Posts Tagged superfood

Unsexy Kale as a Superfood?

As a scientist I’m not particularly impressed with ‘superfoods’ and the idea that certain products have special properties above and beyond conventional nutritional value. Over recent times the diet industry and media has advocated that amongst others, goji berries, beetroot, blueberries or green tea will provide incredible health benefits. The NHS website has looked into superfoods and states that although many of these foods are a healthy option the scientific evidence for any ‘super’ claims is not strong. A well balanced diet is much more important than eating any particular single item.

One such superfood that piqued my interest is Kale, a particularly unsexy plant that appears to sit apart from the other more trendy (and colourful?) foodstuffs. Therefore I was interested to read a recent meta-analysis of the published data about the potential of Kale as a superfood.

Brassica Breeding

Kale is subspecies of Brassica oleracea that has been bred to have more leafy, errr leaves. This species of Brassica is remarkable as other subspecies include a fellow superfood candidate broccoli, hated Xmas ‘treat’ brussel sprouts, boring cabbage and cauliflower, each of which have been bred for different beneficial traits.

a diagram showing the evolutionary background of cabbage, brussel sprouts, kohlrabi, kale, brocolli and cauliflower which all derive from Brassica oleracea

The supposed ‘super’ characteristics of Brassicas result from a high level of glucosinates and antioxidants. Indeed Beneforte Broccoli has been bred to contain higher levels of glucoraphanin. However even their home website will only stretch to a ‘might’ when considering its benefit on cardiovascular health (3).

Kale has been an important part of the human diet for millennia and although it contains many important phytochemicals (plant chemicals) any ‘extra’ beneficial effects in humans have had very limited testing.

The Science

Many ‘superfoods’ are defined by their high levels of antioxidants. These chemicals act as important scavenger molecules that ‘mop up’ damaging free oxygen molecules (termed free radicals) that are produced are part of regular cellular processes. These radicals can indiscriminately damage DNA, which can lead to the formation of cancer if the damage occurs in certain important genes.

A study from 2008 showed that Kale has a higher amount of antioxidants when compared to other Brassicas, including broccoli. However it is extremely challenging to decipher whether it has anti-cancer properties as performing these type of studies in humans is very tricky! A useful proxy test comes from the study of the plant extracts on the growth of tumour cells in a petri dish. Some of these studies have shown that where extracts from Kale, as well as from sprouts and cabbage, have no effect on the growth of normal human cells they will reduce growth in some cancer cell lines. This indicates that they do indeed alter the growth of cancerous cells. However in these studies Kale is no different to other Brassicas or for that matter, members of the onion/ garlic family.

A photo of green, leafy kale leaves on a white background

On a larger scale, Kale also might have legitimate benefits on gut and heart health by either altering potentially damaging stomach microbes or being able to reduce levels of harmful proteins that circulate in the blood.

Eat Kale but not ONLY Kale

The overall conclusion of this analysis is that the authors agreed that Kale, alongside other Brassicas, does have health benefits. Unfortunately and perhaps unsurprisingly there is no study that sets Kale apart from any other species of Brassica!

Overall it will come as no surprise to those skeptical about superfood claims that any benefits of Kale come from the fact it is a vegetable and not because it has some super-plant-power.

In short, keep a balanced diet and you can’t go too wrong!


Dr Geraint Parry, PhD

Geraint is the national coordinator for GARNet, which is a network that supports uptake of new technologies and knowledge dissemination amongst UK and international plant scientists. He is the science communication manager of the EU INDEPTH COST Action ( as well as being the secretary for the Multinational Arabidopsis Steering Committee. He tweets for GARNet from @GARNetweets and personally @liverpoolplants




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