Maximizing the Benefits of Drinking Tea
Tea is the second most consumed beverage in the world after water, and red wine. High polyphenol contents are reported in tea and there is strong evidence that daily intake of foods rich in polyphenols has antioxidant, anti-inflammatory, and vascular health benefits(1) that reduces the incidence frequency of diseases.
Antioxidants
Our exposure to the environment, diet, and stress produces free-radicals. These are highly reactive unpaired molecules that steal energy and eventually destruct cells , leading to cellular aging, cardiovascular disease, cancer, and other illness. Antioxidants can scavenge and stabilize free radicals to stop damaging activity. However, during sustained free-radical action, antioxidant defense is often overwhelmed, which leads to cell damage(1). Thus, a constant supply of antioxidant in sufficient amount is needed.
The first paper we will look at is Ryan and Petit's(2) that carried out multiple experiments on effects of various tea preparations in antioxidant capacity of teas. They used commercial teas containing 2.7-3.3 g of tea per tea bag, infused in 200 ml boiling water. The total antioxidant capacities (TAC) test is used to determine antioxidant status, using a laboratory procedure called modified Ferric iron reducing antioxidant power (FRAP) assay.
Do you need a bag?
Commercial teas were more often than not packaged in teabags for ease of consumption. When antioxidant capacity of teas infused in tea bags was compared with teas removed from the bag, it appears that the use of teabags diminishes its antioxidant capacity. Another notable observation is that maximum antioxidant activity is obtained at a shorter infusion time (2 minutes) in teas removed from teabags, compared to those placed in tea bags that reached its peak antioxidant capacity at 10 minutes.
Brewing Time
When teas were infused in hot water for 1, 2, 3, 4, 5, and 10 minutes, the antioxidant potential improved gradually with increased time. Maximum antioxidant capacity was observed in the longest infusion and lowest when brewed for 1 minute.
Where's my tea latte?
Tea is commonly consumed with addition of protein-rich milk which is believed to reduce its levels of polyphenol content. Researchers added cow's milk with varying amounts (10, 15, and 20 mL) and fat content (whole, semi-skimmed, and skimmed) to commercial teas. The extent at which types and quantities of milk affects antioxidant capacity were determined by comparing its values against tea with added water.
For all brands of tea, dilution with any liquid reduces the antioxidant capacity of teas with greatest reduction observed in skimmed milk. The addition of whole milk to each of the teas also decreased the total antioxidant capacity but to a lesser extent. A similar study by Korir et al(3) shows a dose-dependent reduction of antioxidants with addition of milk. However, this can be attributed to increased dilution rather than milk components.
Why does milk, particularly skimmed milk appear to reduce antioxidants in tea?
This molecular model by Hasni et al(4) visually describes how the protein casein, (particularly beta casein) in milk forms a strong complex with tea polyphenols
thereby affecting its anti-oxidant capacity. Since skimmed milk has low fat content, much of its component is protein, in a form of casein that has a strong affinity to polyphenols in tea(5).
How about soymilk?
Soymilk, derived from soybeans does not contain even a trace of casein. But a study done by Lorenz et al(6) found that adding soymilk to tea appears to reduce its vascular (blood vessel) benefits. They used arterial contraction as measure for vascular benefit and found out that plain tea resulted in more relaxed blood flow. The addition of soymilk is comparable to the hindering effect of cows milk, with more hindering effect observed in milk with added sugar.
Comparing all formulations with plain water (with no benefit), it can be suggested that in terms of health benefits, there might be no sense in drinking tea when combined with interfering foods. They explained that structurally similar soy proteins in soymilk might mimic the effects of caseins in bovine milk in terms of blunting beneficial vascular effects of tea.
What about my sweettooth?
Tea's astringent taste attributed from inherent tannin's interaction with proteins is typically masked by the addition of flavorings and sweeteners. A paper by Sharma(7) investigated the effects of milk and sugar in polyphenol content and free-radical scavenging activity of black teas. Their methods however did not mimic the way we normally consume tea that is using tea bags and steeping it in hot water before adding milk and sugar. Rather, tea powder was used combined with milk or tea before brewing.
Plain black tea seems to be highest in antioxidants. Those who want to get fancy with their tea by adding milk or sugar will end up reducing their benefits from drinking tea. Though it wasn’t mentioned whether this experiment used whole or skimmed milk, it agrees with the paper discussed above that milk indeed reduces antioxidant activity in teas. Sugar appears to have a reducing effect but at a lower extent. Take note that the addition of both milk and sugar produced more stable levels of antioxidants than tea with milk alone, and the exact mechanism behind this is yet to be found.
Still in Korir's study(3), antioxidants in tea is maximized by drinking plain tea, while a little pinch of Stevia doesn’t make any difference. Don’t go overboard though by adding sugar and honey or you’ll significantly reduce the antioxidants by adding these stuff. In fact, adding 10 grams of honey can reduce antioxidants by almost a third and is expected to be further reduced with additional teaspoons.
Though the antioxidant activity of honey was, in this study, expected to positively affect the antioxidant activity of tea, it was found to be the most inhibiting sweetener in both plain and black teas with milk. The mechanism by which sucrose inhibits the antioxidant activity in tea is still not fully understood. They assume that it is due to the formation of glucose-gallic complex, wherein the sugar binds with polyphenols thereby inhibiting its use by the body.
Green or Black tea?
Korir's (3) experiment aimed to determine which tea color is superior in antioxidant properties. Researchers themselves were blinded by labelling 10 commercial tea brands with numbers 1-10, with 1-5 being green teas and 6-10 being black teas. Contrary to other studies citing black tea has higher antioxidants, they found that there is very little difference in antioxidants between the two types of teas. So nothing to worry about choosing the right color.
Timing of Drinking Tea
If your primary reason for drinking tea is its free-radical scavenging effect, then you might be wondering how long it takes to absorb these teas and when does the action start? Well, antioxidant activity can be measured using Glutathione (GSH) levels from the blood and they are most powerful when levels reach its peak. In Korir's(3) mice experiment, blood was drawn after zer0, half hour, 2 hours, 4 hours and 8 hours in mice after drinking green, purple, and black tea (plain and with milk). When GSH levels rise beyond the levels in mice not fed with tea, it indicates that free radical scavenging activity is increased. Their findings report that at half an hour after tea consumption, antioxidant activity increases and reaches its peak at 2 hours. Thus, to maximize health effects in the body system, it might be a good idea drink tea every 2 hours, or better yet replace your liquid intake throughout the day with tea.
Acid and Tea
A recent paper by Moser et al(8) suggests that calcium and magnesium in milk and other food products can interact with polyphenols in tea to form a metallo-polyphenol complex.
So there you have it, a partial list of antioxidant-activity reducing components are:
protein and minerals in milk
sugar
honey
There's no better way to end this article, than to discuss a food component that can help attenuate these interactions.
Majchrzak et al(9) studied the interaction of vitamin C and teas. In this experiment, black and green teas were infused in 100 ml of water. Then total antioxidant capacity (TAC) was measured by photometric method. They found that in black tea, adding 5 to 20 mg of ascorbic acid increased antioxidant capacity in a linear manner. In green teas, 5 mg to 30 mg shows an increasing effect. However, adding more ascorbic acid such as 25 mg in black teas and 35 mg in green teas did not show an increased antioxidant effect, rather it reduces their antioxidant capacities. The mechanism behind this being that there are proteins that transport polyphenols from the intestines to the blood and levels of ascorbic acid influences these proteins, which in turn modulates the levels of antioxidants in the blood10. Higher dose of ascorbic acid may negatively modulate this transport system that results in reduced levels of antioxidants.
Take home message: When you feel like getting a hot cup of tea, throw out the teabag, add a pinch of stevia, creamer with low protein content, and a squeeze of lemon juice. Do this every so often to enjoy the antioxidant benefits of tea.
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References:
1) Ferruzzi, M. G. (2010). The influence of beverage composition on delivery of phenolic compounds from coffee and tea. Physiology & Behavior, 100(1), 33–41. doi:10.1016/j.physbeh.2010.01.035
2) Ryan, L., & Petit, S. (2010). Addition of whole, semiskimmed, and skimmed bovine milk reduces the total antioxidant capacity of black tea. Nutrition Research (New York, N.Y.), 30(1), 14–20.
3) Korir, M. W., Wachira, F. N., Wanyoko, J. K., Ngure, R. M., & Khalid, R. (2014). The fortification of tea with sweeteners and milk and its effect on in vitro antioxidant potential of tea product and glutathione levels in an animal model, 145, 145–153. doi:10.1016/j.nutres.2009.11.005
4) Hasni, I., Bourassa, P., Hamdani, S., Samson, G., Carpentier, R., & Tajmir-Riahi, H.-A. (2011). Interaction of milk α- and β-caseins with tea polyphenols. Food Chemistry, 126(2), 630–639. doi:10.1016/j.foodchem.2010.11.087 polyphenols, 128, 43–49.
5) Bourassa, P., Côté, R., Hutchandani, S., & Samson, G. (2013). Journal of Photochemistry and Photobiology B : Biology The effect of milk alpha-casein on the antioxidant activity of tea
6) Soy, V. T. (2009). Letter to the Editor, 206, 31–32. doi:10.1016/j.atherosclerosis.2009.02.001
7) Sharma, V., Vijay Kumar, H., & Jagan Mohan Rao, L. (2008). Influence of milk and sugar on antioxidant potential of black tea. Food Research International, 41(2), 124–129. doi:10.1016/j.foodres.2007.10.009
8) Moser, S., Chegeni, M., Jones, O. G., Liceaga, A., & Ferruzzi, M. G. (2014). The effect of milk proteins on the bioaccessibility of green tea fl avan-3-ols, 66, 297–305.
9) Majchrzak, D., Mitter, S., & Elmadfa, I. (2004). The effect of ascorbic acid on total antioxidant activity of black and green teas. Food Chemistry, 88(3), 447–451. doi:10.1016/j.foodchem.2004.01.058
