It's Not What You Eat, It's How You Cook It

We spend so much time talking about what to eat that we sometimes forget something fascinating: the exact same food can deliver nutrients differently depending on what you do to it before it reaches your mouth.

Sometimes cooking helps. Sometimes raw is better. Sometimes chopping matters. Sometimes adding another food changes absorption dramatically. Your kitchen is basically a tiny chemistry lab, except nobody is wearing goggles and somebody is looking for the salt.

Take tomatoes. Lycopene is the red carotenoid tomatoes are famous for. Cooking breaks down parts of the plant structure and generally makes lycopene more bioavailable. Add a little fat, such as olive oil, and absorption improves further because lycopene is fat soluble. So tomato sauce cooked with olive oil isn't simply a tastier tomato. In one important nutritional sense, it can actually give you more accessible lycopene than the raw tomato you started with.

Garlic plays almost the opposite game. When you chop or crush garlic, you bring an enzyme called alliinase into contact with compounds that ultimately produce allicin. But here is the useful little kitchen trick: crush your garlic and let it sit for about 10 minutes before cooking it. That gives the chemistry time to happen before heat inactivates much of the enzyme. Cooking garlic isn't “bad,” and it still contains other beneficial sulfur compounds, but preparation changes what you end up getting.

Then there is turmeric. Curcumin itself is poorly absorbed. Black pepper contains piperine, which can substantially increase curcumin bioavailability. Curcumin is also fat soluble, so using turmeric as part of a meal containing some fat makes more sense than simply throwing turmeric powder into water and expecting magic.

Carrots are another interesting one. Cooking softens their plant cell walls and can increase the bioaccessibility of beta carotene. And because carotenoids are fat soluble, eating those carrots with some healthy fat can help your body absorb them.

Spinach gives us a perfect example of why “raw is always healthier” doesn't work as a rule. Cooking spinach reduces its volume tremendously, so you can easily eat more of it, and heating can reduce some compounds that interfere with mineral availability. On the other hand, heat can reduce some heat sensitive nutrients. Raw spinach and cooked spinach aren't competitors. They simply offer somewhat different nutritional profiles.

Broccoli has its own trick. Chopping it before cooking allows an enzyme called myrosinase to help form sulforaphane, a compound researchers have studied extensively. Heavy cooking can inactivate that enzyme. Interestingly, adding a little raw mustard powder to cooked broccoli can provide myrosinase and increase sulforaphane formation. That's one of my favorite examples because who would look at broccoli and mustard and think, “These two need to have a meeting”?

Flaxseed is another big one. Whole flaxseeds can travel through the digestive system surprisingly intact. Grind them, and suddenly your digestive system has much better access to their nutrients, including their omega 3 fat ALA and lignans. Sometimes the difference between eating a nutrient and accessing it is literally a coffee grinder.

Nuts and seeds have another interesting relationship with preparation. Soaking can reduce some phytate, although the effect varies considerably by food and method. Cooking, fermenting, sprouting, and other traditional preparation methods can also change phytate levels and mineral availability. This is one reason traditional food preparation practices are more scientifically interesting than they sometimes appear.

Iron gives us another easy pairing. Plant foods contain nonheme iron, which isn't absorbed as efficiently as the heme iron found in animal foods. But vitamin C can substantially improve absorption of nonheme iron. Lentils with tomatoes or peppers, beans with lime, spinach with lemon. Suddenly what you put beside the food matters almost as much as the food itself.

And then there are foods where heat works against you. Vitamin C is sensitive to heat and water, so long boiling can cause substantial losses, particularly when the cooking water is discarded. Steaming or shorter cooking times generally preserve more than prolonged boiling.

Even potatoes change depending on what happens after cooking. Cook a potato and then cool it, and some of its starch reorganizes into resistant starch, which isn't digested exactly like ordinary starch. Reheating doesn't necessarily erase all of that change.

Oats, rice, legumes, onions, berries, cabbage, peppers, mushrooms, nuts, seeds and herbs all have their own little chemistry stories. There really isn't one universal rule saying raw is best, cooked is best, or one preparation method “unlocks” everything. And that may be the most interesting part. Nutrition isn't only about WHAT is sitting on your plate. It is also about what your body can actually extract, absorb and use from what is sitting there. Your food can look healthy and still be useless.