Dear EarthTalk: I would like to make my holiday gifts matter this year. Where can I find ideas for green gifts? -- Mary Baumgartner, via email

The holidays are a great time of year to share your enthusiasm for protecting the environment with family and friends. One meaningful gift -- a fashion-forward T-shirt from Rain Tees -- can help fight environmental destruction far away while raising awareness here at home. Every Rain Tee is hand-made in the U.S. from eco-friendly fabrics and features original artwork created by children living in countries facing rampant deforestation. For every T-shirt the company sells, proceeds help the cause and Rain Tees' charity partner, Trees for the Future, will plant a tree in a critically endangered part of the world.

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Another way to link your gifting and philanthropic tendencies is to donate to the Paradigm Project to help purchase clean burning stoves for poor families in Africa. Your donation goes toward reducing deforestation and respiratory disease in a developing country, and the Paradigm Project will send you a unique holiday ornament in exchange.

Many other nonprofits also provide holiday season incentives to donate to their causes in the name of a friend or loved one. To wit, the NRDC's Green Gifts website offers dozens of gift opportunities related to various campaigns the organization is conducting around the world. By donating through the Green Gifts program, you and your gift recipient can help defend polar bears, protect clean water, revive rainforests or promote renewable energy, among other options. Similar land and species "adoption" programs that can be leveraged as holiday gifts are available from groups such as the Nature Conservancy, WWF, Defenders of Wildlife and the Whale Museum.

If not spending money is a priority this holiday season, you can make artwork or functional items out of leftover materials otherwise headed for the trash can or recycling bin. Handmade gifts in any form are always appreciated and will likely be cherished for much longer than anything store-bought.

But if making your own presents isn't your thing, a wide range of green gifts, large and small, can be found online. Some companies that specialize in fairly traded, sustainably sourced gift-worthy items include The Hunger Site Store, Branch, Low Impact Living, BGreen Apparel, A Greener Kitchen, Green Heart and Organic Bug, among many others. And once you've completed your green shopping, wrap up your gifts in the festive designs of Earth Presents, which sells 100 percent recycled/recyclable gift wraps.

For still more ideas on where to source that perfect green gift, check out the website of the nonprofit Green America, which provides links on its website to dozens of firms that sell sustainable wares.

No doubt it feels good to go green over the holidays, given the excess we typically associate with gift-giving. And given the poor state of the economy, it makes sense to give gifts that will last, whether they involve furthering important environmental work or providing items that haven't caused unnecessary environmental destruction in their manufacture and that won't break down once the holidays are over.

Contacts: Rain Tees, www.raintees.com; Paradigm Project, www.theparadigmproject.org; NRDC Green Gifts, www.nrdcgreengifts.org; Nature Conservancy's Holiday Giving, support.nature.org/site/PageServer?pagename=holidaygiving_xx_hgg; WWF Gift Center, www.worldwildlife.org/gift-center/; Whale Museum's Orca Adoption Program, www.whale-museum.org/programs/orcadoption/orcadoption.html; Green America, www.greenamerica.org.

Dear EarthTalk: Given the preponderance of carcinogenic chemicals out there today, is it true that eating certain foods like garlic or onions can actually help prevent cancer? -- M. Stone, Boston

Natural healers have extolled the cancer-preventing virtues of garlic and onions for years, but only recently do we have enough scientific research to draw some conclusions. Several animal studies showing promising results using garlic and other members of the allium family (onions, leek, shallot, and chive) to prevent tumors have led to hundreds of studies involving human garlic eaters. While it is near impossible to pinpoint a direct link between garlic consumption and cancer prevention, the National Cancer Institute reports that "several population studies show an association between increased intake of garlic and reduced risk of certain cancers, including cancers of the stomach, colon, esophagus, pancreas and breast."

To wit, a multi-year study of 25,000 people from Switzerland and Italy found that those who ate the most garlic and onions were up to 88 percent less likely to develop various types of cancer (including cancers of the esophagus, mouth, throat, colon, breast, ovary, prostate and kidney) than those who said they ate little or none.

"High onion intake, for example, was associated with a 56 percent lower risk of colon cancer and a 25 percent lower risk of breast cancer compared to no onion intake," reported Karen Collins of the nonprofit American Institute for Cancer Research.

According to Collins, another study found a 32 percent lower colon cancer risk among Iowan women who ate at least one garlic clove a week compared to others who ate one once a month or less, while an analysis of several studies worldwide "linked a 31 percent lower risk of colon cancer with consumption of about four to five cloves of garlic weekly."

And the results of several studies conducted in China show that those who eat five cloves of garlic a week are half as likely to develop stomach cancers than non-garlic-eaters. Meanwhile, AICR reports that isolated components of garlic have shown the ability to slow or stop the growth of tumors in prostate, bladder, colon and stomach tissue.

Just how do allium plants prevent cancer? "Like many vegetables, onions and garlic contain antioxidants that can block highly reactive free radicals from damaging cell DNA and starting the cancer process," reported Collins. "Laboratory studies have shown that onion and garlic compounds can increase enzymes that deactivate carcinogens in the body, enhancing our ability to eliminate carcinogens before they do any damage."

Some researchers, however, say that study limitations -- that is, the accuracy of reported amounts and frequency of garlic consumed and the inability to compare data from studies that used different garlic products and amounts -- make a definitive declaration on the topic unlikely anytime soon. And without such definitive conclusive proof of a causal link, the U.S. Food and Drug Administration will not allow food purveyors to state the health benefits of the garlic in their products on their labels.

NCI would like to see better-designed human dietary studies using predetermined amounts of garlic to discern potentially effective intakes as well as more studies directly comparing various garlic preparations. "Given this protective potential, the challenge now is to identify amounts that will provide optimal effects," said Collins. In the meantime, don't skimp on the garlic and onions.

Contacts: National Cancer Institute, www.cancer.gov; American Institute for Cancer Research, www.aicr.org.

EarthTalk is written and edited by Roddy Scheer and Doug Moss and is a registered trademark of E - The Environmental Magazine ( www.emagazine.com). Send questions to: earthtalk@emagazine.com. Subscribe: www.emagazine.com/subscribe; Free Trial Issue: www.emagazine.com/trial.