Green tea contains a chemical called EGCG (epigallocatechins). One of the functions of EGCG is to inactivate an enzyme called DHFR (dihydrofolate reducatase). DHFR's function is to absorb folate (folic acid). Reduced folic acid levels have been linked to depression.
Folic acid can fuel cancer growth. This is probably one of the reasons (the other is inhibition of iron absorption) why Green Tea has been shown to protect against cancer.
RE: Green Tea and Iron
Green Tea inhibits the absorption of iron, it is not an iron chelator. Curcumin is an iron chelator. Reducing iron stores and intake is one of the major keys to longevity. Iron is implicated in every major disease of aging. The Medical community appears to be blind regarding the toxicity of iron and what safe levels of iron are. The current acceptable levels of iron are dangerously high.
This is a great book if you can find it:
http://books.google....W...;q=&f=false
splitastone,
there seem to be quite a few studies saying that Green Tea's ingredients chelate iron, rather than just inhibit the absorption of Iron (see below for my pasted examples).
It may well be true that reducing 'iron stores and intake is one of the major keys to longevity'. But that doesn't mean that slight reductions in iron could not trigger a lower mood at least temporarily. Especially in conjunction with some of the other factors that people have mentioned (like your mention of green tea decreasing the ability of the body to use folate by inhibiting the DHFR enzyme and also lowering of blood sugar).
Good things for longevity does not always equal good things for mood/feelings of wellbeing, just ask some of the people who practice Caloric Restriction!
Iron is an essential mineral responsible for transporting oxygen around the body, so when it’s in a slightly lower supply, oxygen levels in the brain may fall a little. Not to mention the fact that iron is involved in neurotransmitter synthesis.
One way to test whether it's the slight Iron depletion that might be the primary cause of a particular person's lower mood feelings after drinking green tea would be as follows. Try drinking the green tea along with the following and see if you can discern a difference after trying this a number of times (recording how you feel say 45 minutes after finishing each meal/green tea):
- a meal with plenty of iron, preferably in its more absorbable heme iron form (for examples of iron rich foods, see below).
- a low iron meal, preferably with other variables being almost identical to the other meal mentioned (so for example about the same amount of protein, carbohydrates and fats, and folate as well for each meal).
www.purewellness.com.au/docs/Pure%20Iron%20Deficiency.doc
[Some foods and their iron content:]
100g steamed clams 22.0mg
100g cooked chicken liver 8.5mg
100g cooked oysters 8.5mg
100g cooked beef liver 6.3mg
100g cooked beef (roast) 3.5mg
85g cooked minced beef 2.2mg
100g cooked chicken 2.1mg
100g cooked lamb 1.8mg
100g canned tuna 1.3mg
100g cooked fish 1.0mg
2008 American Society for Nutrition J. Nutr. 138:1578S-1583S, August 2008
Supplement: Proceedings of the Fourth International Scientific Symposium on Tea and Human Health
Targeting Multiple Neurodegenerative Diseases Etiologies with Multimodal-Acting Green Tea Catechins1,2
Silvia A. Mandel, Tamar Amit, Limor Kalfon, Lydia Reznichenko and Moussa B. H. Youdim
Eve Topf Center for Neurodegenerative Diseases Research and Department of Pharmacology, Faculty of Medicine, Technion, Haifa, Israel
From the full text at
http://jn.nutrition....teid=nutrition:"...Collectively, the accumulated data support and extend the emerging view that green tea catechins are multimodal-acting, brain-permeable natural iron chelators-antioxidants endowed with polypharmacological activities and acting at multiple brain targets to prevent or delay neuronal death in the degenerating brain..."
Effect of Green Tea on Iron Status and Oxidative Stress in Iron-Loaded Rats
Authors: Ounjaijean, S.; Thephinlap, C.; Khansuwan, U.; Phisalapong, C.; Fucharoen, S.; Porter, J. B.; Srichairatanakool, S.
Source: Medicinal Chemistry, Volume 4, Number 4, July 2008 , pp. 365-370(6)
Publisher: Bentham Science Publishers
Abstract:
Plasma non-transferrin bound iron (NTBI) is potentially toxic and contributes to the generation of reactive oxygen species (ROS), consequently leading to tissue damage and organ dysfunction. Iron chelators and antioxidants are used for treatment of thalassemia patients. Green tea (GT) contains catechins derivatives that have many biological activities. The purpose of this study was to investigate the iron-chelating and free-radical scavenging capacities of green tea extract in vivo. Rats were injected ip with ferric citrate together with orally administered GT extract (GTE) for 4 months. Blood was collected monthly for measurement of iron overload and oxidative stress indicators. Plasma iron (PI) and total ironbinding capacity (TIBC) were quantified using bathophenanthroline method. Plasma NTBI was assayed with NTA chelation/ HPLC. Plasma malonyldialdehyde (MDA) was determined by using the TBARS method. Erythrocyte oxidative stress was assessed using flow cytometry. Levels of PI, TIBC, NTBI and MDA, and erythrocyte ROS increased in the ironloaded rats. Intervention with GT extract markedly decreased the PI and TIBC concentrations. It also lowered the transferrin saturation and effectively inhibited formation of NTBI. It also decreased the levels of erythrocyte ROS in week 4, 12 and 16. Therefore, green tea extract can decrease iron in plasma as well as eliminate lipid peroxidation in plasma, and destroy formation of erythrocyte ROS in the rats challenged with iron. The bifunctional effects could be beneficial in alleviating the iron and oxidative stress toxicity. In prospective, these GTE activities should be further examined in thalassemic animals or humans.