Green tea - low in tannins and caffeine

    Very popular in Asian countries and increasingly so in Europe and America due to its antioxidant and fat-burning properties.
    Green tea contains little or no tannins and less caffeine than black tea, but contains high amounts of a polyphenol antioxidant called EGCG.

Herbal tea - normally no tannins or caffeine

    Herbal tea isn't really made from tea (which is a specific kind of plant), it is really just an infusion of leaves, seeds, roots or bark, extracted in hot water.
    Varieties include ginger, ginkgo biloba, ginseng, hibiscus, jasmine, rosehip, peppermint, rooibos (red tea), chamomile, and echinacea.
    Herbal teas each normally have their own 'medical' reason for being drunk e.g. peppermint/ginger for digestion and bloating, chamomile for insomnia, rosehip/rooibos are high in vitamin C and antioxidants which are good for your skin and immune system.

The effects of caffeine

Caffeine inhibits Vitamin D receptors within your body, which limits the amount absorbed when you take supplemental forms such as Vitamin D3. Reduced Vitamin D levels affect the absorption and use of calcium in building strong bones. Caffeine is also diuretic which causes you to urinate more frequently, flushing out water-soluble vitamins such as the B-Complex vitamins and Vitamin C.  Caffeine significantly reduces the absorption rate of Iron in your intestines - believed to be up to 80%.

Summary: Black tea and Green tea stop efficient absorption of Iron, Vitamin D and B-Complex vitamins.
The effects of tannins

Tannins are a type of polyphenol found in plants, fruits and vegetables and have a bitter taste. They are responsible for the bitter taste in black tea, red wine and unripe fruits, it is this bitterness which is believed to protect plants, fruits and vegetables from being eaten by insects and plant predators.

Tannins don't effect the absorption of vitamins, but they do bind (chelate) to iron and block its absorption into the body from your intestines.

Summary: Black tea stops efficient absorption of Iron.
The effects of EGCG 

EGCG has been found to bind to iron in the intestine, preventing its absorption - instead simply being excreted out. Iron is necessary to carry oxygen from the lungs throughout the body and for other cell functions.

Summary: Green tea stops efficient absorption of Iron.
Why is Iron so important in the body?

Most of the Iron in the body is found in the haemoglobin of red blood cells. Iron helps red blood cells deliver oxygen from the lungs to cells all over the body. Once the oxygen is delivered, iron then helps red blood cells carry carbon dioxide waste back to the lungs to be exhaled. Iron also plays a role in many important chemical reactions in the body.

Low levels of Iron result in Iron deficiency anaemia. In people with Iron deficiency anaemia, the red blood cells can't carry enough oxygen to the body because they don't have enough Iron. People with this condition often feel very tired.
Recommendations

Taking vitamin and iron supplements with black and green teas is best avoided and you should wait at least an hour to eat or take any supplements if you are a tea or coffee drinker. Drinking tea and coffee can significantly inhibit the absorption of Iron by your body.

Some herbal teas however, such as rosehip or thyme are high in Vitamin C which actually enhances the absorption of iron.
As high doses of green tea extract supplements for weight loss become more popular, potential liver toxicity becomes a concern. In the last decade, dozens of people have been diagnosed with the condition. However, drinking green tea in the weeks before taking supplements likely reduces risk, according to researchers in Penn State's College of Agricultural Sciences.

Researchers gave mice high doses of the green tea polyphenol epigallocatechin-3-gallate (EGCG). The dosage was equivalent to the amount of the polyphenol found in some dietary supplements taken by humans.

One group of mice was pretreated with a diet containing a low level of ECGC for two weeks prior to receiving high doses of the polyphenol. Another group was fed a diet that did not include EGCG prior to receiving the high, supplement-like doses. After three days of high doses, the scientists tested the blood of the mice to determine how their livers handled the EGCG. Pretreated mice had a 75 percent reduction in liver toxicity compared to untreated mice.

The research data show that dietary pretreatment with the green tea polyphenol protects mice from liver toxicity caused by subsequent high oral doses of the same compound, explained Josh Lambert, associate professor of food science. He suggested that the research has relevance to people who are taking or are considering taking supplements containing green tea extract.

"We believe this study indicates that those who are chronic green tea consumers would be less sensitive to potential liver toxicity from green-tea-based dietary supplements," he said. "If you are going to take green tea supplements, drinking green tea for several weeks or months ahead of time may reduce your potential side effects."

Lambert has another suggestion for people considering green tea supplements -- drink green tea instead.

"Drinking green tea rather than taking supplements will allow you to realize the benefits and avoid the risk of liver toxicity," he said. "The beneficial effects that people have reported as being associated with green tea are the result of dietary consumption rather than the use of supplements. The relative risk of using supplements remains unclear."

Tea -- Camellia sinensis -- is rich in catechins, polyphenols that are natural antioxidants. A number of animal studies have shown the preventive effects of green tea polyphenols against obesity. And Lambert pointed out that a recent analysis of 11 human trials with green tea preparations reported a nearly three-pound average body weight loss in intervention groups compared to control groups.

Green tea's effect on weight loss may be more noticeable if a person exercises. In research published last year, Lambert showed that mice on a high-fat diet that consumed decaffeinated green tea extract and exercised regularly experienced sharp reductions in final body weight and significant improvements in health.

Approximately 34 percent of adults in the United States are classified as obese, Lambert noted, leading to a strong interest in the potential benefits of including green tea and green tea supplements in weight-loss efforts. The liver toxicity research, recently published online in Food and Chemical Toxicology, revealed a unique property of the green tea polyphenol EGCG.

"It appears that EGCG can modulate its own bioavailability and that dietary treatment may reduce the toxic potential of acute high oral doses of EGCG," said lead researcher Sarah Forester, assistant professor of chemistry, California State University, Bakersfield, a former Penn State postdoctoral fellow.

"These data may partly explain the observed variation in liver toxicity response to dietary supplements containing green tea."

Some people drink surprisingly large volumes of green tea, according to Lambert, as much as 10-20 cups a day, but liver toxicity has never been reported in that context.

"No person can sit down and drink 16 cups of green tea all at once," he said. "However if you take a supplement you can get that type of green tea extract dose, so there is some indication that the dosage form has an influence on the potential to cause liver toxicity."
Does Coffee Kill the Benefits of Vitamins?
By Fred Cicetti | February 22, 2010 02:59am ET

        

    

    MORE 

This Week’s Question: Does coffee kill the benefits of vitamins?

Any beverage or food containing caffeine such as coffee, tea, chocolate and some sodas can inhibit the absorption of vitamins and minerals and increase their excretion from the body.

This raises a more important question: What are the benefits of vitamins?

It’s very important to talk with your doctor before you take any vitamin and mineral pills, especially if you take prescription medicines, have any health problems or are elderly. Taking too much of a vitamin or mineral can cause problems with some medical tests or interfere with drugs you’re taking.

Vitamins and minerals are “micronutrients” your body needs in small but steady amounts. Your body can't make most micronutrients, so you must get them elsewhere.

Vitamins are natural substances found in plants and animals. There are two types of vitamins: water-soluble and fat-soluble.

Water-soluble vitamins are easily absorbed by your body. Unlike fat-soluble vitamins, they don’t have to be absorbed using bile acids (fluids used to digest fats). Your body doesn’t store large amounts of water-soluble vitamins. The water-soluble vitamins you don’t need are removed by your kidneys and come out in your urine

Your body has to use bile acids to absorb fat-soluble vitamins. Once these vitamins are absorbed, your body stores them in body fat. When you need them, your body takes them out of storage to be used.

Here are some water-soluble vitamins: Vitamin C, biotin and the seven B vitamins — thiamin (B-1), riboflavin (B-2), niacin (B-3), pantothenic acid (B-5), pyridoxine (B-6), folic acid (B-9) and cobalamin (B-12). Here are some fat-soluble vitamins: A, D, E or K.

Minerals come from the earth or from water. Plants and animals absorb them to get nutrients. The “major minerals” are calcium, phosphorus, magnesium, sodium, potassium, sulfur and chloride. They are considered major minerals because adults need them in large amounts.

The “trace minerals” are chromium, copper, fluoride, iodine, iron, manganese, molybdenum, selenium and zinc. Your body needs them in smaller amounts.

It would be hard to “overdose” on vitamins or minerals that you get from the foods you eat. But if you take supplements, you can easily take too much. This is even more of a risk if you take fat-soluble vitamins.

Whole foods are your best sources of vitamins and minerals. They offer three main benefits over supplements:

1. They contain a variety of the micronutrients your body needs. An orange, for example, provides vitamin C but also beta carotene, calcium and other nutrients. A vitamin C supplement lacks these other micronutrients.

2. They provide dietary fiber, which is important for digestion and can help prevent certain diseases such as cancer, diabetes and heart disease. Adequate fiber intake can also help prevent constipation.

3. They contain other substances such as antioxidants which slow down the natural process that leads to cell and tissue damage.

If you depend on supplements rather than eating a variety of whole foods, you miss the potential benefits of these substances.

For some people, including those on restrictive diets, multivitamin-mineral supplements can provide vitamins and minerals that their diets often don't. Older people and pregnant women have altered nutrient needs and may also benefit from a supplement. 
Caffeine

Coffee, tea, cola and other caffeine-containing drinks and foods have a mildly diuretic effect on your body. Moderate consumption of caffeine should present no problem for people with well-balanced diets that supply all the nutrients their bodies need to function properly. However, because B vitamins are water soluble and are flushed out of the body through excretion, heavy caffeine users may need to supplement with B-complex vitamins to compensate for nutrients lost through diuresis. Naturopathic doctor Linda Page, author of “Healthy Healing,” says excessive caffeine consumption hits your body’s stores of thiamine particularly hard.
Stress

The B-complex family of vitamins plays a key role in maintaining the health of your nervous system. When you’re under stress, your body calls upon its store of B vitamins to cope with this added pressure, according to nutritionist/pharmacist James B. LaValle, author of “Cracking the Metabolic Code.” Particularly essential in stressful situations are B-5, or pantothenic acid, niacin and folic acid. Although it is virtually impossible to avoid stress altogether, steering clear of stressful situations can prevent rapid depletion of these nutrients.
Green tea is widely recognized as a natural beverage with many health benefits.  As a purveyor of tea, we highly agree.  What is it that makes green tea so good for you?  A rich supply of vitamins and minerals are just a couple of the health benefits from drinking green tea.

Vitamins
Vitamins, minerals, carbohydrates, fats, and proteins make up the five primary essential types of nutrients used by the human body.  Although vitamins are essential, your body usually does not produce enough of them or even worse, it does not produce them at all.  Therefore, vitamins must be acquired through food and/or beverages like fruits, vegetables and tea.  Green tea is proven to be a good source of vitamins A, C, E and many of the B vitamins.

There are 13 essential types of vitamins:  A, C, D, E, K and B vitamins (Thiamine (B1), Riboflavin (B2), Niacin (B3), Pantothenic acid (B5), Biotin (B7) Folate (B9), Pyroxidine (B6), Cobalamin (B12).  Vitamins are classified as either water or fat soluble.  Water soluble vitamins must be replenished frequently because they are not easily stored in cells.  Fat soluble vitamins can be stored and consumed as needed.  A deficiency in even one of these 13 vitamins can result in a multitude of symptoms and problems. Be careful when taking fat soluble supplements like vitamins A, D and E.  Too much can be harmful and reach toxic levels in our bodies.  A well balanced diet with green tea is nearly impossible to reach levels of toxicity in normal healthy adults.

Green tea is known for having more vitamins in higher concentrations than many foods. This fact alone should make green tea your beverage of choice.  Regularly drinking green tea is an easy way to supplement some of the vitamins and minerals in your diet.

Minerals

Minerals play an important role as bodily regulators. Tea contains around 5-7% minerals, mainly potassium (K), calcium (Ca), phosphorus (P), and magnesium (Mg), as well as small quantities of manganese (Mn), zinc (Zn) and copper (Cu).

Catechins
Catechins are a type of phenolic compounds found in tea, cocoa and berries with potent antioxidant effects. The primary active catechin found in green tea is Epigallocatechin-3-gallate (EGCG).  Catechins are believed to have the following health benefits.

    Decreases blood cholesterol
    Cancer prevention
    Antioxidant
    Tooth decay prevention, antibacterial effect
    Anti-influenza effect
    Inhibits high blood pressure
    Anti-hyperglycemic effect
    Bad breath prevention (deodorizing effect)

Caffeine
We all know the stimulating effects of caffeine. When used in moderation, caffeine can be quite beneficial.  Green tea releases small amounts gradually which is much safer and useful for general wellness.  Other benefits of caffeine include the following.

    Increases alertness (decreases tiredness and drowsiness)
    Increases stamina
    Hangover prevention
    Mild diuretic

Theanine
Theanine has tremendous medicinal potential. Theanine has been studied for its potential ability to reduce mental and physical stress, improve cognition, and boost mood and cognitive performance in a synergistic manner with caffeine.

    Neural cell protection
    Relaxation effect (promotes α wave production)
    Lowering of blood pressure