Meet the genetically modified super-carrot, now fortified with calcium

Blogging on Peer-Reviewed ResearchFor centuries, mothers have wrongly told their children that eating carrots will improve their vision. The sight-enhancing properties of these iconic vegetables is be a myth (albeit a fascinating one involving Nazis and fighter pilots) but if Jay Morris has anything to say about it, they may soon be better known for building strong bones.

Types of carrotsMorris, together with Kendal Hirschi and other Texan colleagues, has found a way to double the calcium content of carrots through genetic modification, making them a rich source of the element that is so vital for bones

The team loaded their super-carrots with a protein called sCAX1, which pumps calcium into the plant’s cells. The protein originally hailed from the plant-of-choice for geneticists, Arabidopsis thaliana, where it exists in a larger version. Morris’s team lopped off a small piece from its tip that stops the protein from funnelling in more calcium once a certain amount has been reached.

In this shortened form, sCAX1 is relentless in its import of calcium and the researchers have found that it can greatly increase the calcium content of several vegetables including tomatoes, potatoes and carrots. These super-charged vegetables could help to reduce the risk of osteoporosis, one of the world’s leading nutritional disorders, where a lack of calcium leads to brittle bones.

Missing calcium

In general, vegetables, fruits and other plant-based foods are being increasingly pushed by health organisations as a way of stemming the rising global levels of obesity as well as reducing the rates of several chronic diseases. But vegetarian menus aren’t the final word in nutrition; vegetables are certainly loaded with nutrients but compared to a carnivorous menu, vegetarian ones lack certain key nutrients, including calcium.

One solution is to artificially boost the levels of missing nutrients in these foods. Morris’s team proved that this is feasible by growing their altered sCAX1 carrots and running them through animal and human trials.

They grew the carrots using hydroponics; rather than soil, they were ‘planted’ in a solution containing important minerals. This nutrient bath included a very mildly radioactive isotope of calcium that was taken up by the carrots and acted as a label for their calcium content. It revealed that the edible parts of the super-carrots had twice the amount of calcium of normal ones.

The researchers then fed the labelled carrots to mice. Sure enough, the rodents managed to build up the same amount of calcium by eating half the amount of sCAX1 carrots as normal carrots.

CarrotHuman trials were also successful, but to a lesser extent. Thirty volunteers munched on the enhanced carrots, this time labelled with a different non-radioactive isotope of calcium. Morris measured this isotope in urine samples, marking the first time that such labels have been used to reveal the true nutritional value of genetically modified foods. Pound for pound, the diet of super-carrots provided people with 42% more calcium than the regular varieties.

Benefits and risks

Morris’s tinkered carrots are not only more nutritious but also more long-lasting and more productive. Again, calcium is the key. Farmers have known this for some time. Many growers soak apples in calcium solutions to keep them firm during shipping and fresh on the shelf. Potato crops are also sprayed with extra calcium, which helps them to tolerate hot conditions and ward off infections. There’s good reason to believe that the modified carrots would also enjoy similar benefits.

Morris is clear that the carrots are not the sole answer to calcium deficiencies. Enriched though they are, they can only provide a small proportion of a person’s calcium intake. But Morris argues that the technique is readily transferable to other vegetables. The key will be to increase calcium levels across a whole range of food.

Some might decry the need for such biological tinkering at all. After all, calcium supplements are already widely available. Even so, Morris argues that science is generally finding that these supplements are far less beneficial to health than nutrients obtained directly from our diets. In some cases, they could even be harmful.

It might also be worth noting that the carrot has already been driven away from its natural state. In its original Central Asian form, it is a purple or yellow vegetable. The familiar orange hue is a Dutch invention form the 15th or 16th century, when the colour symbolised the ruling House of Orange and appealed to patriotic growers.

History aside, it is encouraging that Morris is taking the safety of the super-carrot seriously. His paper ends on a cautious note. The main concern for the moment is that sCAX1 is not a one-trick protein. As well as calcium, it will also absorb other similarly charged metal ions including zinc, which is good, and cadmium, which is not.

Cadmium is a potent carcinogen and it would be a bad move to breed vegetables that soak up and store large amounts from the surrounding soil. In Morris’s experiments, the sCAX1 carrots were grown in hydroponic solutions that were free of any cadmium. What would happen in real farming conditions is a matter for another experiment.

Reference: Morris, J., Hawthorne, K.M., Hotze, T., Abrams, S.A., Hirschi, K.D. (2008). Nutritional impact of elevated calcium transport activity in carrots. Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0709005105


12 Responses

  1. doesn’t “genetically modified (beyond color)” = “bad (in the long run)”

    that’s what’s been beaten into my head by all this “organic” business. i don’t know what to believe anymore

  2. My vegetarian wife will like this. Thanks.

  3. It’s not that simple (although I don’t blame you for thinking it might be). GM crops have a large number of potential benefits and drawbacks that need to be weighed very carefully. Certainly, my feeling is that the knee-jerk attitude of “GM = bad; organic = good” that seems to have taken hold in Europe is nonsense on both counts.

    So far, the best summary I’ve read on the issue is in the Rough Guide to Ethical Living, which very clearly lays out both sides of the debate. You could also try the Royal Society’s numerous reports on the topic.

    Essentially, I think that GM crops pose certain risks that biotechnologists need to be aware of (see the cadmium issue above). However, the 21st century poses numerous problems of malnutrition (even in affluent countries), a growing population, insufficient food and insufficient land to grow it on. GM crops can help to mitigate many of these problems and a pragmatic stance should be taken.

  4. ah…i see.

    It’s just hard for people (myself included) to get over eating stuff that has been “altered” or “optimised,” even if we have been doing it to our food in different ways for centuries. I guess it’s the mention of “labs” and “science” that causes some of the hesitance.

  5. Its good to remember that “labs” and “science” are also the source of things like aspirin and plastics.

    It seems that biologists will have to deal with a problem that chemists have been dealing with for the last 50 years – the idea that synthetic or modified is bad.

    If you continue the example above, aspirin comes from an organic acid that has a negative effect on stomachs. Scientists “tweaked” the molecule ad managed to keep all the good stuff and still removed upset stomachs

  6. @ Mike F: quite.

    Likewise, the flipside credo that ‘natural is good’ might be challenged by compounds like strychnine and ricin which are among the nastiest poisons we know of. The natural pesticides that plants use to defend *themselves* are far more numerous than those that we spray on them.

  7. […] Posted on 19 January, 2008 by Ed Yong On Thursday, I wrote about a way of genetically modifying carrots to turn them into rich sources of calcium. The method could be more widely used in vegetables to […]

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  9. […] starter of genetically enhanced, calcium fortified super-carrot soup from Ed Yong at Not Exactly Rocket Science. Genetically enhanced the carrots may be, but they […]

  10. what technique did they use?

  11. I’m not entirely clear – in the paper, they just reference an earlier paper they published, which presumably lays out the technique more fully. However, I don’t have access to the relevant journal so I can’t comment – if you’re interested, I suggest following the reference trail.

  12. oh..i thought the technique was “transformation”…

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