In “What Makes You Fat: Too Many Calories, or the Wrong Carbohydrates?” Gary Taubes argues that avoiding carbohydrates, rather than an excess of calories, will lead to weight loss. The right nutrition question instead should be “What should we eat to have the longest, healthiest life?”

There are many ways to lose weight and still become sick and die. I know this firsthand after losing 25 pounds and then suffering a cardiac arrest. And many dieters die of heart disease after losing weight with a high-fat, low-carbohydrate diet.

My reading of the research leads me to conclude that a whole-food, plant-based diet low in fat and high in carbs reduces disease and, as a nice side effect, weight.

John Tanner
Monrovia, Calif.


In “Labels for GMO Foods Are a Bad Idea” [Science Agenda], the editors tell readers not to be alarmed by the unproved dangers of genetically modified foods and argue that labels identifying such food should not be required by law because such labeling would increase fears and lead to an elimination of such foods in the marketplace.

Although genetically modified foods have not been proved to be dangerous, that is not the same as being proved safe. The drug thalidomide (which was later found to cause birth defects) was not proved to be dangerous when it was released. Neither was partially hydrogenated oil (which raises “bad cholesterol”) or high fructose corn syrup (a major component of the obesity epidemic in the U.S.).

Genetically modified foods represent a long-term experiment. Should you wish to partake in that study, I have no quarrel. But to say that everyone should become unwilling participants is disingenuous.

Eric Armstrong
Mountain View, Calif.

The editors make a weak argument against labeling genetically modified organisms (GMOs) and a strong one in support of genetic crops. The premise that if you support genetic research, you must oppose labeling is simplistic. Supporting GMO labeling need not mean opposing genetic research. This is akin to opposing traffic lights because you believe in safe driving! Eventually both sides will win. Genetic manipulation seems embedded in our evolutionary gene, and the future will likely be filled with GMOs as science improves and corporations become more responsible. Equally, GMO labeling will evolve as consumers become more aware and governments more responsive.

For now, a tentative start in GMO labeling is better than keeping more than 300 million consumers in the dark. We should embrace knowledge sharing and not shun it based on unfounded fears.

Ashok Vasudevan
CEO, Preferred Brands International

The GMO path is not as clear-cut as “The Truth about Genetically Modified Food” by David H. Freedman, suggests in arguing for expanded GMO deployment and safety testing.

GMO seeds have been used commercially only since 1994, perhaps not long enough to determine any lasting effects. There is reason to suspect that GMOs may be responsible for the sharp increase in the past two decades of celiac disease, irritable bowel syndrome and inflammatory bowel diseases such as Crohn's.

Holly Bittinger

Both the editors and Freedman focus on safety but omit the issues of genetic diversity and control of intellectual property.

We need to restore the genetic diversity that we had prior to the pervasive industrial monoculture farming we have now. This standardization has made our food system more dependent on energy sources and more vulnerable to disease and climate change. The one-size-fits-all GM crops we have seen so far continue the low-diversity approach.

GM techniques can in theory help with increasing crop diversity. But the objective so far seems to be corporate ownership of genetic codes and reducing the options that farmers and consumers have.

We should write laws to govern the genetic engineering of organisms that benefit everyone, not just vested interests.

Mark Mezger
via e-mail

GMOs often contain trans-species genes that code for proteins no other food plants contain. There have been very few actual studies of the toxicity of these proteins in humans. Bt is a bacterium, and the protein its gene codes for has been linked to an increase of certain antibodies and cytokines in rodents.

Bruce Hlodnicki
via e-mail

THE EDITORS REPLY: Regarding Hlodnicki's letter, Bt toxins are, in fact, some of the safest pesticides ever used. Many studies—including experiments by researchers with no ties to the biotech industry and at least two long-term studies—have concluded that Bt toxins rarely harm insects other than targeted pests and do not hurt fish or people and other mammals. In one study from the 1950s, people ate large amounts of Bt with no ill effects. To learn more, see


George Church neglects the most important reason to clone the woolly mammoth in his arguments in favor of doing so in “George Church: De-Extinction Is a Good Idea” [Forum]: it would be an incredibly inspirational scientific moment; our generation's moon landing.

In the 1950s and 1960s physics was the premier science; today it is biology, and this would be its pinnacle achievement. Furthermore, unlike the moon landing, it would surely be an international achievement and so would have an even stronger unifying effect.

Carter Edman
via e-mail

The mammoths and other megafauna of the late Pleistocene made the Arctic a far more productive ecosystem than it has been since the time of their extinction. Those who object to the idea of reanimation seem not to be aware that North America has had a drastically impoverished fauna in the past 13,000 years and that impoverished fauna are less productive and resilient.

Unlike Church, I would like to see mammoths re-created as close as possible to the way they were, and I want the rest of the megafauna as well—the glyptodonts, the ground sloths, the extinct great cats.

Tim Cliffe
Emmitsburg, Md.


I agree that “enlisting bacteria and fungi from the soil to support crop plants is a promising alternative to the heavy use of fertilizer and pesticides,” as reported by Richard Coniff in “Microbes Help Grow Better Crops.

Those of us who are proposing the use of biochar, a carbon-rich soil additive that is created by decomposing biomass with heat and limited air, find that it can increase the effectiveness of this approach. Biochar serves as a host for bacteria and fungi and increases their availability to plants. This technique was practiced several centuries ago by the natives of the Amazon, leading to a thriving economy.

Richard S. Stein
Amherst, Mass.