They instructed three groups to follow different eating plans. The first followed a general healthy eating and exercise regime. The second a reduced-calorie Mediterranean-style diet (men were allowed 1,500-1,800 calories, while women ate 1,200-1,400 calories a day) low in refined carbs, rich in vegetables and with fish replacing red meat. The third group followed a similar diet but added three to four cups of green tea daily and 100g of frozen cubes of Mankai duckweed in a shake, along with 28g of walnuts.
The results were impressive: despite no difference in their overall calorie intake, over six months, the “green” Mediterranean diet group lost more weight (an average of 13.6lbs or 6.2kg compared with 11.9lbs or 5.4kg on the more standard Mediterranean diet), more centimetres from their waistlines (8.6cm compared with 6.8cm) and saw a 4 per cent drop in cholesterol levels (again, greater than the other groups).
The researchers put the benefits down to the addition of the greens – but as yet, they don’t really know why.
“There is probably no one mechanism in which the ‘green’ dietary elements impact human metabolism and health,” says lead researcher Dr Gal Tsaban, internal medicine senior physician. One reason could be the dietary polyphenols found in green tea and Mankai and their antioxidant effects, while other factors include “the additional dietary fibre content of Mankai, the low glycaemic index of the Mankai dinner substitute, and the reduced oxidative stress following lower red meat consumption,” says Tsaban. “These are all theories that remain to be directly explored.”
Duckweed has been attracting interest for its nutritional benefits for some time –- specifically the wild version, known as Wolffia Globosa, which has been eaten in south- east Asia for hundreds of years in the form of soup, as a vegetable or in an omelette.
“Mankai is being hailed as the ‘super tiny mighty green’,” says nutritionist Bridgette Hutchins. “It’s being cited as revolutionary because it’s apparently the only plant source in the world to contain the complete protein profile which contains all nine essential amino acids, and is also rich in bio-available iron, B12, zinc, folate and fibre, with 1oz containing as much protein as an egg and nine times more iron than kale, so it’s certainly something that we should look at seriously.”
A paper in the American Diabetes Association’s journal, Diabetes Care, found that Mankai could help stabilise blood sugars after eating carbohydrates. Its high protein content seems to help dieters feel fuller for longer.
Mankai has also been shown to lower cholesterol and boost iron and folic acid levels (women are particularly deficient in iron, which can cause tiredness among other symptoms).
“Mankai contains bio-available amino acids and iron as well as, surprisingly, true vitamin B12,” Tsaban says. Amino acids are involved in almost every bodily function, from growth to repair to digestion, while Vitamin B12 is needed to produce an adequate amount of healthy red blood cells. “In my view, Mankai greatly contributed to the beneficial metabolic effects seen with the green Mediterranean diet,” says Tsaban.
And Mankai is green in both senses of the word. Unlike other fashionable ingredients that get promoted to superfood status – notably avocados – research by German food scientists in 2017 suggested that duckweed could help tackle food and farming shortages around the world, thanks to its small size, its fast-growing properties and ability to grow on water rather than on land.
“It’s especially interesting at a time when more than ever we need to be working hard towards sustainability. Anything that can rival the meat market in protein and nutritional value is worth exploring,” says Hutchins.
The bad news is that it’s not currently available in the UK or anywhere in the EU, as it is classed as a ‘novel’ food, meaning more scientific research is required for its health claims. But as the supplement is available widely in the US, it seems likely that it will make its way over here. In the meantime, Shabir Daya, co-founder of Victoria Health and Member of the Royal Pharmaceutical Society, suggests that Moringa Powder, which can come in a Green Superleaf Powder, is an excellent alternative. “Moringa leaves contain one of the highest concentrations of plant protein with 24% per cent protein and nine amino acids,” she adds. Other experts say it has similar properties to seaweed, also widely available in the UK.
So is the green diet truly the secret to health and easy weight loss?
It’s becoming pretty indisputable that cutting out red meat and eating more plant-based foods will do you good – and help you shed pounds. But Hutchins advises caution with any proposed new superfood, pointing out that the diet also included green tea – which stimulates metabolism – and walnuts, which contain ALA, an omega 3 known to benefit heart health and help with appetite control. So whether Mankai really was the magic ingredient remains to be shown.
Hutchins says Mankai does deserve attention as evidence builds for its effects on metabolic health and cholesterol. “I would be the first to hail its glory if it means we can lower the risks of heart disease and diabetes and improve metabolic health and cholesterol, while at the same time help the environment, but to my mind you would want to see more robust evidence before you jump onto the bandwagon.”
The green Mediterranean diet at a glance
Cut calories to 1,500-1,800 for men and 1,200-1,400 for women per day
Swap red meat for fish and poultry; avoid all processed meat
Drink up to four cups of green tea a day
Add 28g of walnuts per day
100g daily portion of Mankai duckweed in a plant-based shake
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