Availability

The presence of micronutrients does not ensure availability for metabolic processes. Mineral availability is reduced by the presence of phytic acid and phytates. Phytic acid (myoinositol 1,2,3,4,5,6-hexakis dihydrogen phosphate) accounts for a substantial proportion (usually over 50%) of the total phosphorus in cereals, and this phosphorus is not fully available for digestion and absorption. Phytic acid accounts for about 1% of whole-grain cereals. However, phytic

Table 12 Mineral and vitamin contents of barley, oat and rye products; representative values per 100 g fresh weight (water contents as per Table 5)

Pearl barley, Pearl barley, Oatmeal Oatmeal, Oat Wholemeal Rye Rye uncooked boileda porridge? bran rye flour crispbread bread

Table 12 Mineral and vitamin contents of barley, oat and rye products; representative values per 100 g fresh weight (water contents as per Table 5)

Sodium (mg)

3

1

21

560

4

1

220

580

Potassium (mg)

270

92

360

46

586

410

500

190

Calcium (mg)

20

7

54

7

79

32

45

80

Magnesium (mg)

65

22

110

18

241

92

100

48

Phosphorus (mg)

210

71

380

47

723

360

310

160

Iron (mg)

3.0

1.0

4.0

0.5

6.1

2.7

3.5

2.5

Zinc (mg)

2.1

0.7

3.3

0.4

4.2

3.0

3.0

1.3

Copper (mg)

0.40

0.14

0.36

0.03

0.31

0.42

0.38

0.18

Manganese (mg)

1.30

0.44

3.80

0.46

5.80

0.68

3.50

1.00

Vitamin E (mg)

0.40

0.10

1.60

0.21

3.30

1.60

0.50

1.20

Thiamin (mg)

0.12

0.02

0.70

0.06

1.10

0.40

0.28

0.29

Riboflavin (mg)

0.05

0.01

0.10

0.01

0.18

0.22

0.14

0.05

Niacin (mg)

2.5

0.5

0.9

0.1

0.9

1.0

1.1

2.3

Vitamin B6 (mg)

0.22

0.04

0.23

0.01

0.15

0.35

0.29

0.09

Pantothenate (mg)

0.5

0.1

1.1

0.1

1.0

1.0

1.1

0.5

Folate (mg)

20

3

60

4

37

78

35

24

Biotin (mg)

n/a

trace

21

2

38

6

7

n/a

aUnsalted water. bMade with water and salt. n/a, no data available.

Table 13 Mineral and vitamin contents of sorghum and millets; representative values per 100 g fresh weight (water contents as per Table 6)

Millets

Table 13 Mineral and vitamin contents of sorghum and millets; representative values per 100 g fresh weight (water contents as per Table 6)

Millets

Sorghum

Pearl

Foxtail

Proso

Finger

Japanese

Fonio

Sodium (mg)

20.5

7.4

6.8

9.4

15.9

n/a

15.0

Potassium (mg)

285

432

243

215

367

n/a

160

Calcium (mg)

28

39

22

14

321

32

30

Magnesium (mg)

156

125

116

104

129

n/a

40

Phosphorus (mg)

291

335

268

220

251

330

175

Iron (mg)

5.1

8.4

5.3

4.7

4.6

4.3

6.0

Zinc (mg)

2.2

3.2

1.9

1.6

1.3

n/a

3.0

Copper (mg)

0.98

0.50

0.71

1.15

0.53

n/a

1.6

Manganese (mg)

1.84

1.45

1.87

1.64

1.19

n/a

3.0

Vitamin E (mg)

1.13

1.69

2.75

1.94

n/a

n/a

n/a

Thiamin (mg)

0.35

0.34

0.51

0.39

0.35

0.33

0.47

Riboflavin (mg)

0.15

0.17

0.10

0.19

0.10

0.10

0.10

Niacin (mg)

3.8

2.0

3.1

1.3

4.0

n/a

1.9

Vitamin B6 (mg)

0.50

n/a

n/a

n/a

n/a

n/a

n/a

Pantothenate (mg)

1.2

1.1

0.7

1.0

n/a

n/a

n/a

Folate (mg)

19

63

18

n/a

n/a

n/a

n/a

Biotin (mg)

42

n/a

n/a

n/a

n/a

n/a

n/a

n/a, no data available.

n/a, no data available.

acid is concentrated in the bran and germ fractions. Wheat bran and germ contain 3-4% phytic acid, while white endosperm flour contains 0.1-0.2%. Phytic acid reacts with calcium, magnesium, iron, zinc, and copper to form phytates, a process that renders these minerals unavailable for absorption.

Vitamin B6 and niacin in cereals are also of limited availability. The niacin deficiency disease pellagra may develop where maize grits are the dietary staple. However, niacin, which is present in a bound form, is made available by alkali treatment in traditional maize tortilla production. Niacin can also be synthesized in the body from tryptophan; 60 mg of tryptophan yields 1 mg of niacin.

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