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Dietary needs for detoxification process in the human body
Saturday, 16 October, 2021, 08 : 00 AM [IST]
Dr Snehal Giri
As part of normal metabolism, the human body is exposed to a wide number of xenobiotics or toxicants in one’s lifetime, which includes food components, food additives, alcohol, environmental toxins, microorganisms, variety of pharmaceuticals as well as normal body metabolite end products which would become toxic if allowed to build up.

Toxins/toxicants are also called Xenobiotics. Xenobiotics are defined as chemical substances present within, but not made within a living thing- a substance that is ‘a stranger to life'. 

It is generally accepted that today’s exposure to such environmental toxins is on the rise and to compound the problem, we have also refined the nutritional value of our food and replaced it with artificial colorings, preservatives, additives, flavourings. The result is this they provide considerably less of the nutrients that are essential to the detoxification process. Sometimes, our body may not always be equipped to handle the volume of modern, environmental pollutants and toxic substances. The US Centre for Disease Control estimates, over 80% of all illnesses have environmental and lifestyle causes (CDC, 2010). 

Human beings are generally exposed to xenobiotics mainly through the air, water, and soil and absorbed into the bloodstream mainly through the skin, lung, and gastrointestinal tract. The human body has developed highly complex enzymatic mechanisms to detoxify these substances. The detoxification process involves a series of biochemical reactions occurring in the body to convert (often toxic) compounds to less toxic water-soluble (polar) compounds. It is also called biotransformation/xenobiotic metabolism.

Need for detoxification
People should be able to detoxify but an overload of toxins, an undernourished body, a compromised digestive system all make for a less effective detoxification process. In the absence of efficient excretion of constant exposure of excess toxins, gets accumulated in adipose tissues, fatty tissues of brain, nervous system and endocrine glands to hazardous level and are also seen in unborn babies.

A compromised detoxification system leads to the generation of free radicals which further adversely alter lipids, proteins, and DNA. The scientific literature suggests an association between impaired detoxification and diseases, like cancer, fibromyalgia, chronic fatigue/immune dysfunction syndrome, and neurological diseases such as Alzheimer's and Parkinson's disease. 

Liver detoxification
The main organs involved in the detoxification process- the liver, the kidneys, and the intestinal tract. The liver is the major detoxifying organ worked in two phases and the role of various enzymes in the liver is to convert fat-soluble toxins into water-soluble substances that can be excreted in the urine or the bile.  The liver deactivates the xenobiotic, attenuates its biological activity, and accelerate its clearance from the body. 

Phase I: 
Phase I metabolism converts many toxins into their active compounds and converts some chemicals into more toxic metabolites.

This phase initiates reactions that generally involve exposing or adding a “functional group” to the toxic molecule; thus, referred to as “functionalization” which uses oxygen to form a reactive site Ex. cytochrome P450 (CYP450). Essentially this makes the toxic compound “sticky” so that something can be added to it and to make them more soluble. 

Phase I reaction includes oxidation, reduction, hydrolysis, hydration, and dehalogenation. CYP450 activates the toxin by adding a hydroxyl group to the lip-soluble toxin, using nicotinamide adenosine dinucleotide (NADH) as a cofactor. 

Sometimes the toxins transformed into activated intermediates by phase I are substantially more reactive. Unless quickly removed from the body by phase II detoxification mechanisms, they can cause widespread problems, especially carcinogenesis. The rate at which phase I produces activated intermediates must be balanced by the rate at which phase II finishes its processing. Therefore, Phase 1 & Phase 2 must be in balance. 

Phase II:
Phase II conjugation reactions generally follow Phase I activation. Phase II involves the coupling or conjugation of toxin/ functional group activated, or induced in the first phase with water-soluble substance. This makes the toxic molecule larger, inactive, and more water-soluble, and therefore less toxic. Further, these hydrophilic conjugated xenobiotics are excreted from the body via urine, bile, and sweat. This phase is termed “Conjugation”. These reactions require cofactors which must be replenished through dietary sources. The common conjugation reactions are methylation, glucuronidation, sulfation, acetylation reaction, certain amino acids conjugation, and glutathione.

Nutrients and foods that ensure that Phase I and Phase II is working well include-
A high-protein diet enhances rates of oxidative drug metabolism in humans. Low protein decreases the levels of cytochrome P-450 and its reductase by 50-75% 
Vitamin B-rich foods (yeast and whole grains) assist in Phase I activation. Riboflavin: flavins are prosthetic groups of NADPH-cytochrome P-4 reductase and microsomal flavin-containing monooxygenase. 

Vitamin E as an antioxidant, vitamin E appears to block lipid peroxidation, which is postulated to be important in the toxic properties of foreign compounds
Vitamin C-rich foods peppers, cabbage, and tomatoes act as antioxidants to protect during Phase I. 

Sulfur-containing foods (eggs, red peppers, garlic, onions, shallots, broccoli & Brussels sprouts), amino acids (cysteine, methionine, taurine) are essential for effective phase II detoxification.

Glutathione is essential to the majority of the detoxification and is found in fresh fruit and vegetables, brassicas, limonene, asparagus, avocado, walnuts, carrots, red beets, watermelon 
Proanthocyanidins found in grape juice and red wine
Quercetin is found in green and black tea, red wine, garlic, tomatoes, peppers (green and cayenne), broccoli, grapes, berries, and apples. Quercetin plays a crucial role in the liver against DNA damage. It also stimulates the expression of phase II detoxifying enzymes.

Flavonoids are effective in the management of different liver disorders. Flavonoids have high affnity for heavy metal ions, which is dependent on the number and position of free phenol and/or enol groups in the molecule. 

Alium groups are organosulfur components of garlic oil, diallyl disulfide, and diallyl trisulfide have also been shown to increase hepatic detoxification in rat models through enhancement of phase II metabolism via GST.

Citrus foods such as oranges and tangerines as well as caraway and dill seeds contain limonene, a strong inducer of both Phases I and II enzymes.
Brassica-family foods (cabbage, broccoli, and brussels sprouts) family has indole-3-carbinol constituents that stimulate both Phases I and II enzymes.

Turmeric Enhance cellular resistance to oxidative damage, enhance the body’s natural antioxidant glutathione levels.
Inhibits phase I while stimulating phase II. This effect can be very useful in preventing certain types of cancer. Curcumin, a compound in turmeric has been found to inhibit carcinogens, such as benzopyrene (found in grilled meat) 
Green tea compounds increase both phase 1 and phase 2 enzyme activities. In addition, green tea has been shown to block chromosomal (DNA) damage from chemicals in cigarette smoke. 
Garlic appears to induce both phase 1 and phase 2 enzymes. Garlic extract may increase the glutathione level and glutathione-related enzymes which aid in detoxifying the body.
Chicory: is a powerful hepatic stimulant that increases bile secretion 
Milk thistle (Sylibum marianum L.): contain silymarin; 
  • Silymarin has numerous pathways for hepatoprotective e?ects such as antioxidant activity.
  • inhibits detoxi?cation of cytP450 pathways 
  • prevents the metabolism of toxic integrates, including tetrachloride, acetaminophen, and thioacetamide
  • increases glutathione synthesis 
  • prevents depletion of glutathione 
  • protects the liver from damage 
  • Acts as an antioxidant 
  • Increases the rate of liver tissue regeneration 

Foods add to the toxic load
  • Sugar 
  • Alcohol 
  • Caffeine 
  • Processed & fried foods 
  • Hydrogenated fats 
  • Refined carbs and all gluten 
  • Genetically modified foods
  • Refined oils: soybean, corn, canola, safflower 
  • Excess saturated animal fat like sausage, bacon, salami, hot dogs, high-fat dairy products like whole milk, ice cream, and cheese 
  • Chemicals/cigarettes 
  • OTC drugs

The human body is exposed to many toxins in its lifetime. Though the human body has developed complex enzymatic mechanisms to detoxify these substances sometimes due to higher exposure of toxins, poor dietary choices, and low antioxidant stress our systems get overloaded. 

Further secondary metabolites will be formed. These free radicals bring out cellular damage and act as the main cause of the pathogenesis of different human diseases. Therefore, it becomes important to detox our body by cleansing individual organs like the liver, kidney, colon, etc, or by detoxifying the whole body as one unit. Therefore, it is very important to eat a well-balanced diet with plenty of fresh, wholesome foods. 

There are fruits and vegetables, whole grains, spices, and herbs that are rich in vitamins, minerals, and bioactive compounds that encourage the detoxification process and reduce the burden on the major detoxifying organs and the foods or substances (alcohol, cigarette smoke) which disturb the whole detoxification process should be removed.

(The author belongs to Food Science and Nutrition Department, UAS, GKVK, Bangalore)
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