Blood Nutrients: Iron, Folate and B12

Question 1

When is folic acid referred to as folate rather than folic acid?

Answer 1

Folic acid is a stable molecule used in food fortification and supplements. Folate is present in food and in body tissue. The natural form of folate in food is more complex and requires adequate digestion. Several forms of folate is used in cellular processes (TH4, 5-methyl TH4, etc.)

Question 2

Describe the one biochemical function of folate and name the important biomolecules for whose 
metabolism folate is critical.

Answer 2

One-carbon metabolism, transfer of
1. Methyl (-CH3) groups

2. Methylene (-CH2-) groups

3. Formyl (-CH=O) groups

4. Formimino (-CH=NH) groups
5. Methenyl (-CH=) groups
Critical to nucleic acid and amino acid metabolism
1. Synthesis DNA and RNA
2. Protective methylation of DNA and RNA
3. Catabolism of homocysteine

Question 3

In what situations does folate deficiency occur?

Answer 3

Folate deficiency was once called the most common vitamin deficiency. It is no longer due to food fortification. It is now due mostly to increased tissue demands, malabsorption, and effects of some medications.

Question 4

What type of anemia occurs as a result of folate deficiency?

Answer 4

Macrocytic anemia

- megaloblasts
- hypersegmented neutrophils

Question 5

What vitamin deficiency results in the same type of anemia as does folate deficiency?

Answer 5

Symptoms are similar to iron or B12 deficiency

Question 6

Is the RDA for folate intended to help maintain normal blood homocysteine levels and prevent 
neural tube defects during pregnancy?

Answer 6

The RDA is based on maintaining “adequate” tissue levels. It is NOT on optimal prevention of birth defects, which may require higher intake. It is NOT on maintaining lowest homocysteine levels.

Question 7

Why is it necessary to translate micrograms of folate or folic acid into Dietary Folate Equivalents?

Answer 7

It is necessary because it is needed to account for greater bioavailability of folic acid compared to more complex food folate.

Question 8

What types of birth defects are associated with folic acid insufficiency?

Answer 8

Effective for neural tube defects only with periconceptional use (as opposed to use after pregnancy diagnosis) because the neural tube develops soon after conception. (Example from slide: spina bifida)

Question 9

By how much does the folate RDA for pregnancy differ from the RDA for non-pregnant adult 
women?

Answer 9

The requirement for folate increases 50% during pregnancy.

Question 10

When must folic acid be taken to effectively reduce the risk of birth defects?

Answer 10

Folic acid must be taken before conception because the neural tube develops soon after conception.

Question 11

Explain how gene polymorphism can change folate requirements.

Answer 11

Individuals with folate-related gene polymorphism may have higher folate requirements. Interactions between folate and the genome are reciprocal; polymorphisms in key genes influence nutritional requirements, indicating that dietary folate adequacy likely exerts selective pressure and thereby influences genetic variation. Individualizing folic acid dietary recommendations necessitates a detailed understanding of all genetic and physiological variables that influence the interaction of folate with the genome and their relationship to the disease process.

Question 12

What foods are now fortified with folic acid as a result of recent legislation?

Answer 12

It is mandated in refined grain products. (Since then, population homocysteine levels and neural tube birth defects have declined). Food types include: fortified breakfast cereal, orange juice (from concentrate), spinach (cooked), asparagus (cooked), lentils (cooked), garbanzo beans (cooked), lima beans (cooked), bread, pasta (cooked), rice (cooked)

Question 13

What foods are naturally rich in folate?

Answer 13

Green leafy veggies (foliage), citrus juices, legumes

Question 14

What is the amount of supplemental folic acid that requires a prescription? What is the concern that 
led to restrictions on non-prescription potencies of folic acid supplements?

Answer 14

Amount restricted to <1000 mcg per dose due to concerns about detecting B12 deficiency. When extra folate is available, B12 is less needed for recycling methyl-folate back to the active form for DNA synthesis. Therefore, high intake of folic acid could “mask” the evidence (anemia) of B12 deficiency.

Question 15

Why is taking folic acid supplements as soon as the woman knows she is pregnant not the best 
strategy for preventing neural tube defects?

Answer 15

Because the neural tube develops soon after conception

Question 16

Describe the evidence linking folic acid, homocysteine, and cardiovascular disease.

Answer 16

Article 1: Hyperhomocysteinemia has been associated with other vascular effects such as atherothrombosis and endothelial dysfunction due to its auto-oxidative potential, thereby increasing the production of reactive oxygen species. Other effects may involve neurodegenerative diseases such as Alzheimer or dementia praecox of the elderly.

Article 2: A recent meta-analysis of clinical trials has confirmed that folic acid supplementation reduces the risk of stroke, particularly in individuals without a history of stroke. Although primarily aimed at reducing neural-tube defects, folic acid fortification may have an important role in the primary prevention of CVD via tHcy lowering.

Question 17

What are some explanations for why some B-vitamin trials have not shown a protective effect 
against heart disease?

Answer 17

Folic acid and other B-vitamins prevent vascular events in patients with genetic homocystinuria.

Impact on vascular disease risk in populations with milder hyperhomocysteinemia is unclear:

- does not seem to be helping patients with    preexisting vascular disease
- may reduce stroke risk in otherwise healthy people, especially those not using fortified foods

May help prevent first strokes

Question 18

How may adequate folate intake help prevent cancer? For which cancer is the role of folate most 
promising? What factors may affect the influence of folate on cancer risk?

Answer 18

Moderate intakes to prevent deficiency may help prevent breast and colorectal cancer. It is most promising for breast and colorectal cancer. Factors that may affect the influence of folate on cancer risk is alcohol drinkers and those with specific genetic polymorphisms
Factors continued:
-May depend on genetic individuality:
-Article 1: Folic acid holds a key position in DNA synthesis and mitosis as well as DNA methylation and regulation of gene expression. Folic acid deficiency has been associated with site- and gene specific DNA hypo- and hypermethylation. Furthermore thymidylate synthesis is restricted by folic acid deficiency which causes misincorporation of nucleotides and DNA strand breaks. Observational studies show that individuals with the homozygote genotype for the MTHFR (677C–>T) polymorphism are at higher risk when folic acid supply is low.

- May help migrate risk related to alcohol consumption:
	- Article 2: ethanol impedes the bioavailability of dietary folate and is known to 		inhibit select folate-dependent biochemical reactions.

- Most recent meta-analysis of RCT’s using large doses found neither benefit nor risk in 	the short term:
	- Article 3: Folic acid supplementation does not substantially increase or decrease 		incidence of site-specific cancer during the first 5 years of treatment. Fortification 	of flour and other cereal products involves doses of folic acid that are, on average, an order of magnitude smaller than the doses used in these trials.

Question 19

When might excessive folic acid intake increase cancer risk?

Answer 19

Too much later in life may support growth of existing precancerous lesions

Question 20

Explain the consequences of treating a vitamin B12 deficiency anemia with folic acid.

Answer 20

Upper level (UL) set at 1000mcg based on concerns about detecting B12 deficiency:

	- B12 deficiency is common in some   populations
	- Anemia is the easiest way to screen for B12 deficiency
	- Large doses of folic acid can correct anemia, though not other B12 deficiency pathologies

Question 21

How are folic acid and vitamin B12 interrelated?

Answer 21

The relationship between folate, vitamin B12, and two important biochemical pathways. We see folate in the form of the TH4-folate coenzyme contributing to nucleic acid synthesis, which supports cell division and cell growth. After this reaction, the resulting byproduct is the folate coenzyme 5-methyl TH4-folate, and this coenzyme is used along with vitamin B12 to convert homocysteine to methionine, which removes potentially hazardous homocysteine and produces methionine for use in methylation reactions and also produces a restored TH4-folate coenzyme that can participate again in nucleic acid synthesis. This is why both a lack of folate or a lack of B12 can similarly impair the nucleic acid synthesis required for cell division, which is why deficiencies of either vitamin can lead to insufficient production of mature red blood cells and anemia.

Question 22

What mineral is contained in the vitamin B12 molecule?

Answer 22

Contains cobalt; only biological function of this mineral

Question 23

Describe the necessary steps for dietary B12 absorption.

Answer 23

1. B12 in natural food is bound to dietary proteins, and protein digestion in the stomach and duodenum must be optimal to release B12 for further processing in the gut. However, free B12 in supplements and fortified foods needs no protein digestion.
2. When B12 is successfully released from food, it must then bind to intrinsic factor (IF), a protective glycoprotein secreted by the parietal cells of the stomach.
3. The B12-IF complex is required to activate a specialized absorption mechanism in the ileum, without which B12 cannot be efficiently absorbed.
4. In the absence of adequate intrinsic factor, B12 absorption declines to as low as 1%. However, oral megadoses can overcome this.

Question 24

Describe the important functions of vitamin B12.

Answer 24

-Recycling of activated folate for DNA synthesis
-Catabolism of homocysteine
Production S-adenosylmethionine, a major methyl donor in hundreds of reactions
-Cofactor for one other enzyme reaction only
-Affects nervous system, but mechanism in unclear

Question 25

List three major causes of vitamin B12 deficiency

Answer 25

1. Insufficient production of gastric hydrochloric acid
   - This condition is called food-bound vitamin B12 malabsorption and is much more common than pernicious anemia
   - B12 used in supplements and fortification is still normally absorbed since they are not bound to food components
2. Insufficient production of intrinsic factor (pernicious anemia)
   - Only 1% of B12 will be absorbed (but oral megadoses will still suffice to prevent anemia)
3. Other causes: malabsorption syndromes, acid suppressing drugs, vegan diets

Question 26

Which age group is at highest risk of vitamin B12 deficiency?

Answer 26

Elderly

Question 27

Explain the difference between pernicious anemia and food-bound B12 malabsorption.

Answer 27

• Anemia is indistinguishable from folate deficiency
  - Oral tissue signs is severe
  - Macrocytosis with megaloblasts

-Other signs/symptoms
-Elevated homocysteine
-Neurologic symptoms
-Probably due to myelin damage
-Can affect sensory, motor, cognition or mood
1. Peripheral neuropathy (numbness, paresthesias)
2. Myelopathy (loss of proprioception, vibration)
3. Cerebral dysfunction (memory loss, etc)
-Can occur without anemia
-Suspicious unexplained neurological symptoms should motivate testing
for low serum B12

-Serum B12 is the standard method of confirmation
-Measurement of metabolic byproducts of insufficient B12 coenzyme activity
may be more sensitive
a. Serum methylmalonic acid
b. Serum homocysteine

-Don’t assume normal CBC means normal B12 status

Question 28

Why may supplemental B12 be more bioavailable than food B12?

Answer 28

All B12 in nature is synthesized by bacteria

- Including gut bacteria in ruminant animals, but not in human gut
- Naturally-present in reliable amounts in animal based foods and fortified foods only
	- Bioavailability of B12 detected in fermented foods and 	other foods of plant origin is uncertain

Question 29

What special diet may result in a vitamin B12 deficiency?

Answer 29

Vegan

Question 30

What are the best vegetarian sources of vitamin B12?

Answer 30

B12 supplements or fortified foods

- Supplements include multiple vitamins, B-complex supplements, and vitamin B12 supplements
- There is no evidence that sublingual B12 is absorbed 	sublingually, although it will be absorbed by the usual mechanisms when swallowed.

Question 31

Drugs that have what kind of effect on stomach function may cause reduced vitamin B12 absorption?

Answer 31

Free B12 from all sources must then bind to intrinsic factor produced by the parietal cells of the stomach. The B12-intrinsic factor complex then travels to the ileum for absorption. Without adequate production of intrinsic factor, as in the disease called pernicious anemia, B12 absorption declines greatly, leading to deficiency. Recently, however, it has been recognized that even at very low absorption, large megadoses of vitamin B12 can be sufficient to prevent and even treat deficiency due to lack of intrinsic factor.

Question 32

What vitamin deficiency results in the same type of anemia as does B12 deficiency?

Answer 32

Folate

Question 33

How does high intake of folic acid make it difficult to diagnose a vitamin B12 deficiency?

Answer 33

The official Upper Level for folate did not consider cancer risk, but was set to 1000 mcg per day based on concerns about the potential effect of high-dose folic acid to make diagnosis of B12 deficiency difficult. Screening for anemia is a routine health exam and can easily detect a B12 deficiency anemia if folate intake is at typical levels. However, as the diagram pictured reminds us, the role of B12 in supporting red blood cell development is to recycle used folate back to its active form. When high doses of folic acid are consumed, recycling the vitamin becomes less important, and a B12 deficiency will not be reflected in low red blood cell production.

Question 34

What are the neurological signs associated with vitamin B12 deficiency?

Answer 34

The effects of B12 deficiency in the CNS has led to speculation that low B12 may be a factor in common cognitive and mood disorders

		- Article 1: cognition is associated with vitamin B-12 status across the 			normal range.  Pending the outcome of better trials, it is suggested that the elderly in particular should be encouraged to maintain a good, rather than 			just an adequate, vitamin B-12 status by dietary means.
		- Article 2: High levels of homocysteine are associated with cerebrovascular 			disease, monoamine neurotransmitters, and depression of mood.

The central nervous system signs that can develop with B12 deficiency sometimes resemble chronic mental disorders such as dementia or depression, and while low B12 is not a common cause of these disorders, it should be ruled out as a complicating factor in all cases.

Question 35

What blood metabolites may be elevated as a result of vitamin B12 deficiency?

Answer 35

Homocysteine

Question 36

What would be the best way to proceed clinically when a patient is diagnosed with megaloblastic 
anemia?

Answer 36

The anemia associated with significant folate deficiencies is a macrocytic or megaloblastic anemia, in which the red blood cells are large and immature. Neutrophils with extra lobes also result, and are another sign detectable when examining a blood sample. This appearance of the blood is identical in B12 deficiency, so additional testing is needed to determine the cause of a macrocytic megaloblastic anemia.

Question 37

At what age are individuals recommended to get vitamin B12 from fortified foods or supplements?

Answer 37

RDA assumes normal absorption

- 2.4 mcg/day for ages 14 and up

Question 38

Where in nature is vitamin B12 synthesized? How does this relate to potential food sources of 
B12?

Answer 38

B12 in natural food is bound to dietary proteins

  - Protein digestion is the stomach and duodenum must be optimal to release B12 for further processing in the gut.
        - -However, free B12 in supplements and fortified foods needs no protein digestion

Question 39

How much vitamin B12 is sufficient to produce a significant reduction in homocysteine levels?

Answer 39

500 mcg/day recommended for homocysteine reduction and treating deficiency in the elderly

Question 40

How does the average intake of vitamin B12 by young adults compare to the RDA?

Answer 40

B12 deficiency is not considered common in younger people, but is a serious problem among the elderly. B12 intake exceeds RDA in young adults and many older adults on Western diets.

Question 41

What are the possible mechanisms by which vitamin B12 deficiency might raise the risk of 
cognitive disorders such as Alzheimer’s disease?

Answer 41

There are many possible signs and symptoms of B12 deficiency, but most involve anemia and neurological dysfunction. Changes to the oral tissues as pictured probably occur only in extreme cases, and may be confused with other deficiencies. The macrocytic anemia and elevated homocysteine is identical to that found in folate deficiency, so testing directly for low serum B12 is usually necessary to distinguish between the two. B12 deficiency does uniquely affect myelinated nerves, which explains the wide range of possible neurological symptoms, including sensory or motor deficits, cognitive problems, or mood changes. Even more surprising may be that these neurological symptoms can occur even when anemia has not developed.

Question 42

How much of a 250 mcg dose of supplemental vitamin B12 will typically be absorbed by passive 
diffusion in the absence of intrinsic factor? How does this amount compare to the RDA for B12?

Answer 42

What are the causes of vitamin B12 deficiency? B12 deficiency is not considered common in younger people, but is a serious problem among the elderly. The problems in this age group are the increasing difficulty in digesting food-bound B12, and the increased incidence of intrinsic factor deficiency. The more common disorder is diminished gastric acid production, but this will only affect the bioavailability of food-bound B12, while supplemental and fortified B12 is still normally absorbed. For this reason, older people are recommended to get a daily source of supplemental or fortified B12. Pernicious anemia, caused by insufficient intrinsic factor production, is much less common, but it affects all forms of B12 and only large megadoses are enough to prevent deficiency. Other causes of deficiency that can occur at any age include malabsorption syndromes, drug effects, and B12-restricted diets.

The RDA assumes normals absorption except in the elderly. The RDA says 500mcg/day for homocysteine and in elderly. At least 1000 mcg/day for treating pernicious anemia

Question 43

Name the important heme-containing molecules in the body and describe their function.

Answer 43

Hemoglobin: oxygen-carrying protein in blood
Myoglobin: oxygen carrying protein in muscle
Cytochromes in mitochondria

Question 44

Explain the functional importance of iron possessing two oxidation states.

Answer 44

Ferrous (+2) or ferric (+3) ions
These two oxidation states permit iron to act as a cofactor in oxidation-reduction reactions.
Ferrous ion is absorbed in the intestines better
Ferric ion is transported and stored better

Question 45

What is the function of the peptide hormone hepcidin?

Answer 45

Hepcidin, a peptide hormone produced in the liver, helps in the regulation of iron absorption.

Question 46

What factors influence iron absorption?

Answer 46

Absorption is normally regulated to match losses via the peptide hormone, hepcidin.
Increased by: iron deficiency, growth and pregnancy, and food factors such as heme, vitamin C, and animal flesh proteins.
Decreased by: low HCl production and other GI pathologies, absorption inhibitors, oxalate, phytate from brans (outer coverings of whole grains) and legumes, polyphenols from tea, coffee, etc, and other divalent cations such as Ca2+.
Absorption varies from 3-35%, depending on all of the above factors.

Question 47

Describe the antioxidant and pro-oxidant functions of iron.

Answer 47

Antioxidants: Catalase and peroxidase vs reactive peroxides.
Pro-oxidants: Cell-killing functions of white blood cells utilize iron against infections and dysplasias. There are also potentially hazardous effects of excess iron on normal body tissue.

Question 48

Describe the three levels of iron deficiency. What tests would detect the earliest deficiency stages?

Answer 48

Mild Deficiency: tissue stores of iron become depleted and the ferritin (good choice for early detection, but will be falsely elevated when infection or severe inflammation is present) and transferrin saturation (good to combine with ferritin test when infection or severe inflammation is present because these conditions have the opposite effect on transferrin saturation) tests are good early indicators of deficiency at this stage.

Moderate Deficiency: tissues that depend on iron will begin to experience a decline in function, and plasma iron will decline while serum transferrin receptor rises.

Severe Deficiency: when hemoglobin and red blood cell production decline severely enough to lead to an anemia featuring abnormally small and pale red blood cells. A complete blood count (CBC) only reveals advanced iron deficiency.

Question 49

Describe the appearance of red blood cells in iron deficiency anemia.

Answer 49

Abnormally small and pale red blood cells (microcytosis and hypochromia)

Question 50

When older people develop iron deficiency, what potentially fatal disease may be the cause?

Answer 50

Gastrointestinal cancer (bottom of pg 3)?
“Most anemia in older individuals results from iron deficiency, chronic inflammation, or chronic kidney disease, or it may be unexplained.” (bottom of pg 5)?

Question 51

List the symptoms associated with iron deficiency.

Answer 51

Oxygen/Energy deficits: fatigue, impaired athletic performance and work capacity (even before anemia develops)

Cardiopulmonary compensation: rapid heart rate, rapid breathing
Trying to increase blood circulation and oxygenation when hemoglobin is in short supply

Tissue degeneration: nail beds (koilonychia), oral tissues (glossitis, angular stomatitis
Result of impaired energy production and reduced activity of iron-containing enzymes essential to tissue growth

Question 52

Which individuals are at increased risk of iron deficiency?

Answer 52

Increased requirements: Growth- ages 6 months to 4 years, adolescence
Pregnancy- 50% higher requirement

Increased losses: Chronic blood loss- pre-menopausal women
  	  GI losses (polyps or tumors)
  		  Athletes engaging in regularly intense exercise (30% higher requirement)

Reduced absorption: Vegetarians- bioavailability reduced almost 50%
		  GI disease (celiac disease)

Question 53

Why might vegetarians be at greater risk for iron deficiency than non-vegetarians?

Answer 53

The absorption of both iron and zinc is lower with vegetarian diets, which is why the requirements are set at almost 50% higher.

Question 54

Why might certain athletes be at greater risk for iron deficiency?

Answer 54

Athletes who are in intense training: small but persistent blood loss that occurs from exercise-related microtrauma to the GI tract, the GU tract, and even the red blood cells circulating under the heel of the foot.

Question 55

How much greater are the iron requirements of menstruating and pregnant adult women compared to other adults?

Answer 55

Menstruating: about 3mg more per day (18mg/day)
Prego: almost 2x the amount per day (27mg/day)

Question 56

List the enhancers and the inhibitors of non-heme iron absorption.

Answer 56

Non-heme iron: found in both animal and plant-based foods, fortified foods, and supplements

Dietary inhibitors: Phytate in legumes and whole grains
Oxalate in spinach
Polyphenols in fruits, veggies, tea, coffee, wine

Dietary enhancers: Vitamin C and other organic acids
Animal protein

Question 57

Which beverages are not advisable to drink with meals because they contain inhibitors of non-heme iron absorption?

Answer 57

Tea, coffee, and wine

Question 58

Which adults tend to consume less iron than the RDA?

Answer 58

Toddlers?

Question 59

Which foods are good sources of well-absorbed iron?

Answer 59

Protein/amino acids containing heme iron

Food acids that reduce dietary ferric iron to the more absorbable ferrous iron
Ascorbic acid- high in citrus, tomatoes
Citric, malic, tartaric and lactic acid, found mostly in fruits and vegetables

Some fermentation products

Question 60

Which foods are good sources of iron, but the iron is not well-absorbed?

Answer 60

Polyphenols such as tannins and other compounds present in foods and beverages
Especially tea, coffee, chocolate and some herbal infusions

Phytic acid- (phytates) in whole grains, lefumes, rice (sprouting or leavening with yeast reduces phytate content)

Soy protein, egg, fiber, calcium

Question 61

What are the possible side effects of therapeutic levels of iron supplements? What measures may be taken to minimize these effects?

Answer 61

Side effects: GI upset
Minimize: Using other iron compounds, taking iron with meals, or dividing doses throughout the day may reduce the risk of this side effect.

Question 62

Under what conditions may iron interact with minerals such as zinc such that absorption is impaired?

Answer 62

Iron can antagonize the absorption of zinc but only when taken in large amounts with zinc on an empty stomach
Calcium can antagonize the absorption of iron but not enough to cause depletion of iron stores in the short term (3 months)

Question 63

What aspect of child development may be impacted by iron status?

Answer 63

Some research has shown iron deficiency affects the developing brain, so it is important to ensure adequate iron intake in children of all ages, and to assess iron status in those who appear to have learning difficulties.

Question 64

Explain the controversy regarding iron supplementation during pregnancy.

Answer 64

Iron is present in all pre-natal supplements, but actual role of iron in pregnancy outcome is still debated. Iron deficiency anemia is a risk factor for pregnancy complications, but excess iron may also be a risk factor. Only women with low hemoglobin levels should take pre-natal iron.

Question 65

Why may iron be both helpful and detrimental to a person suffering from an infection?

Answer 65

An impaired immune system needs iron, but so do pathogens. The normal body response to infection includes removing iron from circulation. However, some infections (e.g. malaria) may be worsened by iron.

Question 66

What genetic and hereditary conditions can contribute to the occurrence of iron overload?

Answer 66

Hemochromatosis: genetic disorder of excessive iron absorption, related to Northern European and African descent
Hereditary anemias (e.g. thalassemia, sickle cell anemia): the body tries to help defective RBC production by increasing iron absorption. Many cases of iron overload may be due to repeated transfusions or mistaken diagnosis and treatment of iron deficiency.

Question 67

What is the likelihood that iron from dietary or supplemental sources could increase the risk of cardiovascular diseases or certain cancers? How might this depend on individual differences in dietary sources or genetics?

Answer 67

Early research suggesting increased heart disease risk with higher iron levels in the body has not been confirmed by many subsequent studies, while risks for other diseases such as cancer and diabetes are somewhat more consistent. It may be that people with poorer regulation of iron absorption may be more susceptible to the damaging effects of iron, or that diets high in heme iron from meat are most likely to be a problem. One thing is clear, there is no benefit to increased iron intake by people who are not deficient, whereas there is potential risk, so iron consumption should only be as much as necessary to prevent deficiency.