Cost-benefit analysis: legumes

The topic: legumes, a class of plants that includes lentils, beans, and peanuts

The costs:

Legumes contain a few compounds known as anti-nutrients, according to Holly Niles, CNS, functional nutritionist at The UltraWellness Center in Lenox, Massachusetts. (Cooking dramatically lowers their presence and impact—more on that below—but some experts argue that they're harmful.) 

First up: lectins, natural proteins that bind to cells in the digestive system, where they may trigger inflammatory responses and disrupt healthy bacterial function in the gut.

Then there’s oxalate, another protective nutrient that binds to calcium in the body and gets stored in the kidneys, says Niles. High intake can increase your risk of developing calcium oxalate kidney stones. If you’re prone to them, limit your intake of high-oxalate foods like beans and peanuts to four or five servings per day.

Combine these anti-nutrients with the high fiber content in most legumes and you have a recipe for gas, bloating, and fatigue in people who are susceptible to these issues, says Niles. 

Finally, if you’re on a low-carb diet, leave legumes off the menu. Though they contain complex carbs (the healthier kind), they’re still high in the macro. A cup of chickpeas, for example, has close to 20 grams.

The benefits:

Compared to other plants, legumes are high in protein across the board, with about seven grams in half a cup, says Niles. (You’ll get the same amount from an egg.)

Legumes’ fiber has the potential to cause digestive issues, but it also slows down the rate at which you digest carbs. In turn, you'll feel satiated and your blood sugar and energy levels will stay stable, which will help you avoid hitting the wall during tough workouts. 

That’s not the only way these plants further your fitness. They contain B vitamins like folate that are crucial for energy production, Niles explains. Legumes also provide iron and potassium, which help the muscles function properly by maintaining electrolyte balance and delivering performance-boosting oxygen and nutrients.

The final analysis:

If you have a chronic inflammatory condition or digestive issues, you’re best off limiting—or completely avoiding—legumes.

Otherwise, you can make sure they aren’t contributing to fatigue or bloat by first eliminating them for three to four days, Niles says. Then, eat two servings per day and see if you notice any changes in digestion or energy levels. If you don’t feel any negative effects, you’re cleared to make them part of your meals on a daily basis. 

To minimize the impacts of the anti-nutrients, soak and cook dried beans and lentils according to package instructions, she adds. These processes break down the protective compounds, making them a lot easier on your digestive system. (It has similar benefits to massaging kale before you eat it.)

If the instructions include a range (for example, to soak the lentils for one to two hours or to cook them for 30 to 40 minutes), stick to the longer end of it.

Because of the carbs and protein they provide, legumes work well as pre-workout fuel, Niles notes. Eat a single serving one to two hours before you train.

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