You really will see better if you eat carrots. But there’s a catch. Carrot therapy only works if your vision problems are due to a deficiency in vitamin A. This is a rarity in North America, but sadly not in the developing world. An estimated 250,000 to 500,000 cases of childhood blindness are caused by a diet that is deficient in vitamin A, or in its precursor, beta-carotene, which the body can convert to the vitamin.
What does vitamin A have to do with vision? Retinol, as the vitamin is also known, is absorbed from the digestive tract and is chemically modified to become retinal in the body. The retinal then complexes with a protein in the eye that is known as opsin. When light hits the opsin-retinal complex, a chemical change ensues, unleashing a cascade of events that lead to the transmission of an impulse up the optic nerve. Given that vita-min A is found in meat and fish, a dietary deficiency in North America is unlikely. Even vegetarians are safe. Although vitamin A occurs only in animal products, our bodies can make it from beta-carotene, the orange-colored molecule found in carrots and numerous other vegetables. Rice, however, has virtually no beta-carotene, and as a consequence, vitamin A deficiency in rice-based societies, such as India, China, and Indonesia, is common. As a result, these populations experience widespread childhood blindness, and tragically more than half of those who lose their sight die within a year.
Various attempts have been made to supplement the diet with vitamin A. In Indonesia, for example, it has even been added to packets of the widely used flavor enhancer MSG. But the problem persists. That’s why so much excitement was generated in 2000, when recombinant DNA technology made possible the insertion into rice of a gene that codes for the production of beta-carotene. This gene, taken from daffodils, allowed the newfangled rice to produce enough beta-carotene to actually color it yellow—hence the term “golden rice.”
Proponents of genetically modified crops highlighted the development of golden rice as a breakthrough and suggested it would be a useful way to put a dent into the vitamin A deficiency problem. Opponents pointed out that the amount of beta-carotene—roughly one and a half micrograms per gram of rice—was too little to have any practical impact. They claimed that the whole golden rice issue was an industry ploy to push for wider acceptance of genetic modification. Researchers countered that the technology was new, and that improvements would surely be forthcoming. And they were right! A team at Syngenta Seeds in Britain has found that a gene taken from corn and inserted into rice is far more adept at churning out beta-carotene than the original one from daffodils. This second-generation golden rice contains almost twenty-five times as much beta-carotene as the original version. A typical daily serving of 200 grams could then provide the minimal vitamin A requirement. Studies still have to be carried out to examine how cooking affects the beta-carotene content, however, and the efficiency of absorbing the nutrient from rice remains to be investigated. And, even though this is a truly remote possibility, any potential harmful effects will have to be ruled out.
Rice enhanced with beta-carotene can do more than help with visual problems. Vitamin A deficiency can lead to abnormal bone development as well as a greater susceptibility to infections. Low blood levels of vitamin A have even been linked with an increased risk of cancer. And should you think that Syngenta is just an evil multinational, trying to capture the rice market in developing countries with overly optimistic promises, know this: the company has donated the rights for golden rice to the non-profit Humanitarian Rice Board, which will make it available to farmers for free. India and the Philippines have already approved trial plantings, despite objections from anti–genetic modification groups that claim golden rice is a pie-in-the-sky approach and will not solve the vitamin A deficiency problem. But scientists have never claimed it would. Golden rice is just one method of providing extra vitamin A. And we do have to be impressed by the fact that, in just five years, researchers have found a way to increase the beta-carotene content of golden rice twenty-fivefold! Imagine the breakthroughs that the next few years may bring.
These potential advances are not limited to rice. In India, there is hope that a genetically modified potato will help combat malnutrition. Much of the population is vegetarian, but pulses and legumes, the main sources of protein, are expensive and often in short supply. Potatoes can be grown easily, but they don’t contain much protein. This can be remedied, however, through the addition of a gene isolated from a South American plant known as amaranth. The gene in question codes for the production of a protein rich in the essential amino acids lysine and methionine. Too little methionine in the diet is known to affect brain development. Amaranth is commonly eaten in South America, so the transfer of a gene from it into potatoes does not present a health risk.
Admittedly, many people remain suspicious of this new technology in spite of its potential to address nutritional problems. They don’t want their food genetically modified. Little do they realize that virtually everything we eat has been modified, although not necessarily through the use of recombinant DNA. Centuries of crossbreeding, as well as treatment of seeds with chemicals or radiation to induce mutations, have resulted in extensive genetic modification of plants. In most cases, thousands of genes with unknown function may be involved. People don’t worry about this (and shouldn’t), yet they become extremely concerned when a single specific gene with a known function is transferred. I guess this isn’t too surprising, given that a recent survey showed that 43 percent of Americans believe that only genetically modified tomatoes contain genes. Maybe if they ate more carrots, modified to contain vitamin A, they would see this situation better.