The Latest Finds on Tea and Health

This article is from the Tea & Coffee Trade Journal (Aug '04). This publication contains many interesting articles on both tea and coffee. It is a great place to learn about tea and the growing regions.

Staff Report

Researchers have unlocked more of tea’s secrets, but is the full story yet to be revealed? Unilever’s Conrad Astill shared some of the latest findings at the last Tea & Coffee World Cup Symposium in Rome, and we dropped by to listen in.

Conrad Astill comes across as a larger-than-life scientist, an expert with a keen sense of humor and a solid scientific pedigree. Although originally from Holland, Astill speaks English better than many Englishmen do, a talent the Dutch are rather good at.

He joined the food and beverage industry as a research chemist in 1978 after spells in the pharmaceutical and mining industries before joining Unilever in 1990. A graduate of UK’s University of Salford, Astill is entitled to the letters BA, MSc, MRSC and CChem after his name, which makes him much smarter than most of us when it comes to deciphering the molecular clues to tea’s invigorating reputation -- and to supplying the raw data needed by the marketers’ desire to hype “proven” health attributes.

Astill opened his presentation with a reminder of how legend tells us of the world’s first tea drinker and health advocate, a Chinese gentleman by the name of Shei Nuang who, while sitting underneath a tea tree, noticed some of the leaves fall into the water he was boiling. After drinking the water thus infused, he noticed that he now felt “revived.” The refreshing properties of tea, then, have been noted for over 4,000 years. As a subjective opinion among tea drinkers, the reviving properties of tea are well known, as millions around the world daily experience them. But what is it in tea that gives it its “kick”? Is there any proof that tea is actually beneficial to health? What can we discover about the molecular and chemical processes involved in the digestion and utilization of tea by human bodies, and what appending research can be brought to bear on a particular health claim to verify or debunk the “science behind the hype,” which incidentally was the title of Astill’s presentation and what he works on professionally in his capacity as Unilever’s tea chemistry group leader.

Various myths and legends about tea’s health benefits have been touted through the years; some are provable, some are not. Certainly, no one has seriously contended that drinking tea may be bad for you, and there is a common consensus among tea drinkers that it is actually good for you. But to actually claim a health benefit for a product, you need to substantiate your claim with hard, incontrovertible, scientific facts, or risk facing expensive litigation and market disruption from consumer, health and government groups. While a range of government, professional, medical and consumer groups are anxious to validate and assess the results of research into health issues, tea marketers are equally keen to get in on the action. “Unsubstantiated” health claims have been touted on packaging and in advertising campaigns in the past, and this can expose the entire industry to legal repercussions and image problems when these claims are debunked or dragged into public scrutiny.

Ongoing research into the properties and possible benefits of tea are therefore of tremendous importance to the industry as it struggles to promote tea over other beverage choices and to establish, once and for all, the veracity of the various health claims espoused for tea. One thing is for sure though: regardless of how you drink your tea, green, black, with milk, lemon, sugar or even from a can, it is certainly better for you than a fizzy soft drink.

Fact or Fiction?

Many specific claims have been made for tea’s health benefits over the years. We examine some of the more common ones and find out if they are true or not.

Tea is a good source of vitamins...

Tea is not a good source of vitamins. Its meager rations of riboflavin, niacin, folate and ascorbic acid make no appreciable difference to your daily intake.

Tea is a good source of amino acids

Among several amino acids found in tea, theanine (5-N-ethylgltamine) is unique. It accounts for over 50% of the free amino acids in tea leaf and 1- 2% of the total dry weight in both green and black teas. Japanese researchers have discovered that this compound has a relaxing effect on humans, based in increased alpha-wave activity. Additional research has indicated theanine in tea assists our natural immune responses to viral and fungal infections. Scientists speculate that in combination with caffeine, theanine might be partly responsible for tea’s reputation for being a “pick-me up” drink that both relaxes and revives at the same time.

Tea is a good source of minerals

While potassium makes up the majority of the mineral content of tea, its score of less than 5% of reference nutrient uptake (RNI) deriving from tea “is no basis for any claim or significant statement,” according to Astill. Manganese is also present, but as science has yet to find a proven health benefit from manganese ingested from tea and no RNI has been established, this doesn’t work either, and neither does aluminum, which tea is naturally high in. Unfortunately, many consumers equate aluminum to Alzheimer’s disease, so more damage control is needed here and it comes in the form of research that consistently suggests that there is little or no scientific evidence to suggest that aluminum in tea poses any risk to human health.

Fluoride from the soil accumulates naturally in the tea plant, but this is a double-edged sword; on one hand, fluoride has been shown to have a role in helping bones and teeth grow and to prevent diseases such as dental carries; on the other, too much fluoride has been associated with enhanced rates of bone cancer and skeletal and dental fluorosis. Never fear, even if you drink four to five cups of tea made with fluoridated water every day, you’ll still be ingesting amounts of fluoride well below the level of concern.

So overall, fairly tenuous evidence for pro-health enthusiasts, but reassuring for those concerned with possible effects of aluminum and fluoride.

Tea does not count towards your fluid intake because it is a diuretic

Despite misleading advice that continues to be handed out, such as on certain British airlines where tea is mentioned as a drink to avoid for its diuretic properties that will “cause the body to lose even more water than normal,” tea is in fact perfectly fine to drink in an environment where dehydration is of concern. As Astill points out, this information is based on the supposition that you will lose more fluid than you take in, whereas in fact diuresis occurs only after a caffeine dose of over 250mg. A cup of tea contains somewhere around 50mg, therefore drinking five cups of black tea “can make a significant contribution to the target intake of 35ml of fluid/kg of bodyweight,” according to Astill.

Tea is good for the heart

While drinking a couple of cups of tea every day won’t necessarily prevent a heart attack, laboratory tests indicate tea demonstrates a likely decrease in CVD risk with moderate tea consumption. Other studies claim endothelial function has been shown to improve convincingly by moderate tea consumption and that tea can help lower cholesterol. So, can we start making claims for tea efficacy in combating heart disease? Not yet, as the scientific jury is still out, but certainly “tea is thought to be beneficial for the heart” could be a reasonable comment.

Tea contains caffeine, and that is bad for your health

Tea does contain caffeine, black tea usually more than green tea, but nowhere near as much as coffee, and anyway, who says caffeine is bad for your health? Certainly not most scientists, who believe a moderate intake of less than 300mg a day has no adverse effects on your health. Although noting that caffeine is “mildly addictive,” they point out that “withdrawal symptoms can be minimized if intake is reduced gradually.” Maybe so, but a low-to-moderate (60-300mg a day) intake of caffeine “has been shown to have beneficial effects on mood and performance.” While most of us know this already, it’s nice to see scientists agreeing with us for a change!

Also on the positive side, caffeine consumed in doses noted above have no measurable adverse consequences for a human fetus, no significant effect on calcium balance and bone mass, and there is little or no evidence that caffeine consumption increases the risk of cardio-vascular disease (CVD) or cancer.

Despite claims surrounding caffeine’s supposed protection against Parkinson’s disease, more research is needed before scientists can come up with any conclusive evidence to support or reject this hypothesis.

Tea inhibits iron absorption

Yes, tea flavonoids are known to partially inhibit absorption of iron from plant foods, but not from animal sources. However, the amount of iron leeched from the system is not enough to constitute an iron deficiency threat even in a vegetarian, and if tea is not consumed until an hour after eating, the inhibitory effect is greatly reduced. Adding vitamin C, such as a slice of lemon, to tea serves to counteract the inhibitory effect to some extent.

Tea protects against cancer

While tests and studies on cancer cells show that “green, black and oolong tea and the polyphenols in them arrest the initiation, promotion and progression of cancer cells and the flavonoids in black and green tea have been shown to inhibit the occurrence of tumors in different organ sites in experimental animals,” the overall epidemiology of tea consumption and lack of relevant in vivo studies “does not support the idea that tea consumption is protective against cancer.” So no, you can’t make that claim and justify it at present.

Tea is rich in antioxidants

Antioxidants are compounds that help clean harmful compounds from the blood. Tea contains several different types of antioxidants in the polyphenol family, including catechins, flavonoids, tannins and theraflavins. Flavonoids comprise an important sub-group of the polypheonols and green tea leaves contain high levels of flavonoid compounds, among them catechins (flavinols), and a related flavonoid, flavonis, is found in both green (unfermnented) and black (fermented) tea leaves. These and similar antioxidants are found in fruit and vegetables, but one or two cups of tea provides a similar “radical scavenging environment” as five portions of fruit or vegetables.

Green tea is often regarded as being more beneficial in this regard, but this is likely because more research has been conducted on green tea. In fact, both green and black tea score highly in antioxidants.