Sunflower and soy lecithin

What it is

Lecithin is a fatty mixture rich in phosphatidylcholine, extracted from soybeans or sunflower seeds, and a major dietary source of choline. It is widely used as an emulsifier in processed foods and sold as a supplement.

What the research says

Lecithin is claimed to help memory, cholesterol and blocked milk ducts. A Cochrane review of twelve trials found no clear benefit for dementia. One small uncontrolled cholesterol study reported very large drops, which needs confirmation. The phosphatidylcholine in lecithin is turned by gut bacteria into TMAO, which is associated (not proven causal) with heart events. Soy lecithin holds trace soy allergens.

Evidence grade: Not supported by the research.

What goes wrong

In a cohort study, higher blood TMAO, a product of gut bacterial metabolism of dietary phosphatidylcholine, was associated with a higher rate of heart attack, stroke and death; the study measured an association and did not test lecithin supplements. (Source 1)

• Cohort study, Low certainty.
• Size: 4,007 patients.
• Who: Adults undergoing elective coronary angiography (US)
• How long: 3 years follow-up.
• Result: HR 2.54 (95% CI 1.96-3.28) highest vs lowest TMAO quartile for major adverse cardiovascular events.
• Funding: Independent (NIH and others)

Increased plasma levels of TMAO were associated with an increased risk of a major adverse cardiovascular event (hazard ratio for highest vs. lowest TMAO quartile, 2.54; 95% confidence interval, 1.96 to 3.28; P<0.001).

Soy lecithin contains trace soy proteins including allergens; the source says it apparently does not contain enough to provoke reactions in most soy-allergic people, but raises the possibility that the most sensitive might react. (Source 2)

• Official position, Low certainty.
• Size: Not stated.
• Who: Soy-allergic consumers.
• How long: Not applicable.
• Result: Rates not reported.
• Funding: Academic (University of Nebraska FARRP)

Yet, there is, of course, the possibility that some of the more sensitive soybean-allergic consumers might react to ingestion of soybean lecithin.

Very high choline intakes, of which lecithin is a source, are associated with fishy body odour, vomiting, sweating, low blood pressure and liver toxicity. (Source 3)

• Official position, Certainty not rated.
• Size: Not applicable.
• Who: Not applicable.
• How long: Not applicable.
• Result: Basis for UL of 3,500 mg/day choline.
• Funding: Government.

High intakes of choline are associated with a fishy body odor, vomiting, excessive sweating and salivation, hypotension, and liver toxicity.

What the evidence supports

One trial in people with subjective memory problems gave a strongly positive result, which the review did not treat as enough to change its conclusion. (Source 4)

• Randomized trial, Very low certainty.
• Size: 90 patients (subjective memory group)
• Who: Adults with subjective memory problems.
• How long: Not stated.
• Result: Described as 'dramatic' in favour of lecithin.
• Funding: Not stated.

A dramatic result in favour of lecithin was obtained in a trial of subjects with subjective memory problems.

A small study giving 500 mg soy lecithin daily reported 40-42% falls in total cholesterol and 42-56% in LDL; it had no control group described in the abstract and the effect size is implausibly large for this dose. (Source 5)

• Case series, Very low certainty.
• Size: Not stated in abstract.
• Who: Hypercholesterolaemic patients in Brazil.
• How long: 2 months.
• Result: Total cholesterol -40.66% (1 month), -42.00% (2 months); LDL -42.05% and -56.15%.
• Funding: Not stated.

The results showed a reduction of 40.66% and 42.00% in total cholesterol and of 42.05% and 56.15% in LDL cholesterol after treatment for one and two months, respectively.

What the evidence does not support

A Cochrane systematic review of twelve randomised trials found no clear clinical benefit of lecithin for Alzheimer's disease or Parkinsonian dementia. (Source 4)

• Systematic review, Low certainty.
• Size: 12 trials; 265 Alzheimer's, 21 Parkinsonian dementia, 90 subjective memory patients.
• Who: People with dementia or memory complaints.
• How long: Varied.
• Result: No clear clinical benefit for dementia.
• Funding: Independent (Cochrane)

Evidence from randomized trials does not support the use of lecithin in the treatment of patients with dementia.

Where the research disagrees

Oral lecithin for mastitis and blocked milk ducts

• Commentary in International Breastfeeding Journal (2023) on the Academy of Breastfeeding Medicine Protocol #36 (2022), Expert commentary; the protocol's lecithin recommendation rests on a study of milk fat loss during pumping, not on mastitis outcomes: This includes recommendations to use 'lymphatic drainage' massage, therapeutic ultrasound, and oral lecithin. (Source 6)

How much

• Reference intake: No intake is set for lecithin itself. For choline, the AI is 550 mg/day for adult men and 425 mg/day for adult women (Food and Nutrition Board, reported by NIH ODS). (Source 3)
• Upper limit: No UL for lecithin itself in the sources we read; the choline UL for adults is 3,500 mg/day (reported by NIH ODS). The EFSA 2017 re-evaluation of E322 could not be fetched. (Source 3)
• Studied: One soy lecithin capsule (500 mg) daily for two months in hypercholesterolaemic patients. (Source 5)
• Studied: Trials in the Cochrane review gave lecithin to people with Alzheimer's disease, Parkinsonian dementia and subjective memory problems. (Source 4)

A common belief, and what the research shows

The belief: Lecithin supplements improve memory or protect against dementia.

What the research shows: The Cochrane review concluded: 'Evidence from randomized trials does not support the use of lecithin in the treatment of patients with dementia.'

Questions and answers

What is it?

Lecithin is a fatty mixture extracted from soybeans or sunflower seeds, rich in phosphatidylcholine. It is a major dietary source of choline. (Source 4)

What does it do in the body?

It supplies choline and fats used in cell membranes. Gut bacteria also turn part of its choline into TMAO, a compound linked in studies with heart risk. (Source 1)

Is it good or bad for you?

Lecithin as a food ingredient is widely eaten. As a supplement, trials do not show benefit for dementia, cholesterol evidence is weak, and high TMAO levels are associated with heart events. (Source 4)

How do you get more of it?

Most people take it in without meaning to: the NIH fact sheet describes lecithin as an emulsifying agent used in processed foods such as gravies, salad dressings and margarine. That fact sheet does not give supplement doses for lecithin, so none is stated here. (Source 3)

If it is harmful, what reduces it?

For most people this does not apply. The source says soy lecithin apparently does not contain enough soy protein to provoke reactions in most soy-allergic people, while allowing the possibility that the most sensitive might react. (Source 2)

Why might someone be low in it or missing it?

Lecithin itself is not essential, but its choline is. Low choline has been seen in people on long-term intravenous feeding without choline, and diets low in choline-rich foods. (Source 3)

Which whole foods contain it or feed it?

Soybeans and sunflower seeds are the sources of lecithin; choline is richest in animal foods such as meat, fish, dairy and eggs. (Source 3)

What happens if you do not have it?

Nothing specific happens without lecithin if choline comes from other foods. Choline deficiency can cause muscle and liver damage and fatty liver. (Source 3)

How can you test for it?

There is no routine test for lecithin; choline status is not routinely measured in healthy people. (Source 3)

References

1. New England Journal of Medicine. Intestinal Microbial Metabolism of Phosphatidylcholine and Cardiovascular Risk. 2013. PMID 23614584, DOI 10.1056/NEJMoa1109400. Read the source
2. Food Allergy Research & Resource Program, University of Nebraska-Lincoln. Soy Lecithin (Opinions and Summaries). 2018. Read the source
3. NIH Office of Dietary Supplements. Choline - Health Professional Fact Sheet. 2022. Read the source
4. Cochrane Database of Systematic Reviews. Lecithin for dementia and cognitive impairment. 2000. PMID 11034695, DOI 10.1002/14651858.CD001015. Read the source
5. Cholesterol (Hindawi). Influence of Soy Lecithin Administration on Hypercholesterolemia. 2010. DOI 10.1155/2010/824813. Read the source
6. International Breastfeeding Journal. Does the Academy of Breastfeeding Medicine's Clinical Protocol #36 'The Mastitis Spectrum' promote overtreatment and risk worsened outcomes for breastfeeding families? Commentary. 2023. PMID 37670315, DOI 10.1186/s13006-023-00588-8. Read the source