
June celebrates a Vitamin of the Month. Since it's our first Vitamin, we'll start with the first of the B vitamins.
In case you missed the 2nd Tuesday program about vitamins, let's first do a little review about vitamins in general. Humans have long understood that certain foods cured certain illnesses. It wasn't until 1929, however, that 2 men shared the Nobel prize in medicine for their discovery of "vital amines" and the formulation of the "vitamin theory" of disease. Research continued in earnest to identify these "vital amines," which became the vitamins we know and love today.
A vitamin, by definition, is an organic compound required as a nutrient in tiny amounts by an organism. Vitamins are usually categorized as being either water or fat soluble and have a number of functions in the body. While there are exceptions, we can make some generalizations about vitamins. They are (mostly) not made in the human body, so are required to be supplied in the diet. The water soluble vitamins (all the Bs and C) are not stored by the body. Amounts taken in beyond the current body requirement are processed, mostly by the kidneys, and excreted. Therefore, the body needs a constant supply of these vitamins. This also makes the water soluble vitamins very non-toxic.
Vitamin B1, aka Thiamin, has a longer history of being known
of, than actually
known. The disease beriberi is caused by a deficiency of thiamin and was recognized as early as 2600 B.C! In 1855 a Japanese naval officer cured most of his crew who were suffering from beriberi by feeding them milk and meat. But scientists of the time believed firmly that beriberi was caused by bacteria. The story goes that a Dutch physician was trying to prove this bacteria theory by injecting chickens with infected blood. He wasn't having much luck with this tactic when he noticed that all the chickens - not only the injected ones - were having trouble walking in the yard, and showed other symptoms similar to his beriberi patients. Further investigation revealed that the chickens had been fed polished rice instead of brown rice. Returning brown rice in the feed cured the chickens and the notion of dietary deficiency was born!
It was later discovered there was a certain compound in the husks of rice that was then named Vitamin B. And later than that it was discovered that there were multiple compounds in those husks and the first one, Vitamin B, got renamed Vitamin B1. In 1936, Roger R. Williams was the first to synthesize Vitamin B1 in the lab and he named it thiamin because it had a thio sulfur group and an amine side chain. (You chemists will understand that, the rest of us just skimmed over that sentence!)
Functions of Vitamin B1. Thiamin has three known enzyme reactions in the body. Two of these reactions are critical for making ATP - the body's basic energy source. The third is involved with the conversion of sugars and nucleic and fatty acid synthesis. It is required for the production of HCl (hydrochloric acid) and helps stabilize glucose control. For those of you who would like to see some of the biochemistry involved with these enzymatic reactions, follow this link:
Pyruvate Dehydrogenase Complex (Watch at the beginning for TPP - thiamin pyrophosphate.) Thiamin also plays a role in the function of nerve membranes and nerve conduction, but that role is still unclear. It seems to stabilize brain chemistry.
Deficiency of Vitamin B1. As mentioned earlier, beriberi is the deficiency disease associated with the lack of thiamin. There are two forms of beriberi - wet and dry. Dry beriberi is found mostly in older adults and thought to be the result of chronic thiamin deficiency, especially when combined with a high carbohydrate diet. Symptoms are muscle weakness and wasting, mostly in the legs, as well as peripheral neuropathy with tingling and numbness. Wet beriberi has significant cardiovascular involvement leading to right-sided heart failure and respiratory involvement with edema.
Beriberi is, obviously, the severe end of the thiamin deficiency scale. There are other observable signs of more moderate deficiencies that affect mostly the nervous and cardiovascular system. In adults, these include loss of appetite, mental confusion, indigestion, constipation, fragile skin, cheilosis, rapid heart rate and palpitations. In infants, symptoms may occur very suddenly and severely and can be life-threatening.
Thiamin deficiency is also associated with alcoholism in a condition called Wernicke's encephalopathy. Alcohol dependence contributes to this because of decreased intake of the vitamin and decreased absorption of it, as well as in increased requirement for it with liver damage.
Sources of Vitamin B1. Thiamin is common in many foods including meat, legumes, whole grains, sunflower seeds, wheat germ and some vegetables too, like collard greens and asparagus (which is now in season - great opportunity!) As a supplement, thiamin is best absorbed in an acid medium so the best supplements will have it as Thiamin HCl.
Vitamin B1 Interference. Already mentioned, alcohol greatly interferes with appropriate levels of thiamin. Raw fish and shellfish (as in sushi) contain compounds called thiaminases that destroy the vitamin. So be aware that your sushi/sake meal is not giving you the thiamin you need! Occasionally that's not a problem, in 3 meals/day, you'll want to reconsider your menu. Tannins in black tea and coffee can oxidize thiamin and decrease its activity. Chlorinated water inactivates and pharmaceutical loop diuretics may also deplete Vitamin B1.
Recommended Amounts & Toxicity. Many of you know I believe the RDA/RDI/DRI/AI recommended amounts of vitamins are way too low. In fact, the original RDAs were established in amounts to prevent the deficiency disease in healthy adults. So, if you get 1.2 mg/day of Vitamin B1, you won't get beriberi. That's a good thing, of course! None of us want beriberi! But I believe there is somewhat of a chasm between
not getting beriberi and having optimal health! 15-30 mg/day is probably a healthier goal. In regard to toxicity, the risk here is very low. There are no ill effects known in humans up to 200X the RDA and the LD50 in animal tests are at levels of 125-350 mg/kg of body weight. Even at the low end of that scale, that works out to over 8000 mg for a 150 pound human!
Very high doses of thiamin are used in some rare inborn errors of metabolism and other metabolic disorders. These situations are beyond the scope of this newsletter, but if you have, or know someone with one of these conditions, you are probably already aware of this treatment.
Please note! Except for in special circumstances, the B vitamins should not be taken as supplements singly. Ideally you get plenty in your regular diet of whole grains, beans and asparagus. But if you're supplementing vitamins, get your Bs in a B-Complex or in a multi-vitamin that contains the full spectrum of the Bs.
There
is a fancy test that can be done to assess your Vitamin B1 status. It measures erythroctye transketolase activity in hemolyzed whole blood. Transketolase is an enzyme in one of those biochemical processes mentioned earlier that is dependent on thiamin. But this test is on the expensive side and unless there's some genetic problem, or you just REALLY want to know, given the incredibly low level of toxicity and the relative inexpense of B vitamins, it would be a whole lot easier to just eat better and take some if you think you're low! My two cents....!
Enjoy Good Health with all the B Vitamins!