Occurrence and Requirements

Ascorbic acid is ubiquitous in nature since plants, as well as many of the animals eaten by humans, can synthesize it (A). The most important sources in Western nutrition are fruits, vegetables, and potatoes.

Oxidation during storage renders ascorbic acid inactive, a process enhanced by high temperatures, as well as by the presence of catalysts like iron. In acidic environments, as in certain fruits, vitamin C is relatively stable. Here is a rule of thumb: the more inactive, compact, and acidic the food, and the colder and more humid the environment, the lower the losses. For instance, green peas lose about 4 % vitamin C per day in the fridge; at room temperature they lose 12%. During modern storage at controlled temperatures (CA storage), losses are minimized: at 3° C, high CO2 and low O2 content in the air, daily vitamin C losses range between 0.1-0.3 %. In sterilized, fully preserved, or deep-frozen foods, losses can be enormous. Immediate blanching can be used to prevent losses in fruit and vegetables since this inhibits vitamin C-destroying enzymes in the outer layers. Up to an additional 50% of vitamin C is lost in further processing; in particular, cooking not only renders vitamin C inactive but leaches it into the cooking water.

Recommended intakes (B) for vitamin C are the subject of considerable controversy; 100-200 mg/d are needed to maintain maximal concentrations in plasma and tissues. Symptoms of vitamin C deficiency—which are used to establish the recommendations—can be safely prevented with 100 mg/d. Pre-emies and neonates have an increased requirement of 6 mg/kg body weight.

During pregnancy and lactation, during antibiotic therapy, and under hemodia-lysis, requirements are also elevated. It has been known for a long time that smokers have lower plasma vitamin C levels. This is likely to be caused by an increased need due to free radical formation. Therefore, the new recommended intakes are higher for smokers. On average, vitamin C intake is adequate in children and teenagers, largely due to consumption of fruit juices and vitaminized fruit drinks. Insufficient intake is common in the elderly. Vitamin C hypervitaminosis is rare and occurs only from megadosing. Symptoms are mainly diarrhea, but also precipitation of sickle-cell crises, and kidney stones (long-term overuse). The UL is 2000 mg/d for adults.

Scurvy is the classic vitamin C deficiency symptom (C). Earliest stages are characterized by bleeding of mucosal membranes and pain in more intensely used muscles, particularly calf muscles. After a few months, the skin turns pale-yellowish and follicular hyperkeratosis develops. Bleeding into the musculature begins in the frequently used muscles such as behind the knees—in the bedridden, the back and bottom. Gingivitis (inflammation of periodontal tissues) practically always accompanies vitamin C deficiency.

- A. Occurrence and Daily Requirement-

The daily requirement of 100 mg vitamin C is contained in:

9g rosehips 60g tangerines, oranges, lemons, limes, grapefruits

900g apricots, peaches

1.5 kg pears

800g apples, cherries 70g bell peppers 80g broccoli, brussels sprouts

- A. Occurrence and Daily Requirement-

The daily requirement of 100 mg vitamin C is contained in:

1.5 kg pears

800g apples, cherries 70g bell peppers 80g broccoli, brussels sprouts

Bell Pepers Nutrient Deficenciesw

1.3 kg carrots 650g potatoes

900g Belgian endives

250g radishes 250g bok choy, mache

250g Swiss chards, leeks

450g sauerkraut 200g spinach, kohlrabi 400 g tomatoes 100g fennel, kale

130g cauliflower i- B. Recommended Intakes (DRI/AI*, 2000) and UL —i

Life Stage and Gender Group

Age

(mg/d)

Vitamin (limol)

(mg/kg)

UL (mg/d)

Infants

0 - 6 mo 7-12 mo

40* 50*

227 256

~ 6* ~ 6*

No supplements

Children

1- 3 y 3 - 8 y

25

85 142

400 650

Adolescents

9 - 13 y

45

256

1200

Adolescent males

14- 18y

75

426

1800

Adolescent females

14- 18y

65

370

1800

Men

> 19 y

90

511

2000

Women

> 19 y

75

426

2000

Pregnancy

14 - 18 y 19 - 50 y

05 88

454 483

1800 2000

Lactation

14 - 18 y 19 - 50 y

115 120

568 682

1800 2000

C. Deficiency Symptoms

Typical extensive subcutaneous hemorrhage caused by vitamin C deficiency

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