Thiamin (or Vitamin B1)

Vitamin B1, also called thiamin, is one of the vital B vitamins that we need for full health. Being water soluble and not stored to any significant degree in the body, thiamin needs to be consumed regularly. 

Function

Thiamin as part of the enzyme, thiamin pyrophosphate (TPP) helps us break down carbohydrates, fats and branched chain amino acids (part of proteins), for energy. Its primary concern is helping to break down carbohydrates. As part of another enzyme, transketolase, it is responsible for producing a molecule (NADPH), that enables us to make our own fats including myelin sheath fats, for lining our nerves.

Deficiency

We may not get enough thiamin if we drink too much alcohol on a regular basis, abuse diuretics, have weight loss surgery, anorexia or have poor intestinal absorption. Of these alcohol abuse is probably the most prevalent in the first world. It causes a double whammy, as it reduces levels of the transporter that both helps us absorb thiamin from the gut, and reabsorb it after it has been filtered in the kidneys. Add to this that most alcohol abusers do not eat enough, and that in some cases their urinary flow is greater than normal, and you see a recipe for a quick route to thiamin deficiency.

The brain and nervous system, rely heavily on carbohydrate for energy as well as myelin (see above) to ensure proper nerve communication. The heart also relies heavily on carbohydrate metabolism. These areas are the areas most affected when we are deficient in thiamin. 

It is not rare to be deficient. One in every forty of us could be damaging our health through inadequate vitamin B1 status(1). In other words you probably know at least 10 people who seriously need to up their intake to improve their health. It is also worth remembering that if you exercise a lot then your need for thiamin increases.

Beriberi

The classic disease of serious thiamin deficiency is beriberi. It was first described in China thousands of years ago, where it was associated with a high carbohydrate diet consisting of white, polished rice. Symptoms begin with sensory nerve damage in the hands and feet followed by the limbs. Muscle wasting and paralysis follow. This has become known as "dry beriberi". It can also manifest itself with fluid retention and eventual heart failure, these symptoms being called wet beriberi".

Wernicke-Korsakoff syndrome

In cases of chronic alcohol abuse thiamin levels plummet and both Wernicke's encephalopathy and Korsakoff's psychosis are experienced together. These are sometimes referred to as cerebral beriberi. Symptoms include abnormal eye movements (nystagmus) and body movements (ataxia), and profound recent memory loss (Korsakoff's syndrome).

Gastrointestinal beriberi

A recent finding of gastrointestinal beriberi has been made, in which an accumulation of lactic acid causes nausea and abdominal pain. This may be a lot more common than thought, as during induced thiamin deficiency experiments in the 1940's these gastrointestinal symptoms were seen in nearly all participants(2).

Disease treatment and prevention

In diseases where deficiency in thiamin is a factor, then treatment with thiamin is indicated. There is however not a case for using thiamin in large doses for anybody with adequate thaimin status.

Congestive heart failure

Drugs called diuretics are often used to treat heart failure patients. Since diuretics lower thiamin levels it is logical to assume that thiamin supplementation could help in these cases. There is good evidence that it does(3).

Diabetes

High blood sugar is a hallmark of diabetes. It also seems to reduce thaimin levels in the blood as well as reducing insulin levels. This is a vicious circle as one effect supports the other. It has been found that thiamin supplementation in diabetic patients has reduced their blood sugar levels(4).

Genetic diseases

The following genetic diseases may be treated with vitamin B1 therapy as in some instances, it is the metabolism of thiamin that is at fault.

  1. Basal ganglia disease
  2. Megaloblastic anaemia
  3. Maple syrup urine disease
  4. Pyruvate dehydrogenase complex (PDHC) deficiency 

Testing for B1 status

Your thiamin status is determined by what is known as an ETK (erythrocyte transketolase) test. Transketolase is one of two enzymes in our body that thiamin helps to work. Its level in red blood cells (erythrocytes) falls early on if you become deficient in thaimin. By measuring its level in red blood cells you get a good indication of thiamin status. I can test this for around £20, although you may be better off testing your status of all B vitamins, which would cost in the region of £50. The test involves administering excess vitamin B1 to your red blood cells, to compare transketolase activity with its normal activity level of 1.0. A level below 1.15 is considered OK(5). 

Which foods contain thiamin

Most meat, especially liver contains good amounts. Good non-meat sources include asparagus, cabbage, kale, oranges and potatoes. Eggs, nuts and seeds also contain good amounts of thaimin.

Many processed foods are fortified with thiamin, including virtually all cereal products. For this reason most people in the first world are not deficient.

Should I supplement thiamin

It is unlikely that you would supplement thiamin on its own as most people who are short on vitamin B1 will also be short on other B vitamins. As such it is best taken as part of a B-complex supplement or multivitamin pill. 

Thiamin absorption from the gut is by an active transport mechanism that can get saturated. Think of a turnstile into a sports venue with a queue. With saturated transporters there is a much slower absorpton via passive diffusion. In terms of supplements this means that high levels of thaimin (e.g. 50mg+ per day) are not very well absorbed. It is more important to have a regular dose (e.g. 20mg per day) than to take a few mega doses.

Supplements normally come in the form of thaimin hydrochloride. Intakes of up to 50mg per day are well tolerated by most people. It is unlikely that you could overdose on thiamin, especially if you take it orally. There is no upper limit set on intakes by the various national nutrition boards.

In rare cases there have been reactions with intravenous and intramuscular injections. If you have cancer then consult your oncologist before supplementing, as thiamin can help certain tumours grow more quickly.

References

1) http://www.ncbi.nlm.nih.gov/pubmed/438830

2) http://www.redorbit.com/news/health/110093/gastrointestinal_beriberi_a_previously_unrecognized_syndrome/

3) http://www.ncbi.nlm.nih.gov/pubmed/7733128?dopt=Abstract

4) http://www.ncbi.nlm.nih.gov/pubmed/20652275

5) http://www.biolab.co.uk/index.php/cmsid__biolab_test/Vitamin_B1_(Thiamine)_-_transketolase_activity