Food as Medicine: Oats, Avena sativa

FOOD AS MEDICINE:
OAT,
AVENA SATIVA
By
Kevin KF Ng, MD, PhD
Former Associate Professor of Medicine
Division of Clinical Pharmacology
University of Miami, Miami, FL. USA
Email: kevinng68@gmail.com
A Slide Presentation for HealthCare Provider Feb 2020

Lecture Outline
▪ Origin
▪ History & scientific classification
▪ Top producing & consuming countries
▪ Nutrient composition
▪ Pharmacology of β-glucans
▪ Benefits of β-glucans
▪ Clinical studies
▪ Health claims
▪ Summary

What is oat?
▪ Oat is a species of cereal grain grown for its seed.
▪ Oats are used for human and livestock consumption.
▪ Oats are mainly eaten as porridge in breakfast cereals, and in baked goods
(oatcakes, oat cookies, and oat bread).
▪ Over the past few decades, oats have become a very popular "health food”

Origin of oat cultivation
▪ The wild ancestor of Avena sativa and the closely related minor crop,
A. byzantina, is the hexaploid wild oat, A. sterilis.
▪ Genetic evidence shows the ancestral forms of A. sterilis grew in the
Fertile Crescent of the Near East.
▪ The Fertile Crescent in the Middle East curves from the Persian Gulf,
through Iraq, Syria, Lebanon, Jordan, Israel and northern Egypt.
▪ Modern oats probably originated from the Asian wild red oat which grew
as a weed in other grain crops.
▪ Oats were introduced to North America with other grains by Scottish
settlers in 1602 . They gradually became a major crop until about
1920, when machines began to replace horsepower.

History of oats through the ages
https://quatr.us/west-asia/oats-come-west-asia.htm

Top 10 Oat Producing Countries
https://www.atlasbig.com/en-us/countries-oat-production

Which Country Consumes the Most Oats in the World?
1. Russia
2. Canada
3. Poland
4. Australia
5. Finland
https://www.indexbox.io/blog/which-country-eats-the-most-oats-in-the-world/

Scientific classification of oat (Genus Avena L.)
https://plants.usda.gov/java/ClassificationServlet?source=profile&symbol=AVENA&display=31
Avena sativa

Structural representation of the oat grain presenting different oat tissues:
(the bran, germ and endosperm) and the
nutrient distribution/organization within these tissues.
https://pubs.rsc.org/en/content/articlehtml/2018/fo/c7fo02006f

Structural levels of oat, from the plant to extracted β-glucan, and
some oat forms commonly consumed:
steel cut oat grain, oat flakes, oat flour, oat bran and purified β-glucan. (2018)
https://pubs.rsc.org/en/content/articlehtml/2018/fo/c7fo02006f

Varieties of commercial oatmeals
▪ Traditional oatmeal is referred to as rolled oats,
because the whole-grain oats are softened by
steam and flattened on rollers to form flakes.
▪ Steel-cut oats, also known as Irish or Scotch
oatmeal, are oats cut by steel blades into small
pieces without being flattened.
▪ Quick-cooking (one-minute) and instant oatmeal
are steamed, cut and flattened in progressively
smaller pieces to cook more quickly.

Difference between whole grains and refined grains
▪ Whole grains:
▪ bran and germ remain intact
▪ richer source of fiber, vitamins, minerals and phytochemicals.
▪ Refined grains:
▪ the bran and germ are removed
▪ contain only endosperm
▪ less fiber, vitamins, minerals, and phytonutrients
https://www.quakeroats.com/oats-do-more/for-your-
health/fiber-and-whole-grains/what-are-whole-grains

Nutrient compositions of oatmeal vs wheat flour
https://www.researchgate.net/figure/Nutritional-composition-of-oatmeal-and-wholemeal-wheat-flour_tbl1_266324474
macronutrients
minerals
vitamins

Approximate nutrient composition in 100 g raw oats
https://fdc.nal.usda.gov/fdc-app.html#/food-details/340734/nutrients

What is a β-glucans?
https://en.wikipedia.org/wiki/Beta-glucan
Horizontal linkageVertical linkage

Oat beta (β)-glucan
▪ 4.5-5.5% of oat groat
▪ Located in cell wall of endosperm
▪ Outer wall contains water insoluble β-glucans
▪ Inner wall contains water soluble β-glucans
▪ Molecular weight of β-glucans 2x106 -3x106 Da

What is an oat β-glucan?
https://healthjade.net/beta-glucan/
A chain of glucose molecules joined by β-linkages
β-(1-3)

Location of β-glucan in the cell wall of an oat
https://www.cerealsgrains.org/publications/plexus/cfw/pastissues/2006/Documents/CFW-51-0062.pdf

β-Glucan in the cell wall of oat stained with calcofluor.
s, subaleurone; e, endosperm.
https://www.researchgate.net/figure/b-Glucan-in-the-cell-wall-of-oat-
stained-with-calcofluor-a-aleurone-s-subaleurone-e_fig1_266324648

The β-glucan content and the percentage and molecular weight of extracted β-glucan
from oat bran and rolled oats using
hot water (90.8C for 2 h with Termamyl) or physiological in vitro digestion method(2014)
oat bran
rolled oats
British Journal of Nutrition, Volume 112, Supplement S2

Chemistry of Oat β-Glucans
▪ Oat β-glucans are nonstarch polysaccharides.
▪ In starch, the glucose molecules are connected by
α-bonds:.
▪ In oat, the glucose molecules in long chains are
connected by β-bonds.

Chemistry of Oat β-Glucans
▪ Oat β-glucans, like cellulose, are linear glucose polymers, but oat β-glucans have
both β-(1➝4) and β-(1➝3) links, creating a cellulose chain with β-(1➝4) links
interrupted by β-(1➝3)–linked glucose units.
▪ Approximately 70% of the links are β- (1➝4), and the rest are β-(1➝3). The
distribution is not random: the (1➝3) linkages always occur singly, and most of the
(1➝4) linkages occur in groups of three or four.
▪ The intestine does not contain enzymes that can digest oat β-glucans, so they are
by definition a fiber.
http://www.oatingredients.com/fileadmin/template/creanutrition/files_
redakteur/news_internet/CFW_vol_49_no_6_pg_320_Duss_P.pdf
β- (1➝4)β-(1➝3)β- (1➝4) β- (1➝4)

Pharmacological actions of oat β-glucans
▪ A major proposed mechanism is that dietary oat β-glucan forms a viscous
layer in the small intestine.
▪ The viscous layer attenuates the intestinal uptake of dietary cholesterol and
the re-absorption of bile acids (which the body makes from cholesterol)
▪ Modulation of gut microbiome

What happens to the oat β-glucan in the gastrointestinal tract?
Soluble
β-glucan
Insoluble
β-glucanGastrointestinal tract
Feces

Fate of oat β-glucan in the gastrointestinal tract

Population of bacteria in the gastrointestinal tract
http://www.anti-agingfirewalls.com/2012/02/20/gut-microbiota-probiotics-prebiotics-
and-synbiotics-%E2%80%93-keys-to-health-and-longevity/
2
12

Fate of oat β-glucan in the gastrointestinal tract
20-48%
2-5%
35-55%
Products of fermentation

Biological actions of lactic and succinic acids and the predominant
short chain fatty acids produced by bacteria in the GIT (2017)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5666883/

How does β-glucan stimulate the immune system?
http://www.putus.org/news/2009/0113/8.shtml

Oat β-glucan activation of macrophages
http://www.putus.org/news/2009/0113/8.shtml

Disease prevention by oats
▪ Cardiovascular disease
▪ Type 2 diabetes
▪ Cancer
▪ Obesity
▪ High blood pressure
▪ High blood cholesterol
▪ Lower risk of all-cause mortality by 17%

Meta-analysis: Hierarchy of evidence in clinical studies

Cholesterol-lowering effects of ≥ 3 g oat β-glucan:
a meta-analysis of randomized controlled trials (2014)
LDL TC

Cholesterol-lowering effects of ≥ 3 g oat β-glucan:
a meta-analysis of randomized controlled trials (2014)
HDL TG

Meta-analysis of the association between
whole grain intake and mortality:
All-cause (A), CVD (B), and cancer mortality (C) in prospective cohort studies (2016)

The benefit of secondary prevention with oat fiber in
reducing future cardiovascular event among CAD patients
after coronary intervention (2019)
Kaplan-Meier estimates of survival free of
cardiovascular events, including
(A) myocardial infarction;
(B) stroke,
(C) revascularization treatment and
(D) total cardiovascular event in subjects
categorized according to whether oat is
used.
https://www.nature.com/articles/s41598-019-39310-2
+
Oat (-)
Oat (+)
myocardial infarction stroke
revascularization treatment total cardiovascular event

Effect of oat intake on fasting blood glucose (FBG).

effect of oats intake on glycosylated hemoglobin A1c (HbA1c).

Dietary Fiber and Blood Pressure:
A Meta-analysis of Randomized Placebo-Controlled Trials
https://jamanetwork.com/ on 02/14/202

Whole-Grain Intake and Mortality from
All Causes, Cardiovascular Disease, and Cancer:
A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies (2016)
high consumption of whole grains (combination of total whole grains and specific whole-grain foods) was inversely associated with all-cause mortality

Whole grain and body weight changes in apparently healthy adults:
A systematic review and meta-analysis of randomized controlled studies (2013)
https://www.researchgate.net/figure/Forest-plot-of-the-results-of-the-fixed-
effects-meta-analysis-of-change-in-the-percentage_fig3_255955030
Mixed
Oat
Wheat

Total numbers of NK cells in peripheral blood of cancer patients
before and after 60 day β-1,3-glucan supplementation.
G—glucan group, C—placebo group. (2019)
beforebefore after after

Effects of 30 days of oral glucan on salivary immunoglobulins
G—glucan group, C—placebo group. 2019
beforebefore after after

Recommended dose of β-glucans
≥ 3 g/day

Potential risk of contaminated oat: gluten
▪ Although oats don't contain gluten, in rare cases, they are grown in the same fields
as wheat or barley, and these crops can sometimes contaminate oats with gluten.
▪ Therefore, those who have gluten intolerance or celiac disease may have to exercise
caution when eating oats.
▪ Gluten is a group of proteins, called prolamins and glutelins, which occur with starch
in the endosperm of various cereal grains. This protein complex supplies 75–85% of
the total protein in bread wheat.

Comparison of nutrients in different varieties of oats
https://www.cookinglight.com/eating-smart/smart-choices/which-kind-of-oatmeal-is-healthiest
instant oatsrolled oats
steel-cut oatswhole oat groats

Approval of health claims of oats by FDA
▪ Under current FDA regulations, products
▪ low in saturated fat and cholesterol and
▪ high in soluble fiber
▪ are able to claim that they reduce the risk of coronary heart disease.
▪ The fiber contained in whole oat is called beta-glucan soluble
fiber, and is found in
▪ oat bran
▪ rolled oats
▪ whole oat flour.
▪ At least 0.75 g soluble fiber per 4 servings is needed to
provide
▪ 3 grams of beta-glucans per day

Some examples of oatmeals and oat cookies

Summary
▪ Oat is a cereal grain that is rich in dietary fiber known as beta-
glucans.
▪ The soluble fraction of beta-glucans has been shown to reduce the
risks of cardiovascular disease.
▪ Beta-glucans reduce total-cholesterol, LDL-cholesterol, HBA1C and
high blood pressure
▪ Meta-analysis of clinical studies also show that mortality from all
causes, cardiovascular diseases and cancers are reduced by whole
grains.
▪ The health benefits of oats have earned the approval of oats as a
“health food’’ by FDA in 1997

ANY QUESTION?
Please contact
Kevin KF Ng, MD, PhD
Email: kevinng68@gmail.com

Food as Medicine: Oats, Avena sativa

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