The Saga of Sodium Nitrite
• Nitrite and nitrate have been used for some 5000
years or more to cure and preserve meat
• 1891 – first publication showing that nitrate-to-nitrite
conversion by bacteria was the source of preservative
effects
• 1899 – first suggestion of nitrite as the source of
cured meat color
• 1901 – discovery that nitric oxide from nitrite was
source of cured meat color
• 1925 – first regulatory (USDA) limits for nitrate and
nitrite were established
The Saga of Sodium Nitrite (cont’d)
• 1920’s-1950’s – Industry and university researchers
refined curing processes
- role of nitrite in cured meat clarified
-potent antimicrobial agent
-powerful antioxidant
-distinctive cured meat flavor
-unique, attractive color that is stable
The Saga of Sodium Nitrite (cont’d)
• 1956 – a problem emerges…; first report of
carcinogenic nitrosamines found in fish meal cured
with very high nitrite concentrations
• 1960’s – intensive studies of the relationship
between nitrite, nitrosamines and human cancer…
…nitrosamines were found in some cured meats
and the perceptions of cured meats as a
contributor to human cancer became
firmly entrenched
The Saga of Sodium Nitrite (cont’d)
• Mid 1970’s – Extensive research in meat curing
showed that nitrosamines were not an issue with
proper control of nitrite concentrations
- use of reductants and improved understanding
of time/temperature relationships in meat
curing reduced residual nitrite to very low
concentrations and eliminated nitrosamines
The Saga of Sodium Nitrite (cont’d)
• Late 1970’s – discovery of endogenous
nitrate/nitrite in the human intestine and in saliva
begins to suggest a biological role for these
compounds
-leads to discovery of nitric oxide as a very
important biological molecule
-beginning of the turnaround in scientific
perceptions of nitrite
• 1986 – Nitric oxide found to be “the body’s
messenger” resulting in explosion of
research in biology and physiology
Nitric oxide…
-regulates blood pressure and blood flow
-provides neurotransmission/brain function
-kills bacteria and other immune system
challengers
-promotes healing
(also provides critical role in the function of
the drug Seldinafil)
2002 – Importance of nitric oxide for blood
transfusions suggested
-25% greater heart attacks/strokes observed
following transfusions
- collected blood loses NO within hours of
collection to 30% of initial after one day; 17%
after 7 days and virtually none at 42 days
- work with dogs showed decreased heart attacks
with NO-treated transfusions
Reynolds et al., Proc. Nat. Acad. Sci. 104:17058(2007).
• 2005 – Protective role of nitric oxide in endothelial
function, cardiovascular disease and heart attacks
suggested
- first reports of nitrite as major storage form
of NO in blood and tissue
- role for dietary nitrate and nitrite suggested
for cardiovascular health
• Source of nitric oxide (NO) in biology is nitric oxide
synthase (NOS) conversion of arginine to citrulline
L-arginine + O2 → L-citrulline + NO + H2O
• Nitrite serves as a low-oxygen source of NO
thus nitrite may be a critical protective component
for increasing blood flow when oxygen is limited
• Current questions
– role of blood and tissue nitrite concentrations?
– role of dietary nitrite?
Dietary nitrite in mice
• Insufficiency of dietary nitrite (7 days) decreased
steady state nitric oxide and increased injury from heart
attacks
• Dietary supplementation with nitrite restored NO
homeostasis within 7 days, reversed injury and
improved survival from heart attacks
• Dietary nitrite intake can restore NO homeostasis and
blood and tissue nitrite to a greater extent (emphasis
mine) than change in NOS activity
• Dietary supplementation reduced plaque formation in
genetically modified, atherosclerotic-susceptible mice
Bryan et al., Proc. Nat.
Acad. Sci. 104:19144(2007)
Human Daily NOx Intake Varies with Diet
Western Menu
Breakfast
350
NOx (mg)/Serving
300
Menu
Bagel w/ Cr Cheese
Toast w/ Jam & Butter
Black Coffee (12 oz)
Cappuccino
NOx
(Espresso + Milk)
AM Snack
250
200
Lunch
150
100
50
PM Snack
0
Western Menu
Mediterranean
Mediterranean
Menu
Dinner
Carrot Nut Muffin
Yogurt (Strawberry)
Diet Coke (12 oz)
Carrot Juice (12 oz)
Big Mac
Mediterranean Wrap
Large French Fried
Garden Veg. Soup
Diet Coke (12 oz)
Mineral Water (12 oz)
Snickers
Trail Mix
Black Coffee (12 oz)
Orange Juice (12 oz)
Cheese Pizza (4
slices)
Salmon (Smoked)
Diet Coke (12 oz)
Red Wine (12 oz)
from Bryan, MIRC (2007)
Importance of Dietary Nitrate/Nitrite
• Reduction of blood pressure by 5%-10%, and even attenuates
sodium-induced hypertension
Mean arterial
pressures in
animals treated
with high salt (4%
of diet) and nitrate
(0.08 or 0.8
g/day).
Carlstom et al., Cardio. Res.
89:574 (2011).
Importance of Dietary Nitrate/Nitrite
• Improves exercise performance
– 200 mg beetroot consumption 60 minute prior to improved
running performance (speed in second half of trial) by 5%
Murphy et al., J. Acad. Nutr. Diet. 112:548 (2012)
•
Many competitive-class athletes now utilize beetroot
supplements to enhance performance
Cermak et al., Int. J. Sports Nutr. Exer. Met. 22:64 (2012)
Importance of Dietary Nitrate/Nitrite
Metabolic Activity and Circulatory Responses to Maximal Exercise After Dietary
Supplementation with Nitrate
Max O2
Max HR O2 Pulse
Nitrate 3.62* 183
Placebo 3.72
183
*significantly different
(ml/beat)
19.8
20.5
Time/Exh.
Max Lac.
(seconds)____________
563*
10.9
524
10.5___
Conclusion: reduced oxygen consumption and improved endurance = improved
muscle efficiency
Larsen et al., Free Rad. Biol. Med. 48:302 (2010)
Importance of Dietary Nitrate/Nitrite
• Nitrite concentration in human breast milk (colostrum)
– Increases dramatically for the first three days after birth
• Declines by 60% at 4th day, 90% after 8 days
– Hypothesized to be important to infants before G.I. tract
bacteria are established
– Documented to prevent newborn necrotizing enterocolitis
resulting from limited intestinal blood flow by nursing
mothers and by administration of nitrite as therapy for
NEC
“Most provocatively, these studies suggest that the
cardioprotective effects of leafy green vegetables could
derive from nitrite, in addition to the often cited antioxidant
effects of these food groups.”
Gladwin et al. Nat. Chem. Biol. 1:308-314(2005)
“The solution to these problems should…lead to the
potential consideration of nitrite as an “essential
nutrient”…”
Gladwin et al. Nat. Chem. Biol. 1:308-314(2005)
“Could it be that the stringent regulations on
nitrite/nitrate in drinking water and in foods
contribute to the contemporary diseases of today
due to inadequate nitrite or nitrate in the diet and
NOS activity unable to supply enough nitrite to
maintain cellular homeostasis?”
Bryan, Free Rad. Biol. and Med. 41:691-701(2006)
“Therefore, nitrite and nitrate may serve as essential
nutrients for optimal cardiovascular health and
may provide a treatment modality for
cardiovascular disease.”
Bryan et al., Proc. Nat. Acad. Sci. Early Ed. (2007).
www.pnas.org/cgi/doi/10.1073/pnas.0706579104
Nitrite:
• Has profound effects on human physiology
• Dietary intake may be protective and maintain/restore
endothelial function
• Dietary supplementation may inhibit onset and progression
of atherosclerosis
• Dietary levels of nitrite and nitrate should be reconsidered
for optimal health
• Increasing steady state NOx concentrations is a natural
physiological response in humans and highlights the
physiological justification and safety of such intervention
from Bryan, MIRC (2007)
In addition, very recent work shows
that dietary nitrite results in:
• Faster wound healing (revascularization)
• Reduced blood triglycerides
- sunlight effect (see handout), besides blood pressure
decrease, may also partially explain winter
weight gains, summer weight losses (or lesser gains!)
There are several human clinical trials currently
underway on the use of nitrite
1.
2.
3.
4.
5.
6.
7.
Nitrite Infusion Studies
Condition: healthy
Nitrite Infusion in Healthy Volunteers
Condition: healthy
The Role of Nitrite in Preconditiioning Mediated Tolerance to
Ischemic Stress
Conditions: ischemic stress; transient non-lethal ischemia
Dietary Nitrate and Nitrite to Increase Nitric Oxide in Patients With
Coronary Artery Disease
Condition: coronary arteriosclerosis
Biomarkers for Cardiovascular Disease
Condition: coronary artery disease
Endothelial Cell Dysfunction in Pulmonary Hypertension
Condition: hypertension, pulmonary
Heart Disease in Sickle Cell Anemia
Conditions: sickle cell anemia; pulmonary hypertension
•
Nitric Oxide: Biology and Chemistry. Although one of the simplest biological molecules in
nature, nitric oxide has found its way into nearly every phase of biology and medicine ranging
from its role as a critical endogenous regulator of blood flow and thrombosis to a principal
neurotransmitter mediating erectile function to a major pathophysiological mediator of
inflammation and host defense. These major discoveries have stimulated intense and extensive
research into a vast array of fields including chemistry, molecular biology, and gene therapy.
Nitric Oxide: Biology and Chemistry provides a forum for the rapid publication of scientific
investigation of the highest quality across the broad field of nitric oxide research.
Research Areas Include basic and clinical topics in:
• Cell Biology
• Molecular biology
• Biochemistry
• Immunology
• Pathology
• Genetics
• Physiology
• Pharmacology
• Disease processes
•
Editor-in-Chief:
J.R. Lancaster
Nitric Oxide Dietary Supplement
•
Commercially available as “NEO40 Daily”
(www.neogenis.com)
– Composed of proprietary blend of beetroot (nitrate),
Hawthorn berry (nitrate reductase), citrulline and nitrite
– Promoted for individuals over 40 when endogenous NO
begins to decline
– Daily use shown to increase plasma nitrite and nitrate, and
decrease blood tryglycerides
• For a long time in meat curing, nitrite has been MAGIC!
• Now for human health, nitrite is TRULY MAGIC!
Is nitrate/nitrite the newly discovered “Vitamin N”?
• Nitrate/nitrite offer new preventative or therapeutic strategies and new
dietary guidelines for good health relative to diseases characterized by
NO deficiency
• Definition of a vitamin = a group of organic substances essential in
small quantities to normal metabolism, found in minute amounts in
natural foods, deficiencies of which produce specific disorders.
N. Bryan, Institute of Molecular Medicine for Prevention
of Human Diseases, University of Texas. Encyclopedia of
Meat Sciences (in press)