Individual B Vitamins: B1 through B7

In the previous topic, you learned that the B-complex family shares a common set of eight functions, from building blood to insulating nerves. But each member of this family also has its own story: a specific role in the body and a specific set of problems that arise when that particular vitamin runs low. Think of the B vitamins as a team where every player has a shared playbook but also a unique position on the field. This topic walks through each one individually, from B1 all the way to B7, so you can see exactly what each vitamin does and what goes wrong without it.

Vitamin B1 (Thiamine): Energy, Nerves, and the Heart

How Thiamine Powers Your Cells

Every cell in your body needs a steady supply of energy, and that energy mostly comes from glucose (the sugar your body gets from food). Thiamine sits at the heart of this process. It is part of the enzyme system that takes glucose and oxygen and converts them into usable energy:

$Glucose + O_2 \xrightarrow{\text{enzyme (B1)}} Energy$

When thiamine is missing, this conversion slows down. Cells do not get enough energy, and the body starts to feel the effects almost everywhere.

Beri-Beri: The Deficiency Disease

A lack of Vitamin B1 causes a condition called beri-beri. The earliest signs are fairly general:

• Muscle weakness — muscles do not receive enough energy to function properly
• Lethargy — a persistent feeling of tiredness and lack of motivation

But the damage runs much deeper than tired muscles.

Nerve Damage: Demyelination and Memory Loss

Thiamine is needed to maintain the myelin sheath (the fatty insulating layer that wraps around nerve fibres). When thiamine levels fall, the body’s ability to produce myelin drops. The existing myelin starts to break down, a process called demyelination. As the insulation on nerve fibres thins out:

• Paralysis can set in, as nerve signals fail to reach the muscles
• Memory weakens, because the nerve pathways involved in storing and retrieving memories are damaged
• Overall cognitive function declines over time

The Alcohol Connection

There is a well-established link between alcohol and thiamine. Regular alcohol consumption reduces the absorption of thiamine from food in the gut. This means that even if someone eats a diet with adequate thiamine, heavy drinking can prevent the body from actually taking it in. The result is the same nerve damage described above, and one of the most noticeable early effects is poor memory.

Heart Complications

Thiamine deficiency does not spare the heart. Here is how the damage unfolds:

1. The heart muscle cells weaken because they are starved of energy (the same glucose-to-energy pathway that thiamine supports).
2. Weakened heart cells try to compensate by enlarging themselves, attempting to pump the same volume of blood with less force per cell.
3. This enlargement is not sustainable. Over time, the enlarged, weakened heart can no longer keep up, and the person develops heart failure.

It is important to understand what heart failure actually means. It does not mean the heart stops beating. Heart failure is the condition where the heart fails to maintain the supply of the right amount of blood to the body’s vital organs, including the brain. The organs are still receiving blood, but not enough to function at their best.

Vitamin B2 (Riboflavin): Skin, Mouth, and Tongue

Riboflavin deficiency shows up in the body’s delicate surface tissues. Three conditions stand out:

• Dermatitis — the skin becomes inflamed, red, and irritated. “Dermatitis” literally means inflammation of the skin.
• Glossitis — the tongue swells up and becomes inflamed, making eating and talking uncomfortable. The term comes from “glossa” (tongue) and “-itis” (inflammation).
• Cheilosis — this affects the lips and the corners of the mouth. The lips develop cracks and fissures (deep splits), become swollen, and the damage is painful enough to cause bleeding. When the cracking and ulceration happens specifically at the angles (corners) of the mouth, it is called angular stomatitis (fissuring and ulceration at the mouth corners). In some individuals, riboflavin deficiency also produces a rash on the scrotum or vulva, along with the skin inflammation seen elsewhere.

Vitamin B3 (Niacin): Tryptophan, Maize, and the 4 D’s

The Tryptophan Connection

Here is something unique about Vitamin B3. Your body can actually manufacture niacin on its own, but it needs a specific raw material to do so: an essential amino acid called tryptophan. “Essential” means the body cannot make tryptophan internally; it must come from the food you eat. So a person can become niacin-deficient in two ways: either by not consuming enough niacin directly, or by not eating enough tryptophan-rich foods.

Pellagra: The Deficiency Disease

When niacin runs too low, the result is a disease called pellagra. The name comes from the Italian words “pelle agra”, meaning sour or rough skin, which gives a clue about its most visible symptom. Pellagra is described by four progressively worsening stages, known as the 4 D’s:

1. Dermatitis — rough, inflamed, cracked skin (the symptom that gave the disease its name)
2. Diarrhoea — persistent digestive disturbance
3. Dementia — a memory and cognitive disorder where thinking, remembering, and reasoning deteriorate
4. Death — if the condition is left untreated, it can be fatal

Why Maize-Dependent Populations Are at Risk

Populations that rely on maize (corn) as their primary staple food are especially vulnerable to pellagra. The reason is straightforward: maize is naturally deficient in the essential amino acid tryptophan. Since the body depends on tryptophan to produce niacin, a diet built heavily around maize can leave the body unable to make enough of this vitamin, even if other nutrients are present.

Vitamin B5 (Pantothenic Acid): Digestion and Burning Feet

Pantothenic acid deficiency affects two broad systems:

• Gastrointestinal (GIT) disorders — the digestive system suffers, producing symptoms of indigestion (difficulty breaking down food), constipation (difficulty passing stool), and anorexia (in this context, anorexia means loss of hunger or appetite, not the eating disorder)
• Nervous disorders — the nervous system is affected, though the effects are more general compared to the specific nerve damage seen with B1 or B6 deficiency

The most distinctive symptom, however, is burning feet syndrome. The person experiences a burning sensation in the soles of the feet, sometimes described as a pinpricking feeling, as if small needles are pressing into the skin. This is considered a hallmark sign of pantothenic acid deficiency.

Vitamin B6 (Pyridoxine): Blood Builder and Nerve Signal Maker

Pyridoxine stands out because it plays a direct role in two critical processes.

Building Blood: Haemoglobin and Red Blood Cells

Vitamin B6 is essential for the synthesis of haemoglobin ($Hb$) and red blood cells (RBCs). Haemoglobin is the protein inside red blood cells that picks up oxygen in the lungs and carries it to every tissue in the body.

When pyridoxine is lacking, the body cannot produce enough haemoglobin. The red blood cells that are produced end up smaller than normal because they contain too little haemoglobin. This condition is called microcytic anaemia (“microcytic” means abnormally small cells). The smaller, haemoglobin-poor cells cannot carry as much oxygen, leaving the body’s tissues short of the oxygen they need.

Nerve Signalling: Neurotransmitter Synthesis

Vitamin B6 is also essential for synthesising the chemical neurotransmitter molecules that nerve cells use to pass signals across the synaptic gap between neurons. When B6 levels drop, neurotransmitter production falls, and nerve impulse transmission becomes unreliable. The result is a nervous disorder that can manifest as seizure: abnormal, involuntary shaking movements of the hands and legs, accompanied by loss of consciousness.

Digestive Problems

Like B5 and B7, pyridoxine deficiency also causes gastrointestinal (GIT) disorders, including indigestion, constipation, and anorexia (loss of appetite).

Vitamin B7 (Biotin): Three Broad Effects

Biotin deficiency produces three categories of problems:

• Gastrointestinal (GIT) disorders — digestive disturbances similar to those seen with B5 and B6 deficiency
• Nervous disorders — disruptions to normal nervous system function
• Excessive loss of water — the body loses more water than normal, a symptom that is somewhat unique to biotin deficiency among the B vitamins

Quick Reference: B1 through B7 at a Glance

Vitamin	Chemical Name	Key Role	Deficiency Disease / Condition	Distinctive Symptoms
B1	Thiamine	Energy production (glucose + $O_2$ to energy)	Beri-beri	Muscle weakness, demyelination, heart enlargement, heart failure
B2	Riboflavin	Surface tissue health	Dermatitis, glossitis, cheilosis	Skin inflammation, swollen tongue, cracked/bleeding lips, angular stomatitis
B3	Niacin	Synthesised from tryptophan	Pellagra (4 D’s)	Rough skin, diarrhoea, dementia; maize-dependent populations at risk
B5	Pantothenic acid	Digestion and nerve support	GIT and nervous disorders	Burning feet syndrome (burning/pinpricking in soles)
B6	Pyridoxine	$Hb$/RBC synthesis, neurotransmitter synthesis	Microcytic anaemia, seizures	Small RBCs, involuntary shaking, loss of consciousness
B7	Biotin	Metabolic support	GIT and nervous disorders	Excessive water loss from the body

Notice how several of these vitamins share overlapping symptoms, particularly gastrointestinal disturbances (B5, B6, B7) and nervous system problems (B1, B5, B6, B7). This is why doctors often look at the combination of symptoms rather than any single symptom to determine which specific B vitamin is lacking.