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Interview with professor Jan Geuns about stevia

On Wednesday, October 26th, 2011, Professor Jan Geuns of the KU Leuven gave an exclusive interview about the imminent approval of stevia in Europe and about the future of the sweet leaf.


On a sunny Wednesday afternoon I find myself a bit lost in the majestic Castle Park of Arenberg on the campus of Leuven University. I have an appointment with professor Jan Geuns in the Laboratory for Functional Biology. The past few weeks have been a crazy rollercoaster for him, he tells me. Today alone, no less than eight people have visited him for an interview, all of them on stevia. I'm number seven. It appears that stevia is more popular in the media than I first thought... So I don't plan on wasting any time with my questions:

How did you discover stevia for the first time?

"In the early eighties, a Flemish man came to visit me in my laboratory, which was still situated in the center of Leuven back then. He had a few stevia plants with him and asked me if I could analyze them. At that time, I couldn't find the time for it, but a few years later I went to Romania where they were growing stevia plants, and I was asked the same question. That's how I got into stevia and since then it has been taking up all of my time.

I've always had a keen interest in isoprenoids in plants –  compounds that are among others responsible for the aromatic substances in pine trees. Another derivate from isoprenoids is cholesterol, for example. There are thousands of these components found throughout the world, and this subject greatly fascinates me."

What about the approval of stevia in Europa and the US? There seems to be a bit of confusion on the Internet regarding the types of substances that will be approved.

"In America, the mixture of steviol glycosides has been officially granted GRAS approval since 1998. There is one condition though: the mixture has to be at least 95% pure. Soon - in early November - there will be an approval in Europe for steviol glycosides with a purity of 95% as well.

Stevia plants are another story: in Europe, the plant and dried leaves are not approved. That's because someone from the Ministry of Public Health took the now infamous "novel food" claim to the European Institutions in 1997, claiming that stevia was a new food type.

Despite the fact that the very same Ministry of Public Health had approved the selling of stevia extracts in 1984, stevia was categorized as novel food in 1997. That meant that I had to file a report for approval, which led me to discover that stevia was in fact already being sold all over Europe at that time.

Unfortunately, the approval of new food types is based on negative argumentations. It's impossible to claim that a certain product has no side effects whatsoever on the human body - positive or negative. You can only prove that there are no harmful side effects when a food type is used within a certain range, like a daily amount. In the US, certain products are approved when food types are proven to be safe within a certain range: that's the so-called GRAS status. Should harmful side effects be discovered later on, those products are taken off the shelves immediately. In Europe, however, there is a holier-than-thou attitude about accepting new food types, and that has been the base of the problem until now."


"The legislation on “novel food” originated through the interference of large food concerns. Big companies are toying with our health by releasing unhealthy foods onto the market, but most citizens don't stop to think about things like that."


"A large company wanting to grow, has no other choice but to eliminate the smaller ones and take their market share. That's exactly what happens when refined products are released into the stores. Novel food really has nothing to do with public health, but with keeping small players from establishing themselves. On average, submitting a report on novel food will set you back about $18 million. Small companies can't afford that sort of money. If the goal is truly to keep European food safe, then we should submit sugar to the same standards as novel foods and analyze it accordingly. I'm certain that it would be banned immediately."

Which brand of stevia do you use yourself? Do you grow your own plants?

"We have had our own plants at home in the past, but during one hot and long summer we forgot to water them, and they died. Since then we have stopped intensively growing stevia, although we still have some plants in our greenhouse. I buy my stevioside from a company in Japan and that's what my family uses."

There is a lot of speculation going on online about the benefits and dangers of stevia, but which of these can be backed up with hard evidence, and which are bogus?

"First and foremost, you have to take into account the amount of stevia you will be using to sweeten food. On average, you could say that people are going to consume 200 to 300 grams of stevia each day, at the most. Those kinds of low doses will not cause any effects. If you're considering the treatment of high blood pressure, for example - which you should always do only under the supervision of a doctor - we're talking about consuming 750 to 1500 mg a day.

There are a large number of scientific articles, proving that stevia lowers high blood pressure and that it doesn't affect people with normal of low blood pressure. That's the first proven theorem.

A second aspect is that stevioside regulates blood sugar levels in people suffering from type 2 diabetes. Not only does it lower these levels, but stevioside also greatly increases insulin sensitivity and slows down insulin resistance to a great extent. These effects have also been proven.

We have patented our own research towards the effects of arteriosclerosis. Stevioside actively battles the hardening of the arteries. It lowers the "bad" cholesterol and increases the "good". All of these effects influence lipids and have been proven unequivocally.

There are also a number of cancers - such as skin cancer - that are slowed down thanks to stevioside, when applied topically or when ingested. Since last year, we have found an explanation for all of these effects: all of the aforementioned ailments - high blood pressure, type 2 diabetes, arteriosclerosis and some forms of cancer - are related to so-called "oxygen radicals".

I'll explain what they are with the help of a simple example: picture a coal stove. In order to achieve optimal combustion, we have to meticulously regulate the air flow. Well, our body has thousands of these tiny "stoves", called the mytochondria, which we use to burn sugars. If you pour a whole bottle of soda on a well-functioning stove, toxins are released. If we continuously have too much sugar in our blood, that sugar will combine itself with enzymes, which in turn will no longer function properly. Subsequently, the sugar is not combusted properly, which creates these toxins called radicals.

Stevioside actively avoids these radicals. In our bodies, radicals are produced continuously, but we have a system that balances out their formation and detoxification; our enzymes can handle that.

But when we constantly expose our bodies to unhealthy foods, an over-production of radicals occurs, which we can no longer eliminate on our own. Stevioside diminishes these radicals and - if there are any left - detoxificate them too. So you could say that we have found the common link that explains all of these phenomena."


"People used to call me crazy because all of this seemed too good to be true. But many of these studies have now actually been proven."


"However, I know that there are a number of people telling the strangest tales about stevia: for example, a group of children in China that had been playing under an orange tree for years, and suddenly started fighting amongst themselves. People noticed that someone had planted stevia plants under the tree, and started to claim that stevia's glycosides had affected the oranges somehow, making these children violent. Complete nonsense, of course, but the sad thing is that these kinds of stories have quickly started spreading all over the world."

Making the lobbies very happy, no doubt.

"Evidently. Now that you mention the lobbies: there was a very negative report on stevia, issued by the former European Scientific Committee on Food, which stated that stevioside was detrimental to male fertility, which makes no sense whatsoever. They pointed to fake articles which even stated that animal subjects handn't even been exposed to stevia extract. Still, these so-called "scientists" concluded that stevia caused fertility problems. These reports are full of rubbish made up by people who are opposed to stevia. That has absolutely nothing to do with scientific integrity."

Which studies are currently taking place?

"It is commonly accepted that there are about 36 substances in stevia that we currently know about, some of them in really small concentrations. We are developing methods to precisely measure the amounts of these sweeteners. We have developed an internal method of research that is truly one of a kind, and that I can confidently call the best in the world at this point in time.

We will be organising another ring test soon, in which several laboratories from all corners of the world will participate. We will then await those results and present them in our next symposium.

I'm also working on a kind of genetic database in association with EUSTAS, the European Stevia Association. Some stevia plants are more sweet than others, and if you start working solely with the sweet variants, you will eventually end up with plants which are all sweet. Those can then be used as cultivars - mother plants. Right now, we have about seven or eight of these. We are measuring certain growth parameters, like the best climatological circumstances to grow the plants in. This enables us to select certain plant types which are able to germinate in moderate climates, like our own.

Aside from stevia rebaudiana, we are experimenting with other stevia varieties so we can crossbreed, which will produce more resistant plants."

What about genetic manipulation of the plant?

"The other thing we are doing in our project, is to make sure we don't have any GMO's (Genetically Modified Organisms), because we're not interested in spreading those. Let's look at things on a global scale for a minute: steiva is being cultivated all across the world, but it's still very much a culture-bound plant that we still don't know a whole lot about. Compared to corn, wheat, or potatoes - things that are common to us: there are tons of books written on a multitude of cultivars. In this respect, stevia is still an unknown plant. That's what we will strive to change in the future."

How do you see the future of stevia? Do you think it has the potential to cause major uproars, both on a national and international scale?

"Most definitely. In France, stevia was approved two years ago, and in that time the market has soared. Granted, the market growth has stagnated a bit over the past six months or so. That's because only rebaudioside A has been approved in France, and reb A is about five times more expensive than the stevioside mixture. Stevia producing companies are now waiting for an approval of stevioside, so that they can develop new and cheaper products and recipes. But there is no doubt that stevia has a big future ahead of it."

Exactly how busy is your schedule nowadays?

"Next week I'm leaving for Milan and Poland. This year, I have been to India, Mauritius, Paris, London, The Netherlands, Germany and Denmark. The plan was to visit Paraguay as well, but that was cancelled due to time constraints. I also have other work to do, and classes to teach. Usually, someone drops me in a hotel close to the airport, because I have to give a lecture early in the morning in one country, then fly back to Belgium because I have a class to teach. I'm going straight from the hotel to the airport and back, and I never really have the chance to really visit any of these countries. All that back and forth really gets under your skin sometimes."

Is there a lot of interest from the European press?

"A Belgian news show has already stopped by to film: the broadcast can be seen on December 1st. I generally try to talk about stevia as little as possible, because there are already thousands of emails hitting my inbox every day. I get rid of about 200 of them daily, but they just keep popping up again the next day. There is a lot of interest.

Prominent Belgian magazines have visited me, as well as German tv and radio stations. The French national tv station was here too: that broadcast will air some time soon. I simply can't recall most of them anymore.

We are in desperate need of a healthy sweetener, and now we've finally got it. A lot of people are a bit worried about the licorice-like taste of stevia. Obviously, you can't compare steviosides to sugar that way. But once you get used to the taste, you will probably like it even better."

Europe has until Saturday, October 29th to disregard the positive advice that stevia has received, but professor Geuns doesn't expect any more trouble. Keeping in mind all of the paperwork involved, the official approval will come halfway through November and after that, it can still take up to one month before the first products with stevia will hit the shelves. You might want to highlight December 15th on your calendars and shopping lists!

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