Plant sterols are the plant kingdom’s equivalent of cholesterol. They play key roles in plant cell wall health, helping regulate:
- Cell wall structure
- Cell wall permeability
- Activity of cell membrane-bound enzymes
A useful analogy is to think of plant sterols as a gatekeeper that helps determine what gets into the cell and what stays out. Interestingly, early human diets were rich in phytosterols, providing up to 1 g/day. More traditional Western diets provide much less, a paltry 150 mg—an 85% decrease. Moreover, roughly only 10% of the phytosterols we ingest are absorbed, meaning you have to eat a bountiful amount to get the benefit.
The primary plant sterols are:
- Beta-sitosterol
- Campesterol
- Stigmasterol
- Sitostanol
- Campestanol
Musculoskeletal Benefits of Phytosterols
As previously mentioned, phytosterols have a chemical structure similar to cholesterol. High levels of cholesterol are associated with increased whole-body inflammation and oxidative stress. Chronic inflammation and oxidative stress drive musculoskeletal diseases including osteoarthritis (joint degeneration), osteoporosis (weak bones), and sarcopenia (loss of muscle mass and weakness).
Phytosterols have been shown to decrease cholesterol levels, which in turn helps reduce chronic inflammation, oxidative stress, and protect joints, bones, and muscles. While the exact mechanisms of cholesterol, inflammation, and oxidative stress reduction are still being defined, research suggests:
- Phytosterols block the absorption of cholesterol in the digestive tract.
- Phytosterols dislodge cholesterol in cell walls and dampen the transmission of the inflammation signal from outside the cell to the inside.
- Phytosterols neutralize high-energy oxygen free radicals.
- Phytosterols boost the production of key joint-building blocks.
Selected Evidence
Phytosterols Boost Joint Health
French researchers investigated the effect of a concentrated form of phytosterols (Avocado Soybean Oil Unsaponifiables) on a group of patients with hip arthritis. At the end of the study trial period, the treatment group on average exhibited less progression of arthritis by X-ray compared to the placebo group. Furthermore, the same authors looked at symptom relief using a similar extract on patients with knee and hip arthritis. After three months, the treatment group reported less pain, better function, and less NSAID use (Maheu et al., 1998; Maheu et al., 2014).
Stigmasterol’s Effects on Osteoarthritis
Chinese investigators examined the effects of stigmasterol on a rabbit model of osteoarthritis. The authors found that stigmasterol administration significantly reduced the production of enzymes, called matrix metalloproteinases (MMPs), which destroy cartilage cells (Wei-Ping et al., 2012).
Precautions
Phytosterols from natural foods are generally well tolerated. Optimal amounts can be obtained from a balanced, healthful diet. The European Scientific Committee on Foods has published an upper limit of 3 g/day. Excessive intake of supplemental phytosterols may cause gastrointestinal symptoms such as nausea, indigestion, diarrhea, and constipation. Any consideration of supplementation should be discussed with a qualified health professional familiar with your unique medical history.
References
- Conde Nast. (2014). Foods highest in stigmasterol in fats and oils. Retrieved from http://nutritiondata.self.com/foods-004076000000000000000.html?maxCount=17
- Conde Nast. (2014). Foods highest in stigmasterol in fruits and fruit juices. Retrieved from http://nutritiondata.self.com/foods-009076000000000000000.html?maxCount=2
- Conde Nast. (2014). Foods highest in stigmasterol in legumes and legume products. Retrieved from http://nutritiondata.self.com/foods-016076000000000000000-1w.html
- Conde Nast. (2014). Foods highest in stigmasterol in nuts and seed products. Retrieved from http://nutritiondata.self.com/foods-012076000000000000000.html?maxCount=13
- Conde Nast. (2014). Foods highest in stigmasterol in vegetables and vegetable products. Retrieved from http://nutritiondata.self.com/foods-011076000000000000000.html?maxCount=5
- Bouic, P. J. (2001). The role of phytosterols and phytosterolins in immune modulation: A review of the past 10 years. *Current Opinion in Clinical Nutrition & Metabolic Care*, 4(6), 471-475.
- Chen, W. P., Yu, C., Hu, P. F., Bao, J. P., Tang, J. L., & Wu, L. D. (2012). Stigmasterol blocks cartilage degradation in rabbit model of osteoarthritis. *Acta Biochimica Polonica*, 63(4), 537-541. https://doi.org/10.18388/abp.2016_1335
- Ferraz-Filha, Z. S., Michel Araújo, M. C., Ferrari, F. C., Dutra, I. P., & Saúde-Guimarães, D. A. (2016). *Tabebuia roseoalba*: In vivo hypouricemic and anti-inflammatory effects of its ethanolic extract and constituents. *Planta Medica*, 82(16), 1395-1402. https://doi.org/10.1055/s-0042-105878
- Gabay, O., Sanchez, C., Salvat, C., Chevy, F., Breton, M., Nourissat, G., & Berenbaum, F. (2010). Stigmasterol: A phytosterol with potential anti-osteoarthritic properties. *Osteoarthritis and Cartilage*, 18(1), 106-116. https://doi.org/10.1016/j.joca.2009.08.019
- Gylling, H., & Simonen, P. (2015). Phytosterols, phytostanols, and lipoprotein metabolism. *Nutrients*, 7(9), 7965-7977. https://doi.org/10.3390/nu7095374
