Termites are important members of soil macrofauna in various regions of the world. Mostly because food is not simply a means to acquire the basic nutrition needed but much much more. The effects of earthworms in the soil differ according to the ecological category of the species Bouché, ; Lavelle, involved:. We don't need it, and its been connected with all sorted of maladies. Leguminous species are very important as part of a cereal crop rotation in view of their capacity to fix N from the atmosphere through symbiotic associations with rootdwelling bacteria. While there is anecdotal evidence that cats do well on vegetarian food,  studies on commercial and homemade vegetarian cat foods have found nutritional inadequacies. Decomposition is essentially a biological process.
The most commonly used and readily available method for assessing magnesium status is measurement of serum magnesium concentration, even though serum levels have little correlation with total body magnesium levels or concentrations in specific tissues [ 6 ]. Other methods for assessing magnesium status include measuring magnesium concentrations in erythrocytes, saliva, and urine; measuring ionized magnesium concentrations in blood, plasma, or serum; and conducting a magnesium-loading or "tolerance" test.
No single method is considered satisfactory [ 7 ]. Some experts [ 4 ] but not others [ 3 ] consider the tolerance test in which urinary magnesium is measured after parenteral infusion of a dose of magnesium to be the best method to assess magnesium status in adults. To comprehensively evaluate magnesium status, both laboratory tests and a clinical assessment might be required [ 6 ].
DRI is the general term for a set of reference values used to plan and assess nutrient intakes of healthy people. These values, which vary by age and sex, include:.
Table 1 lists the current RDAs for magnesium [ 1 ]. For infants from birth to 12 months, the FNB established an AI for magnesium that is equivalent to the mean intake of magnesium in healthy, breastfed infants, with added solid foods for ages 7—12 months. Magnesium is widely distributed in plant and animal foods and in beverages. Green leafy vegetables, such as spinach, legumes, nuts, seeds, and whole grains, are good sources [ 1 , 3 ]. In general, foods containing dietary fiber provide magnesium.
Magnesium is also added to some breakfast cereals and other fortified foods. Some types of food processing, such as refining grains in ways that remove the nutrient-rich germ and bran, lower magnesium content substantially [ 1 ]. Selected food sources of magnesium are listed in Table 2.
DVs were developed by the U. Food and Drug Administration FDA to help consumers compare the nutrient contents of products within the context of a total diet. The DV for magnesium is mg for adults and children aged 4 and older. However, the FDA does not require food labels to list magnesium content unless a food has been fortified with this nutrient.
Magnesium supplements are available in a variety of forms, including magnesium oxide, citrate, and chloride [ 2 , 3 ]. The Supplement Facts panel on a dietary supplement label declares the amount of elemental magnesium in the product, not the weight of the entire magnesium-containing compound.
Absorption of magnesium from different kinds of magnesium supplements varies. Forms of magnesium that dissolve well in liquid are more completely absorbed in the gut than less soluble forms [ 2 , 11 ]. Small studies have found that magnesium in the aspartate, citrate, lactate, and chloride forms is absorbed more completely and is more bioavailable than magnesium oxide and magnesium sulfate [ ]. Magnesium is a primary ingredient in some laxatives [ 17 ]. Although such a dose of magnesium is well above the safe upper level, some of the magnesium is not absorbed because of the medication's laxative effect.
Magnesium is also included in some remedies for heartburn and upset stomach due to acid indigestion [ 17 ]. Dietary surveys of people in the United States consistently show that intakes of magnesium are lower than recommended amounts.
An analysis of data from the National Health and Nutrition Examination Survey NHANES of — found that a majority of Americans of all ages ingest less magnesium from food than their respective EARs; adult men aged 71 years and older and adolescent females are most likely to have low intakes [ 21 ]. In a study using data from NHANES — to assess mineral intakes among adults, average intakes of magnesium from food alone were higher among users of dietary supplements mg for men and mg for women, equal to or slightly exceeding their respective EARs than among nonusers mg for men and for women [ 22 ].
When supplements were included, average total intakes of magnesium were mg for men and mg for women, well above EAR levels. No current data on magnesium status in the United States are available.
Determining dietary intake of magnesium is the usual proxy for assessing magnesium status. NHANES has not determined serum magnesium levels in its participants since [ 23 ], and magnesium is not evaluated in routine electrolyte testing in hospitals and clinics [ 2 ]. Symptomatic magnesium deficiency due to low dietary intake in otherwise-healthy people is uncommon because the kidneys limit urinary excretion of this mineral [ 3 ].
Early signs of magnesium deficiency include loss of appetite, nausea, vomiting, fatigue, and weakness. As magnesium deficiency worsens, numbness, tingling, muscle contractions and cramps, seizures, personality changes, abnormal heart rhythms, and coronary spasms can occur [ 1 , 2 ]. Severe magnesium deficiency can result in hypocalcemia or hypokalemia low serum calcium or potassium levels, respectively because mineral homeostasis is disrupted [ 2 ]. Magnesium inadequacy can occur when intakes fall below the RDA but are above the amount required to prevent overt deficiency.
The following groups are more likely than others to be at risk of magnesium inadequacy because they typically consume insufficient amounts or they have medical conditions or take medications that reduce magnesium absorption from the gut or increase losses from the body. The chronic diarrhea and fat malabsorption resulting from Crohn's disease, gluten-sensitive enteropathy celiac disease , and regional enteritis can lead to magnesium depletion over time [ 2 ].
Resection or bypass of the small intestine, especially the ileum, typically leads to malabsorption and magnesium loss [ 2 ]. The magnesium loss appears to be secondary to higher concentrations of glucose in the kidney that increase urine output [ 2 ].
Magnesium deficiency is common in people with chronic alcoholism [ 2 ]. In these individuals, poor dietary intake and nutritional status; gastrointestinal problems, including vomiting, diarrhea, and steatorrhea fatty stools resulting from pancreatitis; renal dysfunction with excess excretion of magnesium into the urine; phosphate depletion; vitamin D deficiency; acute alcoholic ketoacidosis; and hyperaldosteronism secondary to liver disease can all contribute to decreased magnesium status [ 2 , 26 ].
Older adults have lower dietary intakes of magnesium than younger adults [ 20 , 27 ]. In addition, magnesium absorption from the gut decreases and renal magnesium excretion increases with age [ 28 ]. Older adults are also more likely to have chronic diseases or take medications that alter magnesium status, which can increase their risk of magnesium depletion [ 1 , 29 ].
Habitually low intakes of magnesium induce changes in biochemical pathways that can increase the risk of illness over time. This section focuses on four diseases and disorders in which magnesium might be involved: Hypertension is a major risk factor for heart disease and stroke. Studies to date, however, have found that magnesium supplementation lowers blood pressure, at best, to only a small extent.
A meta-analysis of 12 clinical trials found that magnesium supplementation for 8—26 weeks in hypertensive participants resulted in only a small reduction 2. The authors of another meta-analysis of 22 studies with 1, normotensive and hypertensive adults concluded that magnesium supplementation for 3—24 weeks decreased systolic blood pressure by 3—4 mmHg and diastolic blood pressure by 2—3 mmHg [ 31 ].
A diet containing more magnesium because of added fruits and vegetables, more low-fat or non-fat dairy products, and less fat overall was shown to lower systolic and diastolic blood pressure by an average of 5. However, this Dietary Approaches to Stop Hypertension DASH diet also increases intakes of other nutrients, such as potassium and calcium, that are associated with reductions in blood pressure, so any independent contribution of magnesium cannot be determined.
Several prospective studies have examined associations between magnesium intakes and heart disease. The Atherosclerosis Risk in Communities study assessed heart disease risk factors and levels of serum magnesium in a cohort of 14, white and African-American men and women aged 45 to 64 years at baseline [ 33 ].
Over an average of 12 years of follow-up, individuals in the highest quartile of the normal physiologic range of serum magnesium at least 0. However, dietary magnesium intakes had no association with risk of sudden cardiac death. Another prospective study tracked 88, female nurses in the United States to determine whether serum magnesium levels measured early in the study and magnesium intakes from food and supplements assessed every 2 to 4 years were associated with sudden cardiac death over 26 years of follow-up [ 34 ].
Another prospective population study of 7, adults aged 20 to 75 years in the Netherlands who did not have cardiovascular disease found that low urinary magnesium excretion levels a marker for low dietary magnesium intake were associated with a higher risk of ischemic heart disease over a median follow-up period of Plasma magnesium concentrations were not associated with risk of ischemic heart disease [ 35 ].
Higher magnesium intakes might reduce the risk of stroke. One limitation of such observational studies, however, is the possibility of confounding with other nutrients or dietary components that could also affect the risk of stroke. A large, well-designed clinical trial is needed to better understand the contributions of magnesium from food and dietary supplements to heart health and the primary prevention of cardiovascular disease [ 38 ].
Diets with higher amounts of magnesium are associated with a significantly lower risk of diabetes, possibly because of the important role of magnesium in glucose metabolism [ 39 , 40 ]. Hypomagnesemia might worsen insulin resistance, a condition that often precedes diabetes, or it might be a consequence of insulin resistance [ 41 ].
Diabetes leads to increased urinary losses of magnesium, and the subsequent magnesium inadequacy might impair insulin secretion and action, thereby worsening diabetes control [ 3 ]. Most investigations of magnesium intake and risk of type 2 diabetes have been prospective cohort studies. A meta-analysis of prospective cohort studies of the association between magnesium intake and risk of type 2 diabetes included 13 studies with a total of , participants and 24, cases of diabetes [ 43 ].
The mean length of follow-up ranged from 4 to 20 years. Investigators found an inverse association between magnesium intake and risk of type 2 diabetes in a dose-responsive fashion, but this association achieved statistical significance only in overweight body mass index [BMI] 25 or higher but not normal-weight individuals BMI less than Again, a limitation of these observational studies is the possibility of confounding with other dietary components or lifestyle or environmental variables that are correlated with magnesium intake.
Only a few small, short-term clinical trials have examined the potential effects of supplemental magnesium on control of type 2 diabetes and the results are conflicting [ 40 , 44 ]. After 30 days of supplementation, plasma, cellular, and urine magnesium levels increased in participants receiving the larger dose of the supplement, and their glycemic control improved.
The American Diabetes Association states that there is insufficient evidence to support the routine use of magnesium to improve glycemic control in people with diabetes [ 44 ]. It further notes that there is no clear scientific evidence that vitamin and mineral supplementation benefits people with diabetes who do not have underlying nutritional deficiencies. Magnesium is involved in bone formation and influences the activities of osteoblasts and osteoclasts [ 48 ].
Magnesium also affects the concentrations of both parathyroid hormone and the active form of vitamin D, which are major regulators of bone homeostasis. Several population-based studies have found positive associations between magnesium intake and bone mineral density in both men and women [ 49 ]. Other research has found that women with osteoporosis have lower serum magnesium levels than women with osteopenia and those who do not have osteoporosis or osteopenia [ 50 ].
These and other findings indicate that magnesium deficiency might be a risk factor for osteoporosis [ 48 ]. Although limited in number, studies suggest that increasing magnesium intakes from food or supplements might increase bone mineral density in postmenopausal and elderly women [ 1 ].
Diets that provide recommended levels of magnesium enhance bone health, but further research is needed to elucidate the role of magnesium in the prevention and management of osteoporosis. Magnesium deficiency is related to factors that promote headaches, including neurotransmitter release and vasoconstriction [ 52 ]. People who experience migraine headaches have lower levels of serum and tissue magnesium than those who do not. However, research on the use of magnesium supplements to prevent or reduce symptoms of migraine headaches is limited.
The authors of a review on migraine prophylaxis suggested that taking mg magnesium twice a day, either alone or in combination with medication, can prevent migraines [ 53 ]. In their evidence-based guideline update, the American Academy of Neurology and the American Headache Society concluded that magnesium therapy is "probably effective" for migraine prevention [ 54 ].
Because the typical dose of magnesium used for migraine prevention exceeds the UL, this treatment should be used only under the direction and supervision of a healthcare provider. Too much magnesium from food does not pose a health risk in healthy individuals because the kidneys eliminate excess amounts in the urine [ 28 ]. However, high doses of magnesium from dietary supplements or medications often result in diarrhea that can be accompanied by nausea and abdominal cramping [ 1 ].
Forms of magnesium most commonly reported to cause diarrhea include magnesium carbonate, chloride, gluconate, and oxide [ 11 ]. The diarrhea and laxative effects of magnesium salts are due to the osmotic activity of unabsorbed salts in the intestine and colon and the stimulation of gastric motility [ 55 ].
Symptoms of magnesium toxicity, which usually develop after serum concentrations exceed 1. The risk of magnesium toxicity increases with impaired renal function or kidney failure because the ability to remove excess magnesium is reduced or lost [ 1 , 28 ]. The FNB has established ULs for magnesium that apply only to supplemental magnesium for healthy infants, children, and adults see Table 3 [ 1 ].
Several types of medications have the potential to interact with magnesium supplements or affect magnesium status. A few examples are provided below. People taking these and other medications on a regular basis should discuss their magnesium intakes with their healthcare providers. Use of magnesium-rich supplements or medications and oral bisphosphonates should be separated by at least 2 hours [ 55 ].
These antibiotics should be taken at least 2 hours before or 4—6 hours after a magnesium-containing supplement [ 55 , 60 ]. Sticky substances on the skin of earthworms and those produced by fungi and bacteria help bind particles together. Earthworm casts are also more strongly aggregated bound together than the surrounding soil as a result of the mixing of organic matter and soil mineral material, as well as the intestinal mucus of the worm. Thus, the living part of the soil is responsible for keeping air and water available, providing plant nutrients, breaking down pollutants and maintaining the soil structure.
The composition of soil organisms depends on the food source which in turn is season dependent. Therefore, the organisms are neither uniformly distributed through the soil nor uniformly present all year. However, in some cases their biogenic structures remain. Each species and group exists where it can find appropriate food supply, space, nutrients and moisture Plate 2.
Organisms occur wherever organic matter occurs Ingham, Therefore, soil organisms are concentrated: For this reason, they are most prevalent in forested areas and cropping systems that leave a lot of biomass on the surface. Plate 2 Termites create their own living conditions near their preferred food sources. Inside the colony life is highly organized.
The activity of soil organisms follows seasonal as well as daily patterns. Not all organisms are active at the same time. Most are barely active or even dormant. Availability of food is an important factor that influences the level of activity of soil organisms and thus is related to land use and management Figure 3.
Practices that increase numbers and activity of soil organisms include: Different groups of organisms can be distinguished in the soil Brussaard and Juma, Table 1 classifies them by size. Table 2 classifies them by function. Fresh residues consist of recently deceased micro-organisms, insects and earthworms, old plant roots, crop residues, and recently added manures.
Crop residues contain mainly complex carbon compounds originating from cell walls cellulose, hemicellulose, etc. These carbon chains, with varying amounts of attached oxygen, H, N, P and S, are the basis for both simple sugars and amino acids and more complicated molecules of long carbon chains or rings.
Depending on their chemical structure, decomposition is rapid sugars, starches and proteins , slow cellulose, fats, waxes and resins or very slow lignin. Figure 3 Fluctuations in microbial biomass at different stages of crop development in conventional agriculture compared with systems with residue retention and high organic matter input. Bioturbating invertebrates and plant roots, mycorrhizae and some other micro-organisms.
Mostly micro-organisms and plant roots, some C protected in large compact biogenic invertebrate aggregates. Mostly micro-organisms and plant roots, some soil- and litter-feeding invertebrates.
Various saprophytic and litter-feeding invertebrates detritivores , fungi, bacteria, actinomycetes and other micro-organisms. Plants, mycorrhizae and other fungi, nematodes, bacteria and various other micro-organisms, collembola, earthworms, various predators. Plant roots, various insects crickets, beetle larvae, ants, termites , earthworms, vertebrates, micro-organisms and their by-products. Rhizobia, mycorrhizae, actinomycetes, diazotrophic bacteria and various other rhizosphere micro-organisms, ants.
During the decomposition process, microorganisms convert the carbon structures of fresh residues into transformed carbon products in the soil. There are many different types of organic molecules in soil.
Some are simple molecules that have been synthesized directly from plants or other living organisms. These relatively simple chemicals, such as sugars, amino acids, and cellulose are readily consumed by many organisms.
For this reason, they do not remain in the soil for a long time. Other chemicals such as resins and waxes also come directly from plants, but are more difficult for soil organisms to break down. Humus is the result of successive steps in the decomposition of organic matter.
Because of the complex structure of humic substances, humus cannot be used by many micro-organisms as an energy source and remains in the soil for a relatively long time. Non-humic organic molecules are released directly from cells of fresh residues, such as proteins, amino acids, sugars, and starches. This part of soil organic matter is the active, or easily decomposed, fraction. This active fraction is influenced strongly by weather conditions, moisture status of the soil, growth stage of the vegetation, addition of organic residues, and cultural practices, such as tillage.
It is the main food supply for various organisms in the soil. Carbohydrates occur in the soil in three main forms: The simple sugars, cellulose and hemicellulose, may constitute percent of the organic matter in most soils, but are easily broken down by micro-organisms.
Polysaccharides repeating units of sugar-type molecules connected in longer chains promote better soil structure through their ability to bind inorganic soil particles into stable aggregates. Research indicates that the heavier polysaccharide molecules may be more important in promoting aggregate stability and water infiltration than the lighter molecules Elliot and Lynch, Some sugars may stimulate seed germination and root elongation.
Other soil properties affected by polysaccharides include CEC, anion retention and biological activity. The soil lipids form a very diverse group of materials, of which fats, waxes and resins make up percent of soil organic matter.
The significance of lipids arises from the ability of some compounds to act as growth hormones. Others may have a depressing effect on plant growth. Small amounts exist in the form of amines, vitamins, pesticides and their degradation products, etc. The rest is present as ammonium NH 4 - and is held by the clay minerals.
Humus or humified organic matter is the remaining part of organic matter that has been used and transformed by many different soil organisms. It is a relatively stable component formed by humic substances, including humic acids, fulvic acids, hymatomelanic acids and humins Tan, It is probably the most widely distributed organic carbon-containing material in terrestrial and aquatic environments.
Humus cannot be decomposed readily because of its intimate interactions with soil mineral phases and is chemically too complex to be used by most organisms. It has many functions Box 2. One of the most striking characteristics of humic substances is their ability to interact with metal ions, oxides, hydroxides, mineral and organic compounds, including toxic pollutants, to form water-soluble and water-insoluble complexes.
Through the formation of these complexes, humic substances can dissolve, mobilize and transport metals and organics in soils and waters, or accumulate in certain soil horizons. This influences nutrient availability, especially those nutrients present at microconcentrations only Schnitzer,