5.2 Vitamins and Minerals: PDRI Values, Food Sources, Bioavailability, Stability, and Toxicity
Key Takeaways
The PDRI 2015 sets vitamin A at 700 µg RE for men and 600 µg RE for women aged 19-29, with 1 µg RE equal to 1 µg retinol or 12 µg beta-carotene.
The PDRI 2015 iron recommendation for women aged 19-49 is 28 mg/day, a level that cannot be met by usual diet alone, compared with 12 mg/day for men.
Vitamin C, thiamin, and folate are the vitamins most easily lost in cooking, through heat, oxygen, alkali, and leaching into cooking water; riboflavin is destroyed by light.
Heme iron from meat, fish, and poultry is absorbed better than non-heme iron, whose absorption is increased by vitamin C and meat and decreased by phytates, tea and coffee polyphenols, and calcium.
Toxicity is most likely with supplements: excess preformed vitamin A causes liver damage and birth defects, excess vitamin D causes hypercalcemia, and excess vitamin B6 causes sensory neuropathy.
The basic nutrition area asks examinees to list macronutrients and micronutrients, their recommended intakes and roles, their food sources, bioavailability, and stability in cooking and processing, and to relate deficiency and toxicity to symptoms. Biochemical roles are covered in the vitamin and mineral biochemistry sections; this section focuses on practical knowledge.
PDRI 2015 Values for Adults
The Philippine Dietary Reference Intakes (FNRI, 2015; summary tables revised 2018) set these recommended intakes for adults aged 19-29. Values marked AI are adequate intakes.
| Nutrient | Men | Women | Notes |
|---|---|---|---|
| Vitamin A | 700 µg RE | 600 µg RE | +300 in pregnancy, +400 in lactation |
| Vitamin D (AI) | 5 µg | 5 µg | 10 µg at 50-59 years; 15 µg at 60 and above |
| Vitamin E (AI) | 10 mg alpha-TE | 10 mg alpha-TE | |
| Vitamin K (AI) | 61 µg | 53 µg | |
| Thiamin | 1.2 mg | 1.1 mg | |
| Riboflavin | 1.3 mg | 1.1 mg | |
| Niacin | 16 mg NE | 14 mg NE | 60 mg tryptophan provide 1 mg niacin |
| Vitamin B6 | 1.3 mg | 1.3 mg | Higher from age 50 |
| Vitamin B12 | 2.4 µg | 2.4 µg | |
| Folate | 400 µg DFE | 400 µg DFE | +200 in pregnancy |
| Vitamin C | 70 mg | 60 mg | +10 in pregnancy, +35 in lactation |
| Calcium | 750 mg | 750 mg | 800 mg for women 50 and above and everyone 60 and above |
| Iron | 12 mg | 28 mg | 10 mg for women 50 and above; requirement for women of reproductive age cannot be met by diet alone |
| Zinc | 6.5 mg | 4.6 mg | |
| Iodine | 150 µg | 150 µg | +100 in pregnancy and lactation |
| Selenium | 38 µg | 33 µg | |
| Magnesium | 240 mg | 210 mg | |
| Phosphorus | 700 mg | 700 mg |
Conversion factors from the PDRI tables: 1 µg retinol equivalent (RE) equals 1 µg retinol, 12 µg beta-carotene, or 24 µg of other provitamin A carotenoids. One µg of vitamin D (calciferol) equals 40 IU. One dietary folate equivalent (DFE) equals 1 µg food folate, 0.6 µg folic acid from fortified food or supplements taken with food, or 0.5 µg folic acid taken on an empty stomach.
Food Sources in the Filipino Diet
| Nutrient | Rich sources |
|---|---|
| Vitamin A (retinol) | Liver, egg yolk, whole milk, fortified margarine and cooking oil |
| Provitamin A carotenoids | Malunggay, kangkong, kamote tops, saluyot, squash, carrots, ripe mango, ripe papaya |
| Vitamin D | Sunlight on skin, fatty fish (tuna, sardines), egg yolk, fortified milk |
| Vitamin E | Vegetable oils, nuts, seeds, green leafy vegetables |
| Vitamin K | Green leafy vegetables (malunggay, pechay, spinach), soybean oil; also made by colonic bacteria |
| Thiamin | Pork, whole grains, legumes (munggo), enriched rice |
| Riboflavin | Milk, eggs, liver, green leafy vegetables |
| Niacin | Meat, fish, poultry, peanuts, legumes |
| Folate | Green leafy vegetables, legumes, liver, fortified flour products |
| Vitamin B12 | Only animal foods: meat, liver, fish, shellfish, eggs, milk |
| Vitamin C | Guava, papaya, calamansi, dalandan, mango, malunggay, tomatoes |
| Calcium | Milk, cheese, small fish eaten with bones (dilis, tuyo), tokwa set with calcium, malunggay |
| Iron | Liver, red meat, blood (dinuguan), shellfish, legumes, green leafy vegetables, iron-fortified rice |
| Zinc | Oysters, shellfish, meat, poultry, legumes, whole grains |
| Iodine | Iodized salt, seafood, seaweed |
Bioavailability: Enhancers and Inhibitors
| Nutrient | Enhancers | Inhibitors |
|---|---|---|
| Non-heme iron | Vitamin C, meat, fish, and poultry (the "MFP factor"), fermentation | Phytates (whole grains, legumes), polyphenols (tea, coffee), calcium, oxalates |
| Calcium | Vitamin D, lactose in infants, adequate protein | Oxalates (spinach, kangkong), phytates, very high fiber |
| Zinc | Animal protein | Phytates, high-dose iron supplements |
| Carotenoids | Dietary fat, cooking and pureeing | Very low-fat meals |
| Folate | Synthetic folic acid is better absorbed than food folate | Alcohol |
Heme iron is absorbed at roughly 15-35%, while non-heme iron absorption is lower and depends heavily on the meal. A practical counseling message is to eat vitamin C-rich fruit with plant sources of iron and to drink tea or coffee between meals rather than with them.
Stability During Storage and Cooking
| Nutrient | Destroyed or lost by | Practical tip |
|---|---|---|
| Vitamin C | Heat, oxygen, alkali, copper and iron, leaching | Cut just before cooking, use little water, cook briefly, serve promptly |
| Thiamin | Heat, alkali (baking soda), sulfites, leaching | Avoid baking soda in vegetables; do not over-wash or discard rice cooking water needlessly |
| Riboflavin | Light (ultraviolet) | Store milk in opaque containers |
| Folate | Heat, oxidation, leaching | Steam or stir-fry leafy vegetables quickly |
| Vitamin A and carotenoids | Oxidation, light, prolonged high heat | Store in cool, dark, airtight containers |
| Vitamin E | Oxidation, repeated deep-frying | Do not reuse frying oil many times |
| Vitamin D, niacin | Relatively stable | Losses mainly through leaching or discarded drippings |
| Minerals | Not destroyed, but leach into water | Use cooking liquid in soups such as tinola and sinigang |
Deficiency and Toxicity Summary
| Nutrient | Deficiency signs | Toxicity (mainly from supplements) |
|---|---|---|
| Vitamin A | Night blindness, Bitot's spots, xerophthalmia, follicular hyperkeratosis | Liver damage, raised intracranial pressure, birth defects (adult UL 3,000 µg preformed retinol) |
| Vitamin D | Rickets, osteomalacia | Hypercalcemia, kidney stones, soft-tissue calcification |
| Vitamin E | Hemolysis, neuropathy (rare) | Bleeding risk with anticoagulants |
| Vitamin K | Bleeding; hemorrhagic disease of the newborn | Rare; interferes with warfarin control |
| Thiamin | Beriberi, Wernicke-Korsakoff syndrome | Not established from food |
| Riboflavin | Angular stomatitis, cheilosis, magenta tongue | Not established |
| Niacin | Pellagra (dermatitis, diarrhea, dementia) | Flushing, liver damage with high-dose nicotinic acid |
| Vitamin B6 | Dermatitis, microcytic anemia, seizures | Sensory neuropathy with high-dose supplements |
| Folate | Megaloblastic anemia, neural tube defects | High folic acid can mask B12 deficiency |
| Vitamin B12 | Megaloblastic anemia, neurologic damage | Not established |
| Vitamin C | Scurvy (bleeding gums, poor wound healing) | Diarrhea; kidney stones in susceptible people |
| Calcium | Osteoporosis, tetany if blood calcium falls | Constipation, kidney stones, hypercalcemia |
| Iron | Microcytic anemia, fatigue, koilonychia | Accidental overdose in children; iron overload |
| Zinc | Growth failure, poor taste, dermatitis, poor wound healing | Copper deficiency with long-term high intake |
| Iodine | Goiter, cretinism, hypothyroidism | Thyroid dysfunction |
| Fluoride | More dental caries | Dental and skeletal fluorosis |
| Selenium | Keshan cardiomyopathy | Selenosis (hair and nail loss) |
The adult upper limits quoted here follow the Institute of Medicine values widely used in clinical references; check the PDRI tables when a question asks for Philippine upper limits.
A mother serves her family ginisang munggo with malunggay and rice. Which addition would most improve the absorption of the non-heme iron in this meal?
A glass of hot tea with the meal
A glass of milk with the meal
A fiber supplement taken with the meal
Fresh guava or papaya for dessert
Which preparation practice best preserves vitamin C and folate in leafy vegetables such as pechay and malunggay?
Soaking chopped leaves in water for an hour before cooking
Steaming or briefly stir-frying them just before serving
Boiling them with baking soda to keep the color bright
Cooking them early in the morning and reheating at dinner
A woman takes 25,000 IU of preformed vitamin A daily from supplements in early pregnancy. What is the main risk?
Birth defects and liver toxicity from excess preformed retinol
Night blindness from vitamin A excess
Orange skin that is harmless to the fetus
Iron deficiency anemia from vitamin A competing with iron
Sections you finish are checked off in the contents.