2021; Helgadottir et al., 2020).

Side Effects of Plant Sterols

The following side effects have been reported or are theoretically possible with plant sterol supplements and fortified foods:

  • Diarrhea
  • Fatty stools (steatorrhea)
  • Abdominal discomfort
  • Skin rash
  • Fatty growths under the skin
  • Reduced levels of provitamin A and fat-soluble vitamins
  • Atherosclerosis 

Toxicity & Risks of Phytosterols (High Plant Sterol Blood Levels)

1) Increase the Risk of Atherosclerosis and Heart Disease

A 2020 Icelandic study on a huge sample finally showed that fortifying foods with phytosterols wasn't a good idea. Experts describe it as a game-changer. Dietary phytosterols intake was clearly linked with heart disease for the first time—something a handful of scientists have been warning about for a while (Helgadottir et al., 2020). 

"Our results indicate that both dietary cholesterol and phytosterols contribute directly to atherogenesis," the authors of the Icelandic study conclude.

This study compared genetic variants that affect both cholesterol and phytosterols to variants that affect cholesterol only. Higher phytosterol absorption directly increased the risk of coronary artery disease in people who are high cholesterol absorbers, which is about a fourth of the population (Helgadottir et al., 2021).

The genetic variant that the study focused on is called ABCG5/8—G5/8 for short. G5/8 is a pump in the gut lining and liver that prevents both plant and cholesterol sterols from building up in the body. It kicks out 45% of the cholesterol and 95% plant sterols from food back into the gut. 

If your G5/8 pump is “broken,” more dietary cholesterol and phytosterols enter your body. In turn, you’ll have higher LDL and greater heart attack risk.

There was a 40% increased risk from G5/8 phytosterol variants compared to variants that affect cholesterol only! Meaning, the extra 40% risk is just from sluggish plant sterol trafficking in the body. 

Since every fourth person has a sluggish G5/8 variant, it’s safe to caution everyone against foods with added plant sterols. 

These are the same genes that don’t work at all in people with sitosterolemia, a rare genetic disorder that causes massive plant sterols buildup in the body and various health issues. 

Aside from genetics, aging increases the chances of the G5/8 pump becoming more leaky to cholesterol and plant sterols. 

In a small German study in older patients undergoing cardiac catheterization (heart cath), poor cholesterol production was linked with an increased risk of heart complications and death. Low cholesterol producers tend to be high cholesterol and plant sterols absorbers (Weingärtner et al., 2019). 

In earlier studies on mice prone to atherosclerosis (APOE- mice), supplementation did reduce blood cholesterol levels but increased phytosterol levels. Increased phytosterols in the blood were associated with damage to the blood vessels and fatty deposits in the brains of the animals (Weingärtner et al., 2011). 

To sum it up, the latest research suggests plant sterols may clog arteries, increase the risk of atherosclerosis, and contribute to heart disease. 

2) Predict Heart Disease Complications

In one Japanese study, high plant sterol levels could predict heart disease complications in patients with acute coronary syndrome and high cholesterol (Yamaguchi et al., 2018). 

Acute coronary syndrome is an umbrella term for heart attacks, unstable angina, and other conditions where blood flow to the heart becomes suddenly blocked.

3) May Build Up in the Heart & Cause Damage

One study showed that mainly plant sterols, not cholesterol, can build up in the heart tissue and cause narrowing of the heart’s aortic valve (Luister et al., 2015). 

The study looked at 104 heart samples from patients with severe narrowing of the aortic valve. These patients also had high levels of oxidized plant sterols, suggesting that oxidative stress and inflammation also contributed.

“Stigmasterol accumulation causes cardiac injury and promotes mortality,” one animal study concluded (Tao et al., 2019). 

Stigmasterol is a plant sterol commonly found in plant fats and oils. The researchers observed an increased risk of death from high plant sterols in animals despite a 50% reduction in blood cholesterol.

Animal studies warn that stigmasterol buildup may damage the heart’s ventricles, lead to excessive heart tissue scarring, and heart inflammation. This type of damage is often irreversible and greatly reduces the heart’s ability to pump blood. Researchers suggest that drugs that block plant sterol absorption may help prevent such complications (Tao et al., 2019). 

4) Reduce the Response to Statins 

Statins are the typical, first-line drugs prescribed to people with high total and LDL cholesterol and others at risk of heart disease. 

But, it’s not only your total and “bad” LDL cholesterol that affects your risk of heart problems—plant sterols may be even more important! The problem is: statins don’t affect plant sterol levels. 

In one famous trial, the statin atorvastatin lowered LDL cholesterol in patients with diabetes on hemodialysis but had no effect on heart attacks and increased stroke risk (Wanner et al., 2005). 

High absorbers of cholesterol and plant sterols don’t respond well to statins. In the Scandinavian Simvastatin Survival Study (4S), patients with the highest absorption suffered more heart disease complications when prescribed statin therapy (Weingärtner et al., 2010). 

Statins shouldn’t be prescribed as the first choice to patients on dialysis and to others at low risk of heart disease either, according to the most recent clinical research data (Olyaei et al., 2011). 

New findings can help doctors personalize therapy to people who tend to absorb cholesterol and plant sterols in excess. 

For example, adding Zetia (ezetimibe) to statin therapy for people who are high cholesterol absorbers seems to help. Zetia blocks cholesterol and plant sterols absorption in the gut. 

Adding Zetia to statin therapy helped lower the plant sterol sitosterol and LDL cholesterol in one trial of 197 heart disease patients after 12 weeks. The combo was also more effective than statins alone in high cholesterol absorbers in two other studies (Watanabe et al., 2015; Hagiwara et al., 2017; Lütjohann et al., 2019). 

Some studies also suggest that Lactobacillus Reuteri (NCIMB 30242) may help support normal cholesterol absorption in hyperabsorbers. In a placebo-controlled clinical trial of 127 people, L. Reuteri NCIMB 30242 capsules taken over 9 weeks decreased three plant sterols in the blood that act as absorption markers by up to 41% (Jones et al., 2012).  

Talk to your care provider about trying L. reuteri probiotics.

5) May Cause a Re-narrowing of Heart Stents

Just like plant sterols can build up in blood vessels, they can latch onto heart stents and cause restenosis. Restenosis is when a part of the blocked artery the stent was placed in becomes narrowed again. In one human study, higher cholesterol and plant sterols absorption increased the risk of restenosis (Otto et al., 2019). 

6) Linked with Death in Hemodialysis Patients

In a study on over 300 people, hemodialysis patients with higher markers of cholesterol and plant sterols absorption were at a greater risk of dying from any cause (Rogacev et al., 2012). 

7) May Contribute to Nutrient Deficiencies

According to an analysis of 41 trials involving over 3000 people, plant sterol and stanol intake lowers blood levels of carotenoids like beta carotene, lycopene, lutein, and zeaxanthin (Baumgartner et al., 2017).

Carotenoids are antioxidants and provitamin A. They maintain immune and eye health.

In Europe, foods enriched with plant sterols must contain a warning about this side effect along with a recommendation to increase fruit and vegetable intake to help maintain carotenoid levels. 

Plant sterols may also reduce the absorption and blood levels of vitamin E, but it’s uncertain to what extent. Increasing vitamin E foods is likely a good idea (Richelle et al., 2004; Baumgartner, 2017; Tuomilehto et al., 2008).

8) May Trigger Endocrine and Metabolic Disruption

People with common mutations in the G5/8 pump are more likely to experience blood plant sterol levels way above the normal range (Patel, 2009). 

Researchers have been warning that a buildup of plant sterols may disrupt hormonal balance ever since the early 2000s when massive food fortification took place. High levels of plant sterols absorbed through diet may enter reproductive tissue, bind to sex hormones, and act as endocrine and metabolic disruptors (Nieminen et al., 2002). 

This is not surprising given the chemical similarity between plant sterols, cholesterol, and sex hormones. 

Possible consequences of plant sterol buildup include abnormal red blood cells, anemia, giant platelets, increased bleeding, and adrenal and ovarian failure. The data are still limited, and more research is needed (Mushtaq & Wright, 2007; Patel, 2009).

Plant Sterols FAQs

Are plant sterols bad for you?

The latest research suggests plant sterols may increase the risk of atherosclerosis and contribute to heart disease. 

Can you take too much plant sterols?

Expert analyses suggest that it’s very easy to take in excessive amounts of plant sterols with fortified products. It’s best to avoid foods fortified with plant sterols altogether. Children and pregnant and breastfeeding women should be especially cautious. 

Can plant sterols cause weight gain?

No studies have yet linked plant sterols to weight gain. 

However, this is theoretically possible since plant sterols may disrupt sex hormones and metabolism. Also, consuming margarine spreads and refined oils in large amounts is not healthy and may contribute to weight gain. More research is needed. 

Can plant sterols cause liver damage?

No human studies have yet linked plant sterols to weight gain, but more safety data is needed. 

Plant sterols triggered liver damage in animal experiments. Formulas with high levels of plant sterols also cause liver injury in infants and children who need to be fed through an IV (Kasmi et al., 2017; Hukkinen et al., 2017). 

Do plant sterols increase heart disease?

The latest research suggests that plant sterols may increase the risk of heart disease. People who eat foods fortified with plant sterols and are prone to high cholesterol and plant sterols absorption may be at higher risk. More research is needed.

Can plant sterols raise blood pressure?

Research suggests that plant sterols may contribute to atherosclerosis, which can lead to high blood pressure. However, additional studies need to explore whether plant sterols can directly raise blood pressure. 

How Can I Optimize My Plant Sterol Levels?

High cholesterol and plant sterol absorbers can’t be identified easily, but we know that they make up ~25% of the general population. Meanwhile, plant sterols are found everywhere, so cutting out otherwise healthy plant-based foods is not the solution. 

For most people, the takeaway is to eat a balanced whole food diet and avoid fortified, processed foods. 

The next step for some is to consider natural blockers of cholesterol absorption like L. Reuteri NCIMB 30242. 

People with heart disease and those at high risk should talk about the best therapy options (like Zetia in addition to a statin) with a healthcare provider knowledgeable about phytosterols science. 

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Ana Aleksic, MSc (Pharmacy)

Ana is an integrative pharmacist and scientist with many years of medical writing, clinical research, and health advising experience. She loves communicating science and empowering people to achieve their optimal health. Ana has edited 800+ and written 200+ posts, some of which reached over 1 million people. Her specialties are natural remedies, drug-supplement interactions, women’s health, and mental health. She is also a birth doula and a strong advocate of bridging scientific knowledge with holistic medicine.

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Ana Aleksic

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