14.2 Nutrition Biochemistry: Dietary Standards (RENI to PDRI 2015), Food Guides, Protein Quality, Energy Expenditure, Breast Milk, Vitamins, Minerals & Blood Components
Key Takeaways
The 2015 Philippine Dietary Reference Intakes (FNRI-DOST) replaced the 2002 RENI and include the EAR, REI/RNI, AI, UL and AMDR; food labels now use %REI/RNI based on adult men aged 19 to 29 (FDA Circular 2023-009).
Pinggang Pinoy groups foods as Go (energy), Grow (body-building protein) and Glow (regulating vitamins and minerals) on a single plate.
Cereals such as rice are limited in lysine and legumes in methionine; eating them together (complementation) improves protein quality; egg protein has the highest biological value.
Total energy expenditure is basal metabolic rate (about 60% to 70%) plus the thermic effect of food (about 10%) plus physical activity.
Human milk has more whey and lactose and less protein and minerals than cow's milk, with lactoferrin, lysozyme and secretory IgA; it is low in vitamin K and D, so newborns get vitamin K at birth.
Why this area matters
The TOS lists:
- nutrition and health;
- the food pyramid;
- protein quality;
- nutritional status (types, requirements, assessment);
- the recommended energy and nutrient intake (RENI);
- energy expenditure;
- breast milk;
- vitamins and minerals;
- hemostasis and blood components.
The Philippines carries a "double burden" of malnutrition: stunting, wasting and micronutrient deficiencies alongside rising overweight and obesity. Pediatrics and Preventive Medicine build on this foundation.
Dietary standards: from RENI to the PDRI
The Recommended Energy and Nutrient Intakes (RENI, 2002) were the Philippine standard until the Food and Nutrition Research Institute (FNRI-DOST) released the 2015 Philippine Dietary Reference Intakes (PDRI). The PDRI uses several levels:
| Reference value | Meaning |
|---|---|
| EAR (Estimated Average Requirement) | Meets the needs of half of healthy people in a group; used to assess the adequacy of group diets |
| REI/RNI (Recommended Energy/Nutrient Intake) | Adequate for nearly all healthy people; the target for individuals |
| AI (Adequate Intake) | Used when an EAR cannot be set |
| UL (Tolerable Upper Intake Level) | Highest intake unlikely to cause harm |
| AMDR (Acceptable Macronutrient Distribution Range) | Share of energy from carbohydrate, fat and protein linked to lower chronic-disease risk |
Under FDA Circular No. 2023-009, prepackaged food labels declare %REI/RNI "Based on PDRI 2015", computed for adult men aged 19 to 29 unless the product targets another group. Adolescents have the highest recommended energy and protein intakes; FNRI cites about 2,800 kcal and 68 g of protein for boys and 2,200 kcal and 59 g for girls.
Food guides and nutrition and health
- The food pyramid (Daily Nutritional Guide Pyramid for Filipinos) places cereals and root crops at the base, vegetables and fruits next, protein foods above, and fats, oils and sugars at the top, to be used sparingly.
- Pinggang Pinoy (FNRI) shows proportions on a single plate:
- Go foods: rice and other carbohydrates, for energy.
- Grow foods: fish, meat, eggs and legumes, for body-building.
- Glow foods: vegetables and fruits, for regulating body processes.
- Water and physical activity are included.
- The Nutritional Guidelines for Filipinos promote exclusive breastfeeding, adequate complementary feeding, diverse diets, iodized salt, and limiting salt, sugar and fat.
Protein quality
- Indispensable (essential) amino acids must come from food. The limiting amino acid determines how well a protein can be used:
- lysine is limiting in rice, corn and wheat;
- methionine (sulfur amino acids) is limiting in legumes.
- Complementation combines foods so each supplies what the other lacks, as in rice with mongo beans, or rice with fish.
- Measures of quality:
- biological value (nitrogen retained ÷ nitrogen absorbed); egg is the reference, near 100;
- net protein utilization;
- chemical score;
- PDCAAS and DIAAS (digestibility-corrected scores).
- Animal proteins generally score higher than plant proteins.
Assessing nutritional status (ABCD)
- Anthropometry:
- children: weight-for-age, height-for-age (stunting), weight-for-height (wasting) and BMI-for-age as WHO z-scores, plus mid-upper arm circumference (MUAC below 11.5 cm means severe acute malnutrition in children 6 to 59 months);
- adults: BMI. Asian cut-offs flag overweight at a lower BMI (23) because Asians carry more risk at a given BMI. Waist circumference is also used.
- Biochemical: hemoglobin, ferritin, serum retinol, albumin and prealbumin, urinary iodine.
- Clinical: pallor, goiter, Bitot spots, edema, hair and skin changes.
- Dietary: 24-hour recall, food frequency, food records.
Energy expenditure
Total energy expenditure = basal metabolic rate + thermic effect of food + physical activity (plus growth, pregnancy and lactation when they apply).
- Basal metabolic rate is about 60% to 70% of the total. It is higher with more lean mass, fever, hyperthyroidism and growth, and lower in starvation and hypothyroidism. It is estimated with formulas such as Harris-Benedict or WHO/FAO equations.
- The thermic effect of food is about 10%, highest for protein.
- Physical activity is the most variable component.
- Energy values: carbohydrate and protein give 4 kcal/g, fat 9 kcal/g, alcohol 7 kcal/g.
- Pregnancy adds energy in the second and third trimesters, and lactation adds more, as set out in the PDRI tables.
Breast milk
| Component | Human milk compared with cow's milk |
|---|---|
| Protein | Lower total protein; whey-predominant (easier to digest); rich in lactoferrin, lysozyme and secretory IgA |
| Carbohydrate | More lactose (supports calcium absorption and healthy flora); human milk oligosaccharides act as prebiotics |
| Fat | Contains lipase, essential fatty acids and long-chain polyunsaturated fats (DHA) for brain and retina; the fat-rich hindmilk comes later in a feed |
| Minerals | Lower sodium, calcium and phosphate (lower renal solute load); iron is low but highly bioavailable |
| Vitamins | Low in vitamin K (hence vitamin K at birth) and low in vitamin D (supplement or sunlight) |
Colostrum, produced in the first days, is yellow, high in protein, secretory IgA and vitamin A, and acts as a mild laxative that clears meconium. Exclusive breastfeeding for 6 months, then breastfeeding with complementary foods to 2 years and beyond, is the WHO and DOH recommendation. It is supported by the Milk Code (EO 51) and the Expanded Breastfeeding Promotion Act (RA 10028).
Clinical Nutrition and Vitamin Pathophysiology
Vitamins are organic micronutrients that function primarily as coenzymes in intermediary metabolism. They are divided into fat-soluble and water-soluble groups.
Fat-Soluble Vitamins (A, D, E, K)
Fat-soluble vitamins depend on intact biliary and pancreatic micellar absorption; deficiency occurs in cystic fibrosis, celiac disease, and cholestatic liver disease.
| Vitamin | Active Chemical Forms | Key Physiological Functions | Deficiency Syndrome | Toxicity Manifestations |
|---|---|---|---|---|
| Vitamin A | Retinol, Retinal, Retinoic Acid | Visual phototransduction (rhodopsin in rods); epithelial differentiation; immune regulation | Night blindness (nyctalopia), xerophthalmia, Bitot spots (keratin debris on conjunctiva), keratomalacia, follicular hyperkeratosis | Pseudotumor cerebri (benign intracranial hypertension), hepatomegaly, dry peeling skin; potent teratogen (cleft palate, cardiac anomalies) |
| Vitamin D | Ergocalciferol (), Cholecalciferol (), Calcitriol () | Intestinal absorption of calcium and phosphate; bone mineralization; PTH feedback | Rickets in children (rachitic rosary, craniotabes, bowed legs, pectus carinatum); Osteomalacia in adults (bone pain, pseudofractures) | Hypercalcemia, hypercalciuria, nephrocalcinosis, confusion; seen in granulomatous diseases (sarcoidosis due to epithelioid -hydroxylase) |
| Vitamin E | -Tocopherol | Lipid-soluble antioxidant; scavenges free radicals to protect erythrocyte membranes from lipid peroxidation | Hemolytic anemia, acanthocytosis, spinocerebellar ataxia, peripheral neuropathy, loss of vibration/proprioception (mimics Friedreich ataxia or B12 deficiency without megaloblastic anemia) | Least toxic fat-soluble vitamin; high doses can antagonize Vitamin K, potentiating bleeding risks with warfarin |
| Vitamin K | Phylloquinone (), Menaquinone () | Obligate cofactor for -glutamyl carboxylase; post-translational carboxylation of clotting factors II, VII, IX, X, Protein C, and Protein S | Prolonged PT/INR and PTT; mucosal hemorrhage, hematuria, ecchymoses; Hemorrhagic Disease of the Newborn (prevented by routine IM vitamin K at birth) | Hemolytic anemia and kernicterus in neonates with synthetic menadione |
Water-Soluble Vitamins: The B-Complex and Vitamin C
| Vitamin | Coenzyme Form | Critical Enzymatic Reactions | Deficiency Clinical Syndromes |
|---|---|---|---|
| Vitamin B1 (Thiamine) | Thiamine Pyrophosphate (TPP) | PDH, -KGDH, Transketolase (PPP), Branched-chain -ketoacid dehydrogenase (BCKDH) | Dry Beriberi: Symmetrical peripheral neuropathy, muscle wasting; Wet Beriberi: Dilated high-output cardiomyopathy, edema; Wernicke-Korsakoff Syndrome: Confusion, ophthalmoplegia/nystagmus, ataxia, mammillary body atrophy (always give thiamine before IV dextrose); Philippine context: beriberi was historically common where diets relied on polished white rice. |
| Vitamin B2 (Riboflavin) | FAD, FMN | Complex I (FMN), Complex II / Succinate dehydrogenase (FAD), Glutathione reductase | Cheilosis (angular stomatitis / fissuring at lip corners), glossitis ("magenta tongue"), corneal neovascularization, normocytic normochromic anemia. |
| Vitamin B3 (Niacin) | , | Dehydrogenases in glycolysis, Krebs cycle, -oxidation, PPP; DNA repair (PARP) | Pellagra: The classic "4 Ds": Diarrhea, Dermatitis (photosensitive, bilateral symmetrical hyperpigmented rash / "Casal necklace"), Dementia, and Death. Precipitated by Hartnup disease, carcinoid syndrome, or prolonged isoniazid therapy. |
| Vitamin B5 (Pantothenate) | Coenzyme A (CoA), 4'-Phosphopantetheine | Acyl group transfer (citrate synthase, fatty acid synthase, PDH, -KGDH) | Extremely rare: "burning feet syndrome" (paresthesias), enteritis, dermatitis, alopecia. |
| Vitamin B6 (Pyridoxine) | Pyridoxal Phosphate (PLP) | Transamination (ALT, AST), Decarboxylation (GABA, histamine, catecholamines), ALA synthase (heme), Cystathionine -synthase | Peripheral neuropathy (classically induced by Isoniazid therapy; must co-administer pyridoxine), sideroblastic anemia, seizures, hyperhomocysteinemia. |
| Vitamin B7 (Biotin) | Carboxybiotin | Carboxylases requiring ATP and : Pyruvate Carboxylase, Acetyl-CoA Carboxylase, Propionyl-CoA Carboxylase | Rare; precipitated by excessive ingestion of raw egg whites containing avidin (which binds biotin with extreme affinity); dermatitis, alopecia, enteritis. |
| Vitamin B9 (Folic Acid) | Tetrahydrofolate (THF) | One-carbon transfer in purine and dTMP synthesis (thymidylate synthase) | Megaloblastic anemia with hypersegmented neutrophils; elevated homocysteine with NORMAL methylmalonic acid (MMA); NO neurological deficits; maternal deficiency causes neural tube defects (spina bifida, anencephaly). Small body stores (depletes in months). |
| Vitamin B12 (Cobalamin) | Methylcobalamin, Adenosylcobalamin | Methionine Synthase (homocysteine to methionine), Methylmalonyl-CoA Mutase (methylmalonyl-CoA to succinyl-CoA) | Megaloblastic anemia with hypersegmented neutrophils; ELEVATED homocysteine AND ELEVATED methylmalonic acid (MMA); Subacute Combined Degeneration (SCD) of spinal cord (dorsal columns and corticospinal tracts). Caused by pernicious anemia (anti-intrinsic factor antibodies) or terminal ileal resection. Massive liver stores (depletes in years). |
| Vitamin C (Ascorbic Acid) | Ascorbate | Hydroxylation of proline and lysine in collagen synthesis; dopamine -hydroxylase; intestinal absorption of non-heme iron () | Scurvy: Swollen bleeding spongy gums, loose teeth, perifollicular petechiae, "corkscrew hairs", subperiosteal hemorrhages, hemarthroses, impaired wound healing. |
Minerals
- Iron: absorbed as Fe2+ in the duodenum through DMT1, exported by ferroportin (blocked by hepcidin), carried by transferrin and stored as ferritin. Heme iron from meat is absorbed better than non-heme iron. Vitamin C helps absorption; tea and phytates reduce it.
- Iodine: needed for thyroid hormone. Deficiency causes goiter and cretinism; salt iodization addresses it.
- Zinc: a cofactor for more than 300 enzymes. Supplements are given with ORS in childhood diarrhea. Deficiency causes acrodermatitis and growth failure.
- Calcium and phosphate: bone, nerve and muscle function. Regulated by PTH, calcitriol and calcitonin.
- Copper: lysyl oxidase, cytochrome c oxidase, ceruloplasmin. Deficiency causes anemia; excess accumulates in Wilson disease.
- Selenium: glutathione peroxidase. Deficiency causes Keshan cardiomyopathy.
Hemostasis and blood components (biochemical view)
- Vitamin K is the cofactor for gamma-glutamyl carboxylation of factors II, VII, IX and X and proteins C and S. The carboxyglutamate residues bind calcium and phospholipid. Warfarin blocks vitamin K epoxide reductase.
- Plasma proteins: albumin (oncotic pressure, transport), globulins, fibrinogen, transport proteins (transferrin, ceruloplasmin, haptoglobin).
- Blood components for transfusion:
- packed red cells: raise hemoglobin by about 1 g/dL per unit in adults;
- platelet concentrates;
- fresh frozen plasma: all clotting factors; used for warfarin reversal when prothrombin complex concentrate is unavailable, and in DIC with bleeding;
- cryoprecipitate: fibrinogen, factor VIII, von Willebrand factor, factor XIII.
A 42-year-old chronic alcoholic male is brought to the emergency department in an obtunded state. Neurological examination reveals horizontal nystagmus, bilateral lateral rectus palsy, and profound truncal ataxia. Which metabolic enzyme requires the micronutrient cofactor that must be promptly administered to this patient prior to initiating intravenous dextrose infusions?
Cystathionine beta-synthase
Glucose-6-phosphate dehydrogenase
Alpha-ketoglutarate dehydrogenase
Acetyl-CoA carboxylase
A family's diet relies mainly on rice. A health worker advises adding mongo (mung) beans to meals to improve protein quality. What is the biochemical basis of this advice?
Legumes contain more carbohydrate, which spares protein from oxidation
Beans contain enzymes that digest rice protein into essential amino acids
Rice is limited in lysine and legumes are richer in it, so combining them supplies a more complete amino acid pattern
Rice protein is limited in methionine, which beans supply in abundance, so the mixture has a complete amino acid pattern
Why does the Department of Health recommend intramuscular vitamin K for every newborn, including those who will be exclusively breastfed?
Breast milk is low in vitamin K and the newborn gut lacks vitamin K-producing bacteria
Vitamin K is needed to prevent physiologic jaundice, because it speeds bilirubin conjugation in breastfed infants
Breast milk contains anticoagulant proteins that inactivate thrombin
Vitamin K is the main source of calcium for bone mineralization in infants
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