Steaming versus Boiling Vegetables

It seems you just can’t escape food controversies anymore. No matter what scientific evidence is presented, someone will claim it’s wrong or that it’s part of a Big Food Company conspiracy. Honestly, some of these culinary fear-mongers make UFO conspiracy theorists seem almost well-adjusted. It feels like that’s all we hear now. Statements like, “Genetically-Engineered Foods (GMOs) are bad for you” (even though we’ve been eating genetically-engineered foods for over 3,000 years— the only difference now is that we manipulate genes directly rather than using selective breeding), “Meat is bad for you” (even though meat is one of the few ‘complete’ foods humans can survive on), “Vegetables are bad for you” (even though, without them, your body would need to use valuable muscle-building proteins for energy, not to mention the fiber…) and the list goes on. The most ridiculous controversy I’ve heard recently is the debate on steaming vs. boiling vegetables.

Understanding Cooking and Its Effects

It may seem a bit obvious, but to dive into this topic, we need to understand what cooking is—and what it isn’t. First, let’s kill the myth that raw foods are the natural human diet and are best for us. This is pure rubbish. There are only a few foods that humans can efficiently digest raw, such as certain fruits, nuts, and raw meat. While some vegetables can be eaten raw, they are tough on the digestive system. Most of what we eat would be inedible in its raw state, such as potatoes, rice, most grains, and most beans. Some are even toxic in their raw form, like kidney beans and rhubarb. Early on, Homo erectus discovered that cooking food greatly expanded the available sources of nourishment and helped ensure survival through difficult times, like droughts and ice ages. It also allowed us to colonize the entire planet, not just the African savannahs.

Cooking is the process of transferring heat energy into the tissues of food, causing chemical reactions that affect its texture, taste, and digestibility. The heat breaks down certain chemicals and renders them into more easily assimilated forms. A small loss of nutrients is unavoidable, as physics tells us you can’t get something for nothing. But the trade-off between a slight nutrient loss and the ability to digest food more easily—and access a wider range of food—is more than worth it. All cooking results in some nutrient loss, and food cooked to the same degree using any method—whether fried, boiled, steamed, or baked—will lose the same amount of nutrients. Heat is heat, period. The differences in methods come from how moisture, oils, and fats are absorbed or dehydrated during cooking.

Two of the most heat-affected nutrients are folic acid and Vitamin C. One of the favorite quotes from the pro-steam camp is that a USDA study showed steaming results in a 15% loss of folic acid and Vitamin C, while boiling leads to losses of 25% and 35%, respectively. However, the flaw in this argument is that the study didn’t consider the fact that boiling water can be used, along with the vegetables. The additional loss from boiling occurs because the nutrients leach into the water. They haven’t disappeared. You can use the leftover liquid as a base for stock or sauces, easily recovering the nutrients. Chefs and savvy cooks rarely toss out leftover liquids.

Another point the pro-steamers overlook is that steamed vegetables are usually cooked to a much lesser degree than boiled vegetables. Most veggies are steamed until they just start to become tender. Boiled vegetables, on the other hand, are typically cooked all the way through. There are also vegetables that simply don’t respond well to steaming. For instance, potatoes become sticky, starchy, and unappealing, while trying to steam raw beans can actually be dangerous. Steamed tomatoes quickly turn to mush (though they can be used in this form). The vegetables that respond best to steaming are fibrous and leafy, such as cabbage, Brussels sprouts, cauliflower, broccoli, carrots, corn on the cob, and celery.

Someone once said that if you tell a lie long enough, people will start to believe it. A perfect example of this is the myth that you can’t overcook food by steaming it. This fallacy has persisted for decades (though I don’t know why). You can easily disprove this yourself. Fire up your steamer and put some fresh broccoli in it. Cover it and leave it for an hour or two. When you return, you’ll find nothing but a greenish, mushy mess. No cooking method is immune to the risk of ruining food due to inattention or incompetence.

The choice between steaming and boiling vegetables ultimately depends on what you’re trying to achieve. Steamed veggies taste different from boiled ones, but not necessarily better. It depends on your preference. No food on the planet is more nutritious and extracts more from the ingredients than a pot of soup. Ounce-for-ounce, it provides more nutrition than anything else you can eat. However, steamed vegetables do tend to retain more color and texture, so if you want bright-green Brussels sprouts to accent the colors of your poached salmon, steaming is the way to go. Similarly, bright orange steamed carrots can complement your meal well. Broccoli is often steamed to retain its bright-green color, which quickly turns into a dull olive-drab green when boiled due to the chlorophyll leaching into the water.

The bottom line is this: cook your food the way you like it. Most meals contain far more nutrients than you need anyway, so I wouldn’t stress over the small amount you might lose with a specific cooking method. You’re likely to make it up with additions like bread, butter, side dishes, dessert, and whatever you drink with your meal. As far as I know, no one has died or suffered serious health issues directly attributed to steaming or boiling vegetables.