Selenium: Benefits, Sources, and Risks

Selenium, an essential trace element, plays a crucial role in various bodily functions, including antioxidant defense and thyroid hormone metabolism. Plant foods serve as the primary dietary sources of selenium worldwide, with their selenium content determined by the soil in which they are grown. This soil selenium content varies significantly by region, influencing local dietary intake levels.

In the United States, the high plains of northern Nebraska and the Dakotas are notable for their selenium-rich soils. Consequently, residents of these areas have the highest selenium intakes in the country. In stark contrast, regions in China and Russia have soils with very low selenium levels, leading to frequent dietary deficiencies. These deficiencies are linked to various health issues, including Keshan disease, a potentially fatal condition affecting the heart.

Beyond plant foods, selenium is also present in certain meats and seafood. Animals consuming grains or plants grown in selenium-rich soils tend to have higher selenium levels in their muscles. In the United States, meats and bread are significant sources of selenium, reflecting the country’s agricultural practices. Nuts, particularly Brazil nuts and walnuts, are exceptional sources of selenium, often providing more than the daily recommended intake in just a few servings. Recent studies have highlighted the importance of these nuts in preventing selenium deficiency and supporting overall health.

While adequate selenium intake is beneficial, excessive selenium can pose health risks. Chronic high intake can lead to selenosis, characterized by symptoms such as gastrointestinal distress, hair loss, white blotchy nails, and mild nerve damage. In severe cases, it can cause more serious issues like respiratory distress, kidney failure, and even death. Thus, a balanced diet, avoiding excessive supplementation, is crucial for maintaining optimal health and preventing selenium toxicity.
Selenium: Benefits, Sources, and Risks

Arachidic acid

Fatty acids are a large group composed of linear saturated and unsaturated hydrocarbonated chains with a carboxylic acid function. Commonly found saturated fatty acids range from butyric (C4) to arachidic fatty acids (C20).

Arachidic acid is a saturated fatty acid with a 20 carbon chain. Arachidic acid occurs naturally in fish and vegetable oils. It is used in lubricants, greases, waxes and plastics. Diets rich in saturated fats like arachidic acid are associated with increased levels of serum low density lipoproteins.

Earthnut oil, expressed in the cold, contains about 4-5 p.c. of arachidic acid ; that expressed with the aid of heat contains about 6 p.c. It is sometimes used to adulterate olive-oil, and its presence may be detected by separating out the arachidic acid.
Arachidic acid

Sources of pectin

Pectin is a complex carbohydrate component found in the middle lamella of plant cells. Pectins are polyuronides and consist of mixture of pectic substances like protopectin, pectin, pectinic acid and calcium pectate. Pectins with a high molecular weight and a high proportion of methyl ester groups have the best jelly ability.

The pectin content of fruits is variable and depends not only on the type of fruit but also on its maturity or ripeness. Under certain conditions, in presence of sugar and acid, it forms jelly like mass. If jellies or jams are made at home, it is best to add commercial pectin to ensure that there is sufficient pectin to form a gel.

The levels of pectin vary for the different plant tissues; apple pomace, sugar beet pulp., and sunflower heads are major sources of this fiber, ranging in pectin concentration from 15 to 25 g/100 g.

Purified pectin is made from apple cores and skin (apple pomade) and from the white inner skin (albedo) of citrus fruits. It is available in either liquid or granular form. The granular products have a longer shelf life than the liquids.

Pectin also has been manufactured from citrus peel for more than 50 years. All citrus contains pectin and the richest sources are limes, lemons, oranges and grapefruit in decreasing importance.

The soft, white spongy layer called albedo, just under the colored portion of the peel is the principle source of pectin.

Low-methyl pectin can be obtained by demethylating pectin with enzymes, acid or alkali until it is 20-40 % esterified.

Since these pectins gel with divalent ions and need no sugar, they can be used commercially for the production of low-calorie jams, jellies, or desserts.
Sources of pectin

What is an animal fat?

Animal fats are isolated from animal tissues and animal sources. Primarily, animal fats include lard, tallow and butter fat. The lipid isolated from animal fat depots, mainly triacylglycerols.

Both animal fats and fish oil are highly digestible energy sources for animals, and fish are also an excellent source of omega-3 fatty acids and vitamins A and D.

Some fats are also produced from inedible tissues by rendering plants. Overall, animal fats are saturated. That is, carbon atoms of fatty acids joined to the glycerol molecules in their triglyceride contain all possible hydrogen atoms.

The most common long-chain saturated fatty acids of animal tissues are palmitic acid and stearic acid. Since animal fat are high in saturated fatty acids they are usually solid, and have fairly high melting temperatures.

Feed-grade animal fats consist of rendered fats from beef or pork by-products which are mainly slaughterhouse offal or supermarket trimmings from the packaging of meats, and poultry fat includes fats from 100% poultry offal.

Fat rendered commercially from beef and sheep carcasses is commonly called tallow. Beef tallow is hard and typically contains as a percentage of total fatty acid, 26% palmitic, 17% stearic, 43% oleic and 4% linoleic acids.
What is an animal fat?

Food contamination by bacteria

Most of the bacteria are transmitted via food and water as a result of contamination with feces.

The main bacteria that cause food infections via colonization in the intestinal via colonization in the intestinal tract are Salmonella, Listeria monocytogenes, Yersinia enterocolitica and Shigella.

None of the bacteria can multiply in food or water or indeed outside the body of the host in which they developed. If they occur in food or water, one hopes that they will be inactivated or killed before they can infect a consumer or the vehicle.

There are a number of reasons and sources which result in the prevalence of bacterial contamination in food products, such as:
*Premises which are difficult to clean
*Lack of staff discipline
*Incorrect staff and product flow
*Poor air quality
*Incorrect direction of air movement

Food that is cooked and then not contaminated before being served is unlikely to serve as a vehicle for most of the bacteria.

Salmonella is the second most common cause of illness traced to contaminated foods and water. Foods most susceptible to Salmonella contamination are meat, fish, poultry, eggs and dairy products.

Much of the bacterial contamination of foods in restaurants, commissary kitchens and commercial processors are due to the poor personal hygiene of workers. Failure to wash hands after using the bathroom, sneezing and coughing into food, and picking noses and skin blemishes can all transmit pathogenic bacteria to food.
Food contamination by bacteria 

Food sources of manganese

Estimated average dietary manganese intakes in the United States range from 2.1 to 2.3 mg/d for men and 1.6 to 1.8 mg/d for women.

The best food sources of manganese are of plant origin. Tea, coffee, nuts, cereals and some fruits are the best food sources of manganese. Some estimates suggest that coffee or tea supplies as much as 20 to 30 percent of our daily manganese intake.

People eating vegetarian diets and Western diets emphasizing whole grains may have manganese intakes as high as 10.9 mg/d.

Fair sources of manganese are brewer’s yeast, liver, most fruits and vegetables, orange pekoe tea and white enriched bread.  Dairy products, meat fish and poultry are poor sources of manganese.
Food sources of manganese

Herbs containing calcium

Calcium is the element in the form of carbonate, phosphate, silicate and fluoride is essential for the formation or growth of teeth and bones. Studies suggest that calcium adds mineral density to bone, which can help prevent osteoporosis.

Burdock roots

Rich source of calcium include milk and dairy products, oily fish and herbs. Herbs that contains calcium include alfalfa, burdock root, cayenne, chamomile, chickweed, chicory, dandelion, eyebright, fennel seed, fenugreek, flaxseed, hops, horsetails, kelp, lemongrass, mullein, nettle, oat straw, paprika, parsley, peppermint, plantain, red clover, rose hips, shepherd’s purse, violet leaves, yarrow, and yellow dock.

Other plants contain calcium include raspberry leaf, milky oats, sesame seeds, lamb’s quarters,  toad flax, silver weed, cleavers, meadow sweet, mistletoe, coltsfoot, rest harrow and pimpernel.

A big mug of infusion using any of these herbs (nettle, sage, chickweed, red clover, comfrey leaf, raspberry leaf, oastraw) is equal to 250-300 mg calcium.  By adding a big pinch of horsetail will increase the calcium by 10 percent.
Herbs containing calcium 

Food sources of chromium

The chromium content of the body is approximately 4 to 6 milligrams, mostly in the liver, spleen and bone; the remainder is widely dispersed at very low concentrations.

Significant dietary sources of trivalent chromium are available in various food sources. Group by rank of some common food sources of chromium:

*Rich sources: blackstrap molasses, cheese, eggs, liver
*Good sources: apple cider, banana, beef, beer, bread, brown sugar, butter or margarine, cornflakes, cornmeal, flour, oysters, potatoes, vegetable oils, wheat bran, whole wheat
*Fair sources: carrots, green beans, oranges, spinach, strawberries

One of the best food secures of the metal is brewer’s yeast, which can contain up to 5 mg/kg, though levels in different samples can be vary widely. Chromium-enriched yeast is widely used as a nutritional supplement for humans as well as animals.

Chromium is also found in many mineral or multivitamin supplements. Cooking acidic foods in stainless steel container leaches some chromium into the food.

It is estimated that as many as 90 percent do all American diets are low in chromium. Eating a lot of highly processed foods may contribute to this problem because foods lose chromium during the refining process.
Food sources of chromium

What is anthocyanidin?

When the sugar moiety of an anthocyanin is hydrolyzed, the aglycone (non-sugar hydrolysis product) is referred to as an anthocyanidin.

The color of anthocyanins and anthocyanidins results from excitation of molecule by visible light. At pH values lower than 3, the anthocyanidin appears as the red flavylium cation, and at pH values higher than 6 it is preset as the blue quinonoidal base form.

The richest sources of anthocyanidins to the diet are red wine and fruit, particularly berries. Foods can have one or a variety of anthocyanidins and the concentration is influenced by environmental conditions, ripeness, cultivar, cultivation site, processing and storage.

Only three types of anthocyanidins have been identified in plant tissues. Pelargonidin, cyanidin and delphinidin are wide spread in nature with cyanidin the most common.

Cyanidin is the anthocyanidin found in red cabbage, pelargonidin occurs in radishes and red-seeded varieties of bean and delphinidin occurs in aubergines.

Anthocyanidins are less water soluble than their corresponding glycosides (anthocyanins) and they are not found free in nature.

Freezing may be the best method of preserving anthocyanidins in foods so as the consumption can continue throughout the year even when particular foods such as berries are not in season.
What is anthocyanidin?

Dietary sources of vitamin A

Actual intake of vitamin A depends on the patterns of consumption of vitamin A-bearing animal food products and provitamin A-bearing fruits and particularly in green leafy vegetables. Animal sources of vitamin A include meat, liver, eggs, cow’s butter or ghee, milk and poultry.

The richest readily available dietary source of vitamin A is fish liver oil, especially cod liver. In particular, all–trans dehydroretinol, previously known as vitamin A2, is a vitamin A-related compound found in freshwater fish flesh and liver and to a lesser extent, on some marine fish. Cod liver and halibut fish oil contain high levels of vitamin A and have been used therapeutically.

Margarine, fluid milk and dry milk are typically fortified with retinyl palmitate in many countries. These products play a dramatic role in preventing vitamin A deficiency in countries where fortification is mandatory.

In the United States, milk is fortified with not less than 2000 IU vitamin A (retinyl palmitate).

The principal source of vitamin in the diet is likely to b from the carotenes which are widespread in those plant foods that have high green or yellow coloring.

There is a direct correlation between the greenness of a leaf and its carotene content. Dark green leaves, such as beet greens, collards, dandelion, greens, kale, mustard greens, spinach, Swiss chard, and turnip greens are rich in carotene.
Dietary sources of vitamin A

Food sources of calcium

Early humans are thought to have consumed a diet rich in calcium from a wide range of plant sources.

Milk and dairy products are the richest food source of calcium.  In the last few years, an enormous increase in diversity of food sources of calcium has become available in North America through extensive fortification.

Milk and other dairy foods provided 84% of the calcium from foods in the United States in 1889-1993. Milk and milk products such as yoghurt and cheeses are outstanding sources of calcium.

Now, calcium requirements can be met through consumption: naturally occurring foods, calcium-fortified foods, and supplements.

There are also food plants contain plenty of calcium that is highly bioavailable: cauliflower, watercress, parsley, Brussels sprouts, rutabaga, kale, mustard greens, bok choy, broccoli and turnip greens.

Eventhough green leafy vegetables contain less calcium per serving than milk, but calcium in these vegetables is absorbed well or slightly better than calcium from milk.

Although slightly less bioavailable, calcium is also abundant in almonds, sesame seeds, pinto beans and sweet potatoes. Mineral waters are also often a good natural source of calcium.
Food sources of calcium

Glucose, the simple carbohydrate

A 6-carbon sugar, glucose is one of the simplest carbohydrates found in foods. It is one of the most important carbohydrates in plant and animal metabolism.

The compounds D-glucose or dextrose is 2,3,4,5,6-pnetahydroxyhexaldehayde, or conventionally expressed as C6H12O6 with a molecular weight of 180,6 kDa. Glucose is readily soluble in water in a powder form.

Glucose is also the primary repeating sugar unit of most complex carbohydrates or starch.

While many foods contain traces of glucose, it is found in significant amounts only in fruits, such as grapes.

Photosynthesis converts carbon dioxide and water to glucose, which is stored in leaves, stems, fruits, roots, pods and seeds, as glucose, as other sugars or as starch.

The small, amount of glucose in the blood and cells provides the energy need for human body’s daily activities. Any galactose or fructose that is absorbed into the blood is converted to glucose by enzymes present in the liver.  It is an essential energy source for the adult human brain.

Glucose is stored as glycogen, an α-link polymer, predominantly in the liver and muscles.  On average m a 70 kg man may store 500g of glycogen.
Glucose, the simple carbohydrate

Glutathione in food

Glutathione is a tri-peptide found in both plants and animals and is important as a source of endogenous thiols, which act as scavengers of free radicals and active electrophiles. It is a small protein composed of three amino acids: cysteine, glutamic acid and glycine.

Glutathione is an important anticancer agent that helps detoxify and eliminate toxins such as heavy metals, pesticides and solvents.

Glutathione attacks cancer in two ways:
*Glutathione hampers the effects of free radicals unstable oxygen molecules that can damage healthy cells and cause them to become cancerous.
*Glutathione prevents other cancer-causing chemicals called carcinogens from damaging DNA, the chemical blue print that tells how to function.

Glutathione’s combination of detoxification and free radical protection makes it one of the most important cancer and aging fighters in human cells.

It plays a vital role in liver health and is especially helpful in the detoxification of drugs and pollutants. Experts on antioxidants believe that glutathione is essential for a strong immune system.

Human can easily boost intake of glutathione.  All berries, oranges, grapefruit, cantaloupe, watermelon, bananas, apples, peaches, pears, avocados and tangerines are loaded with glutathione.

A small mount of glutathione can also be made directly from methionine. Likewise, when methionine or cysteine is deficient, glutathione levels decrease.

As long as the diet contains enough methionine or cysteine, glutathione levels are likely to be adequate.

Vegetables such as carrot, yams, lettuce and other leafy greens, cucumbers, tomatoes, asparagus, okra, cabbage and green pepper, and nuts such as walnuts, peanuts, almonds, and sesame seeds are also good sources.

Glutathione serves several roles in the cellular antioxidant defense system. First, glutathione directly scavenges a variety of radicals, including hydroxyl and carbon centered radicals, by donating a hydrogen atom.

A second key antioxidant function of glutathione is to remove both hydrogen and organic peroxide during reaction catalyzed by the enzyme glutathione peroxidase.
Glutathione in food

Saturated fatty acids: Lauric acid

Lauric acid has 12 carbons and no double bonds. Lauric acid is absorbed partly with chylomicron triglycerides and partly into the portal circulation as a free fatty acid.

Of the saturated fatty acids, lauric acid has greater antiviral, activity than other caprylic acid, capric acid or mysristic acid. According to published research, lauric acid is one of the best ‘inactivating’ fatty acid, and its monoglyceride is an even more effective antimicrobial than fatty acid alone.

Lauric acid is common constituent of vegetable fats, especially coconut oil and laurel oil.

There are only a few basic foods that contain lauric acid in more than trace amounts. These foods include the following: extracted lauric oils (coconut, palm kernel), whole coconut, creamed coconut (bar), coconut cream (fresh or canned), coconut milk (fresh or canned), heavy cream, table cream, half and half, whole milk.

Lauric acid derivatives are used widely as a key raw material on the manufacture of soaps, detergents and lauryl alcohol because of their foaming properties.

It also has uses in chocolate and confectionary coatings, margarines, simulated dairy products, baker filling and icings, dressings and spreads.
Saturated fatty acids: Lauric acid

Sparkling water

Sparkling waters are salt-free, contain no caffeine, no calories and are available with or without added fruit flavor. Sparkling water originates from either mineral or tap water.

The mineral water is taken from an underground well or spring and is still bubbly. Still waters are often carbonated to produce sparking water. Still waters are often carbonated to produce sparkling water.

Perrier, the sparkling water from Languedoc in the south of France, is largely given credit for starting the current bottled water craze in the United States.

Although all soft drinks are predominantly water, sparkling waters are in a class by themselves.

Sparkling water can be healthful alternative to soda and alcoholic beverages but if it loaded with fructose and other sweeteners, it may be no better than soda pop.

Sparkling water shimmering bubbles are said to aid digestion, and its liveliness enhances wine, liqueurs, liquors such as Scotch, rye and gin and fruit and vegetable juices.

Chilled sparkling mineral water is the quintessential aperitif when served in a long-stemmed wineglass with a slice of lemon or lime.

Study published in Journal of Nutrition, found out that drinking of sparkling water brought about significant reductions in the level of LDL cholesterol, as well as a significant increase in levels of HDL cholesterol.

Many sparkling waters now come flavored with fruit essences, which are made from oils obtained from the skin of various fruits.

People suffering from intestinal disorders or ulcers should avoid drinking carbonated water because it may be irritating to the gastrointestinal tract.
Sparkling water

Food sources of vitamin K

Vitamin K is part of a family of chemical, all fat-soluble naphthoquinones. They are including phylloquinone (K1), menaquinones (K2) and menadione (K3).

The first is vitamin K1 (phylloquinone or phytonadione), which comes from plants and makes up human dietary vitamin K. Phylloquinone is the predominant dietary form of vitamin K and is present in foods of plant origin.

These include green leafy as the major quantitative source and contribute approximately 60% of total phylloquinone.

Certain plant oils and margarine, spreads and salad dressings derived from these plant oils are also important dietary sources of phylloquinone.

The second is vitamin K2 (menaquinones), which is produced by bacteria present in the large intestine. It is found in butter, cow liver, chicken, egg yolks, fermented soybean products, and some cheese.

The fats of grass-fed animals are especially good sources of vitamin K2. For vegetarians who would shun animal fats, natto, the Japanese fermented food, is a good source of vitamin K2.

Third, there is vitamin K3 (menadione), is neither found naturally in food nor made by intestine bacteria. It is synthetic, man-made substance.
Food sources of vitamin K

Food sources of fat soluble vitamins

The fat soluble vitamins (A.D.E and K) are soluble in oil. Fat soluble vitamins accumulate primarily in the fatty tissue in the body and to a small extent can be excreted through bile. Several plants and animal products serve as excellent sources of fat soluble vitamins.

Common dietary sources of vitamin A and D are livers, especially the liver of marine fish and oils obtained from the livers of shark, cod, halibut and tuna. Fish livers are used as raw materials to obtain oils with high concentrations of these vitamins.

Milk has about 500 IU of vitamin A/cup and cheddar and Swiss cheeses (1 oz) contain about 285 IU and 200 IU of vitamin A, respectively.

Some products, such as margarine and breakfast cereals, may be fortified with vitamin A. Fortified milk also is a good source of vitamin D.

For vitamin E, the richest sources are vegetable oils, and the produces made from these oils, such as margarine, shortenings and salad dressings. Other sources of vitamin E include nuts, seeds and green leafy vegetables.

Green vegetables, such as broccoli, cauliflower, spinach and parleys leaves, complement the diet with vitamin E and K because they contain amounts of phylloquinone.

The fat soluble vitamins remain reasonable stable in stored foods. At usual cooking temperatures, some destruction of vitamin A and E occurs. Losses are greater at higher temperatures, such as with deep frying.
Food sources of fat soluble vitamins

Food sources of pyridoxine

Pyridoxine (Vitamin B6) is part of the enzyme system and act as coenzyme in the transmitting process, for the decarboxylation and racemization of amino acids, and as the essential coenzyme for glycogen phosphorylase.

It is also needed for the utilization of certain amino acids. Pyridoxine assists in the metabolism and use of glycogen that has been stored as a fuel.

Deficiency manifestations are dermatitis around the eyes, eyebrows, and angles of the mouth. They may so be a sensory neuritis and a decrease in certain white blood cells and increase in others.

Foods rich in vitamin B6 include bananas, barley, beef and beef organs, cabbage, raw carrots, yellow corn, lamb and the organs of lamb, malt ,molasses, peanuts, pork and the organs of hogs, potatoes, rice, salmon, sardine, tomatoes, tuna, wheat bran and germ, flour and yams. Milk, dairy products and eggs have less pyridoxine than fish and other meats, but they are still good sources.

Certain plant foods contain a unique form of vitamin B6 called pyridoxine glucoside.

Pyridoxine can be lost during processing of frozen foods, luncheon meats and cereal foods.
Food sources of pyridoxine

Food sources of pantothenic acid

Bacteria in the large intestine can make pantothenic acid, but the human body may not be able to absorb it in significant amounts.

Pantothenic acid is available in a variety of foods. The organs of animals (liver, heart, kidneys) and eggs, whole wheat products and peanuts are excellent sources of Pantothenic acid.

The muscular tissue of animals, cheese, beans, cauliflower, broccoli, mushrooms and salmons are very good sources of this vitamin. 

Pantothenic acid is relatively unstable in food. Significant amounts can be lost in commercial processing, packaging, cooking and freezing.

Whole grains are good sources of pantothenic acid, but processing and refining grains may result in a 35 to 75% loss. Freezing and canning of foods have been found to result in similar losses.
Food sources of pantothenic acid

Sphingolipids

Sphingolipids, phosphosphingolipids, and glycosphingolipds, constitute a family of molecules particularly abundant in the nervous system.

Sphingolipids are a diverse group of over 100 bioactive lipids involved in many aspects of cellular function. 

They all share a common sphingosine backbone, which may be linked via an amide bond to a fatty acid, or phosphorylated to form sphingosine-1-phosphate.

As sphingolipids are almost exclusively membrane components, particularly of the plasma membranes, that are suitable to interact with external ligands or other cells though they hydrophilic groups and with protein and lipids partners of the membrane through their hydrophobic groups.

Sphingolipids are found to be associated with plasma lipoproteins and their presence can be influence lipoprotein, including high density lipoprotein, metabolism.

Meat, milk and fish are important sources of sphingolipids in the diet. The sphingolipids is in plants are mainly cerebrosides with glucose, galactose, mannose and inositol.
Sphingolipids