When you think of protein, chances are you envision animal-based sources of proteins – beef, chicken, turkey, and pork – or you think of seafood. Those aren’t your only options. There are a number of getting protein from plant sources including soy-based foods, lentils, beans, nuts, and whole-grain foods. It’s possible to supply your body’s protein requirements with a vegetarian or vegan diet. In fact, there are a number of competitive athletes and bodybuilders that eat a vegan diet exclusively. What are the pros and cons of getting protein primarily from animal foods?
Does Vegetarian Protein Expose You to Fewer Toxins?
When animals are exposed to toxins from the environment, including pesticides, these toxins are stored in their fat tissue. When you eat them, you also ingest those toxins. Larger animals that are higher in the food chain will have more of these toxins stored in their fat tissue than animals lower on the food chain. One way to limit your exposure is by eating only very lean sources of meat or minimizing the amount of meat you eat. Non-organic meats may also contain traces of antibiotics.
Although fish is an excellent source of protein and many are rich in heart-healthy omega-3s, when you eat some fish you may be exposing yourself to mercury or other toxins like PCBs and dioxins. Fish that are farmed or from polluted coastal waters, rivers or lakes have higher levels of dioxins and PCBs. That’s why it’s best to choose smaller fish that come from deeper parts of the ocean where they haven’t accumulated a lot of toxic chemicals.
Plant Proteins Offer Other Benefits You Don’t Get From Animal Sources
Meat and dairy products are a good source of protein, but they lack the fiber and natural phytochemicals found in whole grains, soybeans, lentils, beans, and nuts. Why is this important? Plant-based phytochemicals have natural antioxidant and anti-inflammatory benefits. People who meet their protein needs exclusively from meat and dairy sources often don’t get enough fiber in their diet, at least not enough to meet the recommended daily fiber requirements. One way to get more fiber is to eat more plant-based foods. A cup of black beans has almost 16 grams of protein but also gives you 10 grams of fiber, more than a third of the recommended daily requirement.
Research also suggests that eating a predominantly plant-based diet may lower the risk of some chronic degenerative diseases – one more reason to get more protein from plant sources.
Disadvantages of Getting Protein From Plant Sources
There are some drawbacks to getting all of your protein from plant sources. Most plant-based foods are incomplete sources of protein, meaning they don’t offer all of the essential amino acids your body needs but can’t make. One way to get around this is to eat a variety of plant protein sources. For example, whole grains have the essential amino acids that beans and lentils lack and vice versa. Soybeans are the exception. They are a complete source of essential amino acids. Quinoa also comes close to being a complete protein.
One more caveat. Protein from plant sources doesn’t appear to be absorbed as readily as proteins from animal-based foods, so you may have to eat more plant protein to make up for the lower absorption.
Plant-Based Foods Lack Vitamin B12
When you get your protein only from plant sources, you’re at risk for vitamin B12 deficiency since it’s only in meat and dairy foods. Vitamin B12 deficiency can lead to severe anemia, neurological problems, and even paralysis and death. If you choose to eat a plant-based diet exclusively, ask your doctor about taking a B12 supplement. Plant-based diets are also not a good source of zinc.
Some Plant Foods Block Absorption of Minerals
If you’re getting your protein exclusively from plant sources, you’ll need to eat soy-based foods, legumes, and whole grains. These foods contain compounds such as phytates that reduce the absorption of minerals from your digestive tract. Plus, soy foods contain goitrogens that block the synthesis of thyroid hormones, although this is unlikely to be a problem unless you’re eating a lot of soy foods.
The best way to get the benefits of soy protein without the risks is to get it from fermented sources like miso and tempeh, don’t eat large amounts of it and make sure you’re getting enough iodine in your diet.
The Bottom Line?
Both meat and plant-based proteins have their pros and cons. Ideally, it’s best to diversify and get some of both, with an emphasis on seafood and plant-based proteins over red meat.
Bratisl Lek List.2005;106(6-7):231-4.
World’s Healthiest Foods Website