Thiamine, also known as vitamin B1, is a water-soluble vitamin crucial for the proper functioning of the nervous system and muscles. It cannot be synthesized by humans or animals, necessitating its acquisition through diet. Synthesized by bacteria, plants, and fungi, it plays a crucial role as a metabolic precursor to thiamine pyrophosphate (TPP), an essential coenzyme.

Vitamin B1 deficiency can lead to serious illnesses such as beriberi and Wernicke's encephalopathy in humans.

Discovery History of Thiamine

• In the 1880s, beriberi ravaged the troops of the British Indian Army and aboard ships of colonial powers in the Far East, initially considered an infection or intoxication.
• In 1897, Eijkman made a groundbreaking discovery by demonstrating the nutritional character of beriberi. He managed to induce the disease in chickens and cure them with brown rice, earning him the Nobel Prize in Medicine in 1929.
• In 1911, Umetarō Suzuki identified aberic acid in bran, a remedy for beriberi. Unfortunately, his work went unnoticed due to the language barrier.
• In 1912, Kazimierz Funk entered the scene by describing the "vitamine," though he was mistaken in thinking it was the active element against beriberi.
• In 1926, B.C.P Jansen and Willem Frederik Donath isolated vitamin B1 from rice, but they struggled to characterize it accurately.
• In 1933, Robert R. Williams established the chemical formula of vitamin B1, naming it thiamine.
• In 1936, he successfully completely synthesized thiamine and obtained a patent, thus demonstrating its identity with natural thiamine and the profitability of industrial synthesis.

Thiamine production increased from 100 kg in 1937 to 200 tonnes in 1967, a staggering 1999% increase over 30 years.

Human Requirements for Thiamine

The minimum requirements for vitamin B1 are closely related to carbohydrate consumption, as this vitamin is involved in their metabolism. These requirements vary depending on body weight, level of physical activity, and dietary composition. Nutritional recommendations are often expressed in mg per megajoule (mg/MJ) of consumed energy, with a reference of 0.1 mg/MJ for the general population.
In terms of minimum daily intake, adult men generally require about 1.5 mg/day, while for women, the recommendation is 1.2 to 1.3 mg/day, with an increase to 1.8 mg/day for pregnant women. Thiamine is naturally found in foods or can be taken in supplement form.
The best food sources of thiamine include whole grains, pork, and nuts, with amounts ranging from 0.5 mg to 2.2 mg per 100 g of food. Although the human body can also produce thiamine from the microbiota of the large intestine, this source is generally not sufficient to compensate for a deficiency.

However, its stability in food is compromised

Thiamine, essential for our health, can be affected by various factors. Sulfites, often used as preservatives in fruits, vegetables, lean meats, and deli meats, can alter its quality. Similarly, chlorine present in cooking water, as well as copper ions, can lead to a decrease in thiamine.

The stability of thiamine varies depending on the environment. It remains stable in acidic solutions such as fruit juices and acidic drinks, but degrades in neutral or alkaline environments. For example, adding sodium bicarbonate when cooking vegetables to preserve their color can lead to thiamine loss due to the alkaline environment.

Thiamine is also sensitive to various agents, such as oxidizing or reducing agents, as well as radiation. Additionally, it is sensitive to heat and tends to dissolve in cooking water.

In cereals, thiamine is not uniformly distributed. Refining processes, such as bleaching cereal flour or polishing rice, can significantly reduce thiamine content. For example, refined cereal flour can lose over 40% of its thiamine compared to whole grain cereal flour, and polished rice can lose over 75% compared to whole rice.

Different cooking methods, such as roasting or frying, can also lead to thiamine loss, especially for meats. However, fatty meats lose less thiamine when cooked than lean meats, and breaded meat generally contains more thiamine than non-breaded meat.

Steaming is recommended to limit thiamine loss, and parboiled rice generally contains more thiamine than non-parboiled rice. Although food processing may reduce thiamine content, it may sometimes be necessary to remove harmful components.

Absorption and Storage of Thiamine in the Human Body
Thiamine is mainly absorbed in the upper part of the small intestine, called the jejunum. Its absorption varies depending on the amount ingested: at dietary doses below 5 mg, it is actively absorbed, while beyond this dose (at pharmacological doses), it is done by passive diffusion.

Body Management of Thiamine: Absorption, Storage, and Elimination
Thiamine is mainly absorbed in the upper part of the small intestine, called the jejunum. Its absorption varies depending on the amount ingested: at dietary doses below 5 mg, it is actively absorbed, while beyond this dose (at pharmacological doses), it is done by passive diffusion.

In some populations, thiamine absorption may be altered. This includes the elderly, those with absorption disorders, alcoholic individuals, and those taking long-term diuretics. Paradoxically, a high-carbohydrate diet can lead to thiamine deficiency, even with adequate dietary intake.

In the human body, thiamine is mainly stored in high-energy-demand organs such as the heart, brain, liver, and kidneys. It is stored as thiamine triphosphate and has a short half-life, approximately 14 to 18 days. This low reserve, combined with high metabolic demands in these vital organs, underscores the crucial importance of regular and continuous thiamine intake through diet.

On average, an adult has a body reserve of about 25 to 30 mg of thiamine, which is relatively modest compared to other nutrients. These reserves are quickly depleted in case of increased or prolonged need, highlighting the need for regular thiamine intake.

Excess thiamine is mainly excreted in urine, but also excreted in feces (notably those from intestinal bacteria), sweat, and breast milk. The thiamine content in breast milk generally varies between 0.14 and 0.21 mg/L depending on the mother's diet.

Crucial Effects of Thiamine:

• Enzymatic Cofactor: Thiamine acts as a valuable enzymatic cofactor in various biochemical reactions. After absorption, it is converted into its active form, thiamine pyrophosphate (TPP), by the action of thiamine pyrophosphokinase. TPP, as a cofactor, plays a crucial role in enzymatic reactions vital for energy metabolism. It is specifically involved in the functioning of pyruvate dehydrogenase and α-ketoglutarate dehydrogenase, crucial enzymes in ATP production via the Krebs cycle and the pyruvate dehydrogenase pathway.
• Carbohydrate Metabolism: Thiamine is indispensable for carbohydrate breakdown, especially glucose. It catalyzes enzymatic reactions that convert glucose into pyruvate, a crucial step for ATP production in mitochondria. Without adequate thiamine, carbohydrate metabolism is compromised, leading to decreased energy production and deficiency symptoms such as fatigue and neurological disorders.
• Nervous Function: Thiamine is essential for the optimal functioning of the nervous system. In addition to aiding in the synthesis of vital neurotransmitters such as acetylcholine, dopamine, and serotonin, it is involved in synaptic transmission, modulation of neuronal excitability, and regulation of synaptic plasticity.
• Fatty Acid Synthesis: Besides its role in carbohydrate metabolism, thiamine is necessary for fatty acid synthesis. It participates in the formation of essential metabolic intermediates for fatty acid biosynthesis, which are major constituents of cell membranes and precursors of bioactive molecules.
• Cardiac Function: Thiamine is vital for the health of the cardiac muscle. It actively participates in the energy metabolism of the heart by facilitating the conversion of energy substrates into ATP. Thiamine deficiency can lead to cardiac dysfunction, including congestive heart failure.
• RNA and DNA Synthesis: Thiamine is indispensable for the synthesis of nucleic acids, such as RNA and DNA. As a cofactor for certain enzymes involved in nucleotide biosynthesis, it contributes to DNA replication, RNA transcription, and other molecular processes essential for gene regulation and cell growth.
• Digestive Function: Thiamine also plays a role in digestive physiology. It participates in the secretion of hydrochloric acid in the stomach, thus facilitating the breakdown of dietary proteins into amino acids. Additionally, it regulates gastrointestinal motility and promotes the absorption of essential nutrients in the small intestine.

Thiamine Toxicity: Evaluation and Precautions

The toxicity of thiamine hydrochloride, commonly known as vitamin B1, is primarily assessed through LD50 in laboratory mice, ranging between 3 and 15 grams per kilogram of body weight. This measure, representing the lethal dose for 50% of exposed individuals, provides crucial insight into the potential danger of this substance.
It is essential to note that thiamine toxicity in humans is considered negligible or very low when administered orally. This low toxicity is due to the kidneys' ability to effectively eliminate excess thiamine through urine, as long as renal function is normal. Thus, even at daily doses of several hundred milligrams, prolonged oral thiamine administration does not seem to lead to significant side effects.
However, despite this relative safety, precautions should be taken when administering thiamine, especially in individuals with renal insufficiency or allergic histories. In such situations, close monitoring is recommended to avoid any adverse reactions.

Forms of Thiamine:

Natural forms of thiamine:

• Thiamine monophosphate: This is a natural form of phosphorylated thiamine, which is an intermediate in the conversion of thiamine to thiamine pyrophosphate, the active form of vitamin B1.
• Thiamine triphosphate: This is another phosphorylated natural or synthetic form of thiamine, which is present in animal tissues and may play a role in nerve signal transmission.
• Thiamine pyrophosphate: This is the natural active form of thiamine, which is used by enzymes in carbohydrate and amino acid metabolism. It is also known as the thiamine pyrophosphate (TPP) coenzyme.

Hydrosoluble synthetic thiamine form:

• Thiamine hydrochloride: used in dietary supplements and medications. It is readily absorbed by the body and is often used to treat thiamine deficiencies.
• Thiamine mononitrate: used in dietary supplements and medications. It is stable and easily absorbed by the body.

Liposoluble synthetic thiamine form:

In the 1940s, during research on thiamine derivatives, mainly conducted in Japan, allicin was isolated and first studied in the laboratory by Chester J. Cavallito and John Hays Bailey in 1944. This discovery later inspired medicinal chemistry work aiming to create other thiamine disulfides. These efforts resulted in the creation of synthetic compounds analogous to thiamine, such as sulbutiamine, allithiamine, fursultiamine, and benfotiamine. These hydrophobic and liposoluble compounds have the characteristic of easily crossing the intestinal barrier to reach the bloodstream, where they are reduced to thiamine.

• Allithiamine (thiamine allyl disulfide): used to treat thiamine deficiencies. Allithiamine is not a compound naturally present in garlic but rather a synthetic derivative obtained from chemical reactions involving garlic compounds. It is sometimes used in certain dietary supplements for its anti-inflammatory properties.
• Prosultiamine (thiamine propyl disulfide): used to treat thiamine deficiencies. similar to allithiamine. It is not used as dietary supplements.
• Sulbutiamine (isobutyryl thiamine disulfide) : used to treat thiamine deficiencies and asthenia. it easily crosses the blood-brain barrier. It is also used in some dietary supplements to improve memory, concentration, mood, and motivation.
• Benfotiamine (S-benzoylthiamine O-monophosphate): used to treat thiamine deficiencies, pathologies related to diabetes, neurodegeneration, anti-inflammatory property, reduced AGE formation, Nrf2 activator. It is also used in dietary supplements to improve health.
• Fursultiamine (thiamine tetrahydrofurfuryl disulfide): used to treat thiamine deficiencies. It is also used in some dietary supplements for its effects on improving motivation, energy, mood, energy metabolism, and endurance.

In a supplementation context

Thiamine supplementation can be beneficial for certain individuals, especially those at increased risk of deficiency or those wishing to optimize their health and well-being, as well as athletes.

Here are some tips to consider before starting thiamine supplementation.

Choose the form of thiamine that suits you:

Thiamine hydrochloride, mononitrate, pyrophosphate, and free thiamine are the most widely used forms of thiamine in supplements and multivitamins; they are the least expensive forms. If you're just looking to meet daily intake and avoid deficiencies, these forms may be suitable. Dosages range from 1 to 500 mg per day.

Benfotiamine is widely available in supplements, more expensive than the previous forms, but better absorbed. If you're also looking for an effect on blood sugar, anti-inflammatory, antioxidant, and neuroprotective properties, benfotiamine might be suitable for you. Dosages range from 150 to 600 mg per day.

Sulbutiamine and fursultiamine (TTFD) are more difficult to access and slightly more expensive than the other two options mentioned, but they are better suited for individuals looking for more nootropic effects such as improvement in motivation, energy, mood, concentration, and memory.

Dosages for sulbutiamine range from 200 to 1000 mg per day, And dosages for fursultiamine range from 50 to 100 mg per day.

But don't forget:

To consult a healthcare professional before starting any supplementation regimen, especially if you have pre-existing medical conditions or are taking other medications. A healthcare professional can assess your individual thiamine needs and recommend the best approach for your health.
Although supplementation can be helpful in filling nutritional gaps, it should not replace a balanced and varied diet. Make sure to consume a range of thiamine-rich foods such as whole grains, meat, vegetables, and nuts, in addition to your supplement, to maximize health benefits.
By following these tips, you can safely and effectively incorporate thiamine supplementation into your daily routine to support your overall health and well-being.