Manganese

Manganese is an essential mineral with an important role in the body’s biological processes. It is not produced by the body, so we must get it from our diet. Manganese is found in a variety of foods. It is most abundant in cereals (unrefined cereals, buckwheat, bulgur, wheat, and oats), various seeds, wheat germ, shellfish, nuts, legumes, rice, leafy vegetables, pineapple, coffee, black tea, and many spices. Humans only absorb about 1% to 5% of the manganese they consume in food. Infants and children tend to absorb more than adults. Furthermore, the efficiency of manganese absorption increases with lower intakes of manganese and decreases with higher intakes, but little is known about the precise mechanisms regulating absorption. It has been shown that manganese absorption differs between the sexes, with men absorbing significantly less manganese than women. Lower absorption of manganese in the digestive tract of men is associated with iron levels and higher serum levels of ferritin.

Sufficient daily intakes of manganese are 2.3 mg/day for adult men and 1.8 mg/day for adult women. For pregnant women, the recommended intake is 2 mg/day, and for breastfeeding mothers, 2.6 mg/day. For children over 1 year of age, the recommended intake is 1.2 mg. Experimentally induced manganese deficiency has been shown to cause a number of adverse effects, such as stunted growth, poor bone development and skeletal system defects, reduced fertility and birth defects, impaired glucose tolerance, and changes in the fat and carbohydrate metabolism in animals and humans.

Although our bodies require little manganese, it has many beneficial effects. Its positive health effects are evident in the number of functions it has in the body. First of all, manganese is a component of several enzymes that enable biological processes in the body. For example, it forms part of the structure of pyruvate kinase, an enzyme essential for the metabolism of carbohydrates. It helps to regulate blood sugar levels, contributing to glucose balance and reducing the risk of insulin resistance. Manganese is also necessary for the function of enzymes involved in the synthesis and breakdown of fats, such as lipase and acyltransferase. In this way, it contributes to the regulation of energy production in the body. With regard to proteins, manganese is a component of protease, which is important for the synthesis of new proteins and the production of collagen, essential for healthy skin, hair, joints, and bones. Manganese is also involved in the metabolism of other minerals, such as calcium, magnesium, and phosphorus. This is particularly important for maintaining healthy bones and joints. Furthermore, it plays a role in the synthesis of neurotransmitters, which are central to the normal functioning of the nervous system. It is also essential for the growth of connective tissue, coagulation of the blood, the functioning of the immune system, and the normal functioning of reproductive hormones.

Manganese acts as an antioxidant. It is a cofactor for the enzyme superoxide dismutase (SOD), which helps neutralise the free radicals in the body that can damage cells and tissues. SOD is important for reducing oxidative stress, which is also associated with silent inflammation and the development of such contemporary diseases as cardiovascular disease, diabetes, eye diseases, and even cancer. It is precisely because of the antioxidant role of manganese, through enzymes that are involved in the metabolism of macronutrients, that the question arises as to whether manganese deficiency or excess may have an impact on the development of type 2 diabetes. Curiously, there are studies showing that both reduced and increased blood manganese concentrations may be associated with type 2 diabetes. A study in China involving 122 adults with newly diagnosed type 2 diabetes and 429 adults without diabetes, between the ages of 40 and 92, found that those with the highest plasma concentrations of manganese were 7.88 times more likely to develop diabetes than those with the lowest plasma concentrations of manganese. Meanwhile, a study in Sardinia showed that average levels of manganese in the blood were lower in people with type 1 or type 2 diabetes compared to those without the disease. However, other studies have not shown an association between manganese and the incidence of diabetes. Animal studies indicate that manganese supplementation may improve glucose tolerance, reduce oxidative stress, and improve endothelial function in diabetes patients. Studies on diabetic mice have shown that sufficient levels of SOD protect against diabetic complications such as cardiomyopathy, retinopathy, and neuropathy. This discovery raises the possibility of exploiting the effects of SOD in humans, but there have not yet been sufficient clinical studies. Research also suggests that the therapeutic use of manganese may increase insulin secretion, enhancing glucose tolerance and reducing oxidative stress and the risk of endothelial dysfunction seen in diabetes. On the other hand, acute exposure to large amounts of manganese in the diet can cause a decrease in plasma levels of insulin, rapid hyperglycaemia, and hypoinsulinaemia followed by hypoglycaemia.

In addition to type 2 diabetes, there has been a marked increase in the incidence of obesity, insulin resistance, atherosclerosis, hyperlipidaemia, non-alcoholic fatty liver disease, and hepatic steatosis over the last 30 years. The common term used for these metabolic disorders is metabolic syndrome. They are diagnosed on the basis of the following criteria: abdominal obesity, disturbed carbohydrate metabolism, high blood pressure, and dyslipidaemia. Studies have shown that metabolic diseases are linked to oxidative stress and inflammation. Due to its role in enzyme composition, manganese is especially important in the composition of SOD, which is located in the mitochondria and protects them from oxidative stress. If the mitochondria are damaged or malfunctioning, the production of free radicals is increased and oxidative stress is intensified. Studies on the link between manganese and the development of metabolic syndrome have produced mixed results. Chinese researchers have found that metabolic syndrome in men is inversely proportional to the intake of manganese, while in women the risk of developing metabolic syndrome actually increases with higher intake of manganese. On the other hand, higher intake of manganese was also associated with lower abdominal obesity and lower rates of atherosclerosis in men. Korean women with metabolic syndrome had significantly lower intakes of manganese than healthy control subjects. The same results were also observed in women who only had elevated blood pressure. One limiting factor in epidemiological studies are the dietary habits of individuals, which should be taken into account in order to obtain a more accurate picture of the effects of manganese.

Atherosclerosis is a disease of the arterial wall characterised by the accumulation of cholesterol, which can result in heart attacks, strokes, and angina pectoris. Scientific evidence suggests that it is a chronic inflammatory disease of the blood vessel wall, and that the key factors in its development are oxidised low-density lipoproteins and endothelial dysfunction, which are closely linked to imbalances occurring during oxidative stress and the development of inflammation. It has been shown that SOD with manganese reduces LDL oxidation and protects against endothelial dysfunction. This implies that serum levels of manganese may be a promising method for identifying the early stages of atherosclerosis. Several studies have shown that supplements with manganese can reduce glucose-triggered adhesion of monocytes to the endothelium, potentially slowing or stopping the development of atherosclerosis. Even so, epidemiological studies have shown higher concentrations of manganese in the blood of people with atherosclerosis aged 61 to 100 years compared to healthy subjects. All this suggests that more clinical studies are needed to understand the mechanisms of action of manganese, as epidemiological studies do not account for all factors.

The subject of oxidative stress requires a multi-factorial approach, and the monitoring of a very large number of variables. Manganese is definitely one of the important factors, as its role in the body has been known for a long time. However, caution is needed as it can be toxic in high doses. Excessive exposure from the environment or in the workplace is a recognised risk factor in areas where manganese ore is mined, for example in Africa, China, and Australia. In addition to miners who come into contact with manganese occupationally, the general population in contaminated environments is also at risk. Acute exposure to manganese can cause a condition known as manganism. Chronic exposure results in nerve poisoning, which has symptoms similar to Parkinson’s disease, including tremors, problems with motor skills, and behavioural changes. Excessive intake of manganese can also interfere with the absorption of iron and calcium, as these minerals compete for transport in our bodies. Manganese is therefore an excellent example of just how important it is to balance our intake and adhere to recommendations when it comes to certain substances.

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