Excess of Antioxidants

Antioxidants are molecules necessary for protecting the body against certain catabolites produced during cellular respiration: free radicals .

Free radicals (eg singlet oxygen, superoxide anion, hydrogen peroxide ) are ions or molecules present in variable concentrations (environmental and subjective factors) that possess unpaired electrons capable of negatively altering the other surrounding molecules (eg phospholipids, nucleic acids, proteins etc.). Their "cascade" action on cellular structures can be interrupted only by antioxidants, be they endogenous (eg glutathione, superoxide dismutase, catalase, etc.) or exogenous (therefore introduced with the diet above all: selenium, zinc, copper, vit A and carotenoids (lycopene, astaxanthin, etc.), vitamin C, vitamin E, coenzyme Q-10, lipoic acid, etc. ).

NB . There are many other dietary molecules with a more or less antioxidant function, the toxicity of which is NOT known, among which the best known are polyphenols .

Excess of exogenous antioxidants in the diet

The exogenous antioxidants taken with the diet are very useful to prevent / hinder cellular aging processes, depression of the immune system and the onset of diseases or cancers.

Often the exogenous antioxidants in the diet are not sufficient to cover the subject's needs; in this case, it is important that their contribution be increased through the so-called "antioxidant foods" or food supplements based on antioxidants ... BUT IF THEY WERE TOO MUCH?

In general, when present in the right concentrations, free radicals are fundamental for cellular homeostasis, since they act as veritable messengers essential for the correct metabolism of the cell (they play, for example, a fundamental role in the processes of killing and digestion intracellular pathogens by macrophages and granulocytes).
Consequently, by neutralizing an excessive amount of free radicals through the excessive intake of antioxidants, there is a risk of disturbing the normal cellular metabolic balance, putting the health of the entire body at risk.
Until a few years ago, the American Department of Agriculture recommended taking a dietary antioxidant quota of between 3, 000 and 5, 000 ORAC units per day, which can be reached by consuming about five portions of fruit and vegetables. As a precautionary measure, it could therefore be suggested that a possible integration of antioxidants does not exceed 5, 000 ORAC units per daily dose, which will be added to those made by the normal diet. Recently, the ORAC method for estimating antioxidant capacity has been deprecated, due to the poor in vivo reproducibility of the results.

Selenium

Function and food sources: selenium is a fundamental component of the endogenous antioxidant glutathione peroxidase (GSHpx) and of the phospholipid-hydroperoxide-glutathione-selenium-dependent peroxidase - pH-ESHPX-Se (Levander, 1987; Neve, 1989; Burk, 1991 ); the latter catalyzes the degradation of the hydroperoxides formed by the oxidation of polyunsaturated fatty acids in the cell membrane and hinders the enzyme prostacyclin synthetase which favors the formation of pro-inflammatory molecules (Wolffran et al., 1989, Guidi et al., 1984; Schiavon et al., 1984). The foods that bring greater amounts of selenium are fish and offal, meat and cereals, dairy products; its recommended ration is not easily estimated but the EEC recommends an average intake of 40µg / day.

EXCESS of antioxidant selenium and recommended rations: the excess of selenium can cause even serious poisoning; in the USA there have been cases of excess selenium due to out-of-control food integration. The subjects had regularly taken bars that contained 27.3mg of this microelement exceeding exponentially the recommended ration; in this case there were: nausea, vomiting, diarrhea, abdominal cramps, hair loss, nail fragility and peripheral neuropathy (Helzsouer et al ., 1985). In addition to the poisoning due to excessive short-term supplements, even the prolonged intake of 3-7mg / day of selenium seems to determine adverse reactions such as: bullous dermatitis, nail changes, alopecia and neurological abnormalities (paresthesia, paralysis and hemiplegia) (Yang et al ., 1983). Other studies show that even only 0.7-0.9mg / day of selenium determine an excess of this antioxidant related to specific disorders and symptoms (Yang et al., 1989), therefore, it is advisable not to take more than 450 µg / die (Commission of the European Communities, 1993).

Zinc

Function and food sources: zinc is a very important enzyme factor, participates in the maturation of immune cells, stabilizes certain hormonal proteins, is important for the formation of bones and muscles and has a very important antioxidant action. Zinc is contained in meat, eggs, fish, milk and cereals.

EXCESS of zinc antioxidant and recommended rations: the recommended rations of zinc are not known but if deficient it is an essential nutrient. The excess of zinc, in doses higher than 2g / day, becomes toxic and causes nausea, vomiting and fever (Hambridge et al., 1986); moreover, prolonged intake of dosages equal to or greater than 75-300 mg / day can induce alterations: of copper and iron metabolism (impaired synthesis of leukocytes and erythrocytes), and absorption of calcium and magnesium (with likely bone impairment).

Copper

Function and food sources: copper is an enzymatic component of endogenous antioxidants and participates in cellular energy processes as well as the synthesis of connective tissue, keratin of nails and hair and some neuro-active peptides. Copper is contained in the liver, kidneys, molluscs and some fruits.

EXCESS of antioxidant copper and recommended rations: no cases of copper poisoning are known, except for accidental ingestion of contaminating products. The dose tolerated with food is about 35mg / day but the Commission of the European Communities suggests not to exceed 10mg / day.

Vit. A and carotenoids

Function and food sources: for vit. A means both the vit. fat-soluble retinoids (and analogues), both vit. fat-soluble carotenoids (including lycopene, astaxanthin, etc.). Among the two groups, those with greater antioxidant function are certainly carotenoids, especially β-carotene, while retinol and analogues are mainly engaged in the mechanism of vision and cell differentiation. Retinoids are mainly found in animal-type foods (liver and milk derivatives), while carotenoids are better represented in the 6th of the 7 basic food groups (lycopene especially in tomatoes [but not only!] And astaxanthin in shellfish or in some fish that eat it).

EXCESS vit. A and antioxidant carotenoids and recommended rations: The recommended ration of these vitamins and provitamins is evaluated according to the retinol equivalence criterion ( 1 RE = 1 µg of retinol = 6 µg of β- carotene = 12 µg of other carotenoids ) and ranges from 350 to 700 µg RE / day. Acute retinoid excess occurs at doses up to 300mg / day, while in the long term, it depends above all on the ability to store liver; it is recommended not to exceed single doses equal to 120mg / day or however to maintain doses of prolonged integration between 7.5 and 9mg / day (Bauernfeind, 1980; Commission of the European Communities, 1993). In pregnant women doses of retinoids equal to 6mg / day become risky and can cause a teratogenic effect on the fetus, or malformations of the unborn child; on the contrary, carotenoids do not show any side effects except an "orange" hyper-pigmentation of the skin.

Vit. C

Function and food sources: vitamin C (or L-ascorbic acid) is a water-soluble vitamin that performs many functions: enzyme factor, responsible for the synthesis of collagen, cellular defense, protection of vitamin E, reduction of folic acid in its coenzymes and 3+ iron reduction in 2+ iron. The vit. C is contained above all in plants of the 7th of the 7 basic food groups and its recommended ration ranges between 60 and 90 mg / day.

EXCESS of antioxidant vitamin C and recommended rations: the excess of vitamin C (> 500mg / day) increases the excretion of oxalates with urine and decreases the solubility of uric acid; moreover, a possible pro-oxidant effect induced by "megadoses" of the same vitamin has been recently observed (Chen Q. et al, 2008); additions> 10g / day, in addition to the effects mentioned above, cause gastrointestinal disorders (probably triggered by the alteration of the pH) and favor the formation of kidney stones (Flodin, 1988).

Lives

Function and food sources: vit. E (or tocopherol) is a vit. liposoluble which includes 8 different vitamin forms based on metabolic efficacy; therefore, the concentrations and nutritional requirements of vitamin E are expressed in Tocopherol Equivalents or international units: 1 Tocopherol Equivalent = 1 mg a-tocopherol = 1.5 IU = 2 mg βŸ -tocopherol = 3 mg δ-tocotrienol = 10 mg γ -tocopherol. The vit. And it prevents the oxidation of polyunsaturated fatty acids (PUFA) to which it can bind as structural elements . They are rich in vit. And the oil seeds, the germ of cereals and their oils.

EXCESS vit. And antioxidant and recommended rations: the optimal intake of vit. And it is equal to 0.4 TE each gram of PUFA, so about 8mg / day; the toxicity induced by excess vit. And it is very difficult to obtain even by means of pharmacological administrations; these are intestinal symptoms obtainable with megadoses of at least 2, 000 mg / day (Bendich & Machlin, 1988) which in any case do not show any metabolic alterations of any kind.

Coenzyme Q-10

Function and food sources: coenzyme Q-10 or ubiquinone regulates energy metabolism and is a powerful mitochondrial antioxidant, whose concentration tends to decrease with aging; Coenzyme Q-10 supplementation is useful in mitochondrial myopathies, in the prevention or coadjuvation of anti-cancer therapies, in the treatment of neurodegenerative diseases and in migraine. The coenzyme Q-10 food is present in meat and fatty fish, but mostly it is synthesized on an endogenous level through the union of: Acetyl-coenzyme A to a benzoic ring (deriving from tyrosine) and to several lateral methyl groups (deriving from methionine)

EXCESS of coenzyme Q-10 antioxidant and recommended rations: coenzyme Q-10 does not have a recommended ration since most is produced at endogenous level; however, if used in the aforementioned therapies the range of administration is between 10 and 90mg. NB . coenzyme Q-10 is inactivated by some drugs such as statins to lower cholesterol and therefore may require dietary supplementation. An excess of coenzyme Q-10 does not cause a real intoxication; the few symptoms shown are non-specific and of a minor nature: loss of appetite, gastro-intestinal disorders, nausea and vomiting.

Lipoic acid

Function and food sources: lipoic acid is a liposoluble molecule with functions of: energy coenzyme of fatty acids and carbohydrates, antioxidant capable of blocking hydroxyl radicals, hypochlorous and singlet oxygen, and chelating of excess heavy metals. NB . Lipoic acid acts in synergy with dihydrolipoic acid. Lipoic acid is mainly found in red meats.

EXCESS of antioxidant lipoic acid and recommended rations: the dietary intake of lipoic acid should be 25-50mg / day and the pharmacological excess has been observed in different animal species; in humans, referring to a person of average build (about 70kg in weight), the overdose corresponds to about 30-35g / day. Following excessive administration of lipoic acid, there are no severe symptoms and ONLY in hypersensitives can allergic skin and gastric disorders occur; does not appear to have teratogenic effects but, in the absence of more detailed information, it is NOT RECOMMENDED for use in pregnancy.

Bibliography: