Selenium, Probiotics and the Brain and Alzheimer’s Disease

There are many different supplemental nutrients that support healthy brain function including vitamins, minerals, herbs, cell salts, etc. I am focusing on selenium and probiotics today because I recently came across a very important clinical study. Most people are unaware of the existence of a gut-brain hormonal axis (through which the digestive tract and brain communicate), or the fact that the level of brain health is dependent, in part, upon the state of balance or imbalance of your bowel bacteria. The study I came across described the results of a study wherein a combination of selenium and probiotics were given to people suffering with Alzheimer’s Disease (AD). Remarkably, individuals given this specific combination showed an improvement in cognitive functions. Something many doctors consider to be impossible in cases of established AD.

Selenium

Selenium is an essential mineral that supports, among many other things, metabolism, immune system, and thyroid function. Antioxidants protect body cells from damage by free radicals. Over time, this cell damage (referred to as oxidative stress) is a contributory factor to the development of  cancer, heart disease, and the cognitive decline. As an antioxidant, selenium delays the oxidation of polyunsaturated fatty acids and preserves tissue elasticity. This trace mineral protects the cell membrane and the membrane of the mitochondria from lipid peroxidation (oxidation of fats; these membranes contain a high percentage of lipids). In a typical human cell membrane, proteins account for about 50 percent of the composition by mass, lipids (i.e., fats) account for about 40 percent, and the remaining 10 percent comes from carbohydrates.

Selenium is required by cells for the production of certain prostaglandins that promote healthy blood flow. Prostaglandins are a group of lipid compounds (formed by enzymatic interaction with the fatty acid, arachidonic acid) that exert hormone-like action which aids in the control of blood pressure, smooth muscle contraction, inflammation and cellular reproduction.

Selenium deficiency is common. It is estimated that somewhere between 500 million and 1 billion people worldwide are selenium-deficient.

Selenium is found in the brain, kidneys, heart, liver and spleen. Notably, selenium and vitamin E are involved in overlapping systems in the body. Selenium’s antioxidant action parallels the free radical scavenging action of vitamin E. Deficiency symptoms of selenium are similar to those of vitamin E. Thus, when taken supplementally, it is best to take selenium in conjunction with vitamin E. Vitamin E has a greater effect than selenium in reducing lipid peroxidation in certain brain regions. That is why vitamin E is one of the first vitamins to consider for the prevention of AD.

Prolonged selenium deficiency compromise thyroid hormone homeostasis in the brain. Thyroid hormones are essential for normal brain development. Thyroid hormone deficiency may severely affect the brain during fetal and postnatal development, causing retarded maturation, intellectual deficits, and neurological impairment. The thyroid hormone T3 regulates the expression of a large number of genes in the brain, both during its developmental stages during the fetal and childhood periods, as well as in the adult period. Here we see the overlap between the essential nature of selenium for both brain and thyroid functions.

The thyroid gland produces the hormones T4 and T3. The former is the inactive storage form of thyroid hormone. The latter is the active form. Most tissues, including the brain, convert T4 to T3, enabling thyroid hormone to operate on a cellular level. Importantly, the conversion of T4 to T3 is dependent upon selenium (as well as vitamin E). Selenium is critical for the production of the antioxidant enzymes glutathione peroxidase and thioredoxin reductase, some of the highest levels of which are found in the thyroid gland. These enzymes convert potentially destructive hydrogen peroxide into water. Hydrogen peroxide is nevertheless required for the synthesis of thyroid hormones. However, high levels of hydrogen peroxide cause oxidative stress and must be neutralized. These two selenium-dependent enzymes keep the thyroid from self-destructing. 

The form of selenium that I prefer is called selenomethionine.

Similar to other tissues, selenium from selenomethionine is deposited in the brain at higher concentrations than selenium in other forms. 

A selenium containing protein, selenoprotein P, is taken up in greater amounts by the brain but not by other organs in selenium deficient animals, suggesting that selenoprotein plays a critical role in the brain. Selenium influences compounds with hormonal activity (and neurotransmitters) in the brain, and this may be why it influences moods and behavior.^​1​

Given all of this, it is unsurprising that selenium supports the brain’s cognitive functions.

Research shows that selenium’s antioxidant properties fight cellular damage that may contribute to the development, or worsening, of brain and nervous system diseases including Parkinson’s disease, Alzheimer’s disease, and multiple sclerosis. In cases of selenium deficiency, the brain is the organ that remains supplied with this mineral the longest, suggesting that selenium plays an essential role in brain functions.

In the study entitled: Selenium and cognitive impairment: a brief-review based on results from the EVA study, the researchers found that their results were “consistent with the hypothesis that low selenium status is a risk factor for cognitive decline. The concomitant evolution between plasma selenium decrease over a 9-year period and cognitive decline suggested that optimal selenium status is potentially important to maintain neuropsychological functions in aging people.”^​2​

Population studies of nutritional status and cognition have found that older adults with the lowest dietary selenium intake levels showed reduced performance on some measures of cognition.

The effect of low selenium on cognitive function has been found to be more evident in men, which is consistent with sex differences in prioritization of selenium in the body. Selenium is important in the male reproductive system, so there may be less available for the brain when levels are low. Insufficient selenium levels may promote processes, such as oxidative stress, which harm brain cells.^​3​

Studies indicate that selenium levels are altered in the brain and blood of those with dementia. This may be reflective of either, or both, inadequate nutritional patterns and an inability to effectively utilize selenium in the body.^​4​

Combining Selenium and Probiotics for Alzheimer’s Disease

While supplementation of selenium by itself has not been shown to improve cognitive function in dementia patients, selenium in combination with a probiotic had benefit on the same cognitive measures, upon which selenium alone had no effect.

Sleep disorders are known to contribute to the development of neurological diseases.

In a recent study, researchers found that “chronic sleep restriction induced oxidative stress and inflammation and altered gut-brain axis hormones. Oral probiotic administration boosted the antioxidant capacity of the brain, thus limiting the oxidative damage provoked by loss of sleep. Moreover, it positively regulated gut-brain axis hormones and reduced brain inflammation induced by chronic sleep restriction.”^​5​

Important to note here that there is a hormonal axis (pathway of hormonal communication) between the gut and brain. This study demonstrates that imbalances in the gut microbiome directly affects brain function.

Also, this study highlights the connection of chronic sleep disturbance and the development of neurological disorders. I will be discussing this topic in much greater detail next year, when normal sleep will be one of my focuses.

In a study involving the cognitive functions of 79 men and women with Alzheimer’s disease (AD), participants were given a combination of selenium (200 mcg. per day)  plus a probiotic (L. acidophilus; B. bifidum and B. longum), or selenium and a placebo for 3 months. The researchers report: “Compared with only selenium and pacebo, probiotic and selenium co-supplementatiohn resulted in a significant increase in mini-mental state examination.”

This is highly significant as the usual course for AD patients is progressively degenerative. This study demonstrated that AD patients actually improved. The conclusion of the researchers: “Overall, we found that probiotic and selenium co-supplementation for 12 weeks to patients with AD improved cognitive function and some metabolic profiles.”^​6​

I have mentioned previously that the probiotic that I use is a brand called Bio-K Plus. Always use a brand that is stored in the cooler of your health food store. I have not found the probiotics stored on shelves, at room temperature, to have anywhere near as much value. Always take probiotics on an empty stomach with lots of water.

I use selenomethionine. Do not exceed a dose of 200 mcg. (1/5 of one milligram) daily, as selenium is only needed in very small amounts. High doses of selenium can be toxic.

I always use selenium in conjunction with vitamin E. I take 400 i.u. of natural d’alpha tocopherol in a base of mixed tocopherols twice daily, at breakfast and dinner.

Food sources of selenium include: Brazil nuts (the best source; 2 nuts per day will be provide sufficient selenium for the body); grains, nuts, seeds, lentils, garlic, wild, deep-water fish, brown eggs.