The Amazing Anthocyanins in Purple Plant Foods

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Anthocyanins are a specific type of phytonutrient, part of the flavonoid family of polyphenols. And they have become big news in nutrition science due to increasing findings in support of their beneficial impacts on human health.

Anthocyanins provide the vibrant red-orange and purple-blue-violet pigments in fruit, veggies and other plant foods like grains and legumes.

Like many other phytonutrients, anthocyanins are produced by plants as a protective mechanism against environmental stressors. So far, approximately 640 different types of anthocyanins have been identified. But don't get too bogged down in reductionist thinking! 

The most important thing to remember is which foods have the good stuff! Powerful Purple Plant Foods!

Here are a few anthocyanin-rich plant foods:

  • Berries (blueberries, blackberries, raspberries, strawberries, black currants, elderberries)

  • Red, purple and concord grapes

  • Cherries

  • Eggplants (make sure you eat the darkly-pigmented skins!)

  • Plums,

  • Purple carrots

  • Red-skinned apples

  • Beetroot,

  • Blood oranges

  • Red cabbage

  • Black beans

  • Black rice

  • Purple potatoes

  • Purple corn

So far, studies have revealed that anthocyanins have three key actions in the human body:

1. Anthocyanins act as antioxidants

Our cells undergo oxidative stress as part of normal metabolism, but oxidative stress can go into hyperdrive if we are ill, eat an unhealthy diet or are exposed to toxins via pollution. Cells under oxidative stress produce reactive oxygen species (aka free radicals) which can cause a chain reaction of cell and DNA damage.

But because anyhocyanins have this powerful antioxidant capacity, they can dampen-down the free-radical chain-reaction They have been found to be especially protective against lipid peroxidation (aka oxidation of fats), which makes them especially protective of our cells' lipid membranes!

2. Anthocyanins are anti-inflammatory

Acute (short-term) inflammation is the body's healthy response to infection or injury. But chronic, ongoing inflammation has been shown to be harmful to he human body. It has been found to be a key pathophysiological mechanism in many serious diseases, including type 2 diabetes, atherosclerosis and cardiovascular disease, arthritis and dementia. Chronic inflammation has also been colloquially called "inflam-ageing" due to the strain it places on our bodies, and potential to reduce healthy lifespan.

Anthocyanins have been shown to suppress a number of our body's inflammatory factors including  interleukin-1b, tumor necrosis factor-a and nuclear factor kappa B.

3. Anthocyanins promote improved circulation

Anthocyanins have been shown to boost Nitric Oxide (aka NO), a signalling molecule that induces our artery and blood vessel walls to relax (known as vasodilation). This faciiltates improved endothelial function ((how the cells lining our blood vessels perform), enhancing blood circulation, with flow-on benefits ranging from improved blood pressure to improved erectile function!

In addition to vasodilation, anthocyanins have been shown to have a separate significand antiatherogeic effect. In lay terms this means that it can reduce the accumulaion of fatty deposits inside our arteries!

So now that we understand their physiological impact, what exactly does that mean for our health and longevity?

1. Anthocyanin-rich plant foods are good for our Cardiovascular health!

All of the above pathophysiological pathways (oxidation, inflammation, vasoconstriction and atherogenesis) contribute to cardiovascular disease.

So I guess it's no surprise that several epidemiological (population) studies have shown an association between the consumption of anthocyanin-rich foods and reduced incidence of CVD.

In support of this, studies have shown that people fed anthocyanin-rich foods have decreased levels of cholesterol, LDL and triglyceride, as well as reduced blood pressure and aortic stiffness.

2. Anthocyanin-rich plant foods boost Brain health and function

When it comes to diet, what is good for the heart is generally also pretty good for the brain too!

And as with our cardiac system, chronic inflammation, oxidative stress and poor circulation can adversely impact our brain health. So the fact that anthocyanins can address these processes makes them potentially very powerfully protective!

In fact, some of the most exciting anthocyanin studies are in the area of memory enhancement and age-related cognitive decline.

Consumption of anythocyanin-rich foods has been shown to improve various aspects of memory (working, semantic and short-term) as well as other cognitive domains such as ability to learn, executive function and motor performance (balance and physical co-ordination).

3. They may have a role in cancer prevention

Now I want to be absolutely crystal clear about this. Anthocyanins and anthocyanin-rich foods are NOT a cure for cancer. And they are not an "insurance policy" against ever getting cancer either (although I wish there was such a ting!). And for the record: if anyone ever suggests that a single food or nutrient is a cure, then make sure you run very, very far in the opposite direction. And if they do this while trying to sell you something, report them to the Department of Fair Trading so they can be fined and shut down! #micdrop

And now that I have that out of the way, studies have shown that anthocyanins do have some anticarcinogenic activity. But so far, the precise mechanisms are unclear. The impact of anthocyanins on a variety of cancers have been been investigated and so far the most promise seems to be in relation to colon cancer. Check the reference list below for the studies.

4. Other benefits

Even thought there have been thousands of studies on anthocyanins in the last couple of decades, there is still much to learn. Studies show promise in relation to Type 2 Diabetes (via improved insulin sensitivity and reduced post-meal blood-sugar spikes), eye health (via improved circulation and enhanced generation of retinal pigments) and even in relation to obesity and our healthy inner bacteria! 

So what's the takeaway from all of this?

1. Eat a rainbow of vibrantly coloured veggies and fruit and especially make sure you include the red-purple-blues!

I have given you LOTS of excellent reasons to do this above!

2. Get your anthocyanins in the form of vibrantly coloured, unprocessed fruit, veggies, grains and legumes. NOT supplements!

Don't get bogged down in reductionist thinking! Studies have shown that some micronutrients (like beta carotene**) that are incredibly healthy when consumed in their whole-food, unprocessed packages can actually be harmful to human health when consumed in supplement form. 

And one super-important thing to remember is that whole, unprocessed plant foods also contain an array of other amazing micro- and phytonutrients. In fact, science is increasingly uncovering that fruit and veggies contain different phytonutrients in different amounts and combinations that work together to deliver powerful health benefits. Or in science-speak: "plants typically contain a complex mixture of flavonoids that have synergistic bioactivities".*

Oh, and here's a fun fact about anthocyanins! 

Their colour can change if you change the pH/acidity. So if you pour lemon juice into blue butterfly pea flower tea it will change from blue to purple, or if you rinse chopped red cabbage in hard water (with a high pH) it will turn a weird navy colour!

BOTTOM LINE:

  • Red-purple-blue plant foods contain anthocyanins, which science is increasingly showing can have an array of beneficial health impacts.

  • These anthocyanin-rich foods also contain an array of other micro- and phytonutrients.

  • Unless specifically advised to the contrary by an appropriately qualified and registered medical practitioner, always choose whole foods over supplements - especially when it comes to phytonutrients!

So have I got you all excited about adding red-purple-blue plant foods to your diet?

Try these delicious recipes!

* Purple Power Anthocyanin-Rich Salad
* Sweet & Spicy Red Cabbage
* Beetroot Like the Old Days
* Roasted Beetroot Hummus
* Beetroot Roasted in Balsamic Citrus Glaze

HERE ARE A FEW REFERENCES FOR MY FELLOW SCIENCE-NERDS!

* Liu R (2003) Health benefits of fruit and vegetables are from additive and synergistic. Am J Clin Nutr 78, 517S– 520S.

** Omenn GS, Goodman GE, Thornquist MD, Balmes J, Cullen MR, Glass A, Keogh JP, Meyskens Jr FL, Valanis B, Williams Jr JH, Barnhart S. Risk factors for lung cancer and for intervention effects in CARET, the Beta-Carotene and Retinol Efficacy Trial. JNCI: Journal of the National Cancer Institute. 1996 Nov 6;88(21):1550-9.

Pojer E, Mattivi F, Johnson D, Stockley CS. The case for anthocyanin consumption to promote human health: a review. Comprehensive Reviews in Food Science and Food Safety. 2013 Sep 1;12(5):483-508.

Liu C, Sun J, Lu Y, Bo Y. Effects of anthocyanin on serum lipids in dyslipidemia patients: a systematic review and meta-analysis. PloS one. 2016 Sep 2;11(9):e0162089.

Reis JF, Monteiro VV, Gomes RS, Carmo MM, Costa GV, Ribera PC, Monteiro MC. Action mechanism and cardiovascular effect of anthocyanins: a systematic review of animal and human studies. Journal of translational medicine. 2016 Dec;14(1):315.

Fairlie-Jones L, Davison K, Fromentin E, Hill AM. The Effect of Anthocyanin-Rich Foods or Extracts on Vascular Function in Adults: A Systematic Review and Meta-Analysis of Randomised Controlled Trials. Nutrients. 2017 Aug 20;9(8):908.

Cassidy A, Bertoia M, Chiuve S, Flint A, Forman J, Rimm EB. Habitual intake of anthocyanins and flavanones and risk of cardiovascular disease in men, 2. The American journal of clinical nutrition. 2016 Aug 3;104(3):587-94.

Shah K, Shah P. Effect of Anthocyanin Supplementations on Lipid Profile and Inflammatory Markers: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Cholesterol. 2018;2018.

Cassidy A, O’Reilly EJ, Kay C, et al. Habitual intake of flavonoid subclasses and incident hypertension in adults. Am J Clin Nutr. 2011;93(2):338-347.

Cassidy A, Mukamal KJ, Liu L, Franz M, Eliassen AH, Rimm EB. High anthocyanin intake is associated with a reduced risk of myocardial infarction in young and middle-aged women. Circulation. 2013;127(2):188-196.

Jennings A, Welch AA, Fairweather-Tait SJ, et al. Higher anthocyanin intake is associated with lower arterial stiffness and central blood pressure in women. Am J Clin Nutr. 2012;96(4):781-788.

Chiva-Blanch G, Arranz S, Lamuela-Raventos RM, Estruch R. Effects of wine, alcohol and polyphenols on cardiovascular disease risk factors: evidences from human studies. Alcohol Alcohol. 2013;48(3):270-277.

Kent K, Charlton KE, Netzel M, Fanning K. Food‐based anthocyanin intake and cognitive outcomes in human intervention trials: a systematic review. Journal of Human Nutrition and Dietetics. 2017 Jun 1;30(3):260-74.

Wang LS, Stoner GD. Anthocyanins and their role in cancer prevention. Cancer Lett. 2008;269(2):281-290.

Wang LS, Sardo C, Rocha CM, et al. Effect of freeze-dried black raspberries on human colorectal cancer lesions. Presented at: AACR Special Conference in Cancer Research: Advances in Colon Cancer Research; November 14-17, 2007; Cambridge, MA.

Thomasset S, Berry DP, Cai H, et al. Pilot study of oral anthocyanins for colorectal cancer chemoprevention. Cancer Prev Res (Phila). 2009;2(7):625–633.

Guo X, Yang B, Tan J, Jiang J, Li D. Associations of dietary intakes of anthocyanins and berry fruits with risk of type 2 diabetes mellitus: A systematic review and meta-analysis of prospective cohort studies. European journal of clinical nutrition. 2016 Dec;70(12):1360.

Liu Y, Li D, Zhang Y, Sun R, Xia M. Anthocyanin increases adiponectin secretion and protects against diabetes-related endothelial dysfunction. American Journal of Physiology-Endocrinology and Metabolism. 2014 Mar 4;306(8):E975-88.