5. Micronutrient Deficiencies

5.3. Zinc deficiency

The exact prevalence of zinc deficiency worldwide is not known, but is estimated to be similar to that of ID, which makes it an underrecognized public health problem. Zinc is essential for mammalian cell life, function, growth, differentiation, and replication. Yet it is one of the least apparent micronutrient deficiencies. Zinc plays a central role in protecting health and immune function of individuals, as a constituent of more than 200 enzymes and transcription proteins that modulate cell differentiation, nucleic acid synthesis, and the metabolism of proteins, lipids, and carbohydrates.

Zinc supplementation in children with deficiency has been shown to reduce the incidence and prevalence of diarrhea and severe lower respiratory tract infections. Supplementation with zinc also reduces the frequency of malaria infections.

Decreased growth velocity or stunted growth is a consistent and early outcome of even mild zinc deficiency in infants, children, and adolescents. Box 4 shows the multiple clinical features of zinc deficiency.

BOX 4. Clinical manifestations of zinc deficiency

  • Decreased growth velocity
  • Peri-orificial and acral skin lesions
    • Glossitis
    • Alopecia
    • Nail dystrophy
    • Dry inflamed scaly skin
  • Delayed sexual development
  • Erectile dysfunction
  • Behavioral abnormalities
  • Depressed mood
  • Photophobia and impaired ocular adaptation to darkness
  • Delayed wound, burn, and ulcer healing
  • Impaired or loss of taste
  • Low birth weight and prematurity

Risk factors for zinc deficiency include: insufficient dietary intake (low-protein diet); high phytate and/or fiber content in the diet; diarrhea and other malabsorption syndromes; intestinal parasitosis; hot and humid weather; and no breastfeeding.

Young children’s dietary intake of zinc appears to be inadequate in many developing countries and it has been estimated that 80% of women globally and 100% of women in developing countries, have zinc intakes inadequate to meet pregnancy needs. Food sources high in zinc are listed in Table 8 (page 19).

TABLE 8. Food sources high in selected vitamins and minerals

Vitamin A
Food sources, absorption inhibitors, and enhancers Plant foods high in vitamin A (carotenoids): Greens (spinach, chicory, endive, collard, watercress, mustard, beet, turnip, broccoli), leaves of Amarantus, Manioc/cassava leaves, Baobab leaves, carrot, pumpkin, orange flesh sweet potato (the other form is not so rich in vit A), squash (winter acorn, hubbard and butternut), peas, red hot chili and sweet peppers, mango, papaya, apricot, asparagus, tomato, prune, plum.

Preformed vitamin A from animal foods is found in mother’s milk, liver, fish-liver oils, butter, cheese, milk fat, eggs and vitamin A-fortified foods.
Iron
Food sources, absorption inhibitors, and enhancers Heme iron: Meat, fish, and poultry

Non-heme iron: Eggs, dried beans, green leafy vegetables, whole grains, legumes, seeds, dried fruits, cumin seeds, anise seeds, Néré (sumbala a traditionally fermented preparation used in sub-saharan africa with Nere seeds), african snail meat, curry, molase (do not encourage refined sugar), pain de singe (baobab fruit also rich in vit C), dried ants and iron-fortified foods

Absorption enhancers: Foods containing Vitamin C, other organic acids, and animal tissue

Absorption inhibitors: High phytate foods, such as maize, legumes, whole wheat, brown rice and unmilled sorghum. Foods high in tannins (polyphenol) such as tea and coffee
Folic acid
Food sources, absorption inhibitors, and enhancers Green leafy vegetables, such as spinach and romaine lettuce; pinto, kidney, and navy beans; peas; chicken giblets; liver; strawberries; citrus fruits and juices; peanut; whole grain breads, rolls, crackers, and cereals; and fortified cereals, pasta, rice, and flours
Niacin and tryptophan
Food sources, absorption inhibitors, and enhancers Niacin: Meat, poultry, fish, liver, peanuts (groundnuts), legumes, and yeast

Increases the bioavailability of niacin: Alkali processing

Tryptophan (metabolizes into niacin): Milk and eggs
Thiamine
Food sources, absorption inhibitors, and enhancers Thiamine content is very high in fish such as trout, salmon, tuna. Also in seeds such as sunflower seed. Also squash, soy beans and beans. Parboiled rice, whole grain flour and cereals, pulses, nuts, wheat germ, yeast extract, pork, liver, kidney, and vegetables, such as peas, asparagus, and okra

Absorption enhancers: Foods containing vitamin C

Absorption inhibitors: Tea, coffee, alcohol and folate deficiency, betle nut and Thiaminase in some fish and larvae. Also avoid rinsing rice too many times.
Vitamin C (ascorbic acid)
Food sources, absorption inhibitors, and enhancers All citrus juices and fruits, such as orange, lemon, lime, kiwi, guava, and grapefruit; cabbage; tomato; berries; potatoes with skins; green and red peppers; broccoli; spinach; and brussels sprouts
Vitamin D
Food sources, absorption inhibitors, and enhancers Dairy products, fortified milk, fortified cereals, eggs, oily fish, such as herring, salmon, or tuna, and fish liver oils. Try to ensure adequate sun exposure.
Iodine
Food sources, absorption inhibitors, and enhancers Fortified foods, such as iodized salt are required in areas of the world that have an inadequate amount of iodine in the soil
Zinc
Food sources, absorption inhibitors, and enhancers Red meat, liver and other viscera, poultry, lamb, shellfish, eggs, and milk are excellent sources of bioavailable zinc. Peanuts, peanut butter, legumes, okra, sesame, Amarantus leaves, moringa leaves, pumpkin leaves, avocado, unpolished cereals
Vitamin B6 (pyridoxine)
Food sources, absorption inhibitors, and enhancers Milk, whole grain cereals, bread, liver, avocados, spinach, green beans, banana, fish, poultry, meat, nuts, potatoes, green leafy vegetables

Promotion of exclusive breastfeeding for the first 6 months prevents zinc deficiency in infants. Fruits and other vegetables are not good sources of zinc, because zinc in vegetable proteins is poorly bioavailable, in contrast to zinc associated with animal proteins. It is also important to reduce the phytic acid content of the diet because it suppresses zinc ­absorption.

Supplementation offers the most immediate approach to improving zinc status, and fortification should be the primary long-term public health initiative to prevent deficiencies of this micronutrient. Box 5 shows zinc daily recommended intakes.

BOX 5. Zinc daily recommended intake

  • Infants: 5 mg
  • Young children: 10 mg
  • Women: 12 mg
  • Doses in diarrhea: For children under 6 months 10 mg /day, and for children above 6 months 20 mg/day for 10-14 days.

In the management of diarrhea, WHO now recommends supplementation with zinc in combination with oral rehydration solution.