Micronutrient deficiencies and the brain

In the first week of the course, we briefly discussed some metabolic aspects of the brain, such as its energy requirements. However, the brain doesn’t need only a steady supply of water, glucose and oxygen to survive in a healthy state.

Instead, there are micronutrients: vitamins and minerals that are essential to healthy brain functioning. Micronutrient deficiencies are common in case

of chronic malnutrition: vitamin B3, vitamin C or iodine deficiency and their associated syndromes were widespread enough to have a social impact in the Western world such, as in the case of scurvy, pellagra or congenital iodine deficiency syndrome. The last two where, for instance, common in Italy. Pellagra was widespread in the north-east, where farmers mainly ate maize porridge or polenta, while iodine deficiency was reported in the kingdom of Sardinia, in the North West. In this video we will focus on B group vitamins and we will talk about neurological syndromes

associated with a lack of one of these vitamins: vitamin B1, or thiamine. This vitamin is required by fundamental cellular processes, such as the metabolism of sugars and amino acids.

In the brain, it plays additional roles: for instance, it modulates the activity of neurons that use acetylcholine to transmit information. Like all other B vitamins, thiamine is soluble in water. As you might recall from the first week, large water-soluble molecules cannot cross freely the blood-brain barrier and must be transported through it. Due to their importance, all B group vitamins have dedicated transport mechanisms. Once in the brain, these vitamins are used by the cells and their concentration is tightly regulated by homeostatic mechanisms. The lack of vitamin B1 from the diet for prolonged periods causes a condition known as beriberi that can primarily affect the brain the cardiovascular system or the digestive system causing different symptoms.

Beri-beri was first characterized and described in Japanese sailors. During missions, low ranking sailors lived on a diet of polished white rice and casualties linked to malnutrition were common. It was reported that during a single trip from Japan to Hawaii almost half of the crew fell ill and more than 1 in 20 died. Beri-beri was a serious problem in the Japanese Navy and it was studied by doctors such as Takeshi Kaneshiro, but it wasn’t until the first decade of the 20th century that anti beriberi nutrients were discovered in rice and barely brain.

Nowadays in the Western world, thiamine deficiency syndromes are rare, but low-grade deficiencies are still common even if many foods are fortified with thiamine and other micronutrients to avoid public health crisis. In fact the most severe case of thiamine deficiencies can be only observed in people suffering from specific medical conditions. This is the case ,for instance, of long term alcohol abuse. Long term alcohol addicts can suffer from a condition known as Wernicke-Korsakoff syndrome. This syndrome is caused both by the lack of thiamine in their diet and by its reduced absorption due to gut and liver damage.

In the acute phase of these illness, known as Wernicke encephalopathy, people can suffer from confusion, disturbances of walking, disturbances of eye movements, and amnesia for new events depending on the severity of the illness. Most of these symptoms can be treated and improve if the deficiency is treated early on, but if it is allowed to progress to the so called alcoholic Korsakoff syndrome the consequences are permanent cognitive damages coma and even death. Wernicke Korsakoff syndrome is characterized by deficits in multiple cognitive tasks, but one of its defining features is confabulation, or the presence of invented memories taken by the patients as they were true, often to fill in gaps in memory.

Severe deficiency syndromes such as beriberi are the extreme consequence of the lack of micronutrients and underline their importance for a healthy brain. However, marginal deficiencies of micronutrients are still present even in Western countries and can cause symptoms such as a lower mood or poor memory performance. The evidence in that respect is less strong than for more severe deficiencies but there are studies that investigate the effect of vitamins, prebiotic fibers and antioxidants in aging is a preventative measure and to increase well-being. We will partly discuss these arguments in the last video of this week.