Food as Medicine:Onions, Allium Cepa

FOOD AS MEDICINE:
ONIONS
Allium Cepa
By
Kevin KF Ng, MD, PhD
Former Associate Professor of Medicine
University of Miami, Miami, FL, USA
Email: kevinng68@gmail.com
A slide presentation for HealthCare Provider Seminar May 2019

Outline of Lecture
▪ History
▪ Anatomy
▪ Composition
▪ Bioactive compounds
▪ Pharmacology
▪ Health benefits
▪ Adverse effects
▪ Clinical studies
▪ Summary

"I will not move my army without onions !"
March 4, 1869 - March4, 1877
https://www.evld.org/images/ulysses-s-grant-photographjpg

Number of publications (onions) in PubMed from1892 to 2018:
Total=3218
https://www.ncbi.nlm.nih.gov/pubmed/?term=onion

Historical milestones of onion cultivation

Onions, dry, production quantity (tons)
Top 10 countries for 2016
http://www.factfish.com/statistic/onions%2C%20dry%2C%20production%20quantity

Top 10 countries that exported the highest dollar value
(millions) worth of onions during 2017.
http://www.worldstopexports.com/onions-exports-by-country/

Scientific classification of onion (Allium cepa)
https://plants.usda.gov/java/ClassificationServlet?source=display&classid=ALLIU

Anatomy of an onion
https://www.enchantedlearning.com/subjects/plants/printouts/bulbanatomy.shtml

Nutrient composition of onions

Nutrient compositions in a raw medium size onion 140 grams
Macronutrients in g/140 g Vitamins in mg/140 g Minerals in mg/140 g Bioactive compounds
Quercetin
Organosulfor compounds
1-10%
Micronutrients Micronutrients
Adapted from https://www.onions-usa.org/all-about-onions/nutritional-facts-vegetables
Fructans

Major Bioactive compounds in an onion (Allium cepa)
Adapted from https://www.sciencedirect.com/topics/medicine-and-dentistry/s-allyl-cysteine

What is a Fructan?
▪ A fructan is a polymer of fructose molecules.
▪ Fructans with a short chain length are known as
fructooligosaccharides.
▪ Fructans occur in foods such as agave,
artichokes, asparagus, leeks, garlic, onions
(including spring onions), yacón, jícama, and
wheat.

Flavonoids (Quercetin) in onion (Allium cepa)

Proportion of major polyphenol content (%) in onion
(data from Lachman and others 2003).
https://onlinelibrary.wiley.com/doi/pdf/10.1111/1541-4337.12331

Onion chemistry after cutting raw onion
(adapted from Lokke and others 2012)

Formation of major organosulfur compounds in onion
Adapted from https://www.researchgate.net/figure/Formation-of-organo-sulphur-
compounds-during-metabolic-pathways-in-processed-onion
LF synthase

Formation of the major flavor groups during metabolic pathways in
processed onion
(adapted from Griffiths and others 2002)

Higher plasma quercetin levels following oral administration of an
onion skin extract compared with pure quercetin dihydrate in humans
(2017)
https://link.springer.com/article/10.1007/s00394-015-1084-x

Pharmacokinetics and Bioavailability of Quercetin Glycosides
in Humans (2001)
Total quercetin concentration in plasma (mean ± SD) of 12 volunteers after administration of 100 mg (331 µMol) quercetin in the form of an onion
supplement or quercetin-4’-O-glucoside or 200 mg (662 µMol) of quercetin in the form of buckwheat tea or quercetin-3-Orutinoside (rutin) in a
randomized crossover design.
https://ucanr.edu/datastoreFiles/608-67.pdf

Absorption of Quercetin glycoside across the intestinal epithelium
https://www.pureencapsulations.com/newscap-10-30-13

Possible routes after polyphenol (quercetin) consumption.
Adapted from https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/quercetin-glycosides

Pharmcokinetics of quercetin
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4366009/

Health benefits of onion bioactive compounds

Onion (Allium cepa L.) peel extract has
anti-platelet effects in rat platelets (2015)
https://www.researchgate.net/publication/271598486_Onion_Allium_cepa_L_peel_extract_
has_anti-platelet_effects_in_rat_platelets
Effects of OPE on collagen-induced platelet aggregation

Hypoglycemic effect of OPE (onion peel extract) or quercetin
on the OGTT (oral glucose tolerance test) test.
https://www.researchgate.net/figure/Hypoglycemic-effect-of-OPE-or-quercetin-on-the-OGTT-test-After-8-week-administration-of_fig1_50865589
OGTT AUC
(pure quercetin)

Clinical Hypoglycemic Effects of Allium cepa ( Red Onion ) in
Type 1 Diabetic Patients
https://www.semanticscholar.org/paper/Clinical-Hypoglycemic-Effects-of-Allium-cepa-(-Red-Eldin-
Ahmed/c13deef7c8d8429049afb369b765ce5b7be6722c

Active hypoglycemic constituents from ONION AND GARLIC
https://www.researchgate.net/publication/286304551_Current_update_on_anti-diabetic_biomolecules_from_key_traditional_Indian_medicinal_plants
ONION AND GARLIC
ONION AND GARLIC

Onion peel tea ameliorates obesity and affects blood parameters
in a mouse model of high-fat-diet-induced obesity (2013)
https://www.spandidos-publications.com/etm/7/2/379

Fate of frutan in the gastro-intestinal tract
Stomach
• No digestion
Small
intestine
• No digestion
Large
intestine
• Fermentation
by bacteria
GI Tract Frutan

Biological actions of lactic and succinic acids and the predominant
short chain fatty acids produced by bacteria in the GIT (2017)

Health Benefits of quercetin
▪ Decrease cancer tumor initiation
▪ Promote healing of stomach ulcers
▪ Inhibit the proliferation of cultured
ovarian, breast and colon cancer
cells
https://www.onionsusa.org/img/site_specific/uploads/phytochemical_brochure.pdf

Molecular structure of quercetin, quercetin glycoside,
quercetin glucuronide, quercetin sulfate and methylated quercetin.

How quercetin block tumor necrosis factor-α (TNFα)-mediated
inflammation.

Hypolipidemic effects of quercetin
The control group was fed AIN-93G diet, whereas the low and high quercetin (LQE and HQE) groups were fed a diet containing 0.04% and
0.08% quercetin for 6 weeks. Values are mean ± SD (n = 6). Each bar with different letters is significantly different (*P < 0.05, **P < 0.01)
https://pdfs.semanticscholar.org/e47e/c7287c7e2e7e5fdfbd5f3977c9ecf3bb7a41.pdf
Triglyceride Cholesterol HDL-cholesterol

Properties of onion organosulfur compounds
▪ Eye irritant
▪ Flavor
▪ Anti-inflammatory
▪ Immune-modulation
▪ Anti-cancer
▪ Anti-platelet aggregation
▪ Anti-hyperglycemia
▪ Anti-hyperlipidemia
▪ Anti-hypertension

Mean Percentage Changes of Serum Adiponectin, Leptin, and
hs-CRP in the Two Groups After 8 Weeks of eating onion
http://ircmj.com/en/articles/58674.html

The Effects of Raw Red Onion Consumption on Serum Levels of Adiponectin, Leptin, and
hs-CRP in Overweight/Obese Females with Polycystic Ovarian Syndrome:
A Randomized Controlled-Clinical Trial (2017)
http://ircmj.com/en/articles/58674.html

The Effect of Onion Peel Extract on Inflammatory Mediators in
Korean Overweight and Obese Women (2016)

Onion peel extract reduces the percentage of body fat in overweight
and obese subjects: a 12-week, randomized, double-blind,
placebo-controlled study. (2016)
https://www.ncbi.nlm.nih.gov/pubmed/27087901

Consumption of onion juice modulates oxidative stress and
attenuates the risk of bone disorders in
middle-aged and post-menopausal healthy subjects (2015)
▪ twenty-four subjects were divided into two groups and advised to intake 100 mL of
onion juice or placebo for 8 weeks.
▪ Anthropometric measurements and blood samples were collected at the initial,
2(nd), 6(th), 8(th) and 10(th) week.
▪ The BMD of three postmenopausal women was also found to be mildly improved on
supplementation with onion juice.
▪ Onion juice consumption showed a positive modulatory effect on the bone loss and
BMD by improving antioxidant activities and thus can be recommended for treating
various bone-related disorders, especially osteoporosis.
https://www.researchgate.net/publication/284765557

analgesic effects of fresh onion juice in comparison with that of
morphine on hot plate test. (2012)
African Journal of Pharmacy and Pharmacology Vol. 6(23), pp. 1679-1684, 22 June, 2012

Why cutting onions make you cry?

Effects of cooking on contents of S-alk(en)yl-L-cysteine sulfoxides (ACSOs):
meyhiin, isoalliin, propiin and cycloalliin
https://link.springer.com/article/10.1007/s10068-016-0017-7

Effect of cooked onion extracts on human platelet aggregation
in vitro (2012)
Negative values are platelet inhibitory. Positive
values are platelet stimulatory aggregation
https://nutritionj.biomedcentral.com/articles/10.1186/1475-2891-11-76

Summary of health benefits of onion bioactive compounds

Benefits of including onion in the diet
▪ Reduce risk of stomach ulcer in humans.
▪ Reduce risk of brain cancer in humans.
▪ Inhibit platelet aggregation (thrombosis).
▪ Reduce cholesterol, triglycerides and thromboxanes.
▪ Reduce risk of osteoporosis.
https://www.onionsusa.org/img/site_specific/uploads/phytochemical_brochure.pdf

In vitro and in vivo studies of onion
▪ anti-thrombotic
▪ hypo-lipidemic
▪ anti-diabetic
▪ anti-obesity
▪ antioxidant
▪ antiinflammatory
▪ cancer chemopreventive
▪ Antiparasitic
https://www.researchgate.net/publication/235385412_Dietary_spices_as_beneficial_
modulators_of_lipid_profile_in_conditions_of_metabolic_disorders_and_diseases

Hypolipidemic eﬀects of onion (Allium cepa) in experimental
and clinical studies (2013) decreased cholesterol
https://www.researchgate.net/publication/235385412_Dietary_spices_as_benefici
al_modulators_of_lipid_profile_in_conditions_of_metabolic_disorders_and_diseases
decreased cholesterol

Clinical Hypoglycemic Effects of Allium cepa (Red Onion) in
21 Type 2 Diabetic Patients (2010)

A New Proprietary Onion Extract Gel Improves the Appearance of New Scars
A Randomized, Controlled, Blinded-Investigator Study (2010)
Subject-rated improvementInvestigator-rated improvement

Meta-analysis: Hierarchy of evidence in clinical studies

Effects of quercetin on blood pressure:
A systematic review and meta-analysis 0f randomized controlled trials (2016)
Diastolic BPSystolic BP
https://www.ahajournals.org/doi/10.1161/JAHA.115.002713

Effect of flavonol supplementation on measures of
plasma glucose (mmol/L) 2017
https://www.semanticscholar.org/paper/Impact-of-Flavonols-on-Cardiometabolic-
Biomarkers%3A-Menezes-Rodriguez-Mateos/46ef47cb648d777f6378be246e307c231a4cc1d4

Effect of flavonols supplementation on blood lipids :
(a) Triacylglycerols ; (b) Total Cholesterol ; (c) LDL Cholesterol ; (d) HDL Cholesterol .
https://www.semanticscholar.org/paper/Impact-of-Flavonols-on-Cardiometabolic-Biomarkers%3A-
Menezes-Rodriguez-Mateos/46ef47cb648d777f6378be246e307c231a4cc1d4/figure/2

Consumption of Large Amounts of Onion
Reduces Risk for Gastric Cancer in a Meta-analysis (2011)
https://www.gastrojournal.org/article/S0016-5085(11)00441-0/pdf

Foods that may or may not cause cancer
Risk estimates for 20 foods (each studied at least 10 times)from a 2012 meta-analysis
https://fivethirtyeight.com/features/you-cant-trust-what-you-read-about-nutrition/

Common Use of onion products
▪ May be eaten raw as in salads.
▪ May be cooked as in soups.
▪ May be used as thickening agent for curries and gravies.
▪ May be pickled in vinegar and used as snack.

Onion-Drug Interaction
▪ Onion may increase the effect of aspirin.
▪ Onion may increase level of lithium in the body and
result in serious side effects
▪ Onion may potentiate the effect of antidiabetic drugs.
▪ Onions might increase the effects and side effects of
some medications that act on (Cytochrome P450 2E1
(CYP2E1) in the liver.

Summary
▪ Onions have been used for thousands of years as food and medicine.
▪ Onions provide macronutrients, micronutrients and bioactive compounds.
▪ The main bioactive compounds are frutans, quercetin and organosulfur chemicals.
▪ Frutan is an oligosaccharrides with prebiotic and immune-modulatory properties.
▪ Quercetin and organosulfur compounds have been shown to have multiple
properties beneficial for health.
▪ When onion is cut, the volatile organosulfur compounds come into contact with an
enzyme liberating lachrymatory factor which is an eye irritant.
▪ Onions can be eaten raw, boiled, fried, baked or pickled.
▪ Onion may interact with anti-coagulants, lithium, anti-diabetic drugs and drugs that
act on cytochrome P450 in the liver.

Food as Medicine:Onions, Allium Cepa

Food as Medicine:Onions, Allium Cepa

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