A woman carries quinoa in Bolivia. The 'pseudo-grain' may be the most nutritious foodstuff in the world. Photograph: Laurent Giraudou/Corbis
A burst of colour on a monochromatic panorama, a field of flowering quinoa plants in the Bolivian desert is a thing of beauty. A plant ready for harvest can stand higher than a human, covered with knotty blossoms, from violet to crimson and ochre-orange to yellow.
Quinua real, or royal quinoa, flourishes in the most hostile conditions, surviving nightly frosts and daytime temperatures upwards of 40C (104F). It is a high-altitude plant, growing at 3,600 metres above sea level and higher, where oxygen is thin, water is scarce and the soil is so saline that virtually nothing else grows.
The tiny seeds of the quinoa plant are the stuff of nutritionists' dreams, sending demand soaring in the developed world. Gram-for-gram, quinoa is one of the planet's most nutritious foodstuffs. Once a sacred crop for some pre-hispanic Andean cultures, it has become a five-star healthfood for the middle classes in Europe, the US and increasingly China and Japan.
That global demand means less quinoa is being eaten in Bolivia andPeru, the countries of origin, as the price has tripled. There are concerns this could cause malnutrition as producers, who have long relied on the superfood to supplement their meagre diets, would rather sell their entire crop than eat it. The rocketing international price is also creating land disputes.
Royal quinoa, which only grows in this arid region of southern Bolivia, is to the grain what beluga is to caviar; packed with even more protein, vitamins and minerals than the common variety.
Averaging $3,115 (£1,930) per tonne in 2011, quinoa has tripled in price since 2006. Coloured varieties fetch even more. Red royal quinoa sells at about $4,500 a tonne and the black variety can reach $8,000 per tonne. The crop has become a lifeline for the people of Bolivia's Oruro and Potosi regions, among the poorest in what is one of South America's poorest nations.
It is quinoa's moment on the world stage. This year is the UN'sInternational Year of Quinoa as the UN Food and AgricultureOrganisation recognises the crop's resilience, adaptability and its "potential contribution in the fight against hunger and malnutrition".
Evo Morales, the Bolivian leader whose government suggested the special recognition for the grain, said: "For years [quinoa] was looked down on just like the indigenous movement To remember that past is to remember discrimination against quinoa and now after so many years it is reclaiming its rightful recognition as the most important food for life."
However, there are concerns the 5,000 year-old ancestral crop is being eaten less by its traditional consumers: quinoa farmers. "They have westernised their diets because they have more profits and more income," says Mejia, an agronomist. "Ten years ago they had only an Andean diet in front of them. They had no choice. But now they do and they want rice, noodles, candies, coke, they want everything!"
Daysi Munoz, who runs a La Paz-based quinoa farming collective, agrees. "As the price has risen quinoa is consumed less and less in Bolivia. It's worth more to them [the producers] to sell it or trade it for pasta and rice. As a result, they're not eating it any more."
Bitter battles are being fought over prime quinoa-growing land. Last February dozens of people were hurt when farmers fought with slings and sticks of dynamite over what was once abandoned land.
Many people who migrated to cities in search of a better life are now returning to their arid homeland to grow royal quinoa, says Mejia. Most land is communally owned, she adds, so "the government needs to set out the boundaries or there will be more conflicts".
In the village of Lacaya, near Lake Titicaca, the farmers have recently sown quinoa. It grows faster in the wetter conditions but the varietyquinua dulce is less sought after than royal quinoa.
Under the perpendicular rays of the intense altiplano sun, Petrona Uriche's face is heavily shadowed by her felt bowler hat. She says in the three years her village has been farming quinoa it has become the biggest earner. "We produce quinoa just for export, it's more profitable," she said. An 11.5kg arroba sack of quinoa can fetch eight times more than it did a few years ago, around $2 a kg, she adds.
But the Bolivian government – which like its neighbour Peru is heavily promoting quinoa nationally to combat malnutrition – insists Bolivians are eating more of the grain. Annual consumption per person has increased fourfold from 0.35kg to 1.11 kg in as many years "in spite of the high international prices", Victor Hugo Vásquez, Bolivia's vice-minister for rural development and agriculture, said.
Previous government figures, however, indicated domestic consumption had dropped by a third in five years.
Judging by the supermarket shelves in Bolivia's de facto capital, La Paz, where quinoa-based products from pizza crusts and hamburgers to canapes and breakfast cereals are displayed, Bolivia's growing middle class appear to be the principal consumers.
Meanwhile in the Peruvian capital, Lima, shoppers at food markets complain quinoa is becoming a luxury product. Selling at around 10 Peruvian soles per kg (£2.44) it costs more than chicken (7.8 soles per kg) and four times as much as rice. Official figures show domestic consumption has dropped.
"Unfortunately in poorer areas they don't have access to products such as quinoa and it's becoming more and more expensive," Peru's vice-minister for agriculture, Juan Rheineck, said at a breakfast for under-fives at the Casa de los Petisos children's home in Lima. The children are fed boiled eggs and quinoa and apple punch, part of a government programme to promote nutritious breakfasts. "That's what we have to avoid, we have to produce better and more," he said.
Peru's telegenic first lady, Nadine Heredia, is championing a colourful campaign to promote the Andean diet, of which quinoa is a key element, to combat infant malnutrition. In 2012 Peru banked nearly $35m from quinoa exports, tripling what it earned three years ago. In Bolivia exports tripled to around 23,000 tonnes, contributing some $85m to the country's economy,Vásquez said.
But experts say both countries need to boost production to meet the rising external demand and provide the grain at lower prices for internal consumption. Bolivia, which produces nearly half the global supply, says it has given more than $5m in credits to 70,000 quinoa producers and wants to industrialise production to bring added value rather than just exporting the raw material.
Hydrocarbons and minerals are Bolivia's two key exports, but Mejia believes if the country aggressively promoted quinoa agriculture "in 10 years it could easily surpass the income from gas and minerals".
What is quinoa?
Quinoa (Chenopodium quinoa willd) is actually a "pseudo-grain", not belonging to the true grass family but a member of the goosefoot plant family, which includes spinach and sugarbeet.
Its exceptional nutritional qualities led Nasa to include it as part of its astronauts' diet on long space missions. A 1993 Nasa technical paper says: "While no single food can supply all the essential life sustaining nutrients, quinoa comes as close as any other in the plant or animal kingdom."
Quinoa is the only plant food that contains all 10 essential amino acids for the human diet. Its protein content (between 14%-18%) surpasses that of wheat, rice, maize and oats, and can be a substitute to animal protein. Its calorific value is greater than that of eggs and milk and comparable only to that of meat.
It is a source of vitamin E, vitamin B2 (riboflavin) and contains more minerals such as calcium, potassium, magnesium and phosphorus than other grains.
Recent research found quinoa contains phytoestrogens, which are said to prevent or reduce osteoporosis, arteriosclerosis, breast cancer and other conditions that can be caused by lack of oestrogen after the menopause.
• This article was amended on 15 January 2013 to remove the following line: Studies at Kings College London have shown quinoa helps coeliacs (people intolerant to gluten) to regenerate gluten tolerance. This was removed because there is debate about the accuracy of the statement.