Howlers > Cholesterol

Cholesterol in plants

This page discusses the cholesterol content of plants, and is one of a series that discuss common errors in current textbooks of biochemistry.


The other pages in this series are in urgent need of updating (and the information in this one needs to be checked in the light of all current textbooks). The biochemical principles have not changed, of course, but textbooks have: some of those that were current when I first prepared these pages in 2000 have appeared in new editions, and others have ceased to be widely used. New books have appeared that are not discussed. Unfortunately I do not have easy access to any of the commonly used textbooks, as I work in a research (not teaching) environment in a country where English is not the everyday working language. I could buy them, of course, but that would represent rather a large investment for the sake of a few web pages.

Accordingly I should be grateful if someone would collaborate with me in the revision. If you have access to all of the textbooks published in English in the past ten years (say 1996 or later) that are commonly used for teaching biochemistry, and if you would like to help, please contact me at acornish@ibsm.cnrs-mrs.fr.

Sterols in plants

Behrman and Gopalan (2005) suggest the following as an accurate account of the real sterol content of plants:

More than 250 steroids have been described in plants. Of these, perhaps sitosterol, which differs from cholesterol by an ethyl substituent at position 24, is the most common. But plants also contain cholesterol both free and esterified. Cholesterol occurs as a component of plant membranes and as part of the surface lipids of leaves where it is sometimes the major sterol. The quantity of cholesterol is generally small when expressed a percent of total lipid. While cholesterol averages perhaps 50 mg/kg total lipid in plants, it can be as high as 5 g/kg (or more) in animals.

Examples of the problem

Textbooks typically assert that plants do not contain cholesterol, for example,

According to Horton et al. (2002, p. 275),

Cholesterol ... is only rarely found in plants.

Similarly, Zubay (p. 385) says that

Plant cells have no cholesterol.

Other books make statements that are partially correct. For example Voet and Voet (2004, p. 389) follow a correct sentence by one that is more dubious:

Plants contain little cholesterol. Rather, the most common sterol components of their membranes are stigmasterol and β-sitosterol.

Why does it matter?

Correct appreciation of the cholesterol content of different food components is important because diets are often intended to control cholesterol intake, and need to be based on true information. Although the cholesterol content of plants is typically much less than that of animals it is by no means negligible: It can be as high as 5 g cholesterol per kilogram of total lipids in animals, but averages about 50 mg cholesterol per kg of total lipids in plants, and is much lower than this average in certain oils. For example olive oil typically contains 0.5–2 mg cholesterol per kg and sesame oil about 1 mg cholesterol per kg. For designing diets it is also important to understand that labelling laws in the USA (and probably elsewhere) allow amounts less than 2 mg per serving to be shown as zero.

Further reading

I am grateful to Dr E. J. Behrman, of the Ohio State University, for bringing this problem to my attention. The information given here is based on the following forthcoming article:

E. J. Behrman and V. Gopalan (2005) Cholesterol and plants J. Chem. Educ. in press.

Textbook checklist

The list is not complete, because not all the textbooks referred to on other pages have been checked, and those that have been checked are in some cases of more recent publication than those referred to on other pages.

Abeles, Frey and Jencks (not examined)
Campbell (not examined)
Garrett and Grisham (2005) Poor Incorrect in part p. 263
Horton et al. (2002) Bad Cholesterol said to be only rarely found in plants p. 232
Nelson and Cox (2000) Poor Correct information misleadingly presented p. 309
McKee and McKee (not examined)
Mathews, van Holde and Ahern (not examined)
Stryer (2002) Poor Correct information presented in a way that invites misunderstanding p. 325
Voet and Voet (2004) Poor Not quite correct p. 389
Zubay Bad Plant cell membranes said to have no cholesterol p. 385

Other common errors in textbooks

List of books considered