As a follow-up to the post on micronutrients, this is the start of a series of posts on vitamins and minerals. In functional and precision medicine, we talk a lot about micronutrients—and it can be helpful to know what they are, what they do, where you can get them, things that can increase (or decrease) your needs for them, and their target levels.

Let’s start with Vitamin B1, aka thiamin. Thiamin is the first of eight B vitamins and is a real workhorse. All the B vitamins play key roles in energy metabolism—that is, in getting energy from fat, carbohydrates, and proteins. Thiamin is no exception. It is especially important for carbohydrate metabolism and nerve function, and it also acts for a co-factor for over 20 enzymes involved in the energetics of the cell (including the synthesis of ATP – the main currency of energy in our bodies). Its other roles include detoxification, antioxidant defense, and supporting vitamin K and folate metabolism.

Not getting enough thiamin can make it harder to metabolize your food and, specifically, your carbohydrates. Without thiamin, carbohydrates are more likely to build up in your bloodstream. Metabolic products like lactate and pyruvate also build up, which slow down energy production through ATP.  Mild deficiency might show up with vague or subtle symptoms, like fatigue, or irritability, or mild muscle weakness. Severe deficiency—the kind you learn about in medical school—can cause something called beriberi, which can show up in two major ways. In “dry” beriberi, people can experience muscle weakness, numbness and tingling, and loss of reflexes. In “wet” beriberi, the heart gets involved, leading to swelling, shortness of breath, and a rapid heart rate. Thiamin deficiency can also affect the brain, in a condition called Wernicke’s encephalopathy, which involves difficulty with balance, confusion, and weakness of the eye muscles. Korsakoff Syndrome can follow Wernicke’s encephalopathy, and involves severe memory problems, including both anterograde amnesia (which is the inability to form new memories) and retrograde amnesia (which is the loss of pre-existing memories). People who are affected may make up stories to fill in the gaps (and may not be aware that the stories aren’t true).

So thiamin deficiency can make your hands and feet tingle, go numb, or become weak or painful; cause the muscles around your eyes to weaken or twitch; cause heart problems; cause balance issues; make you feel weak or focused; affect your memory; and affect your metabolism. These are things no one wants. And they can be avoided by making sure you have enough thiamin.

How much is enough? The recommended daily amount (RDA) for thiamin is 1.1-1.2 mg per day. With an average diet (and even a poor diet), it isn’t too difficult to reach this amount. Thiamin is in a variety of foods, and the best sources are nutritional yeast, legumes (like lentils, peas, and beans) and whole grains. Enriched flour has thiamin in it (it is added back in after being removed in the refining process).  Several vegetables (brussels sprouts, butternut squash, asparagus, kale, etc) contain smaller amounts of thiamin, as do a variety of meats (fats, however, contain no thiamin). If you want a comprehensive list, you can look at the USDA’s FoodData Central (which, as of this writing, has 14,356 entries for foods containing thiamin, with the amount of thiamin per serving).

Interestingly, though, despite being present in many foods, thiamin deficiency seems to be relatively common, with rates ranging from 20% to as high as 90% depending on the study—even in individuals who were exceeding the RDA by as much as fourfold! In a great piece on the topic, Marrs and Lonsdale suggest that the current RDA may not be enough to meet the “demands of modern living”. Thiamin has a very short half-life, isn’t easily stored in the body, and can be broken down and otherwise depleted by numerous factors. One of the most important of these is gut function. With leaky gut or gut dysbiosis, even with “enough” thiamin in your diet, you might not be able to absorb it. Another key factor is blood sugar control—having high blood sugar causes loss of thiamin. Other factors include liver disease, alcohol abuse (Wernicke and Korsakoff are usually thought of in this group), and even certain foods (raw fish, shellfish, and foods that contain sulfites, for example). This doesn’t mean you shouldn’t eat these things, necessarily, but it does mean that you may need more thiamin if you do. And food doesn’t always have as much thiamin as we think it will—when food is refined or even just stored, thiamin breaks down. In one interesting studying done by NASA that looked at nutritional content in food in spaceflight, the amount of thiamin present in food varied dramatically depending on the food and how it was stored, with some foods having a little as 3% of their original thiamin content! Most of us aren’t eating space food, but most of us aren’t eating food that was harvested that morning either.

How can make sure you are getting enough thiamin? One way is to test your status with a micronutrient analysis, like the Nutreval, or by checking whole blood thiamin levels through Labcorp or similar. If the levels are low, or low-normal, the first step is to try and understand why. Are you getting enough in your diet? If so, are you absorbing it sufficiently? Is your gut health optimized? Do you have diabetes? Thiamin can be supplemented, both orally and intravenously. When given orally, there is no upper limit of safety because it is water soluble and easily eliminated by the kidneys. Doses as high as 500 mg have been given safely (for conditions like Wernicke’s encephalopathy) without issue. Most supplements have 10 to 100 mg of thiamin.

In summary, thiamin, or vitamin B1, is the first of eight B vitamins. It is involved in burning carbohydrates (more so than any other vitamin), making ATP, supporting mitochondria, and supporting the heart and nervous system. Deficiency may be more common than we think. Thiamin can be found in high concentrations in nutritional yeast, legumes, and whole grains, and can be safely supplemented (usually in doses between 10 and 100 mg).

Do you have enough thiamin?  

References

1.         Marrs C, Lonsdale D. Hiding in Plain Sight: Modern Thiamine Deficiency. Cells. 2021;10(10):2595. doi:10.3390/cells10102595

2.         PhD CM. Vitamin B1: Thiamin. Harnessing the Power of Nutrients. Published June 27, 2022. Accessed July 8, 2024. https://chrismasterjohnphd.substack.com/p/vitamin-b1-thiamin

3.         Office of Dietary Supplements - Thiamin. Accessed July 8, 2024. https://ods.od.nih.gov/factsheets/Thiamin-HealthProfessional/

4.         Mrowicka M, Mrowicki J, Dragan G, Majsterek I. The importance of thiamine (vitamin B1) in humans. Biosci Rep. 2023;43(10):BSR20230374. doi:10.1042/BSR20230374

5.         FoodData Central. Accessed July 8, 2024. https://fdc.nal.usda.gov/fdc-app.html#/?component=1165

6.         Dietary factors potentially impacting thiaminase I-mediated thiamine deficiency | Scientific Reports. Accessed July 8, 2024. https://www.nature.com/articles/s41598-023-34063-5

7.         Goulette TR, Zhou J, Dixon WR, et al. Kinetic parameters of thiamine degradation in NASA spaceflight foods determined by the endpoints method for long-term storage. Food Chem. 2020;302:125365. doi:10.1016/j.foodchem.2019.125365

8.         McLaughlin K, Joyal K, Lee S, et al. Safety of intravenous push thiamine administration at a tertiary academic medical center. J Am Pharm Assoc JAPhA. 2020;60(4):598-601. doi:10.1016/j.japh.2019.12.005