My mother-in-law used to be a fairly typical American. At age 64, she was a touch overweight, a bit inactive, and largely dependent on statins to keep her cholesterol in check. Then, last year, she went vegan after learning about Bill Clinton’s now-famous foray into plant-based eating. Within six months, she dropped 35 pounds, had more energy, and no longer needed Lipitor. That one decision likely increased the number of years she’ll have to spend with her grandkids, too, because research shows that a vegetarian diet increases lifespan.

By abstaining from all animal products—including meat, poultry, fish, eggs, dairy, gelatin, and honey—my mother-in-law also directly and powerfully benefits the planet. Think your neighbor’s SUV is bad news? Animal agriculture’s climate footprint is greater than that of all the world’s cars, buses, boats, and trains combined, according to the Food and Agriculture Organization of the United Nations.

Livestock emit massive amounts of greenhouse gases, and they’re a leading player in deforestation, biodiversity reduction, and water pollution. A recent study published in Environmental Research Letters suggests that halving meat consumption in developed countries is the only way to stabilize emissions of the greenhouse gas nitrous oxide. Reducing meat intake is so critical, in fact, the World Wildlife Fund calls it “an environmental imperative.” And don’t get us started on the inhumane and polluting industrial-food systems known as concentrated animal feeding operations (CAFOs).

If you’re considering making the switch to this healthy and environmentally responsible way of eating, here are some facts about going vegan.

Fact #1: You will get enough protein

Protein is the most common concern when transitioning to a vegan diet, but it’s almost impossible to become protein deficient if you’re eating a variety of plant foods. “You’d have to try to make it happen,” says Susan Levin, RD, director of nutrition education at the Physicians Committee for Responsible Medicine (PCRM). The typical American gets twice as much daily protein as the body requires because the macronutrient is so widely available—it’s even in broccoli. And no need for specific combinations; in its most recent position on vegetarian diets, the Academy of Nutrition and Dietetics (formally the American Dietetic Association) says you don’t need to eat “complementary proteins” (for example, beans and rice) in the same meal to get the right proteins.

Fact #2: Calcium isn't just from cows

“Many of us grew up believing we had to get calcium through milk,” says Ginny Messina, MPH, RD, author of Vegan for Life (Da Capo, 2011). Surprise: The calcium in kale and collards is twice as bioavailable as that in cows’ milk. Satisfy your 1,000 mg recommended daily calcium intake by eating those calcium-rich greens (but not chard, beet greens, or spinach, which contain other nutrients that diminish calcium absorption) and cruciferous vegetables, such as brussels sprouts and cabbage. More good sources: tofu with calcium sulfate and calcium-fortified nondairy milks; to get enough bone-strengthening vitamin D, look for products fortified with vegan-sourced vitamin D2 rather than D3, which comes from fish oil or lanolin, a byproduct of sheep’s wool.

Fact #3: You'll feel full

Biologically, you don’t require animal protein to vanquish hunger—you need fiber, an indigestible carbohydrate. “Fiber sits in your gut until it goes down and out,” says Levin. “You’ll feel more full eating heavy fibrous foods like oatmeal or a bean burrito, and you’ll digest fewer calories overall. You should never feel hungry eating this way.” The PCRM recommends 40 grams of fiber per day, but most Americans eat only about 15 grams. To bridge the gap, work fiber into every meal—a cup of quinoa or rice at breakfast, a veggie or bean burger for lunch, and 2 cups of broccoli with dinner, for example. Bonus: A high-fiber diet may help you live longer, according to a recent study of more than 450,000 Europeans.

Fact #4: You won't miss out

You won’t partake in a traditional ham dinner, but “people who have adopted plant-based diets are usually surprised at how much variety is now in their lives as opposed to when they were eating animal products,” says vegan chef Colleen Patrick-Goudreau, author of The 30-Day Vegan Challenge (Ballantine, 2011). Humans are creatures of habit, complete with food ruts. A vegan diet presents options you may have never considered. For example, instead of eating the same old chicken breast with a potato and side salad, you’ll be enticed by recipes like rice-and-nut-stuffed squash or a main-dish salad that combines navy beans, millet, and baby kale. “It’s behavioral change and a shift in the way you perceive meals,” Patrick-Goudreau says.

Fact #5: You don't have to be perfect

Can’t do without Parmesan? Just going vegetarian (which includes dairy and eggs) or nearly vegan yields major benefits for your health and the planet. A recent study in the United Kingdom suggests that in addition to measurably lowering their diabetes, cancer, and heart disease risk, people who ate 2.5 times less red and processed meat than the highest-intake group shrank their climate footprint by nearly half a ton of carbon per year. “It’s not about achieving some kind of purity,” Patrick-Goudreau says. “Even if you make mistakes, you’re doing the best you can to live compassionately and up to your values.”

An avowed flexitarian, Katy Neusteter is a Denver-based freelancer who writes about health, the environment, and travel.