Pamela A. Popper, Ph.D., N.D.

with Paula Szwedowski

Wellness Forum Health

Recently a well-known plant-based nutrition site featured information claiming that drinking tea with the addition of cow’s milk or soy milk interferes with the beneficial health effects of tea consumption. This has led to several inquiries concerning not only drinking tea with soy or other plant milks, but also regarding the combining of Wellness Forum Health’s food-grade green tea with soy and other plant milks in smoothies. Thus far no one has inquired about cow’s milk since most of our readers and followers have already eliminated cow’s milk from the diet.

Let’s start with some basic information about tea.  Green and black tea are both leaves of the Camella sinensis tea bush. The color of tea depends on how much it has oxidized. Oxidation results from breaking the leaves during machine harvesting, and exposure to air, heat, and light. The more oxidation, the darker the tea leaves become, with black tea being the most oxidized. Green tea retains its color because the leaves are steamed or dried shortly after harvest with little exposure to high temperatures so this serves to reduce oxidation.

All types of tea are rich in flavonoids and very powerful antioxidants called polyphenols and catechins.[1]  One of the more powerful polyphenols in green tea is Epigallocatechin Gallate (EGCG). Over 1,300 articles have been published in medical journals regarding the effects of EGCG on cancer. Tea also contains vitamins and minerals such as riboflavin, niacin, potassium and magnesium. The nutrient content of green tea is higher than black tea due to its minimal processing.

Observational studies have shown that both green and black tea are related to a reduction in the risk of cardiovascular disease, but observational studies must be interpreted with caution because other diet and lifestyle factors might play a role in the positive outcome. Consumption of tea is commonly linked to a healthier lifestyle, making it hard to distinguish what is actually responsible for improved health status.[2]

A meta-analyses of studies looking at the effects of tea on cardiovascular health reported conflicting results, with some studies showing a positive effect on cardiovascular health, and others showing none.[3] A Cochrane Review showed that tea consumption reduced risk factors for cardiovascular disease such as blood pressure and cholesterol.[4]

The authors of the meta-analysis state that variability in outcomes may be due to many factors, including that the data were self-reported, and self-reporting has been shown to be almost worthless for obtaining accurate information.[5] [6] The study did not control for variations in the types of tea consumed. The variations could include green tea, black tea, oolong tea, and herbal teas, which are really not “tea” but rather roots, leaves and parts of plants which are brewed like tea. The antioxidant/polyphenol content of these various types of tea varies greatly. The preference for certain teas in various regions may also play a role in outcomes; Europeans drink stronger teas than Americans, for example.

The results are further confounded by differences in overall dietary pattern in the areas in which the studies included in the analysis were conducted. Diets in the UK, US, and Australia, for example, are high in animal foods and processed foods.[7] [8] [9] It is not likely that the addition of tea to a terrible diet will result in health improvement, which might explain why tea drinking did not improve cardiovascular risk factors for people living in these areas.

One factor the researchers explored to explain differences in outcomes is the hypothesis that the addition of milk to tea interferes with its positive effects on health. The reasoning is that “In the United Kingdom, milk is commonly added to tea” but the article did not include data regarding just how many people in the studies actually drank tea with milk, or how much milk was consumed. In support of the idea that milk might interfere with the benefits of tea, the researchers cite a study showing that flavonoids bind to protein[10], and another showing that adding milk to tea eliminated its plasma antioxidant potential.[11] Our research identified a rat study which showed a negative effect, but animal studies seldom have relevance to humans.[12] We also note that the negative effect could be due to the casein content in milk, since casein has been shown to have a negative effect on cardiovascular health.[13]

The researchers also cited studies showing that the addition of milk did not make a difference[14] [15], and concluded that the amount of milk added to tea “…would seem woefully insufficient to increase cardiovascular risk.”

As for soy milk, research shows that while the bioavailability of galloylated catechins was decreased by both cow’s milk and soy milk, the bioavailability of non-galloylated catechins was increased. Milk and casein negatively affected the bioavailability more than soy milk did. From these results one might assume that pure tea might be best, but if adding milk, plant milks are a better choice.[16]  Additionally, soy milk is high in proteins which are thought to cause a reduction in bioavailability of polyphenols and antioxidants from tea[17] but no other plant milks, some of which are lower in protein like rice or almond milk, have been studied. Therefore we don’t know if other types of plant milk interfere with bioavailability.

A research group in India found that tea drinking increased antioxidant activity regardless of whether or not milk was added.[18] Also, the differences in effect between beverages were minor, and after 180 minutes the increase in plasma antioxidant activity was similar for both teas. This research shows that addition of milk might slow the absorption or bioavailability of catechins for a short time, but it does not adversely affect the antioxidant capacity of tea in the long term. This result is interesting because it challenges some the previously discussed articles and points out how focusing on details might keep us from seeing the big picture. Yes, bioavailability of catechins is decreased for a short time but somehow the beneficial antioxidant effect is still achieved.

Based on all of this information, here are our conclusions. Tea, particularly green tea, has many health benefits, due to its high concentration of antioxidants. Its specific effects on health are difficult to quantify due to the fact that tea drinking alone is almost certainly not responsible for better health outcomes for people who consume it. Tea drinkers and populations with a high intake of tea have healthier diets and lifestyles that include tea.[19] There are no magical foods or nutrients, but there are good and bad dietary patterns, and the focus should be on dietary pattern, rather than looking for individual foods or nutrients that can lead to better health.

Our research failed to identify any studies showing that adverse health effects resulted from the addition to milk to tea. And we think that focusing on these types of details is a waste of time. If the goal is to promote better cardiovascular health, a plant-based diet has been shown to be effective for this purpose.[20] Adopting such a diet is a much more productive strategy and adding a cup of tea, with or without milk, to an unhealthy diet will not change health outcomes.

As for concerns about soy or plant milks added to brewed tea, research does not definitively show that this interferes with the health benefits of drinking tea, and the Indian study showed that given enough time after consumption, the addition of milk makes no difference at all. Likewise, there is no reason to be concerned with consuming a smoothie that includes both food-grade green tea and plant milk.

Last, but not least, we take issue with the type of content that generated the inquiries that led to the writing of this article. People are already confused about diet and health, and reports like these add to, rather than resolve confusion. They cause people to “major in the minors”, things like worrying about combining soy milk and tea instead of paying attention to the more important issues like eating more plants and fewer animal foods. It seems that time could be better spent providing content that leads to better dietary decisions.

Serafini M, Ghiselli A, Ferro-Luzzi A. “In vivo antioxidant effect of green and black tea in man.”  European Journal of Clinical Nutrition 1996;50(1):28-32

[1] Sesso H, Gaziano J, Buring J et al. “Coffee and tea intake and the risk of myocardial infarction.” Am J Epidemiol 1999;149:162-167

[1] Peters U, Poole C, Arab L. “Does Tea Affect Cardiovascular Disease? A Meta-Analysis.” Am J Epidemiol 2001;154(6):495-503

[1] Hartley L, Flowers N, holmes J et al. “Green and black tea for the primary prevention of cardiovascular disease.” Cochrane Database Syst Rev 2013 June 18;6:CD009934HChoose Destination

[1] Archer E, Pavela G, Lavie C. “The Inadmissibility of What We Eat in America and NHANES Dietary Data in Nutrition and Obesity Research and the Scientific Formulation of National Dietary Guidelines.” Mayo Clin Proc July 2015;90(7):911-926

[1] Archer E, Hand G, Blair S. “Validity of U.S. Nutritional Surveillance: National Health and Nutrition Examination Survey Caloric Energy Intake Data, 1971-2010.”  PLoS One October 9, 2013 DOI: 10.1371/journal.pone.0076632

[1] Department for Environment, Food and Rural Affairs, 2015. Food Statistics Pocketbook 2014, York: Department for Environment, Food and Rural Affairs.

[1] HF. Wells, JC. Buzby, 2008. Dietary Assessment of Major Trends in U.S. Food Consumption, 1970-2005, s.l.: United States Department of Agriculture.

[1] Australian Institute of Health and Welfare, 2012. Australia’s food & Nutrition 2012, Canberra: Australian Institute of Health and Welfare.

[1] Hasalam E. Plant phenols: vegetable tannins revisited. Cambridge, United Kingdom: Cambridge University Press, 1989:154–219.

[1]  Serafini M, Ghiselli A, Ferro-Luzzi A. “In vivo antioxidant effect of green and black tea in man.” Eur J Clin Nutr 1996;50:28–32.

[1] Lorenz M, Jochmann N, von Krosigk A et al. “Addition of milk prevents vascular protective effects of tea.”European Heart Journal 9 Jan 2007;28(2):219-223

[1] McLachlan C. “β-casein A1, ischaemic heart disease mortality, and other illnesses.” Medical Hypotheses, 2011;56(2), p. 262–272

[1] Hollman P, Feskens E, Katan M. “Tea flavonols in cardiovascular disease and cancer epidemiology.” Proc Soc Exp Biol Med 1999;220:198–202.

[1] van het Hof K, Wiseman S, Yang C, et al. “Plasma and lipoprotein levels of tea catechins following repeated tea consumption.” Proc Soc Exp Biol Med 1999;220:203–9.

[1] Egert S, Tereszczuk J, Wein S et al. “Simultaneous ingestion of dietary proteins reduces the bioavailability of galloylated catechins from green tea in humans.” Eur J Nutr (2013) 52:281–288

[1] Peters U, Poole C, Arab L. “Does Tea Affect Cardiovascular Disease? A Meta-Analysis.” Am J epidemiol 2001;154(6):495-503

[1] Reddy V. 2005. “Addition of Milk Does Not Alter the Antioxidant Activity of Black Tea.” Annals of Nutrition and Metabolism 2005;49:189–195.

[1] Peters U, Poole C, Arab L. “Does Tea Affect Cardiovascular Disease? A Meta-Analysis.” Am J epidemiol 2001;154(6):495-503

[1] Esselstyn C, Gendy G, Doyle J, Golubic M, Roizen M. “A Way to Reverse CAD?” The Journal of Family Practice  July 2014 Vol 63, No 7