VITAMINS - The 13 Micronutrients Required by Human Metabolism

VITAMINS                                     

   A vitamin is an organic molecule (or related set of molecules) that is an essential micronutrient which an organism needs in small quantities for the proper functioning of its metabolism. Essential nutrients cannot be synthesized in the organism, either at all or not in sufficient quantities, and therefore must be obtained through the diet.

The thirteen vitamins required by human metabolism are : vitamin A ; vitamin B1 (thiamine) ; vitamin B2 (riboflavin) ; vitamin B3 (niacin) ; vitamin B5 (pantothenic acid) ; vitamin B6 (pyridoxine) ; vitamin B7 (biotin) ; vitamin B9 (folic acid or folate) ; vitamin B12 (cobalamins) ; vitamin C (ascorbic acid) ; vitamin D (calciferols) ; vitamin E (tocopherols and tocotrienols) ; and vitamin K (quinones).

Before 1935, the only source of vitamins was from food. If intake of vitamins was lacking, the result was vitamin deficiency and consequent deficiency diseases. Then, commercially produced tablets of yeast-extract vitamin B complex and semi-synthetic vitamin C became available. This was followed in the 1950s by the mass production and marketing of vitamin supplements, including multivitamins, to prevent vitamin deficiencies in the general population.

Governments mandated addition of vitamins to staple foods such as flour or milk, referred to as food fortification, to prevent deficiencies. Recommendations for folic acid supplementation during pregnancy reduced risk of infant neural tube defects. Although reducing incidence of vitamin deficiencies clearly has benefits, supplementation is thought to be of little value for healthy people who are consuming a vitamin-adequate diet.

FAST FACTS ON VITAMINS                     

        Here are some key points about vitamins. More detail and supporting information is in the main article.

-       There are 13 known vitamins.

-       Vitamins are either water-soluble or fat-soluble.

-       Fat-soluble vitamins are easier for the body to store than water-soluble.

-       Vitamins always contain carbon, so they are described as "organic".

-       Food is the best source of vitamins, but some people may be advised by a physician to use supplements.

VITAMINS SOLUBILITY                          

Vitamins are either fat-soluble or water-soluble.

Fat - Soluble Vitamins

      Fat-soluble vitamins are stored in the fatty tissues of the body and the liver. Vitamins A, D, E, and K are 4 fat-soluble vitamins. These are easier to store than water-soluble vitamins, and they can stay in the body as reserves for days, and sometimes months. Fat-soluble vitamins are absorbed through the intestinal tract with the help of fats, or lipids.

Water - Soluble Vitamins

      Water-soluble vitamins do not stay in the body for long. The body cannot store them, and they are soon excreted in urine. Because of this, water-soluble vitamins need to be replaced more often than fat-soluble ones. There are nine water-soluble vitamins. Vitamin C and all the Vitamin Bs are water soluble vitamins. Although, the body keeps a small reserve of these vitamins, they have to be taken on a regular basis to prevent shortage in the body. Vitamin B12 is the only water-soluble vitamin that can be stored in the liver for many years.

LISTING OF VITAMINS                         

1. VITAMIN A :

[ RETINOIDS AND CAROTENE (includes retinol, retinal, retinyl esters, and retinoic acid and are also referred to as "preformed" vitamin A. Beta carotene can easily be converted to vitamin A as needed) ]

    - Solubility :  Fat

    - Deficiency Disease :  Night blindness, hyperkeratosis, and keratomalacia

    - Benefits :  Essential for vision Lycopene may lower prostate cancer risk. Keeps tissues and skin healthy. Plays an important role in bone growth and in the immune system. Diets rich in the carotenoids alpha carotene and lycopene seem to lower lung cancer risk. Carotenoids act as antioxidants. Foods rich in the carotenoids lutein and zeaxanthin may protect against cataracts.

    - Overdose Syndrome/Symptoms :  Hypervitaminosis A

    - Good Food Sources :  Fish ; liver and dairy products ; orange ; ripe yellow fruits ; leafy vegetables ;  squash ; spinach ; beef liver ; eggs ; shrimp ; fortified milk ; butter ; cheddar cheese ; swiss cheese ; sweet potatoes ; carrots ; pumpkins ; mangoes ; turnip greens

2. VITAMIN B₁ :

[ THIAMIN ]

    - Solubility :  Water

    - Deficiency Disease :  Beriberi, Wernicke-Korsakoff syndrome

    - Benefits :  Helps convert food into energy. Needed for healthy skin, hair, muscles, and brain and is critical for nerve function.

    - Overdose Syndrome/Symptoms :  Drowsiness and muscle relaxation

    - Good Food Sources :  Pork ; oatmeal ; brown rice ; vegetables ; potatoes ; eggs ; ham ; soymilk ; watermelons ; acorn squash

3. VITAMIN B₂ :

[ RIBOFLAVIN ]

    - Solubility :  Water

    - Deficiency Disease :  Ariboflavinosis, glossitis, angular stomatitis

    - Benefits :  Helps convert food into energy. Needed for healthy skin, hair, blood, and brain.

    - Good Food Sources :  Bananas ; green beans ; asparagus ; milk ; eggs ; yogurt ; cheese ; meats ; green leafy vegetables ; whole and enriched grains and cereals

4. VITAMIN B₃ :

[ NIACIN (nicotinic acid) ]

    - Solubility :  Water

    - Deficiency Disease :  Pellagra

    - Benefits :  Helps convert food into energy. Essential for healthy skin, blood cells, brain, and nervous system.

    - Overdose Syndrome/Symptoms :  Liver damage (doses > 2g/day) and other problems

    - Good Food Sources :  Meat ; fish ; eggs ; many vegetables ; mushrooms ; tree nuts ; poultry ; fortified and whole grains ; potatoes ; peanut butter

5. VITAMIN B₅ :

[ PANTOTHENIC ACID ]

    - Solubility :  Water

    - Deficiency Disease :  Paresthesia

    - Benefits :  Helps convert food into energy. Helps make lipids (fats), neurotransmitters, steroid hormones, and hemoglobin.

    - Overdose Syndrome/Symptoms :  Diarrhea; possibly nausea and heartburn.

    - Good Food Sources :  Meat ; broccoli ; avocados ; wide variety of nutritious foods,  including egg yolk ; whole grains ; mushrooms ; tomato products

6. VITAMIN B₆ :

[ PYRIDOXINE (pyridoxal, pyridoxine, pyridoxamine) ]

    - Solubility :  Water

    - Deficiency Disease :  Anemia, Peripheral neuropathy

    - Benefits :  Aids in lowering homocysteine levels and may reduce the risk of heart diseaseHelps convert tryptophan to niacin and serotonin, a neurotransmitter that plays key roles in sleep, appetite, and moods. Helps make red blood cells Influences cognitive abilities and immune function.

    - Overdose Syndrome/Symptoms :  Impairment of proprioception, nerve damage (doses > 100 mg/day)

    - Good Food Sources :  Meat ; vegetables ; tree nuts ; fish ; poultry ; legumes ; tofu and other soy products ; potatoes ; non-citrus fruits such as bananas and watermelons

7. VITAMIN B₇ :

[ BIOTIN ]

    - Solubility :  Water

    - Deficiency Disease :  Dermatitis, enteritis

    - Benefits :  Helps convert food into energy and synthesize glucose. Helps make and break down some fatty acids. Needed for healthy bones and hair.

    - Good Food Sources :  Raw egg yolk ; peanuts ; leafy green vegetables ; many foods including whole grains ; organ meats ; egg yolks ; soybeans ; and fish

8. VITAMIN B₉ :

[ FOLIC ACID (folate, folacin) ]

    - Solubility :  Water

    - Deficiency Disease :  Megaloblastic anemia and deficiency during pregnancy is associated with birth defects, such as neural tube defects

    - Benefits :  Vital for new cell creationHelps prevent brain and spine birth defects when taken early in pregnancy; should be taken regularly by all women of child-bearing age since women may not know they are pregnant in the first weeks of pregnancy. Can lower levels of homocysteine and may reduce heart disease risk May reduce risk for colon cancer. Offsets breast cancer risk among women who consume alcohol.

    - Overdose Syndrome/Symptoms :  May mask symptoms of vitamin B₁₂ deficiency; other effects.

    - Good Food Sources :  Leafy vegetables ; pasta ; bread ; cereal ; fortified grains and cereals ; asparagus ; okra ; spinach ; turnip greens ; broccoli ; legumes like black-eyed peas and chickpeas ; orange juice ; tomato juice

9. VITAMIN B₁₂ :

[ COBALAMIN ]

    - Solubility :  Water

    - Deficiency Disease :  Pernicious anemia

    - Benefits :  Aids in lowering homocysteine levels and may lower the risk of heart disease. Assists in making new cells and breaking down some fatty acids and amino acids. Protects nerve cells and encourages their normal growth Helps make red blood cells and DNA.

    - Good Food Sources :  Meat ; poultry ; fish ; eggs ; milk ; cheese ; fortified cereals ; fortified soymilk

10. VITAMIN C :

[ ASCORBIC ACID ]

    - Solubility :  Water

    - Deficiency Disease :  Scurvy

    - Benefits :  Foods rich in vitamin C may lower the risk for some cancers, including those of the mouth, esophagus, stomach, and breast. Long-term use of supplemental vitamin C may protect against cataracts. Helps make collagen, a connective tissue that knits together wounds and supports blood vessel walls. Helps make the neurotransmitters serotonin and norepinephrine Acts as an antioxidant, neutralizing unstable molecules that can damage cells. Bolsters the immune system.

    - Good Food Sources :  Fruits and fruit juices (especially citrus) ; potatoes ; broccoli ; bell peppers ; spinach ; strawberries ; tomatoes ; brussels sprouts

11. VITAMIN D :

[ CALCIFEROL ]

    - Solubility :  Fat

    - Deficiency Disease :  Rickets and osteomalacia

    - Benefits :  Helps maintain normal blood levels of calcium and phosphorus, which strengthen bones. Helps form teeth and bones. Supplements can reduce the number of non-spinal fractures.

    - Overdose Syndrome/Symptoms :  Hypervitaminosis D

    - Good Food Sources :  Lichen ; eggs ; certain fish species such as sardines ; certain mushroom species such as shiitake ; fortified milk or margarine ; fortified cereals

12. VITAMIN E :

[ ALPHA-TOCOPHEROL ]

    - Solubility :  Fat

    - Deficiency Disease :  Deficiency is very rare; mild hemolytic anemia in newborn infants

    - Benefits :  Acts as an antioxidant, neutralizing unstable molecules that can damage cells. Protects vitamin A and certain lipids from damage. Diets rich in vitamin E may help prevent Alzheimer's disease.

    - Overdose Syndrome/Symptoms :  Possible increased incidence of congestive heart failure.

    - Good Food Sources :  Many fruits and vegetables ; nuts and seeds ; seed oils ; wide variety of foods, including vegetable oils ; salad dressings and margarines made with vegetable oils ; wheat germ ; leafy green vegetables ; whole grains

13. VITAMIN K :

[ PHYLLOQUINONE, MENADIONE ]

    - Solubility :  Fat

    - Deficiency Disease :  Bleeding diathesis

    - Benefits :  Activates proteins and calcium essential to blood clotting. May help prevent hip fractures

    - Overdose Syndrome/Symptoms :  Decreased anticoagulation effect of warfarin.

    - Good Food Sources :  Leafy green vegetables such as spinach ; egg yolks ; cabbage ; milk ; broccoli ; sprouts ; kale ; collards ; and other green vegetables

DIETARY SOURCES                            

        The 2015-2020 U.S. Dietary Guidelines focus on the overall diet as the best way to get enough nutrients for good health. Vitamins should come firstly from a balanced and varied diet with plenty of fruit and vegetables. However, in some cases, fortified foods and supplements may be appropriate.

A health professional may recommend vitamin supplements for people with certain conditions, during pregnancy, or for those on a restricted diet. Those taking supplements should take care not to exceed the stated maximum dose, as health problems can result. Some medications can interact with vitamin supplements, too, so it is important to talk to a healthcare provider before using supplements.

EFFECTS OF COOKING                         

        The USDA has conducted extensive studies on the percentage losses of various nutrients from different food types and cooking methods. Some vitamins may become more "bio-available" – that is, usable by the body – when foods are cooked. 

The table below shows whether various vitamins are susceptible to loss from heat—such as heat from boiling, steaming, frying, etc. The effect of cutting vegetables can be seen from exposure to air and light.

Water-soluble vitamins such as B and C dissolve into the water when a vegetable is boiled, and are then lost when the water is discarded.

Vitamin	Soluble in Water	Stable to Air Exposure	Stable to Light Exposure	Stable to Heat Exposure
Vitamin A	no	partially	partially	relatively stable
Vitamin C	very unstable	yes	no	no
Vitamin D	no	no	no	no
Vitamin E	no	yes	yes	no
Vitamin K	no	no	yes	no
Thiamine (B1)	highly	no	?	> 100 °C
Riboflavin (B2)	slightly	no	in solution	no
Niacin (B3)	yes	no	no	no
Pantothenic Acid (B5)	quite stable	no	no	yes
Vitamin B6	yes	?	yes	?
Biotin (B7)	somewhat	?	?	no
Folic Acid (B9)	yes	?	when dry	at high temp
Cobalamin (B12)	yes	?	yes	no

RECOMMENDED LEVELS                        

        In setting human nutrient guidelines, government organizations do not necessarily agree on amounts needed to avoid deficiency or maximum amounts to avoid the risk of toxicity.

The table below shows U.S. Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for vitamins, PRIs for the European Union (same concept as RDAs), followed by what three government organizations deem to be the safe upper intake.

RDAs are set higher than EARs to cover people with higher than average needs. Adequate Intakes (AIs) are set when there is not sufficient information to establish EARs and RDAs. Governments are slow to revise information of this nature.

For the U.S. values, with the exception of calcium and vitamin D, all of the data date to 1997-2004.

Nutrient	U.S. EAR	Highest U.S. RDA or AI	Highest EU PRI or AI	Upper limit (UL)			Unit
				U.S.	EU	Japan
Vitamin A	625	900	1300	3000	3000	2700	µg
Vitamin C	75	90	155	2000	ND	ND	mg
Vitamin D	10	15	15	100	100	100	µg
Vitamin K	NE	120	70	ND	ND	ND	µg
α-tocopherol (Vitamin E)	12	15	13	1000	300	650-900	mg
Thiamin (Vitamin B1)	1.0	1.2	0.1 mg/MJ	ND	ND	ND	mg
Riboflavin (Vitamin B2)	1.1	1.3	2.0	ND	ND	ND	mg
Niacin (Vitamin B3)	12	16	1.6 mg/MJ	35	10	60-85	mg
Pantothenic acid (Vitamin B5)	NE	5	7	ND	ND	ND	mg
Vitamin B6	1.1	1.3	1.8	100	25	40-60	mg
Biotin (Vitamin B7)	NE	30	45	ND	ND	ND	µg
Folate (Vitamin B9)	320	400	600	1000	1000	900-1000	µg
Cyanocobalamin (Vitamin B12)	2.0	2.4	5.0	ND	ND	ND	µg

EAR US :-  Estimated Average Requirements.

RDA US :-  Recommended Dietary Allowances; higher for adults than for children, and may be even higher for women who are pregnant or lactating.

AI US and EFSA :-  Adequate Intake; AIs established when there is not sufficient information to set EARs and RDAs.

PRI :- Population Reference Intake is European Union equivalent of RDA; higher for adults than for children, and may be even higher for women who are pregnant or lactating. For Thiamin and Niacin the PRIs are expressed as amounts per MJ of calories consumed. MJ = megajoule = 239 food calories.

UL or Upper Limit :-  Tolerable upper intake levels.

ND ULs have not been determined.

NE EARs have not been established.

SUPPLEMENTATION                            

        “Nutritionists recommend food first because food provides a variety of vitamins and minerals and also dietary factors that is not found in a vitamin or mineral supplement,” said Penny Kris Etherton (Ph.D., R.D.) and Distinguished Professor of Nutrition at the Pennsylvania State University’s College of Health and Human Development.

While diet is the key to getting the best vitamins and minerals, supplements can help. For instance, if you’re doing your best to eat healthy foods but still are deficient in some areas, supplements can help. The key is to ensure they’re taken in addition to healthy diet choices and nutrient-dense foods. They’re supplements, not replacements. Only use the supplements if your healthcare professional has recommended them.

“A supplement will generally provide 100 percent of the daily recommended allowance for all vitamins and minerals,” Kris-Etherton said. “Therefore, many nutritionists will agree that a supplement is OK if nutrient needs are not being met by a healthy food-based diet.”

Dietary supplements are regulated by the U.S. Food and Drug Administration (FDA) as foods, not as drugs. The label may claim certain health benefits. But unlike medicines, supplements can’t claim to cure, treat or prevent a disease.

Evidence does suggest that some supplements can enhance health in different ways. The most popular nutrient supplements are multivitamins, calcium and vitamins B, vitamin C and vitamin D. Calcium supports bone health, and vitamin D helps the body absorb calcium. Vitamins C and E are antioxidants— molecules that prevent cell damage and help to maintain health.

Vitamin B12 keeps nerve and blood cells healthy. “Vitamin B12 mostly comes from meat, fish and dairy foods, so vegans may consider taking a supplement to be sure to get enough of it,” Haggans says.

Research suggests that fish oil can promote heart health. Of the supplements not derived from vitamins and minerals, Hopp says, “fish oil probably has the most scientific evidence to support its use.”

Some people need vitamin supplements because they have particular medical conditions that can lead to deficiencies. People who do not have a regular balanced diet— because they are poor, abuse alcohol, or have dietary restrictions (like being vegans), for example, may well need particular vitamin pills. The same is true for people with various gut conditions, like Crohn's disease, celiac disease, chronic diarrhea, or gastric bypass surgery that interfere with the absorption of vitamins in food. People on dialysis for kidney failure need vitamin supplements. Adults of all ages, who get very little exposure to sunlight, for example, those who are homebound or in an institution, may need vitamin D supplements.