Vitamins, Minerals & Nutrition VN

Many B vitamins become coenzymes that transfer electrons or chemical groups. Thiamine pyrophosphate participates in oxidative decarboxylation and transketolase reactions. Riboflavin contributes FAD/FMN, while niacin contributes NAD+/NADP+. Pyridoxal phosphate supports amino-acid reactions, and biotin carries activated carbon dioxide in carboxylation.

Folate carries one-carbon units important for nucleotide synthesis, while vitamin B12 participates in selected rearrangement and methyl-transfer metabolism. Their pathways intersect, which helps explain overlapping haematological findings with distinct neurological implications.

Deficiency is best learned by linking the missing coenzyme to the blocked biochemical reaction and then to vulnerable tissues, rather than memorizing symptom lists alone.

Vitamin A-related compounds support visual pigment chemistry, epithelial differentiation and gene regulation. Vitamin D functions hormonally in calcium and phosphate homeostasis and bone mineral physiology. Vitamin E contributes antioxidant protection in lipid environments, while vitamin K is required for post-translational modification of selected coagulation-related proteins.

Because fat-soluble vitamins depend on lipid digestion and absorption, cholestatic or fat-malabsorptive states can produce multiple deficiencies. Storage also means excessive intake can produce toxicity more readily for some fat-soluble vitamins than for most water-soluble vitamins.

Clinical interpretation therefore requires intake, absorption, storage, metabolism and physiological role.

Dietary iron is absorbed mainly in proximal small intestine and regulated because the body lacks a large controlled pathway for iron excretion. Iron can be stored in ferritin and transported in plasma bound to transferrin. Most body iron is incorporated into haemoglobin, with additional roles in myoglobin and enzymes.

Hepcidin, produced by liver, is a central regulator of systemic iron traffic. It reduces iron export by promoting loss of ferroportin activity, thereby decreasing intestinal iron entry into plasma and iron release from storage cells. Inflammation can raise hepcidin and restrict circulating iron availability.

Iron deficiency, chronic inflammatory iron restriction and iron overload therefore have different biochemical mechanisms and laboratory patterns.

Calcium serves structural roles in bone and dynamic roles in signalling, contraction and secretion. Plasma calcium is regulated by coordinated actions involving parathyroid hormone, vitamin D-related pathways, bone, kidney and intestine. Phosphate participates in bone, ATP, nucleotides and phosphorylation reactions.

Iodine is required for thyroid hormone synthesis. Zinc participates in many enzymes and regulatory proteins; copper contributes to selected oxidases and iron-related metabolism; selenium is incorporated into proteins involved in redox and thyroid-hormone metabolism.

Deficiency or excess should be interpreted through biochemical function. More is not automatically better: micronutrients have physiological ranges, and toxicity can arise when regulation or intake is abnormal.

Carbohydrate, fat and protein supply energy and structural or biosynthetic substrates, while vitamins and minerals enable essential reactions. Protein quality depends partly on essential amino-acid availability. Essential fatty acids must be obtained from diet because humans cannot introduce double bonds at every required position.

Energy expenditure includes basal metabolic requirements, thermic effects and physical activity, with adaptive changes in different physiological states. Persistent energy imbalance alters body stores, but endocrine, behavioural and environmental factors influence the process.

Malnutrition can involve energy deficiency, protein deficiency, micronutrient deficiency or combinations. Obesity likewise is a complex metabolic state rather than simply a biochemical synonym for dietary fat intake.

Vitamins are organic micronutrients required in small amounts for normal biochemical function. Many water-soluble vitamins become components of coenzymes that transfer electrons or chemical groups in metabolism. Fat-soluble vitamins have diverse roles in vision, gene regulation, antioxidant defence and coagulation-related processes. Deficiency patterns reflect the biochemical pathways that lose function.

Minerals serve structural, catalytic, electrical and regulatory roles. Iron is essential for haem and electron-transfer proteins; iodine is required for thyroid hormone synthesis; calcium and phosphate support bone and signalling; zinc participates in numerous enzymes and transcriptional proteins. Both deficiency and excess can be harmful.

Nutrition integrates energy intake with macronutrient quality, essential amino acids and fatty acids, vitamins, minerals and physiological state. Digestion and absorption determine bioavailability, while liver and other tissues process nutrients after absorption.

Energy balance reflects intake versus expenditure over time, but body composition and metabolic health cannot be reduced to one short equation. Growth, pregnancy, illness, activity and endocrine state change nutritional requirements.

Mechanism map: dietary nutrient → digestion/release → intestinal absorption → transport/storage → biochemical role → loss/turnover. Deficiency symptoms should be traced back to the affected biochemical reaction or tissue function.

Clinical integration includes anaemia, bone disease, malnutrition, vitamin deficiency/toxicity and altered requirements in disease. Laboratory interpretation should be combined with dietary, absorption and clinical context.

Common confusion: a vitamin is not an energy source merely because it participates in energy metabolism. Minerals and vitamins can enable reactions without being consumed as fuel in the same way as carbohydrate, fat or protein.