A diet high in flavonoids, which can be found in black tea can help prevent abdominal aortic calcification, a type of heart disease, in senior women according to a new peer-reviewed study. This may be a good reason to drink a couple of cups of tea whenever you like it.
I have written about black tea previously, and the evidence of a long-term effect on health was limited. Maybe this new study will provide some other evidence.
As I usually do, I will take a look at the study and determine if it is good evidence for having a cuppa black tea every day to reduce your risk of heart disease.
What are flavonoids?
Flavonoids are a class of polyphenolic secondary metabolites found in plants, and thus commonly consumed in the diets of humans. They have many uses in plants including flower coloring (to attract pollinators), photosynthesis, and nitrogen fixation. They are over 5000 different flavonoids, so it would be impossible for me to write a short description of what each does.
Plants that have particularly high levels of flavonoids include parsley, onions, blueberries and other berries, black tea, green and oolong tea, bananas, all citrus fruits, Ginkgo biloba, red wine, sea-buckthorns, buckwheat, peanuts, and dark chocolate with cocoa content of 70% or greater. Since I love dark chocolate (tea, not much), I now have more of an excuse to consume it.
There have been numerous health claims about flavonoids, but none have been shown to be supported by strong evidence. There appears that it has no effect on the risk of cancer and no effect on the risk of cardiovascular disease
What is abdominal aortic calcification?
Abdominal aortic calcification (AAC) is the calcification of the large artery that supplies oxygenated blood from the heart to the abdominal organs and lower limbs. It is associated with cardiovascular disorders, such as heart attack and stroke, as well as late-life dementia.
The black tea and heart health article
In an article published in December 2022 in Arteriosclerosis, Thrombosis, and Vascular Biology, Joshua R. Lewis, Ph.D., Royal Perth Hospital Research Foundation and colleagues studied conducted cross-sectional analyses on 881 females median age of 80 years and median body mass index of 27 kg/m2, all from the PLSAW (Perth Longitudinal Study of Ageing Women). Flavonoid intake was calculated from food-frequency questionnaires.
This is what you need to know:
- Elderly women who drank black tea on a regular basis or consumed a high level of flavonoids in their diet were found to be far less likely to develop extensive AAC.
- Study participants who had a higher intake of total flavonoids, flavan-3-ol, and flavonols were almost 40% less likely to have extensive AAC. In comparison, those who drank two to six cups of black tea per day had up to 42% less chance of experiencing extensive AAC.
- People who do not drink tea can still benefit by including foods rich in flavonoids in their diet, which protects against extensive calcification of the arteries.
The authors concluded that:
In older women, greater habitual dietary flavonoid intake is associated with less extensive AAC.
A diet high in flavonoids, such as black tea, can help prevent abdominal aortic calcification (AAC) in women later in life, according to the Heart Foundation and researchers from Edith Cowan University.
My rating of black tea and heart health
As someone who consumes a lot of flavonoids, I just want this to be true. I’m sure that residents of the British Isles, India, China, and many other countries would agree with my desire.
But these studies are almost always fundamentally flawed — they rely upon the accuracy of the diaries and memories of the study participants. It’s not like a clinical trial, where the study is accurately controlled, since we know how much of a particular drug the patient is taking. In a study like this, we have significant issues with everything from the accuracy of the amounts of flavonoids being consumed to confounding factors that might give false results.
Lastly, this type of study could provide us with convincing evidence of correlation, but there is no evidence of causation. And in science-based medicine, we need a biologically plausible mechanism to show why flavonoids might have an effect on heart health.
Thus, I can give this study only 2 out of 5 stars. It is possible that they are on to something, but I remain unconvinced of whether there is causation between black tea and heart health.
Citations
- Kim ED, Kim JS, Kim SS, Jung JG, Yun SJ, Kim JY, Ryu JS. Association of abdominal aortic calcification with lifestyle and risk factors of cardiovascular disease. Korean J Fam Med. 2013 May;34(3):213-20. doi: 10.4082/kjfm.2013.34.3.213. Epub 2013 May 24. PMID: 23730489; PMCID: PMC3667229.
- Parmenter BH, Bondonno CP, Murray K, Schousboe JT, Croft K, Prince RL, Hodgson JM, Bondonno NP, Lewis JR. Higher Habitual Dietary Flavonoid Intake Associates With Less Extensive Abdominal Aortic Calcification in a Cohort of Older Women. Arterioscler Thromb Vasc Biol. 2022 Dec;42(12):1482-1494. doi: 10.1161/ATVBAHA.122.318408. Epub 2022 Nov 3. PMID: 36325901.
- Romagnolo DF, Selmin OI. Flavonoids and cancer prevention: a review of the evidence. J Nutr Gerontol Geriatr. 2012;31(3):206-38. doi: 10.1080/21551197.2012.702534. PMID: 22888839.
- Wang X, Ouyang YY, Liu J, Zhao G. Flavonoid intake and risk of CVD: a systematic review and meta-analysis of prospective cohort studies. Br J Nutr. 2014 Jan 14;111(1):1-11. doi: 10.1017/S000711451300278X. Epub 2013 Aug 16. PMID: 23953879.
