Water-Soluble Vitamins

Part of Nutrition Science

Detailed coverage of the water-soluble vitamins — vitamin C and the eight B vitamins — including their functions, deficiency signs, food sources, and practical guidance for maintaining adequate intake without supplements.

Why This Matters

Water-soluble vitamins are the most vulnerable of all essential nutrients. They dissolve in water, which means they leach out of food into cooking liquid. They degrade with heat, light, and oxygen. They are not stored significantly in the body — excess is excreted in urine, so they must be consumed regularly. And they are the vitamins most commonly depleted by food processing, extended storage, and restricted diets.

Because the body cannot stockpile them, water-soluble vitamin deficiencies develop faster than fat-soluble deficiencies. A person can go months on inadequate vitamin D before rickets develops (because body stores and sun exposure provide buffer), but vitamin C deficiency manifests in weeks and B12 deficiency causes neurological damage within months to a few years.

In practical terms: these are the vitamins a rebuilding community must think about most actively, because dietary disruptions hit them first and hardest.

Vitamin C (Ascorbic Acid)

See the dedicated scurvy article for clinical detail. Here: the biochemical roles and practical notes.

Biochemical functions:

• Required for prolyl hydroxylase and lysyl hydroxylase — enzymes that crosslink collagen fibers; without C, collagen is structurally weak
• Reduces dietary iron from Fe³⁺ to Fe²⁺ (the absorbed form), significantly increasing non-heme iron uptake
• Regenerates vitamin E from its oxidized form (the antioxidant network is interconnected)
• Required for biosynthesis of carnitine (fatty acid transport into mitochondria)
• Required for synthesis of norepinephrine and serotonin
• Concentrated in immune cells (neutrophils, lymphocytes) — needs increase during infection

Practical notes:

• 65-90 mg/day prevents deficiency; 200-400 mg optimizes tissue saturation
• Requirements increase during illness, stress, and heavy physical labor
• Heat destroys vitamin C: boiling cabbage for 10 minutes destroys ~60-70% of its C content
• Vitamin C is more stable in acidic environments — fermented foods (sauerkraut, kimchi) retain C well
• Cook vegetables quickly or eat raw when possible; steam rather than boil

Best sources per 100g: Bell pepper (red) 128-190 mg | Parsley 133 mg | Rose hips 400+ mg | Broccoli 89 mg | Kale 49 mg | Citrus 50-70 mg | Sauerkraut 15-35 mg

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The B Vitamins

The B vitamins are a group of eight chemically distinct compounds that happen to share water solubility and functional roles in cellular metabolism. They are often found together in the same foods (especially nutritional yeast, liver, legumes, and whole grains), and deficiency of one frequently occurs alongside borderline deficiency of others.

Thiamine (B1)

Function: Cofactor for enzymes in carbohydrate and branched-chain amino acid metabolism. Particularly critical for glucose metabolism in nervous tissue, which has no alternative fuel pathway.

Deficiency disease — Beriberi:

• Dry beriberi: Peripheral neuropathy — numbness, tingling, weakness starting in feet and progressing upward; in severe cases, paralysis
• Wet beriberi: Cardiovascular — enlarged heart, heart failure, severe edema
• Wernicke encephalopathy: Acute brain damage — confusion, abnormal eye movements, ataxia (loss of coordination). Medical emergency requiring immediate treatment.
• Wernicke-Korsakoff syndrome: Chronic alcoholism + thiamine deficiency produces permanent anterograde amnesia

Deficiency context: The classic disease of white rice dependence. Rice bran (removed when polishing) contains most of the thiamine. Populations switching to milled rice without supplementation develop beriberi within months. Also occurs with chronic heavy alcohol use, which both reduces thiamine absorption and increases thiamine utilization.

Stability: Destroyed by heat, especially alkaline cooking. Traditional practice of adding baking soda to beans or greens (to soften them) destroys thiamine. Avoid where thiamine adequacy is a concern.

Best sources: Whole grains (brown rice, whole wheat, oats), pork, legumes, sunflower seeds, nutritional yeast, peas.

Riboflavin (B2)

Function: Component of flavin coenzymes (FAD, FMN) central to energy metabolism; involved in B6 and folate metabolism; antioxidant activity.

Deficiency signs: Angular stomatitis (painful cracks at mouth corners), cheilitis (cracked dry lips), glossitis (swollen, purplish tongue), seborrheic dermatitis, photophobia, corneal vascularization. Not a life-threatening deficiency in isolation, but a reliable indicator that overall B vitamin status is poor.

Stability: Destroyed by light — dairy products in clear glass lose riboflavin rapidly in sunlight. Store in dark containers.

Best sources: Dairy products, eggs, liver, beef, almonds, whole grains, nutritional yeast, dark leafy greens, mushrooms.

Niacin (B3)

Function: Component of NAD and NADP — coenzymes required for over 400 enzymatic reactions including energy production, DNA repair, and cellular signaling.

Deficiency disease — Pellagra: The Four D’s: Dermatitis (sun-exposed skin), Diarrhea, Dementia, Death. See dedicated rickets-pellagra article.

Unique feature: The body can synthesize niacin from the amino acid tryptophan (60 mg tryptophan = 1 mg niacin). Diets adequate in complete protein (containing tryptophan) partially cover niacin needs even if dietary niacin is low.

The corn problem: Corn’s niacin is bound as niacytin, unabsorbable without nixtamalization (soaking in lime water). Populations depending on non-nixtamalized corn develop pellagra.

Best sources: Chicken, tuna, beef, liver, turkey, peanuts, legumes, whole grains, nutritional yeast. Nixtamalized corn (masa, hominy) is an adequate source; unnixtamalized corn is not.

Pantothenic Acid (B5)

Function: Component of coenzyme A (CoA) — central to fatty acid metabolism, the citric acid cycle, synthesis of steroid hormones and neurotransmitters. Present in virtually all metabolic pathways.

Deficiency: Extremely uncommon because pantothenic acid is found in almost all whole foods. Deficiency produces fatigue, headache, numbness, and irritability — described historically only in prisoners of war on extremely restricted diets (“burning feet syndrome”).

Best sources: Liver, egg yolk, avocado, mushrooms, sweet potato, legumes, whole grains, broccoli, dairy. The name comes from Greek pantos (everywhere) — reflects its wide distribution.

Pyridoxine (B6)

Function: Cofactor for over 100 enzymes, primarily in amino acid metabolism. Required for synthesis of neurotransmitters (serotonin, dopamine, norepinephrine, GABA), hemoglobin, and the immune system signaling molecule interleukin-2.

Deficiency signs: Peripheral neuropathy (tingling, numbness), seborrheic dermatitis, glossitis, impaired immune function, microcytic anemia (small red blood cells), confusion, and depression. Secondary B6 deficiency is common in chronic alcoholics.

Stability: Heat-sensitive; cooking reduces B6 by 20-50%. Better retained in meat (protein binding protects it) than vegetables.

Best sources: Chicken, fish (especially tuna and salmon), pork, beef, potatoes (with skin), bananas, chickpeas, sunflower seeds, legumes, whole grains. One large potato provides about 0.5 mg (about 30% of daily needs).

Biotin (B7)

Function: Cofactor for carboxylase enzymes involved in fatty acid synthesis, gluconeogenesis (making glucose from non-carbohydrate precursors), and amino acid catabolism.

Deficiency signs: Hair loss (diffuse thinning), dermatitis, conjunctivitis, neurological symptoms including depression, lethargy, hallucinations. Rare in isolation.

The avidin problem: Raw egg whites contain avidin, a protein that binds biotin with very high affinity and blocks its absorption. Consuming large quantities of raw egg whites can cause biotin deficiency even with adequate dietary intake. Cooking denatures avidin, eliminating the problem. Cooked eggs are safe; raw egg whites are a biotin antagonist.

Best sources: Egg yolk (cooked), liver, sweet potato, almonds, legumes, nutritional yeast, mushrooms, whole grains.

Folate (B9)

Function: Essential for DNA synthesis (specifically the synthesis of thymidine, required for DNA replication), cell division, and the one-carbon metabolic cycle. Critical for rapidly dividing cells — fetal development, immune cells, red blood cells, gut epithelium.

Deficiency disease: Megaloblastic anemia — red blood cells fail to divide normally, producing large, immature, non-functional cells. Folate deficiency is indistinguishable from B12 deficiency by anemia type (both megaloblastic) — critical to identify which is the actual deficiency before treating, because giving folate to someone with B12 deficiency corrects the anemia but allows neurological damage to continue.

Neural tube defects: The most important application. Folate is required during the first 28 days of embryonic development for neural tube closure. Deficiency causes spina bifida and anencephaly. Because neural tube closure occurs before most women know they are pregnant, folate adequacy must be maintained continuously in all women of reproductive age, not just after confirmation of pregnancy.

Stability: Among the most heat-sensitive vitamins. Cooking vegetables reduces folate by 50-80%. Raw or lightly cooked dark greens retain significantly more. Boiling and discarding cooking water wastes most of the folate.

Best sources: Chicken liver 770 mcg/100g; beef liver 290 mcg; lentils (cooked) 181 mcg; chickpeas 172 mcg; asparagus 149 mcg; spinach (raw) 194 mcg; kale 141 mcg; black beans 149 mcg; edamame 311 mcg.

Practical priority: Eat raw or lightly steamed leafy greens multiple times per week. Include legumes in daily meals. Liver once or twice per week. These three habits provide adequate folate from food.

Cobalamin (B12)

Function: Maintains myelin (the insulating sheath around nerve fibers); required for folate metabolism; essential for DNA synthesis; involved in amino acid metabolism.

Deficiency disease:

• Megaloblastic anemia — indistinguishable from folate deficiency in blood tests; corrected by B12
• Subacute combined degeneration of the spinal cord — progressive neurological damage causing sensory loss, weakness, and ataxia; may be IRREVERSIBLE if not treated promptly
• Cognitive impairment and dementia — B12 deficiency is among the reversible causes of dementia; this is critical — treating B12 deficiency in a person diagnosed with “dementia” may restore cognitive function

Deficiency timeline:

• Body stores 2-5 mg in liver (substantial relative to daily requirement of 2.4 mcg)
• Stores deplete slowly — deficiency may not manifest for 3-5 years after dietary sources are eliminated
• This slow onset makes it easy to miss the dietary cause by the time symptoms appear

Animal-only source: B12 is produced only by certain bacteria and archaea. It accumulates in animal tissues through the food chain. Plant foods contain no reliable bioavailable B12. Fermented foods may contain bacterial B12, but in forms with poor bioavailability. Spirulina contains B12 analogues that compete with true B12 and may worsen deficiency.

Critical implication: Any community that eliminates animal products from its diet will develop B12 deficiency over 3-5 years. Children and pregnant women on exclusively plant-based diets are at highest risk for permanent neurological damage. Eggs and dairy (even without meat or fish) provide sufficient B12.

Best sources: Liver (61 mcg/100g — overwhelmingly the richest source), clams (99 mcg), beef (2-3 mcg), fish (1-5 mcg), eggs (0.9 mcg per egg), dairy (0.5-1 mcg per 100g).

Practical Daily Strategy

Achieving adequate water-soluble vitamin intake without supplements:

1. Eat some animal product daily — eggs, dairy, meat, or fish; this covers B12, B2, B6, and provides B12 buffer against eventual deficiency
2. Eat raw or lightly cooked dark leafy greens several times per week — covers folate, vitamin C, K1, and provides minerals
3. Include legumes daily — provides folate, B1, B6, and iron
4. Use whole grains rather than refined grains — whole wheat, oats, brown rice provide thiamine, niacin, B6, and magnesium that refined grains lack
5. Include liver weekly — one to two servings per week is a near-complete micronutrient supplement in food form: covers B12, folate, niacin, B6, B2, vitamin A, iron, zinc, and copper simultaneously
6. Ferment rather than boil — fermentation retains or increases water-soluble vitamins; boiling destroys them

This set of habits, consistently maintained, eliminates virtually all risk of water-soluble vitamin deficiency without requiring any supplement or specialized product.