During the 19th century, scientists studying human nutrition began to identify all of the nutrients required for life. They knew that the body requires nutrients such as protein, fats, and sugars to build tissues and fuel biological processes, but it became clear that even when calories were plentiful, there were some vital nutrients that, when missing, would cause catastrophic illness and death.

One of the first of these deficiency syndromes to be identified was scurvy, a deficiency of vitamin C.  It was the study and pursuit of these vital nutrient deficiencies that led to the discovery of the B vitamins, a group of water-soluble chemicals that work with enzymes to support a wide range of functions in the body.

Beriberi

Among the B vitamins, one of the earliest deficiency syndromes to be discovered was beriberi, a deficiency of vitamin B1 (thiamine). The symptoms of beriberi are weakness and numbness in the feet and legs, swelling, difficulty breathing, and heart failure. Beriberi was eventually traced to a diet of polished white rice. When the rice bran is returned to the diet, the symptoms are reversed.

There are two types of beriberi. Wet beriberi affects the cardiovascular system and dry bereberi, also known as Wernicke-Korsakoff syndrome, affects the nervous system.

1. The symptoms of dry beriberi include:
2. Difficulty walking
3. Numbness or tingling  in hands and feet
4. Muscle weakness or paralysis
5. Confusion
6. Difficulty speaking
7. Pain
8. Nystagmus (eye movements)
9. Vomiting

Wet beriberi can cause additional symptoms like shortness of breath, increased heart rate, and swelling in the legs.

Pellagra

Pellagra is another disease that led to the discovery of a vitamin. Pellagra is caused by a deficiency of vitamin B3 (niacin).

The common symptoms of pellagra are:

1. Hair loss
2. Dermatitis and swelling of the skin
3. Inflamed tongue
4. Insomnia
5. Diarrhea
6. Weakness
7. Ataxia
8. Confusion
9. Aggression
10. Dilated cardiomyopathy
11. Dementia

A lack of niacin in the diet leads to decreased production of nicotinamide adenine diphosphate (NAD). NAD is required for a number of critical metabolic functions in the body. If untreated, it can lead to death in four to five years.

Pellagra is found in populations where the diet is heavily based on corn, and in certain parts of Africa, Indonesia, and China.

In addition to dietary deficiency, pellagra can be caused by conditions that prevent the absorption of niacin, such as Crohn’s disease or other inflammatory disorders of the intestine. Alcoholism can also interfere with absorption leading to pellagra.

B12 Deficiency

Vitamin B12 (cobalamine) is only found in animal food sources. Due to this, people most at risk of B12 deficiency include vegetarians.  Those who have had weight loss surgery are also at a high risk because the surgery disrupts absorption of B12 from food. Other conditions that affect absorptionsuch as celiac disease or Crohn’s disease, can also lead to B12 deficiency. According to the National Health and Nutrition Examination Survey, approximately 3.2 percent of adults over the age of 50 have a B12 deficiency, and up to 20 percent may have levels of B12 that are borderline.

The primary symptoms of B12 deficiency are:

1. Numbness or tingling in hands, legs, and feet
2. Difficulty walking
3. Anemia
4. A swollen tongue
5. Jaundice
6. Cognitive changes
7. Hallucinations
8. Paranoia
9. Weakness
10. Fatigue

In addition to animal-based foods, dietary Vitamin B12 can be obtained from breads and cereals fortified with B12, or through a supplement.

Folate Deficiency

Folate (vitamin B9) is an important vitamin that works with other B vitamins to metabolize proteins, and synthesize both blood cells DNA. Green leafy vegetables, legumes, grains, meats, and organ meats are high in folate. The vitamin is not stored in the body, so levels of folate in the body can become low after just a few weeks of eating a folate-deficient diet. As with other deficiency syndromes above, disorders of the digestive system and alcoholism can contribute to folate deficiency. Additionally, certain medications, hemolytic anemia, and kidney dialysis can result in folate deficiency.

Symptoms of folate deficiency include fatigue, irritability, diarrhea, poor growth, and a smooth or tender tongue. In pregnant women, a deficiency of folate can also increase the risk of neural tube defects in the developing fetus.

For most people, a healthy diet high with a variety of meats, grains, fruits, and vegetables is enough to prevent a deficiency of B complex vitamins. Women who expect to become pregnant are advised to take folate supplements. Older people or those with medical conditions that increase the risk of B vitamin deficiency may also benefit from taking a daily supplement.