When will broccoli be modified to taste like chocolate, have the antioxidants of cranberries, and be available at my grocery store?
-A curious adult from California
August 27, 2008
I bet this is the kind of question lots of people have asked. But don't hold your breath because it won't be happening anytime soon.
Why not? First off, we don't really understand how cranberries make their antioxidants or how chocolate gets its flavor.
Second, once we figure out how these things work, it won't be easy to add these traits to broccoli. This is because lots of different genes are involved in making cranberry antioxidants and chocolate flavor.
Right now it is hard to move a single gene from one plant to another. So moving lots of genes would be even harder.
But great science often starts with questions that are seemingly impossible to answer. So let's take a stab at it.
Antioxidants vs. Free Radicals
There are lots of things around us that can hurt our bodies. One of the real troublemakers is free radicals.
Free radicals come from lots of different things including the food we eat. They damage our cells and our DNA. This causes lots of problems including cancer and aging.
Luckily for us, nature has given us ways to fight these free radicals. They are called antioxidants.
Antioxidants help keep free radicals away from our DNA and cells. They also help make the free radicals less dangerous.
Studies show that antioxidants can help prevent cancer and heart failure. They might even be able to slow down aging! So, they are pretty goods things to have.
So where do we get them? Well, our bodies make some but we get a lot of them from the foods we eat. As you've noted, fruits like cranberries have lots of antioxidants in them. Both our bodies and foods make antioxidants the same way -- with genes.
Genes and Antioxidants
Genes are really just instructions for making proteins. And proteins are the things that do most of the work in our cells (and bodies) including getting rid of free radicals.
There are several kinds of antioxidants and genes play an important role in making all of them. Some genes have the instructions for directly making proteins that get rid of free radicals. An example is Superoxide Dismutase.
Small molecules are another class of antioxidants. It usually takes many proteins to make these molecules. Which means it takes many different genes too. Vitamin C is one of these antioxidants.
Our foods, like us, have both kinds of antioxidants. But the most useful ones from foods are the small molecules. Our stomachs digest the proteins that directly eliminate free radicals. But the small antioxidants can survive.
Unfortunately, the small molecules are the trickiest to get plants to make. Why? Because it takes more than one gene to make this kind of antioxidant. And the more genes you need to put into a plant, the harder it is to do.
This doesn't mean it is impossible. For example, scientists have been able to make a new kind of rice that makes tons of vitamin A. This new kind of rice helps prevent blindness. It is called "Golden Rice" because of its yellowish color.
How did scientists make this rice? They took two genes that help make vitamin A and put them into the rice plant. This "simple" task took over 7 years of work and $2.6 million. So while not impossible, it isn't easy either. Or cheap!
We can't really replicate this with other antioxidants right now because scientists haven't yet worked out the genes plants use to make them. Once they do, then scientists might be able to make a broccoli with more or additional antioxidants. As long as there is a market for it that is.
This story now brings us to chocolate flavored broccoli. No doubt there would be a market for that! But this one is even less likely than a broccoli with the antioxidants of cranberries.
Why? Mainly because we don't yet understand why chocolate tastes the way it does.
Part of the reason for chocolate's bitter taste seems to be a group of chemicals known as flavanols. These chemicals are also antioxidants and are found in green tea, nuts, red wine, and other foods too.
Of course, not all of these chemicals taste the same. So scientists need to find which kinds of flavanols chocolate has.
Then, scientists will have to find the genes that make the flavanols of chocolate and then they will need to put them into the broccoli. What this means is that it will definitely be a while until there is chocolate broccoli.
But all is not lost! As I was working on this question, I got word that the genome of the cacao plant (from which cocoa, and hence chocolate, is made) is being sequenced. In other words, scientists are beginning the hard job of reading the entire DNA of the cacao plant.
Hurray! It will take about five years to complete and the genome will be publicly available through the Public Intellectual Property Resource for Agriculture (PIPRA). Once scientists know more about the cacao plant's genome, they may be able to figure out how it makes its chocolate flavor.
Of course, even if we got chocolate's flavor into broccoli, it still wouldn't be a Hershey bar. No one just eats plain cocoa beans.
Chocolate has many ingredients. To make chocolate the cocoa beans are first processed. Then, milk, sugar, and other things are added. Imagine a broccoli that also makes milk! Not likely. If we do all that to broccoli, it suddenly isn't so healthy either.
After going through all of this, I think you can see that it will be quite a chore to make broccoli like you want it! Most likely it probably won't be worth a scientist's effort (at least not in the near future).
Of course, there is another option. You could take some broccoli, a few cranberries, a bar of dark chocolate, and add it all into a blender. This wouldn't be too tasty but it would have all the ingredients of the broccoli you're looking for. Me, I'll stick with cranberry scones for breakfast, broccoli at dinner time and the dark chocolate for dessert!
Jose Morillo, Stanford University