dietary supplements 3rd edition lecithin

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Lecithin

Description

Lecithin is a phospholipid and is known asphosphatidylcholine.

Constituents

Lecithin is composed of phosphatidyl esters,mainly phosphatidylcholine, phosphatidyletha-nolamine,phosphatidylserineandphosphatidyl-inositol. It also contains varying amountsof other substances such as fatty acids,triglycerides and carbohydrates. One teaspoon(3.5 g) lecithin granules provides on average:energy 117 kJ (28 kcal), phosphatidyl choline750 mg, phosphatidyl inositol 500 mg, choline

100 mg, inositol 100 mg, phosphorus 110 mg.

Human requirements

Lecithin is not an essential component of thediet. It is synthesised from choline.

Action

Lecithin is a source of choline (see Choline)and inositol. It is an essential component of cellmembranes and a precursor to acetylcholine.

Dietary sources

Soya beans, peanuts, liver, meat, eggs.

Metabolism

About 50% of ingested lecithin enters thethoracic duct intact. The rest is degraded toglycerophosphorylcholine in the intestine, andthen to choline in the liver. Plasma choline levels

reflect lecithin intake.

Deficiency

Not established.

Possible uses

Lecithin is claimed to be beneficial in the treat-ment of disease related to impaired cholinergicfunction (see Choline). It has also been claimedto be of benefit in lowering serum cholesterollevels and improving memory. It is sometimestaken for dementia and Alzheimers disease.

Cholesterol

An open clinical trial in the 1970s showedthat oral lecithin in large doses (2030 g daily)

led to a significant reduction in cholesterolconcentration in one out of the three healthysubjects studied and three out of the sevenpeople with hypercholesterolaemia.1

However, in a double-blind study, 20 hyper-lipidaemic men were randomised to receivefrozen yoghurt, frozen yoghurt with 20 g soyabean lecithin or frozen yoghurt with 17 g sun-flower oil. Sunflower oil was used to controlfor the increased intake in energy and linoleicacid from the lecithin. Lecithin treatment hadno independent effect on serum lipoprotein or

plasma fibrinogen levels in this group of men.2A review of 24 papers examining the effect of

consuming lecithin on serum cholesterol raisedconcern about the small size and lack of controlgroups in many of the studies. The authorsconcluded that there was no evidence for aspecific effect of lecithin on serum cholesterolindependent of its linoleic acid content orsecondary changes in food intake. The observedlecithin-induced hypocholesterolaemic effects inthe studies were artefacts caused by the manner

and design of the data analysis, were mediated

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by dietary changes or were due to the linoleicacid present in lecithin.3

Alzheimers disease

A double-blind, placebo-controlled crossoverstudy in 11 outpatients with Alzheimers diseasefound that lecithin 10 g three times a day for3 months was associated with an improvementin tests of learning ability, but there was noimprovement in any of the psychological testsused.4

Two further double-blind studies (one inpatients with Alzheimers disease,5 one in

normal adults6) showed no effect of lecithin onmemory.

Another double-blind RCT in 53 subjectswith probable Alzheimers disease involved theuse of lecithin and tacrine or lecithin andplacebo for 36 weeks. No clinically relevantimprovement was found in any of the groupsover 36 weeks.7

A Cochrane review investigating the efficacyof lecithin in the treatment of dementia orcognitive impairment found 12 RCTs involvingpatients with Alzheimers disease (265 patients),Parkinsonian dementia (21 patients) and sub-jective memory problems (90 patients). Notrials reported any clear benefit of Alzheimersdisease or Parkinsonian dementia. A dramaticresult in favour of lecithin was obtained ina trial of subjects with subjective memoryproblems. The authors concluded that evidencefrom randomised trials does not support theuse of lecithin in the treatment of dementia.A moderate effect could not be ruled out, butthey concluded that results from the small trials

to date do not indicate priority for a largerandomised trial.8

Conclusion

Controlled clinical trials have provided noevidence that lecithin lowers cholesterol orhelps to improve memory in patients withAlzheimers disease. Claims for the valueof lecithin in lowering blood pressure andalso in hepatitis, gallstones, psoriasis andeczema are unsubstantiated. Further trialsare needed to assess the role of lecithin.

Precautions/contraindications

None known.

Pregnancy and breast-feeding

No problems have been reported, but therehave not been sufficient studies to guaranteethe safety of lecithin (in amounts greater thanthose found in foods) in pregnancy and breast-feeding.

Adverse effects

None reported.

Interactions

None reported.

Dose

Lecithin is available in the form of tablets,capsules and powder. Lecithin supplements pro-vide between 20 and 90% phosphatidylcholine

(depending on the product).The dose is not established. On currentevidence, lecithin is unlikely to be useful. Prod-uct manufacturers recommend 12002400 mgdaily.

References

1 Simons LA, Hickie JB, Ruys J. Treatment of hyper-cholesterolaemia with oral lecithin. Aust NZ J Med1977; 7: 262266.

2 Oosthuizen W, Vorster HH, Vermaak WJ, et al.

Lecithin has no effect on serum lipoprotein, plasmafibrinogen and macromolecular protein complexlevels in hyperlipidaemic men in a double-blindcontrolled study. Eur J Clin Nutr 1998; 52:419424.

3 Knuiman JT, Beynen AC, Katan MB. Lecithin intakeand serum cholesterol. Am J Clin Nutr 1989; 49:266268.

4 Etienne P, Dastoor D, Gauthier S, et al. Alzheimerdisease: lack of effect of lecithin treatment for 3months. Neurology 1981; 31: 15521554.

5 Brinkman SD, Smith RC, Meyer JS, et al. Lecithinand memory training in suspected Alzheimers dis-

ease. J Gerontol1982; 37: 49.


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6 Harris CM, Dysken MW, Fovall P, Davis JM. Effectof lecithin on memory in normal adults. Am JPsychiatry 1983; 140: 10101012.

7 Maltby N, Broe GA, Creasey H, et al. Efficacy oftacrine and lecithin in mild to moderate Alzheimers

disease: double-blind trial. BMJ 1994; 308:879883.

8 Higgins JPT, Flicker L. Lecithin for dementia and

cognitive impairment. Cochrane database, issue 4,2000. London: Macmillan.

dietary supplements 3rd edition lecithin

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