Free radicals (eg. singlet oxygen, superoxide anion, hydrogen peroxide) are ions or molecules present in varying concentrations (environmental factors And subjective) which possess unpaired electrons capable of negatively altering other surrounding molecules (e.g. phospholipids, nucleic acids, proteins, etc.). Their "cascade" action on cellular structures can only be interrupted by antioxidants, whether they are endogenous (eg. glutathione, superoxide dismutase, catalase etc.) or exogenous (therefore introduced with the diet especially: selenium, zinc, copper, vit. To and carotenoids (lycopene, astaxanthin etc.), vit. C., vit. AND, coenzyme Q-10, lipoic acid etc.).
NB. There are many other dietary molecules with a more or less antioxidant function of which the toxicity is NOT known, among these the best known are the polyphenols.
, 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 needs of the subject; in this case, it is important that their intake be increased through the so-called "antioxidant foods" or food supplements based on antioxidants ... BUT IF THEY WERE TOO MANY?
- In general, when present in the right concentrations, free radicals are essential for cellular homeostasis, since they act as real messengers essential for the correct metabolism of the cell (for example, they play 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 the risk of disturbing the normal cellular metabolic balance, putting the health of the whole organism at risk.
- Until a few years ago, the American Department of Agriculture recommended that you consume an amount of antioxidants between 3,000 and 5,000 ORAC units per day through your diet, which can be reached by consuming about five portions of fruit and vegetables. therefore to suggest that a possible integration of antioxidants does not exceed 5,000 ORAC units per daily dose, which will be added to those provided by the normal diet. Recently, the ORAC method for estimating antioxidant capacity has been deprecated, due to the poor reproducibility of its results in vivo.
EXCESS of antioxidant selenium and recommended rations: the "excess of selenium can cause even serious intoxications; in the USA there have been cases of excess selenium for out of control food supplementation. The subjects had regularly taken bars that contained 27.3mg of this microelement, exponentially exceeding the recommended ration; in this case cases have occurred: nausea, vomiting, diarrhea, abdominal cramps, hair loss, brittle nails and peripheral neuropathy (Helzsouer et al., 1985).
In addition to intoxication due to excessive short-term supplements, the prolonged intake of 3-7mg / day of selenium also seems to cause adverse reactions such as: bullous dermatitis, nail changes, alopecia and neurological abnormalities (paraesthesia, paralysis and hemiplegia) (Yang et al., 1983)
Other studies show that even only 0.7-0.9mg / day of selenium causes 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 / day (Commission of the European Communities, 1993).
it is a very important enzymatic factor, participates in the maturation of immune cells, stabilizes some 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 antioxidant zinc and recommended rations: the recommended rations of zinc are not known but if deficient it turns out to be 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: in the metabolism of copper and iron (impaired synthesis of leukocytes and erythrocytes), and in the absorption of calcium and magnesium (with likely bone compromise).
cellular 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, shellfish and some fruits.EXCESS of antioxidant copper and recommended rations: there are no known cases of copper intoxication, except for accidental ingestion of contaminating products. The tolerated dose with food is about 35mg / day but the Commission of the European Communities suggests not to exceed 10mg / day.
retinoids (and analogues), both vit. fat-soluble carotenoids (including lycopene, astaxanthin etc.). Among the two groups, those with the greatest antioxidant function are certainly the carotenoids, in particular the β-carotene, while retinol and analogues are mainly involved in the mechanism of vision and cell differentiation. Retinoids are mainly contained in animal-type foods (liver and milk derivatives), while carotenoids are best represented in the VI ° of the 7 basic food groups (lycopene especially in tomatoes [but not only!] And "astaxanthin in crustaceans. or in some fish that feed on it).
EXCESS of vit. A and antioxidant carotenoids and recommended rations: The recommended intake of these vitamins and provitamins is evaluated according to the criterion of retinol equivalence (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. The acute excess of retinoids it occurs with doses that reach 300mg / day while, in the long term, it mainly depends on the overcoming of the hepatic storage capacity; it is advisable not to exceed single doses of 120mg / day or in any case to maintain prolonged supplementation doses 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 have an effect teratogen on the fetus, or malformations of the unborn child; on the contrary, carotenoids show no side effect other than an "orange" hyper-pigmentation of the skin.
(or L-ascorbic acid) is a water-soluble vitamin that performs numerous functions: enzymatic factor, responsible for the synthesis of collagen, cell defense, protection of vitamin E, reduction of folic acid in its coenzymes and reduction of iron 3+ into iron 2 + Vitamin C is contained above all in the plants of the VII ° of the 7 fundamental food groups and its recommended ration varies 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 the urine and decreases the solubility of uric acid; furthermore, a possible pro-oxidant effect induced by "megadoses" of the vitamin has recently been observed itself (Chen Q. et al, 2008); intakes> 10g / day, in addition to the effects mentioned above, cause gastrointestinal disturbances (probably triggered by the alteration of pH) and favor the formation of kidney stones (Flodin, 1988).
which includes 8 vitamin forms, all different on the basis of metabolic efficacy; therefore, the concentrations and nutritional needs 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. 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 the cereals and the relative oils.
EXCESS of vit. And antioxidant and recommended rations: the optimal intake of vitamin E is equal to 0.4 TE per gram of PUFA, therefore about 8mg / day; the toxicity induced by the excess of vit. And it is very difficult to obtain even by means of pharmacological administrations; these are intestinal symptoms obtainable with megadoses of at least 2,000mg / day (Bendich & Machlin, 1988) which in any case do not show any kind of metabolic alterations.
and is a powerful mitochondrial antioxidant, whose concentration tends to decrease with aging; the integration of coenzyme Q-10 is useful in mitochondrial myopathies, in the prevention or aid of anti-cancer therapies, in the treatment of neurodegenerative diseases and in the " migraine. Dietary coenzyme Q-10 is present in meat and fatty fish, but is mostly synthesized endogenously by joining: Acetyl-coenzyme A to a benzoic ring (deriving from tyrosine) and to several lateral methyl groups (deriving from methionine).EXCESS of antioxidant coenzyme Q-10 and recommended rations: coenzyme Q-10 does not have a recommended ration since most of it is produced endogenously; however, if used in the therapies mentioned above, 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 food supplementation. An excess of coenzyme Q-10 does not cause a real intoxication; the few symptoms highlighted are non-specific and mild: inappetence, gastro-intestinal disorders, nausea and vomiting.
and carbohydrates, antioxidant capable of blocking hydroxyl radicals, hypochlorous and singlet oxygen, and chelator of excess heavy metals. NB. Lipoic acid acts in synergy with dihydrolipoic acid. Lipoic acid is mainly contained 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 various animal species; in man, referring to a subject of average build (about 70kg of weight), the overdose corresponds to about 30-35g / day. Following excessive administration of lipoic acid, no serious symptoms occur and ONLY hypersensitive manifestations may arise allergic skin and gastric disorders; it seems to have no teratogenic effects but, in the absence of more detailed information, it is NOT RECOMMENDED for use during pregnancy.
for the Italian population (LARN) - Italian Society of Human Nutrition (SINU).
