PROTEINS IN THE DIET
Humans have about 10kg protein and need to replace about
300g daily:
recycle
~230g
need to eat
~30g
~40g
Most of us >100g/day
meat/fish/egg protein
grain protein per day
FOOD
Meat
Beef
Chicken
Salmon
Grain
Bread
Rice, cooked
Dairy
Milk, whole
Cheese
Eggs
Fruits
Apples
Bananas
Nuts – Almonds
Vegetables
Potato
Corn
Tomato
WATER PROT
FAT
CARB
kcal /100g
62
71
64
32
24
27
5
4
7
0
0
0
180
140
180
36
70
10
3
3
0
50
26
250
120
87
37
74
3
25
13
3
32
11
5
2
1
65
400
160
84
76
5
0.2
1
19
0
0.2
54
15
22
20
60
85
600
75
74
94
2
3
1
0.1
1
0.2
21
21
5
90
90
22
Some grains lack some amino acids
CORN
RICE
WHEAT
SOY
lacks lysine and tryptophan
lacks lysine and threonine
lacks lysine
lacks methionine (need 2g/day of this one)
KWASHIORKOR is common in Africa where corn is almost the
exclusive food consumed: characterized by bloated and swollen belly,
scaly skin, retarded growth and mental apathy
Not generally a problem with a balanced vegan diet in North America
as a variety of seeds and nuts provide all necessary amino acids
From an efficiency standpoint, consuming animal proteins is not
necessarily the best option:
To produce 1kg of animal protein requires the following kg of feed:
Beef
Chicken
Catfish/Carp
20
5
2.5
Pork
Eggs
8
4
Animal protein sources have changed a lot over the last few
decades (chicken was ~ equal to mutton in 1950):
Beef
Pork
Mutton
Chicken
Ocean Fish
Farm Fish
1990 (M tons)
53
70
10
41
85
13
2003
59
96
12
76
93
40
Growth/y World
0.8
2.5
1.6
4.9
0.8
9.7
High protein – low carb diets (Atkins, Zone, Protein Power…)
Result in quick weight loss because eliminating carbohydrates
results in loss of body fluids – but, according to the American
Heart Association, are not effective long term: impede
fat metabolism, generally substitute carbohydrates with fats,
restricts mineral intake, causes ketosis (and nausea)
Some people can’t metabolize excess protein resulting in liver and
kidney disorders
2002: Acrylamide, a potent carcinogen, identified in many
popular foods such as fries, potato chips, cakes, bread,
coffee, cookies
Comes from carb rich foods that are fried or baked
Source identified from amino acid asparagine + dicarbonyl
compound from browned sugars
H2N-CO-CH2CH<COOH
NH2
+ R-CO-CHO
heat
H2N-CO-CH=CH2
Is this a risk? Maybe not: NOAEL (no observed adverse affect
limit) is 500x higher at 0.5 mg/kg body weight than the amount
in a normal portion of the worst offender, french fries (ca. 50
mg/serving)
FOOD - MINERALS AND VITAMINS
RDA/DRI=800/
1000-1300*mg
2mg
*generally higher values are for 15-18 yr olds, and 50+
RDA is old recommended daily allowance, DRI is new joint Canada/US intake values
3(F)-4(M)mg
100-150/150mg
10-18/10(M)-15(F)mg
300-400/320(F)-420(M)
800-1200/700-1250
(15-18y)
/55(F)-70(M)mg
15/12(F)-15(M)
IODINE
Iodine required for Thyroxine which controls the thyroid gland:
regulates rate at which cells use O2 and the base metabolic rate
GOITER = swollen neck (size of head) caused by too much or too
little iodine. All salt in NA has 0.1% KI added to avoid this problem
I
HO
I
NH2
COOH
O
I
I
thyroxine
L-form is active amino acid
VITAMINS
OIL (FAT) SOLUBLE = A, D, E, F, K
WATER SOLUBLE = B, C.
VITAMIN A = RETINOL: derived in body from b-carotene (orange
pigment in carrots)
liver
CHO
CH2OH
oxn
b-carotene
b-carotene
2
retinol (vitamin A alcohol)
retinol
citral
citral
Commercially, citral from lemon grass can be converted to Vitamin A
or carotene
US uses RDA (recommended dietary allowance),
CAN uses RNI (recommended nutrient intakes)
RDA = 5000 IU (International units) (~1500 RE)
= 1.5 mg retinol = 1.72 mg of Vit A acetate ≡ 3 mg carotene
NOW 1000 RE (retinol equivalents) = 1 mg (1000mg) of retinol
These differ by country,
eg. UK = 800RE = 0.8 mg; Canada = 870 RE = 0.87mg and by
gender: F = 80% of male
Function: Vitamin A protects against invading bacteria
- makes mucus secreting cells produce sticky stuff which trap
bacteria;
- prevents night blindness
- (regeneration of retinal pigments);
- keeps skin and tear ducts healthy
DEFICIENCY: Light sensitivity, night blindness, infections
~ 1 million people in India suffer night blindness
EXCESS:
probably most toxic vitamin in excess
irritability, dry peeling skin, pressure in head
severe liver injury if >25,000 IU. only 5x normal dose
also TERATOGENIC: birth defects of eyes, ears, heart
avoid liver if pregnant (limit 8,000 IU)
SOURCES:
CAROTENE:
fish liver oils, egg yolks, apricots, peaches
not poisonous, present in carrots, green vegetables
VIT A is fat soluble so passes up food chain:
highest in polar bear liver (~20,000 IU/g!!)
Adults store a year’s supply in fat
India: diet is deficient; GM modified rice to produce carotene
trans-RETINOIC ACID; RETIN-A; TRETINOIN
Causes the skin to peel: used in cosmetics as an anti-acne agent,
anti-skin damage, anti-wrinkle...OK in limited doses topically
Some questions as to its efficacy: see the FDA site on RENOVA:
http://www.fda.gov/cder/foi/label/2000/21108lbl.pdf
cis-RETINOIC ACID; ISOTRETINOIN; ACCUTANE
Orally for severe acne, BUT it has severe side effects and is
powerful TERATOGEN: requires two pregnancy tests to start
see: http://www.aocd.org/skin/dermatologic_diseases/accutane.html
Tretinoin
Isotretinoin
VITAMIN D (calciferol)
400 IU = 10 mg of Vit D3
US = 5-10 mg; UK 5-7 mg; CAN 3-5 mg
sunlight
HO
7
HO
7-dehydrocholesterol
Sources:
Vit D3 cholecalciferol
Pre-vitamin in cereals, bread, milk
sunlight converts it to active vitamin
Function: Vitamin D controls Ca and P absorption from foods,
metabolism, transport of Ca in bloodstream and formation of bones
DEFICIENCY: soft, deformed
bones (RICKETS) not enough
Ca3(PO4)2 to stiffen them; poor teeth
Stored in fat
Excess is toxic: 250 mg/d for 4 weeks
or 5 mg/d for 2 weeks causes nausea,
vomiting, diarrhea, headache
Too much Ca/P:
stiffens joints
a-TOCOPHEROL
VITAMIN E
USRDA = 30 IU (30 mg) old racemic RH/LH mixture
now use d-(RH) a-tocopherol = 16.7 mg
O
HO
Function:
prevents oxidation of fats
maintains red blood cell membranes
necessary for proper functioning of:
genitals, lungs, liver, kidneys
Not destroyed by heat but sensitive to O2
Not as fat soluble as A or D so storage in body is shorter
DEFICIENCY: edema (water under skin), anaemia in kids,
muscular dystrophy
EXCESS Vitamin E:
recently recognized as a potential health hazard
increases LDL, depresses platelet formation by
causing Vit K deficiency (slows blood clotting),
shows immunosuppresant properties
(see for eg. http://emedicine.medscape.com/article/126268-overview)
Sources:
plenty in grains, meats, eggs, nuts, salmon (oily fish)
VITAMIN F = (w-6)-linoleic acid (see fats section)
D9,12-octadecadienoic acid
HO
O
Function:
Important for structural cell membranes
Sources:
present in all fats, some vegetable oils and many
expensive supplements
DEFICIENCY
coarse sparse hair, eczema (RDA = 1.3 g)
O
VITAMIN K
H
O
n
n = 5-13
Function: Synthesis of prothrombins (blood coagulants)
DEFICIENCY: haemorrhages, slow blood clotting (RDA ~ 80 mg/d)
EXCESS: clotting
Sources:
Found in leafy veg like cauliflower, broccoli
Must watch intake if on blood thinners
ANTI-VITAMIN K:
dicoumarol is found in clover, alfalfa
substitute is warfarin (blood thinner, rat poison)
O
O OO O
OH
O
HO
O
OH
Dicoumarol [Dicumarol]
Warfarin
Inhibits Vit K dependent synthesis of blood clotting factors
WATER SOLUBLE VITAMINS: washed out so need more frequently
B-GROUP
B1
co-enzymes in growth and energy production
THIAMINE
RDA = 1.5mg
N
NH2
N
S
OH
N
+
Cl
-
Function:
carbohydrate metabolism (decarboxylation of
pyruvate and ketoglutarate), energy production,
ATP levels, heart and circulatory system functioning
Deficiency:
Beriberi*, muscular atrophy, nervous disorders
Sources:
grain skin, soybeans, bran, peanuts, meat, liver, eggs
(bread and cerials are enriched: 2.1 mg/100g)
*Beriberi:
laboured breathing, enlarged heart, mental confusion, paralysis
of arms/legs – common with exclusive white rice diet
B2
RIBOFLAVIN
RDA = 1.2-1.8 mg
HO OHOH OH
N
N
O
NH
N
O
Function: used as part of co-enzyme FAD (flavin adenine dinucleotide);
metabolism of fats and proteins
DEFICIENCY: cracks around mouth, sore eyelids, oily skin around
nose, DERMATITIS, fatigue, stops tissue growth
Sources: liver, milk, eggs, leafy veg
Added to enriched bread, cereals: 3.6 mg/100g
B3
COOH (orCONH 2)
NIACIN
RDA 13-20mg
N
Function: part of co-enzyme NAD (nicotinamide adenine dinucleotide)
metabolism and synthesis of carbs, fats, proteins, (alcohol)
Deficiency – the three D’s: Diarrhea, dermatitis and dementia (Pellagra)
Sources:
yeasts, liver, peanuts, whole grains, potatoes
Corn is deficient in niacin so people in SE USA used to get pellagra
Added to enriched bread, cereals: 21 mg/100g
High levels of Niacin have been shown to raise
HDL and lower LDL but high levels of niacin
can also cause liver damage:
http://www.nlm.nih.gov/medlineplus/ency/article/002409.htm
OH
B5 PANTOTHENIC ACID
H
N
Incorporated into Co-enzyme A
O
Function:
Deficiency:
Sources:
OH
HO
O
transfers C2 units in metabolism of fats and carbs
retarded growth
liver, salmon, eggs, nuts, yeasts, broccoli, cauliflower
OH
B6
PYRIDOXINE
1.7-2.0 mg/d
Function:
Deficiency:
Sources:
HO
OH
N
metabolism/synthesis of proteins
oily dermatitis, nausea, vomiting, weakness, dizziness
yeasts, bran, carrots, bananas, liver, eggs, meats
Morning sickness during pregnancy is reduced with extra B6
EXCESS: (100 mg/d): loss of balance, numbness (sold 100-500 mg)
O
B7 BIOTIN 0.3-1 mg/d
NH
HN
COOH
S
Function:
Deficiency:
Sources:
carboxylase coenz (transfer CO2 in food metabolism)
sleepiness, muscle pains, aversion to food,
increase in blood cholesterol, dry scaly skin
most vegetables, liver, milk, nuts
B9 FOLIC ACID
0.15-0.4 mg/d
N
(2x pregnant F)
Function:
Deficiency:
Sources:
N
H2N
N
N
OH
NH
CONH
CHCH2CH2COOH
COOH
coenzymes of growth, especially red blood cells
anaemia, fatigue, poor appetite, forgetfulness
liver, whole grains, yeast, green veg
Folic Acid Controversies
Pregnant women: protects baby from spina bifida BUT
Swedish study suggests increased chance of twins and cerebral palsy
Is this risk > spina bifida risk?
US has made folic acid a compulsory additive in cereals:
reduces blood homocysteine, reduces heart disease
http://www.hc-sc.gc.ca/iyh-vsv/med/folic-folique_e.html
http://www.marchofdimes.com/professionals/690_1403.asp
B12
COBALAMIN
RDA = 6 mg/d
Function: catalyzes synthesis of nucleic
acids, red and white blood cells, RNA to
DNA conversion
Deficiency: pernicious anaemia inability
to absorb vitamin from food (need to
have them injected)
Sources: Meat and dairy, seafood
No significant plant sources
Needs to be formed by bacteria or
consumed in meat
C ASCORBIC ACID
RDA = 50-60 mg/d
Deficiency – Scurvy:
bleeding hair follicles, edges of nails,
bleeding stinking gums, weight loss, black
lungs, damaged liver, swollen legs...
Only need ~ 10 mg/d to prevent scurvy
Sources:
all citrus fruit, potatoes, tomatoes, cabbage
English sailors corrected the deficiency with limes: ‘limeys’
Need 300mg of Vit C in body, of which need to replenish ~60 mg/d
Cannot be stored for long: excrete excessive doses (>200 mg/d)
Pauling advocated (and took) > 2 g/d
Function:
ANTI-OXIDANT that scavenges free radicals
slows or prevents invading viruses (VIT C – Common
Cold connection)
regenerates Vit E in the body
heat and oxygen sensitive (old bottles are not good)
OH
HO
HO
O
HO
O
O
O
HO
O
O
HO
+ 2 e- + 2 H+
O2 + 2 H+ + 2 e-
H2O2