Vitamins - Overview Flashcards
What is the definition of “vitamin”?
“vital amine”
- organic compound distinct from fats, CHO, and proteins
- natural component of foods that is usually present in minute amounts
- essential, also usually in minute amounts, for normal physiological function (maintenance, growth, development, and/or production)
- causes by its absence or underutilization, a specific deficiency syndrome
- not synthesized by the host in adequate amounts to meet normal physiological needs (must be consumed in food to meet adequate requirements)
What are the four main functional categories of vitamins?
- coenzymes
- hormones
- antioxidants
- electron transporters
“Coenzymes” - Enzyme cofactors - Vitamins A, K, and C, Thiamin (B1), Niacin (B3), Riboflavin (B2), Vitamin B6 (pyridoxine), Biotin (B7), Pantothenic acid (B5), Folate (B9), and Vitamin B12 (cobalamin)
Biological antioxidants - Vitamins E & C
Cofactors in metabolic oxidation-reduction reactions - Vitamins E, K and C, Niacin (B3), Riboflavin (B2), and Pantothenic acid (B5)
Hormones - Vitamins A & D
Photoreceptor in vision - Vitamin A
In the experimental phases of nutrition, what two key tools were necessary for the discovery of vitamins?
animal model
purified diet
In the late 19th century, most diseases were thought to result from what?
Germ theory of disease - states that microorganisms known as pathogens or “germs” can lead to disease
According to Dr. Takaki of the Japanese navy in the late 19th century, beriberi was first thought to be due to a deficiency of what diet component?
insufficient dietary protein
Be able to state, in general terms, how the “antiberiberi factor” was discovered by Eijkman.
Pekalharing conducted an animal study to identify the poison that was believed to be causing beriberi.
Animals used in this study were monkeys, rabbits, and dogs.
They were giving the animal’s culture organisms (blood smears) from patients who had beriberi via vaccinations.
The only finding was that adverse effects were found at the site of injection after repeated use. (still believed to be infectious in origin)
Eijkman conducted a further study with chickens to try to identify the origin/cause of beriberi. Over time, he observed that the chickens (both those that received the treatment and those that did not) were showing symptoms of change such as weight loss, staggering gait, difficulty standing, and even death.
They also showed degeneration of the peripheral nerves (specifically in the legs)via autopsy (which explains the change in gait and difficulty standing).
There was a sudden absence of the disease and the only change that occurred over this time period was a change in the diet due to a shipment issue. The chickens were originally being fed polished rice which took away the source of rice husks (which is rich in thiamine - B1). They were now being fed unpolished rice which therefore halted their development of neurological symptoms.
The same results were repeated in monkeys and eventually, human trials determining the beriberi-producing diets “lacked a certain substance of importance in the metabolism of the CNS.” (Gerrit Grijns).
In 1929, Sir Fredrick Gowland Hopkins shared the Nobel Prize with Christian Eijkman. What was the contribution of Hopkins to the discovery of vitamins?
Hopkins saw connections between the accessory factors and the deficiency diseases.
“No animal can live on a mixture of pure protein, fat, and carbohydrate, and even when the necessary inorganic material is carefully supplied the animal still cannot flourish. The animal is adjusted to live either on plant tissues or the tissues of other animals, and these contain countless substances other than protein, carbohydrates, and fats. In diseases such as rickets, and particularly scurvy, we have had for years knowledge of a dietetic factor; but though we know how to benefit these conditions empirically, the real errors in the diet are to this day quite obscure… They are, however, certainly of the kind which comprises these minimal qualitative factors that I am considering.”
Where does the word “vitamin” come from?
Who coined the term vitamin?
“Vital” “Amine”
Vital - pertaining to life
Amine - an organic base and therefore nitrogenous in nature
Casimir Funk
What was so revolutionary about the concept of vitamins, especially as they related to disease?
They suggested that there were other minute amounts of nutrients available in certain foods that were vital for life. This took away from the idea that the germ theory was the only cause for disease.
It changed the entire framework for diet-related science and treatment.
Where did the term “vitamin B” come from?
Vitamin B was named after the concept of a vitamine was generalized to also include non-nitrogenous compounds, thus the antipolyneuritis vitamine became “Vitamin B”
When they were separated into water-soluble and fat-soluble vitamins
Vitamin A = fat-soluble
B vitamins = water-soluble
Where did the term “thiamin” come from?
Thiamin was named by R.R. Williams I 1932 due to the chemical structure.
Thios is the Greek word for sulfur.
Thiamin is known as the vitamin containing sulfur.
