Download Vitamins: a brief guide

Vitamins:
a brief guide
A Sight and Life publication
Vitamins: a brief guide
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What is
a vitamin?
Sorghum crop in Kenya
Vitamins are organic nutrients which are essential for life. The human
body requires these nutrients to ensure normal metabolism, growth and
physical well-being. Most vitamins are not made in the body, or only in insufficient amounts to meet our needs. They therefore have to be obtained
primarily through the food we eat.
Vitamins are classed as micronutrients, and are present in food in
minute quantities compared to macronutrients (protein, carbohydrates and
fat). In industrialized countries, the average adult eats approximately 600 g
of food per day on a dry-weight basis, of which less than 1 g consists
of vitamins.
Each of the 13 vitamins known today has specific functions in the body,
which makes each of them unique and irreplaceable. No single food contains
the full range of vitamins, and inadequate vitamin intake results in vitamin
deficiency disorders. A balanced and varied diet is therefore
vital to meet the body’s vitamin requirements.
Of the 13 known vitamins, four are fat-soluble, namely vitamins A, D, E and
K. The others are water-soluble: vitamin C and the B-complex, consisting of
vitamins B1, B2, B6, B12, niacin, folic acid, biotin and pantothenic acid.
Retinol
β-carotene
Calciferol
Tocopherol
Phylloquinone
Thiamine
Riboflavin
Niacin
Pantothenic acid
Pyridoxine
Biotin
Folic acid
Cobalamin
Ascorbic acid
Vitamin A
Provitamin A
Vitamin D
Vitamin E
Vitamin K
Vitamin B1
Vitamin B2
Vitamin B3
Vitamin B5
Vitamin B6
Vitamin B7
Vitamin B9
Vitamin B12
Vitamin C
1912
1926
1941
1931
1934
1931
1936
1920
1897
1929
1922
1918
1831
1909
Discovery
1928
1948
1941
1935
1938
1938
1936
1933
1926
1939
1936
1932
1831
1931
Isolation
1933
1956
1946
1942
1938
1940
1937
1935
1936
1939
1938
1936
1930
1931
Structure
1933
1972
1946
1943
1939
1940
1994
1935
1936
1939
1938
1959
1950
1947
Synthesis
This data has been assembled in good faith and on the basis of extensive secondary research it should be noted, however, that some
sources disagree concerning individual dates.
Alternative name
Local fruits on a market in Bangladesh
Vitamin
The history
of vitamins
The discovery
of the concept of
vitamins
Various types of rice sold on a market in Bangladesh
A century ago, a Polish-American scientist attempted to isolate the first
vitamin (B1) from rice bran. Casimir (born Kazimierz) Funk named his discovery “vitamine”, believing that this was an amine vital for life. This coinage has come down to us in the slightly altered form of “vitamin.” Funk’s
breakthrough discovery played a decisive role in the development of an entire scientific framework of thought, which the world now takes for granted.
Funk (1884 –1967) was the first scientist to suggest the existence of an
entire family of organic substances essential for life, and the first to give
these substances a name that made their function clear – even though most
vitamins were later shown not to be amines. He was not the only scientist
working in this field at the time, but he was, one might say, the Godfather
of the vitamins movement.
In a distinguished scientific career spanning two world wars, Funk studied
and worked in Europe and the United States. He had roles in academia
and industry, improved manufacturing methods for commercial drugs, and
became President of the Funk Foundation for Medical Research. Although
he never received a Nobel Prize for his work, the Polish Institute of Arts and
Sciences of America presents the Casimir Funk Natural Sciences Award
annually to a Polish-American scientist.
How the vitamins
got their names
Locally grown legumes on a market stall in Zambia
The first vitamin to be named was vitamin A. The use of the letter A was
the brainchild of the American biochemist Elmer McCollum. He rejected
Casimir Funk’s term ‘vitamine’ in favor of ‘Unidentified dietary factor
fat-soluble A’ because the substance discovered by McCollum did not contain
nitrogen (amines are organic compounds derived from ammonia, and
always contain nitrogen).
In 1921, the British biochemist Sir Jack Cecil Drummond suggested combining the use of letters of the alphabet with the term ‘vitamin’ to denote a
range of related organic micronutrients. These micronutrients consequently
became known as vitamins A, B, C and so on.
The eight water-soluble B vitamins were originally thought to be a single
substance class, but were subsequently found to be chemically distinct from
one another, which is why they are differentiated by means of suffixed
numbers – B1, B2 and so forth.
Vitamins in
human nutrition
While plants and micro-organisms can themselves produce the vitamins
necessary for the metabolism, humans and animals lost this ability during
the course of evolution. Lacking the enzymes necessary for synthesizing
vitamins in the body, humans and animals therefore have to take these in
via the diet (with the exception of vitamin D, which is synthesized via
the action of sunlight).
It was recognized more than 3,500 years ago that foods containing vitamins
are essential for health and well-being. The earliest records to have come
down to us on this subject relate to the use of specific foods like liver – which
contains vitamin A – to prevent diseases such as night blindness. Nevertheless the concept of vitamins per se was quite unknown until very recently.
A balanced diet is necessary for adequate vitamin intake. A lack of the necessary vitamins in the diet can lead to vitamin deficiency disorders, such as
scurvy (vitamin C deficiency),and beriberi (vitamin B1 deficiency).
Since the beginning of the 20th century, our knowledge of the biological
function of vitamins on the molecular and cellular level has increased significantly. This understanding is reflected by the award of 20 Nobel Prizes
in this field between 1928 and 1967. Despite intensive research efforts, however, no additional vitamins have been added to the list of 13 vitamins
defined during the 20th century.
Fruits, vegetables, dairy and
animal products provide a well-balanced diet
A
Retinol | β-carotene
Discovery of active ingredient: 1909 | 1831 (Provitamin A)
Isolation: 1931 | 1831 (Provitamin A)
Prime natural sources
Animal products
Vegetable products
Liver | Egg yolk | Dairy products
Fruits | Leafy vegetables | Carrots
Animal products:
Liver, egg yolk, butter, whole milk, cheese
Vegetable products in the form of carotenoids (provitamin A):
Certain fruits (i.e. melon, apricot), green leafy vegetables
(i.e. spinach, broccoli), carrots, pumpkins, palm oil
The role of vitamin A
> Plays a role in mechanisms required for sight (11-cis retinal is the
chromophore in the visual cycle)
> Essential for growth and development
> Required for healthy skin, epithelia and mucosa
> Effects on certain endocrine glands
> Important for fertility
> Essential for proper immune functions
β-Carotene: Provitamin A, biological antioxidant
Physical symptoms of vitamin A deficiency
> Delayed growth and development
> Night-blindness
> Ocular lesions and xerophthalmia
> Cutaneous lesions (dry and rough skin)
> Impaired immune functions
> Destruction of epithelial tissue (i.e. in lungs, intestines,
urinary tract, genitals)
Groups at risk of deficiency:
> Pregnant and lactating women
> Infants and young children
> Populations suffering from poor nutrition (i.e. only rice, maize,
potatoes as staple foods)
Fat-soluble
Vitamin
The prime natural sources of vitamin A
D
D2 Ergocalciferol
D3 Cholecalciferol Discovery of active ingredient: 1918
Isolation: 1932
Prime natural sources
Animal products
Vegetable products
Oily fish | Egg yolk –> D3
Mushrooms –> D2
Animal products (main source for D3 ):
Oily fish, egg yolk
Plant products (main source for D2):
Mushrooms
Other:
Synthesized in the skin by the action of ultraviolet light
Vitamin D3 is superior to vitamin D2 in increasing and maintaining
25(OH)D serum levels
The role of vitamin D
> Regulation of metabolism of calcium and phosphorus
> Essential for normal bone development and maintenance
> Plays a role in innate immunity by stimulating immune cells proliferation
and cytokine production
Physical symptoms of vitamin D deficiency
> Rickets in children
> Osteomalacia in adults
Groups at risk of deficiency:
> Populations suffering from poor nutrition (i.e. only rice, maize,
potatoes as staple foods)
Fat-soluble
Vitamin
The prime natural sources of vitamin D
E
Tocopherols and Tocotrienols
Main vitamin E activity:
α-Tocopherol (Natural RRR- and all-rac α-Tocopherol)
Discovery of active ingredient: 1922 | Isolation: 1936
Prime natural sources
Animal products
Vegetable products
Dairy products | Eggs
Vegetable oils | Vegetables | Nuts
Animal products:
Milk, butter, eggs
Vegetable products:
Vegetable oils, cereal germ, vegetables (i.e. spinach,
lettuce, cabbage, avocados), nuts
The role of vitamin E
> Biological antioxidant
> Protects lipids (cell membranes), proteins, and DNA from
oxidation and thereby contributes to cellular health
> Assists fertility
Physical symptoms of vitamin E deficiency
> Leads to destruction of red blood cells
> Impaired immune function
> Long-term impact includes neuromusclar diseases
Groups at risk of deficiency:
> Newborn babies, particularly premature
> Individuals unable to efficiently absorb fats from the intestine
Fat-soluble
Vitamin
The prime natural sources of vitamin E
K
K1 Phylloquinone
K2 Menaquinones
Discovery of active ingredient: 1929
Isolation: 1939
Prime natural sources
Animal products
Vegetable products
Dairy products | Meat | Liver
Green vegetables | Cauliflower
Animal products (main source for K2):
Some dairy products (i.e. cheese & curd cheese),
meat including liver
Vegetable products (main source for K1):
Green leafy vegetables (i.e. parsley, spinach), cauliflower
Other:
Fermented soybeans
The role of vitamin K
> Essential anti-haemorrhaging agent (promotes blood clotting)
> Helps to maintain bone health
> Emerging evidence for potential role in cardiovascular health
Physical symptoms of vitamin K deficiency
> Ecchymosis
> Petechiae
> Hematomas
> Oozing of blood at surgical or puncture sites
> In infants, birth defects such as underdevelopment of the face,
nose, bones and fingers
Groups at risk of deficiency:
> Newborn babies (due to lack of intake)
Fat-soluble
Vitamin
The prime natural sources of vitamin K
B
1
Thiamine
Discovery of active ingredient: 1897
Isolation: 1926
Prime natural sources
Animal products
Vegetable products
Offal | Fish | Meat
Cereals | Vegetables | Fruits | Pulses
Animal products:
Offal (liver, kidneys, heart), fish, meat (porc)
Vegetable products:
Cereals, leafy vegetables, fruits (dried), pulses, nuts
Other:
Brewer’s yeast
The role of vitamin B1
> Energy metabolism (co-enzyme)
> Essential for metabolism of carbohydrates, lipids, proteins (co-enzyme)
> Required for proper functioning of the nervous system and
muscles, which has implications for proper functioning of the
cardiovascular system
Physical symptoms of vitamin B1 deficiency
> Beriberi (still occurs in South-East Asia)
Groups at risk of deficiency:
> Alcoholics
Water-soluble
Vitamin
The prime natural sources of vitamin B1
B
2
Animal products:
Offal (liver, kidneys, heart), eggs, meat, milk, cheeses
Vegetable products:
Cereals, vegetables
Other:
Brewer’s yeast
The role of vitamin B2
> Essential for the metabolism of carbohydrates, lipids and proteins
(co-enzyme in many reactions)
> General effect on tissues and organs (maintains health of mucosa)
> Stimulates growth and reproduction
> Plays a role in sight mechanisms
> Conversion of vitamin (B6, folic acid and niacin) into their active
co-enzyme forms
Physical symptoms of vitamin B2 deficiency
Riboflavin
> Skin and tissue membrane lesions (lips, tongue,
fissures at corners of mouth)
> Ocular symptoms (corneal vascularisation associated with
sensitivity to bright light, impaired vision, itching)
> Inflamed mucosal membranes
Prime natural sources
Groups at risk of deficiency:
> Individuals whose food intake is unadequate
> The elderly
> Chronic dieters
> Individuals who exclude milk products from their diet
Discovery of active ingredient: 1920
Isolation: 1933
Animal products
Vegetable products
Offal | Eggs | Meat | Milk | Cheeses
Cereals | Vegetables
Water-soluble
Vitamin
The prime natural sources of vitamin B2
B
3
Niacin; PP; Nicotinic Acid; Nicotinic Amide
Discovery of active ingredient: 1936
Isolation: 1936
Identification with nicotinic acid: 1937
Prime natural sources
Animal products
Vegetable products
Offal | Fish | Meat
Cereals | Pulses | Fruits | Nuts
Animal products:
Offal (liver, kidneys, heart), fish, meat
Vegetable products:
Cereals, pulses, fruit (avocados, figs, dates, prunes), nuts
Other:
Synthesized from tryptophan
The role of vitamin B3
> Required for the energy supply to all metabolic reactions in the body
> Required for growth
Physical symptoms of vitamin B3 deficiency
> Pellagra
> Skin lesions
> Digestive inefficiency
> Insomnia
> Fatigue
> Loss of appetite
Groups at risk of deficiency:
> Chronic alcoholics
> Individuals whose staple diet is maize or barley
> Patients with Hartnup’s disease
Water-soluble
Vitamin
The prime natural sources of vitamin B3
B
5
Pantothenic Acid
Discovery of active ingredient: 1931
Isolation: 1938
Prime natural sources
Animal products
Vegetable products
Offal | Meat | Egg yolk Cereals | Nuts | Vegetables
Animal products:
Offal (liver, kidneys), meat (chicken, beef), egg yolk, milk, fish
Vegetable products:
Cereals, nuts, vegetables (i.e. white mushrooms)
Other:
Synthesized by intestinal microorganisms
The role of vitamin B5
> Required for the synthesis of co-enzyme A and acyl carrier protein (ACP)
> Key role in metabolism of carbohydrates, proteins and fats
> Important for maintenance and repair of tissues and cells
(skin, hair, and membranes)
> Helps in healing of wounds and lesions
> Pantethine (dimeric form of vitamin B5) normalizes blood lipid profiles
Physical symptoms of vitamin B5 deficiency
> Nausea
> Vomiting
> Headaches
> Tingling sensations (‘burning feet’ syndrome)
Groups at risk of deficiency:
> Individuals whose diet is lacking in the other B vitamins
Water-soluble
Vitamin
The prime natural sources of vitamin B5
B
6
Pyridoxine
Discovery of active ingredient: 1934
Isolation: 1938
Prime natural sources
Animal products
Vegetable products
Chicken | Liver | Fish Nuts | Cereals | Bread | Vegetables
Animal products:
Chicken, liver (cattle, pig), fish (salmon, tuna, sardines,
halibut, herring)
Vegetable products:
Nuts (walnut, peanut), corn and whole grain cereals,
bread, vegetables, fruit
The role of vitamin B6
> Required for the majority of biological reactions (i.e. amino acid
metabolism, antibody production, neurotransmitter synthesis,
red blood cell formation)
Physical symptoms of vitamin B6 deficiency
> Deficiency of vitamin B6 alone is uncommon;
usually it occurs in combination with a deficit in other B-vitamins
> Poor growth
> Kidney stones
> Depression
> General fatigue
> Dizziness
> Nerve problems
> Irritability
> Convulsions
> Cutaneous lesions
Groups at risk of deficiency:
> Pregnant and breastfeeding women
> The elderly
> Underweight individuals
> Alcoholics
Water-soluble
Vitamin
The prime natural sources of vitamin B6
B
7
Biotin; Vitamin H
Discovery of active ingredient: 1931
Isolation: 1935
Prime natural sources
Animal products
Vegetable products
Offal | Meat | Egg yolk Vegetables | Cereals | Nuts
Animal products:
Offal (liver, kidneys), meat (pork, mutton, poultry), egg yolk
Vegetable products:
Vegetables, cereals, nuts (walnuts, peanuts)
Other:
Synthesized by intestinal bacteria
The role of vitamin B7
> Involved in many cellular reactions
> Intermediary metabolism of carbohydrates, fats and proteins,
particularly in protein metabolism of hair roots and finger nail cells
Physical symptoms of vitamin B7 deficiency
> Deficiency due to lack of dietary intake is rare
> General fatigue
> Nausea
> Neurological problems
> Poor skin and hair quality
Groups at risk of deficiency:
> Patients maintained on total parental nutrition
> People who eat large amounts of raw egg white
> Haemodialysis patients
> Diabetes mellitus sufferers
> Individuals receiving long-term anticonvulsant therapy
Water-soluble
Vitamin
The prime natural sources of vitamin B7
B
9
Folate (including folic acid and naturally occurring folates)
Discovery of active ingredient: 1941
Isolation: 1941
Prime natural sources
Animal products
Vegetable products
Liver | Dairy products | Egg yolk Leafy vegetables | Peanuts | Oranges
Animal products:
Liver, dairy products, milk, egg yolk
Vegetable products:
Dark green leafy vegetables, beets, wheat germ, yeast,
peanuts, oranges
The role of vitamin B9
> Required for the production of nucleic acids and in cell reproduction
(i.e. red and white blood cells, nerve cells)
Physical symptoms of vitamin B9 deficiency
> Tiredness
> Loss of appetite
> Fewer but larger red blood cells (megaloblastic or macrocytic anemia)
> Weakness
> Neurological problems
> Digestive problems
Groups at risk of deficiency:
> The elderly (due to lower food intake)
> Underweight people
> Alcoholics
Water-soluble
Vitamin
The prime natural sources of vitamin B9
B
12
Cyanocobalamin
Discovery of active ingredient: 1926
Isolation: 1948
Prime natural sources
Animal products
Offal | Meat | Eggs | Fish | Dairy products
Animal products:
Offal (liver, kidneys, heart, brain), meat, eggs, fish,
dairy products
The role of vitamin B12
> Required for the formation of red blood cells to prevent anemia
> Essential growth factor
> Regeneration of folate
> Involved in fat and carbohydrate metabolism
> Essential for co-enzyme function, especially in cells of the nervous tissue,
bone marrow and gastrointestinal tract
Physical symptoms of vitamin B12 deficiency
> Pernicious anemia
> General fatigue
> Loss of appetite
> Gastric atrophy
> Neuromuscular pain
> Neurological problems (gait, memory)
Groups at risk of deficiency:
> Vegetarians
> The elderly
Water-soluble
Vitamin
The prime natural sources of vitamin B12
C
Ascorbic Acid
Discovery of active ingredient: 1912
Isolation: 1928
Prime natural sources
Animal products
Vegetable products
Milk | Liver Fruits | Vegetables | Lettuce
Animal products:
Milk, liver (ox /calf)
Vegetable products:
Fruits (especially citrus fruits), vegetables, lettuce
The role of vitamin C
> Multiple roles at a tissue and cell level (synthesis of collagen,
absorption of iron, formation of carnitine and tyrosine)
> Biological antioxidant (free radical scavenger)
> Stimulates the body’s immune system: defenses against infections
and inflammation
Physical symptoms of vitamin C deficiency
> Scurvy (fatigue, loss of appetite and weight,
lowered immune resistance to infections)
Groups at risk of deficiency:
> Smokers (active and passive)
> Individuals with a low-vitamin diet
Water-soluble
Vitamin
The prime natural sources of vitamin C