Micronutrients-minerals.pdf

Micronutrients: Minerals Pr. Roberta FORESTI Professor of Biochemistry, Faculty of Health, UPEC [email protected]  Body composition normal adult male ~70 kg Water...

Micronutrients: Minerals Pr. Roberta FORESTI Professor of Biochemistry, Faculty of Health, UPEC [email protected]  Body composition normal adult male ~70 kg Water 42 kg Glycogen (60% total mass) P Other Mg Ca Cl K Fe Zn Na Cu Women normally have more fat and less muscle and water than men Fat Protein 12 kg 12 kg (17% total mass) (17% total mass) Fat-free mass= muscle+water+bone  Minerals in the body Minerals are present in the body in widely differing quantities: around 1 kg for calcium and phosphorus, a few grams for iron, zinc and fluoride and less than 1 mg for chromium and cobalt. In all, minerals account for about 4% of body weight but are involved in a wide range of functions: mineralisation, controlling water balance, enzymatic and hormonal systems, and the muscular, nervous and immune systems. For example, thyroid hormones cannot be made without iodine, nor haemoglobin without iron and no muscular contraction can occur without calcium, potassium and magnesium. Except for iodine, fluorine and cobalt, all of the mineral elements play multiple roles. Daily intake of minerals compensates for loss, and a balanced and varied diet guarantees adequate intake. Mineral elements are water soluble, which is why there is a certain amount of loss depending on how food is prepared. Calcium and Phosphorus Calcium is the most important mineral in the body- Phosphorus is also abundant in bone (~85% of total the majority (99%) is contained in the skeleton and body phosphorus). In the bone calcium is bound to other mineralized tissue (teeth). phosphorus –hydroxyapatite-. The other 1% is present in blood and extracellular High levels of phosphorus are found in soft tissue fluids. (14 % in muscle, liver, heart and kidney, and only 1 % is present in extracellular fluids. Daily losses of calcium in urine and faeces. Phosphorus homeostasis is intricately linked to that Bone is a reservoir for calcium and other inorganic of calcium because of the actions of calcium- nutrients, and participates in whole-body mineral regulating hormones, such as parathyroid homeostasis through the processes of bone hormone (PTH) and 1,25-dihydroxy-vitamin D formation and resorption. It is a dynamic tissue that (1,25(OH)2D), at the level of the bone, the gut and is continuously remodeled throughout the life the kidneys. course. Phosphorus is found in cellular components, such Calcium has a critical role in many physiological as ATP. functions involved in the regulation of metabolic processes, including vascular contraction and vasodilation, muscle contraction, enzyme activation, neural transmission, membrane transport, glandular secretion and hormone function.  Parathyroid hormone (PHT) and Vitamin D Parathyroid hormone (PHT) and Vitamin D are major regulators of calcium homeostasis in the body. Active form of Vitamin D in the kidney Recommended intakes Main dietary sources of calcium Main dietary sources of phosphorus Dairy products Dairy products Pulses Eggs Nuts Oilseeds Cereal products Fish Leafy vegetables (cabbage, chard, spinach) Offal (mainly liver) Seafood Meat Water with very high calcium content Beverages with high phosphate content (Coca-Cola)  Effects of calcium deficiency If inadequate amount of calcium in the diet there is BONE LOSS, leading to OSTEOPOROSIS OSTEOPOROSIS = disease characterized by low bone mass and ‘microarchitectural’ deterioration of bone, leading to increased risk of fractures Estimates: > 1/3 of women and 1/6 men will suffer from fractures caused by osteoporosis during lifetime Almost all food contains phosphorus, thus deficiency of phosphorus is very rare Iron  Hemoglobin in red blood cells Cyt C oxidase in mitochondria Iron is an essential trace element and plays numerous biochemical roles in the body, including oxygen binding in hemoglobin/myoglobin and acting as a catalytic centre in many enzymes, for example the cytochromes in mitochondria. Two forms of iron are found in food: heme iron and non-heme iron: Heme iron is found exclusively in foods of animal origin, because it is derived from proteins such as hemoglobin. Non-heme iron is found in most foods, regardless of Heme iron Non-heme iron salts whether they are of animal or plant origin. The absorption rate of heme iron is higher than that of non-heme iron. Average absorption from meat-containing meals ~25%. Our ability to absorb dietary iron depends on the body's reserves, the proportion of heme iron in our diet and the presence of compounds that increase absorption, such as vitamin C, or decrease it, such as tannins in tea (see later). Recommended intakes The balance between iron intake and loss is generally well regulated in healthy people, since there is efficient recycling of iron from red blood cells. Regular iron intake also helps maintain a balanced iron status. Groups of people with high iron requirements infants, children and pregnant women (periods of growth) heavy menstrual bleeding in some women, health conditions (bleeding in haemophilia, during inflammation or infection due to poor iron absorption) Issue with vegetarian and vegan diets: low iron intake Main dietary sources of heme iron Main dietary sources of non heme-iron Beef Fortified breakfast cereals Poultry Beans Beef or chicken liver Dark chocolate (at least 45%) Cereal products Lentils Oysters, clams, mussels Spinach Canned sardines Nuts, seeds Canned light tuna  Promoters and inhibitors of non-heme iron absorption Promoters Inhibitors Ascorbic acid (Vit C) Phytic acid (high in cereals) Meat Polyphenols (vegetables and wine) Citric acid Tannins (wine, tea) Some spices (turmeric) Calcium Β-carotene Alcohol Iron supplements: not good when taken with breakfast (tea and tannins). Best is to have the supplement 30 min before breakfast with a glass of orange juice (Vit C)  Effects of iron deficiency More than two billion people worldwide suffer from iron deficiency anemia, most common nutritional deficiency syndrome A lack of iron can lead to "iron-deficiency anaemia". The body becomes less able to transport oxygen to the cells. Symptoms Fatigue and weakness Headaches Dizziness, loss of concentration Shortness of breath Rapid heartbeat, pale skin In children it affects cognitive function that may persist for many years, even if iron levels are normalized with supplements Measurements of hemoglobin and ferritin/transferrin saturation are important indicators for anemia Zinc Zinc is the 2nd most important mineral after iron. It has a major role as a component of metallo- enzymes (over 200 Zn-enzymes). It is involved in nucleic acid synthesis, protein digestion, protein synthesis, bone metabolism, oxygen transport, protection against free radicals (SOD). Basically, a series of very important physiological processes in the body. Zinc bound to DNA and RNA stabilizes the structures. Zinc functions as a neuromodulator (glutamine- containing neurons. Recommended intakes Main dietary sources of zinc Beef Chicken (much less than beef) Wheat, wholegrain (outer shell of the grain) Wheat, white flour (much less than wholegrain) Zinc bioavailability is reduced by phytates. Phytates are ‘antinutrients’: they bind minerals in the Rice digestive tract, making them less available to our bodies. Oysters (very high amounts) Coffee, tea, beans, seeds, cereals contain phytates. Lentils Protein acts as an ‘antiphytic’ agent and increases absorption from phytate containing diets. Zn is associated with protein. Important in the diet  Effects of zinc deficiency It is very rare to be Zn deficient but mild Zn deficiency can occur, especially in the developing world. First observations of Zn deficiency were made in the 60s in Egypt and Iran and subsequently found also in other middle east countries. It is due to poor Zn availability due to a diet rich in unleavened bread (yeast has phytase activity so reduces phytates in the diet) and geophagia (practice of eating clay), which reduces Zn absorption. Symptoms Dermatitis Dwarfism (Zn affects growth hormones) Diarrhea disease Poor immune function It is difficult to assess Zn status Iodine Iodine is vital to the synthesis of thyroid hormones: thyroxine and triiodothyronine, which are crucial regulators of the metabolic rate and physical and mental development in humans. Thyroid hormones play a fundamental role in cell growth and maturation processes, maintenance of body temperature, regulation of energy expenditure and protein synthesis. Iodine also plays a fundamental role in fetal brain development in the first few months of pregnancy. Iodine is rapidly and efficiently absorbed in the intestine Recommended intakes  Main dietary sources of iodine Seeweed Iodised salt (from seaside) Marine fish Mollusk and crustaceans Eggs (depending on animal diet) Milk (depending on animal diet) With the exception of seafood, iodine levels in food depends on the iodine content in soil. Some soils in Africa-Ethiopia, Kenia, Tanzania- have poor iodine content in soil.  Effects of iodine deficiency Iodine deficiency is associated with an increase in the volume of the thyroid gland and the development of goitre. Severe forms of deficiency can lead to hypothyroidism and cause fatigue, sensitivity to cold, weight gain Symptoms Goitre: increase in the volume of thyroid gland (mild) Hypothyroidism (severe) Fatigue (severe) Sensitivity to cold (severe) Weight gain (severe) Mental retardation (or cretinism) if mother is iodine deficient. (see next slide) (severe) First choice for intervention: Iodized salt (not expensive, used by all) Size of thyroid (palpation and ultrasound), urinary iodine and thyroid hormone levels in plasma can be used to assess iodine status  Effects of iodine deficiency Symptoms Mental retardation (or cretinism) if mother is iodine deficient. Fetal brain is very susceptible to iodine deficiency and neurological damage is irreversible (severe) Figure 62.1. A mother and child from a New Guinea village who are severely iodine deficient. The mother has a large goiter and the child is also affected. The bigger the goiter, the more likely she will have a cretin child. This can be prevented by eliminating the iodine deficiency before the onset of pregnancy. Reproduced with permission from Hetzel and Pandav (1996). From: Iodine Deficiency and the Brain, Basil S. Hetzel, in Comprehensive Handbook of Iodine, 2009 Copper/Selenium/Chromium/Fluoride  Copper Main dietary sources of copper Copper is the third most abundant dietary trace metal. Found in a variety of foods in plentiful amounts The major function for copper is as a catalytic Shellfish center in numerous enzymes involved in redox reactions (ex. Cu/Zn superoxide dismutase) Liver Copper Kidney Nuts Wholegrain cereals Dietary deficiency is not known because copper is present in a variety of foods and well absorbed. Menke’s disease: defect in copper absorption leading to severe impairment in mental development and skeletal and vascular problems.  Selenium Main dietary sources of selenium Selenium is present in active site of many proteins and enzyme, including the enzymes responsible for Cereals thyroid hormones production and glutathione peroxidase, a very important antioxidant system. Meat The selenium content in cereals is directly Brazil nuts proportional to selenium in the soil. Thus, dietary intake is lower in regions with low selenium. For ex, Found in a variety of food in Europe our soil is less rich compared to North America: we used to get our grains from North America but now we buy European grain. There may be a general mild deficiency in selenium in Europe. Keshan disease in rural China-soil is very poor in selenium- is a cardiomyopathy affecting children and young women.  Chromium Main dietary sources of chromium Chromium is poorly understood. Meats May have an effect on insulin metabolism and glucose homeostasis, maybe also lipid metabolism. Nuts There may be overlap between iron and chromium Cereal grains metabolism. Brewer’s yeast and molasses (from sugar cane) There is no RNI but rather safe limits (5-100 µg/day in the diet is safe). Prolonged occupational exposure could lead to carcinogenesis (people working in metal plants).  Fluoride Main dietary sources of copper Fluoride is very important for the mineralization of bones and teeth. Found in most foods It also has bacteriostatic action against bacteria in Drinking water (naturally or added deliberately) dental plaque so it protects from dental caries. When present in high amounts (10 mg/L in drinking water) it can lead to fluorosis (toxic, mottled tooth enamel and skeletal fluorosis-increased calcification of ligaments and tendons and hypercalcification of vertebrae). There is controversy in adding fluoride in drinking water in case of excess. Recommended intakes Sodium and Potassium  Sodium Sodium is an essential mineral that is almost entirely present in sodium chloride (common salt). Its main functions are to: Maintain the volume and composition of the extracellular fluid (water balance between the inside and outside of the cell, 1/2 of the amount in human body of ~70 kg) Nerve transmission and muscle contraction For regulating pH (with bicarbonate) Sodium is eliminated in urine and sweat. Urinary sodium is the best way to measure intake The major problem with sodium is that in most people diet there is too much sodium, which has negative effects on blood pressure (see future course-diet and hypertension) and has been linked to stomach cancer. Salt has an irritant effect on the stomach- irritation and inflammation leading to cancer. Big campaigns in several countries (in Europe, Asia- Japan) to decrease sodium in the diet. Sodium was used for food preservation (before refrigerators) and for flavoring. Now only for flavoring because we have refrigerators! Fruits and vegetables contain little sodium. Sodium naturally contained in food is enough for the body’s requirements. What can you do to limit salt consumption? The total amount of salt consumed by the French population is well above the public health recommendations. Given the dietary habits in France, most of the salt consumed comes from bread and rusks, followed by processed meats, condiments and sauces, ready-to-eat meals, cheeses, soups, quiches and pizzas. Consumers are advised to: limit their consumption of the saltiest foods, become familiar with the composition of foods by reading the labels, limit the addition of salt when preparing and serving meals. (Recommendation from Anses) Sodium depletion also occurs: when people excrete too much. Excessive sweating, due to hard work in hot environment-cramps Excessive urinary loss, due to Addison’s disease-failure to reabsorb sodium Excessive gastrointestinal loss, due to vomiting and diarrhea Importance of drinking water (already contains minerals) during sports.  Potassium Potassium is contained in the body in similar amounts to sodium. Most potassium is intracellular and only little extracellular (in contrast to sodium). Most potassium is associated with muscle (lean tissue) and can be considered a good indicator of lean mass. For ex. Potassium in urine gives an idea about lean tissue; if the levels increase we can predict loss of muscle (prolonged fasting); Sodium/potassium ratio is more important than sodium intake alone and this ratio is a better predictor of blood pressure in comparison to sodium alone. Main dietary sources of potassium Potassium depletion also occurs: caused by excessive excretion. Banana From loss of lean tissue (prolonged fasting, Vegetables and fruits diarrhea) Dairy products Diuretics (thiazide) and steroids Chocolate Symptoms: muscle weakness, confusion, heart problems-arhythmias Dietary Approaches to Stop Hypertension During DASH people eat 8-9 portions of (DASH) eating plan. vegetables and fruit/day, together with other healthy food (see example plate below). Developed ~25 years ago after a clinical trial dedicated to testing a nutritional approach There is a strong focus on decreasing sodium fight hypertension. intake and increase potassium in the diet (from vegetables and fruits as well as dairy products). Very efficient and proven nutritional approach to combat hypertension. It is also heart healthy and follows the best advice for a nutritional rich and healthy diet