Becoming a vegetarian, even part-time, is a smart move for your health. Plant-based diets help protect against cancer, heart disease, and a number of other health problems. But there's a healthy way to follow a vegetarian diet and a not-so-healthy way. Sometimes when people decide to go vegan or vegetarian, they cut out meat and dairy but don't replace them with foods that are nutritious, and as a result run the risk of falling short nutritionally. For a healthy vegetarian diet, Reed Mangels, Ph.D., R.D., an adjunct associate professor of nutrition at the University of Massachusetts Amherst suggests that you get enough of these four important nutrients.

1. Protein. Your body uses protein to build tissues, including muscle. The recommended amount of protein is 0.4 gram of protein per pound of body weight each day; 1 gram per pound if you are an athlete. Older adults over 65 may need 0.6 gram per pound because muscle mass naturally declines as we get older. For 150-pound person, that's 60 to 150 grams. Meat and dairy supply a lot of protein even in a small serving. For example, 3 1/2 ounces of chicken breast has 31 grams. Six ounces of nonfat plain Greek yogurt has 18 grams and one large egg has six grams. But there are protein rich plant foods, too. Some examples include: Four ounces of tofu, 18 grams; one cup cooked chickpeas, 15 grams; one cup cooked quinoa, 8 grams; and one cup of cooked bulgur, 7 grams. For a healthy vegetarian diet include a muscle-boosting protein source such as beans, nuts, quinoa, and tofu at every meal.

2. Calcium. This mineral helps build bone and is also important for vascular and muscle function and nerve transmission. The amount you need daily is 1,000 milligrams, but needs increase for men once they reach 70 and women 50 and older. Cut back on dairy products and your intake of the bone-building mineral will probably take a hit. Include foods such as almonds, broccoli, collard greens, kale, fortified soy or other plant milks, and tofu to meet your needs.

3. Iron. In its plant-based form (“nonheme”), iron isn’t absorbed as well as iron in meats (“heme”). Iron needs drop for women after menopause (men’s needs stay consistent), but getting enough can be a challenge for plant-based eaters of all ages. Pair foods containing the anemia-preventing mineral—lentils, soybeans, Swiss chard—with sources of vitamin C like oranges and red bell peppers. Doing so helps boost iron absorption.

4. Vitamin B12. Crucial for the brain and nervous system, vitamin B12 is mainly found in animal foods such as meat, shellfish, and dairy products. But many adults over 50 have difficulty absorbing B12 from the usual sources. So look for fortified almond or coconut milk, breakfast cereals, and meat alternatives, like tempeh.