Information and Evidence
What are Phytosterols (PS)?
Plants and Animals are both living but different life forms. Plants synthesise “Sterol” molecules which are vital to plant health and they are called phytosterols. Humans also synthesise “sterol” molecules because they are vital to human health. Cholesterol is the primary human Sterol it is essential for life. Humans not only synthesise it, but also obtain it from food.
Why are PS added to some foods?
Food manufacturers add PS to foods because they are allowed to make certain health claims on the packaging which are designed to enhance sales. The food must first be approved for sale by Food Standards Australia and New Zealand.
PS are only temporally absorbed by intestinal cells, once recognised as non-cholesterol they are expelled back into the intestines, only a small amount (between 0.5 and 5%) of PS escapes the expulsion process and is absorbed. When PS is in artificially high concentrations this mechanism has the effect of significantly reducing the amount of cholesterol that is absorbed and lowers serum LDLc levels (bad cholesterol); but this also means the amount of PS that escapes expulsion and is absorbed increases, and it replaces cholesterol in vital human tissue.
Could PS consumption increase the risk of Heart Attack and negatively affect Long Term Health Outcomes. (A short layman's explanation)
Cholesterol can accumulate in the walls of coronary arteries (plaque build up), how and why this occurs is extremely complex. This accumulation can eventually narrow the coronary arteries to the point where blood flow is so restricted it causes chest pain and shortness of breath; but this type of restriction does not usually cause heart attacks or strokes and surgical techniques can fix it. Heart attacks and strokes are caused by "unstable plaque" rupturing with the result that a blood clot is released into the artery where it can travel causing a total blockage where it gets "stuck". If it gets "stuck" in the brain it is a stroke, a smaller or same artery in the heart and it is heart attack. Phytosterols mimic Cholesterol and when present they accumulate in the plaque (and other human tissues), and the effect of this is to make the plaque more "unstable" and likely to rupture causing a heart attack or stroke. As well as affecting the plaque it also decreases the flexibility of the artery wall (BAD) damages the microvascular of the eye (and therefore may damage all micro vascular structures) and is implicated in heart valve Stenosis which may require valve replacement or repair. These foods do lower cholesterol, but no evidence exists that their consumption reduces the risk of heart attack or stroke, which is after all the reason for reducing cholesterol levels in the first place. Evidence does exist that indicates long term consumption is likely to result in adverse health outcomes.
The Scientific Evidence Against Phytosterol Enriched Foods and Supplements.
“These findings support the hypothesis that plant sterols might be an additional risk factor for CHD.“ http://www.ncbi.nlm.nih.gov/pubmed/12489060
“Elevations in sitosterol concentrations and the sitosterol/cholesterol ratio appear to be associated with an increased occurrence of major coronary events in men at high global risk of coronary heart disease.” http://www.ncbi.nlm.nih.gov/pubmed/16399487
Food supplementation with PSE impairs endothelial function, aggravates ischemic brain injury, effects atherogenesis in mice, and leads to increased tissue Sterol concentrations in humans. Therefore, prospective studies are warranted that evaluate not only effects on cholesterol reduction, but also on clinical endpoints. (Concentration of Plant Sterols) in Serum and Aortic Valve Cusps; NCT00222950)
“The results suggest that women with elevated ratios of serum squalene, campesterol and sitosterol to cholesterol and low respective lathosterol values have enhanced risk for CAD”
“In CAD women (women with coronary artery disease), serum plant sterol ratios to cholesterol were 21% to 26% (P < .05) higher than in controls (women without coronary artery disease) despite similar cholesterol absorption efficiency.
“This study suggests that the high concentration of phytosterols in CA (Canola Oil) and the addition of phytosterols to other fats make the cell membrane more rigid, which might be a factor contributing to the shortened life span of SHRSP rats.
“To summarize, we have shown that an increase in cholesterol-standardized serum campesterol concentrations observed during long-term consumption of plant sterol ester enriched functional foods correlates with increase in retinal venular diameter. The functional consequences of the increase in retinal venular diameter in terms of affecting health demands further study, although the observed increase of 2.3 μm is certainly relevant when placed in perspective to associations found in for example metabolic syndrome subjects and smokers."
“Furthermore, we examined plasma and aortic valve concentrations of plant sterol in 82 consecutive patients with aortic stenosis. Patients eating PSE-supplemented margarine (n = 10) showed increased plasma concentrations and 5-fold higher sterol concentrations in aortic valve tissue.”
All animals make cholesterol which is a sterol molecule. Could the replacement of cholesterol in our tissues by another sterol affect human health; the answer is yes.
“Triparanol, which inhibits a late step in the (cholesterol synthesis) pathway, was introduced into clinical use in the mid-1960s, but was withdrawn from the market shortly after because of the development of cataracts and various cutaneous adverse effects. These side effects were attributable to tissue accumulation of desmosterol, the substrate for the inhibited enzyme.”
“In summary, dietary supplementation with both PSA and PSE reduced plasma cholesterol concentrations in apoE−/− mice. Mice on a diet supplemented with PSE demonstrated an increase in a ‘pro-atherogenic’ monocyte subpopulation and a less pronounced atherosclerotic lesion reduction. Furthermore, mice on a diet supplemented with PSE showed increased vascular superoxide and lipid hydroperoxide production and, due to enhanced absorbability, higher plasma concentrations and increased plant sterol tissue deposition in major organ systems.
These findings underline the need for clinical studies that evaluate not only the effectiveness of serum cholesterol reduction, but also the clinical effects and safety of a diet supplementation with PSE.” (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3096304/)
What the Authorities Say
Food Standards Australia and New Zealand - Therapeutic Goods Association
The Food Standards Australia and New Zealand (FSA) and the Australian Therapeutic Goods Association (TGA) are responsible for approving novel foods and supplements that make health claims. Neither organisation goes looking for food and supplement manufacturers to produce “healthy products” for Australian consumption, instead they are approached by organisations to obtain approval for the sale of their product and the “Health Claim” that goes with it. The underlying motive for registration and listing is likely to be profit.
Both the FSANZ and the TGA have approved foods and or supplements that contain artificially high levels of PS. Note the French authorities have not approved the sale of PS supplemented foods.
Health Professional Clinical Guidelines.
English (UK) PS Guidelines
Guidelines are produced by the National Institute for Health and Care Excellence in conjunction with the National Clinical Guideline Centre. The guidance given to health professionals can be summarised as stating that under no circumstances should the practitioner advise clients to consume PS enriched food. The British guidelines can be found here.
German guidelines are similar.
Australian PS Guidelines
The Australian Heart Foundation (AHF) website contains contradictory information. A number of documents on the site (for both practitioners and the general public) recommend that 2 to 3 grams a day of Phytosterols be consumed for both primary and secondary prevention of CVD, the only exceptions being lactating women and children. Their statements are qualified with the following comments.
“There is no consistent evidence that would lead to safety concerns associated with the short-term consumption of phytosterols and stanols, although long-term safety studies have not been performed."
"Long-term cholesterol-lowering studies with phytosterol intervention would be needed to demonstrate actual prevention of CVD, but are unlikely to occur."
"Further work is needed to evaluate the effects of phytosterol-rich plant foods as a natural source of phytosterols that may lower cholesterol."
"The role of phytosterols in modifying the development of atherosclerotic plaque warrants further research. Data will continue to be monitored by the Heart Foundation, especially with respect to potential adverse effects. Reduction in carotenoids and possibly tocopherols is one such area.”
Put into plain English the AHF is stating that they don't know if PS enriched food consumption will reduce the chances of heart attack or stroke. The AHF is also stating that long term adverse safety risks are unknown. It could be said that the AHF is recommending an unsupervised epidemiological trial on the general public without their permission when adverse effects are known or certainly suspected with regard to humans.
The Heart Foundation Sends Mixed Messages
The AHF has also published a most comprehensive document titled “Guidelines for the management of Absolute cardiovascular disease risk”.
Below is the only mention of Phytosterols in the document.
“Several other interventions, including soya protein, phytosterols and selenium supplements, have been investigated for their potential benefits on CVD risk factors. In general, soya protein, phytosterols and soluble fibre may have modest hypocholesterolaemic effects, while there is insufficient evidence to determine the effect of selenium supplements on the prevention of CVD. More evidence is required before clear recommendations can be made regarding these interventions."
Yet even though the AHF publishes the statement above it still recommends the consumption of PS enriched foods, and displays the "heart tick logo" on most of these products
Phytosterols and Secondary Cardiovascular Disease (CVD) Prevention.
The most common medication for secondary prevention of CVD are Statins. The AHF recommends that Doctors advise patients to also consume PS enriched foods in conjunction with the Statin treatment. Here the evidence is clear; consumption of PS enriched foods is likely to offer no further preventative benefit whatsoever; and may even reduce the efficacy of the Statin treatment.
This is demonstrated by the IMPROVE - IT clinical trial
This trial compared two groups of people over 7 years. One taking a Statin and the other taking the Statin plus a drug that blocks intestinal Cholesterol absorption (Ezetimibe) as does PS supplementation. Even though LDLc (bad cholesterol) was reduced by a further 28% in the Ezetimibe group, heart attack and stroke events were only reduced by a further 2% and there was no reduction at all in all cause mortality. Could this very marginal improvement also be provided by PS supplementation which also reduces LDLc absorption? The evidence suggests otherwise!
"We previously observed in apoE−/− mice that a diet supplemented with PSE (equivalent to a commercially available spread) induced endothelial dysfunction and led to an increase in ischaemic stroke size in wild-type mice.13 Moreover, we observed that inhibition of cholesterol absorption by a diet supplementation with PSE was associated with twice the amount of atherosclerotic lesion formation compared with ezetimibe treatment (a drug that reduces both plasma cholesterol and plant sterol levels), despite similar plasma cholesterol levels.
Based on the mice experiments it can be expected that PS cholesterol absorption blocking would be far less effective than the EZ cholesterol blocker and will have other detrimental effects (previously mentioned). Hence for secondary prevention of heart disease and stroke where persons are being treated with Statins; PS supplementation is not likely to have any measurable beneficial effect, and could even result in an increased risk.
PS molecules are very similar to, but not the same as, cholesterol. PS mimics cholesterol and is taken up in human cells at sites where cholesterol would normally be present. Had we known the detrimental effects of trans fats and cigarettes when first introduced, would we have allowed their free sale to the public?
Both the Australian Heart Foundation and Food Standards Australia state the long term health safety of PS supplementation is unknown, but much evidence exists to indicate health risks do exist. Considering this, the above information, and the fact that numerous alternative cholesterol lowering methods are available, why are PS supplements and PS enriched food freely available to the public? Even more amazing; why are these products allowed to be sold without a health warning, even if that warning be as feeble as the statements made by the AHF?
It is my contention that PS supplements and PS enriched foods should be removed from public sale and only be available on prescription. They are medicine not food.