Boost Your Health with Food Combining & Preparation

Some people say you are what you eat. But it would be more accurate to say that

you are what you digest. After all, just because certain nutrients are abundant in a food doesn’t mean that they will be absorbed by your body. If nutrients just go in one end and out the other, they don’t provide you with many benefits.

The good news is that there are some specific ways of preparing and combining foods that can enhance nutrient bioavailability. And how food is grown, as well as how long it takes to get to your kitchen counter, also has a huge impact on nutritional quality.

In this article, we’ll look at various methods of food sourcing, preparation, and combining, that can either maximize or impair nutrition.

Food Sourcing & Storage

This may be obvious, but food gets its nutrients from the sun, soil, and atmosphere. Many studies have shown that the same produce can have very different nutritional profiles depending on its “terroir,” which isn’t a scary word or a fancy little French dog, but means a food’s complete natural environment. Even two peaches from the same tree can vary dramatically in beta-carotene, depending on what branch they grew on.

That complete natural environment also includes the farming methods, including whether and what kinds of chemicals are used to fertilize the plant and protect it from pathogens and competition. Pesticides used in the growing season can reduce the food’s nutritional punch. And the residues that make it into your body can cause all kinds of health problems.

Organic Produce

To maximize the benefit of the plant foods you eat, look for organically grown and local produce whenever possible. Organic foods may have higher concentrations of nutrients, especially those all-important antioxidants. And they’re less likely to contain pesticides and pesticide residues.

Local Produce

Local produce, while it may not be organic, also has significant benefits. As the nutrient composition of fruits and veggies degrade after picking, local produce can be much fresher than the stuff that travels around the world in refrigerated ships, planes, and trucks. Also, since shelf-life isn’t the primary consideration, local growers can provide more unusual (and often highly nutritious and delicious) varieties of fruits and veggies that ripen quicker or bruise more easily than iceberg lettuce and tasteless tomatoes. And while some small farmers use season extension techniques like greenhouses, shade cloth, and high tunnels, most of the produce you’ll get from a local grower will be in season — another way to ensure maximal nutritional value.

Home-Grown Produce

Of course, the best, and certainly the most local, kind of produce is the kind you grow yourself or get from a neighbor with a green thumb. One possible “silver lining” of the pandemic is that it has led to a dramatic revival in backyard gardening. For our article on how to start a food garden and take control of your food, click here.

Frozen Produce

Another high-quality source of nutritionally dense fruits and vegetables is your grocer’s freezer section. Frozen fruits and vegetables are picked at peak ripeness and then are flash-frozen, which preserves their nutrients remarkably well. Research published in the Journal of Agricultural and Food Chemistry in 2015 compared the nutritional content of foods that were frozen or refrigerated. For many vitamins, there was no difference. With the exception of beta-carotene, which degraded in the frozen produce, the nutrient levels in frozen foods were “comparable to and occasionally higher than” the fresh refrigerated ones. Of course, you can always grow your own, or buy fresh, and freeze the produce yourself. Here’s our helpful how-to article on food storage and preservation.

Food Preparation

How you prepare your fruits and veggies can also affect how much nutrition you get from them. It turns out that being a little rough on your produce can be a good thing. Cutting or chopping vegetables wounds their flesh, triggering a defensive reaction. The veggie releases polyphenols to prevent further damage.

To understand why this works, it’s helpful to think like a head of lettuce (I mean, it does have a head, so it must think, right?). You’re hanging out in the ground, minding your own business, taking in some rays, and along comes a bunny rabbit who starts chomping you. What are you going to do?

You can’t run away (darn roots!). You can’t hide, and you can’t fight back. But you can make yourself taste bitter, so Flopsy decides that some other leafy green will be a much more pleasant meal. The plant (not just lettuce, but also celery, parsnip, and others) pumps out nasty (to rabbits, anyway) polyphenols, which, remarkably enough, can help protect humans from heart disease, type 2 diabetes, and some cancers.

Foods with high concentrations of vitamin C should be eaten right after cutting, because the polyphenols interact with the vitamin C, and can use it up before it makes its way into our tissues.

The Benefit of Preparing Alliums

Another class of foods that loves us back when we crush it are the alliums, which contain strong-smelling organosulfur compounds. It’s much better to chop or crush garlic than to eat it whole (not that you were considering popping them like candy) because the damage to the bulb releases an enzyme called allicin, which has the nasty habit of putting an Elvis Costello song into my head every time I read the word. This enzyme turns the garlic into a nutrient factory in overdrive, releasing copious amounts of health-promoting chemicals for our benefit. Onions also release organosulfur compounds when their cell walls are broken, which is why we cry while chopping them.

But here’s a little-known fact about onions and garlic: once you cut or crush them, their nutritional power increases for the next 10 or so minutes. For maximum benefit, leave them alone for at least a few minutes after chopping or crushing, before cooking them or eating them raw.

Fermented Foods

Fermenting is another way of increasing good nutrients in some foods, and has the added benefit of reducing phytates. That’s a victory for nutritional bioavailability, as phytates can inhibit the absorption of certain minerals. Researchers working to improve nutritional outcomes in sub-Saharan Africa discovered in 2018 that fermentation increased enzyme activity in cereal grains and legumes. That made nutrients more available for human uptake.

Also, antioxidant properties of fermented foods are elevated compared to their unfermented counterparts due to increased vitamin C activity. (Here’s our article on the benefits of fermentation, along with some easy-to-follow instructions to get started with sauerkraut and plant-based yogurt.)

Soaking Grains and Legumes

That same 2018 African study found that soaking grains and legumes started the germination process and reduced their phytate content — making their nutrients more bioavailable. Beans are already health-promoting superstars; they’re one of the foods most strongly associated with longevity. Soaking them so they begin to germinate makes them even more potent nutrient powerhouses.

Prepare Nutritious Meals by Sprouting

The health food movement has touted sprouting (say “touted sprouting” five times fast) for many decades. We’re starting to see the science to support some of the claims of sprouting advocates. A comprehensive 2019 review of the science of sprouted grains appeared in Nutrients Journal and included the fascinating factoid that fruit flies who were given supplemental wheatgrass shots lived, on average, 6 days longer than their cousins in the wheatgrass-deprived control group. I doubt the equivalent effect occurs in humans – but if it did, that would add about nine years to our life expectancy.

Sprouted beans, grains, nuts, and seeds are more nutritious and digestible than their non-sprouted counterparts. They contain more fiber, and sprouted whole grains in particular are higher in protein. Also, sprouted foods trigger increased production of the neurotransmitter GABA, which plays a key role in regulating mood. Low GABA has been linked to both depressed and manic states. Here’s how to start growing your own sprouts. Whether you share your wheatgrass with your local fruit flies is totally up to you.

As an added bonus, sprouted grains and beans are easier to digest, and are less flatugenic, which is to say, less musically inspiring. Here are some instructions for soaking beans and grains for superior nutrient absorption.

Make Sure You Soak Your Rice

One grain, in particular, should be soaked before cooking. Rice, unfortunately, can contain high levels of arsenic, which is a Group-A carcinogen and one of the worst pollutants found at Superfund sites. Even organic brown rice can contain worrying concentrations of arsenic. But studies show that soaking the rice in a particular way, which we share in this article, can remove much of the arsenic content.

Raw or Cooked?

Whether raw or cooked food is healthier is one of the heated (ha!) debates in the vegan community. I’m happy to offer the definitive answer: Yes.

Some foods are more nutritious in their raw state, while others are better for us after having their proteins denatured by heat. For this discussion, we’ll stick to high-level principles. 

Sulforaphane

One of the most powerful cancer-preventing and cancer-fighting nutrients is sulforaphane, which you can get from raw cruciferous vegetables like broccoli, cabbage, and the heavyweight sulforaphane champion, broccoli sprouts. To activate the sulforaphane, the veggies’ cell walls must be broken, either by cutting or chewing.

So that does mean you should never eat steamed broccoli or stir-fried cabbage? Not at all. Here are a few hacks that can get your cooked cruciferous friends’ sulforaphane levels to rival their raw state. First, you can sprinkle some powdered mustard seeds on your cooked broccoli. Even a small amount activates the sulforaphane. Second, you can combine your cooked crucifers with a little shredded raw cabbage. Third, if you plan ahead, you can perform Dr. Greger’s “hack and hold” technique of cutting the veggies 40 minutes or more before cooking, after which you can heat them to your heart’s content without destroying the sulforaphane. And fourth, you can mix a few raw arugula leaves into your cooked (cabbage family) veggies.

Vitamins

Foods high in water-soluble B vitamins and vitamin C, like leafy greens, broccoli, citrus fruits, sweet potatoes, and tomatoes, will retain the most nutrients when eaten raw or added at the very end of cooking. Heat will draw out the water from these fruits and veggies, and with that water, many of the water-soluble vitamins. A 2017 study out of Korea found that boiled and steamed chard retained absolutely no vitamin C. Zero. So if you do cook your greens and other B- and C-rich foods, do so in a soup or stew, or save the broth or water for later use. Don’t pour your vitamins down the drain.

On the other hand, fat-soluble vitamins such as A, D, E, and K are best eaten cooked. These nutrients actually stabilize when cooked, and in some cases, become more bioavailable.

Nutrient & Food Combining

There are a lot of ideas about food combining out there, and most of them are completely unsupported by science. For example, vegetarians don’t need to pair beans and grains at every meal to equal the supposedly “perfect protein” profile of an egg. And you aren’t going to confuse your digestive system by combining fruits with vegetables. You are also permitted to drink water with meals – it won’t dilute your stomach’s digestive juices to the point of impairment unless you drink a quart of water with a meal, which isn’t recommended.

But some principles of food combining are valid, and following them will provide you with increased absorption of key nutrients.

So let’s talk about what foods to eat with other foods for maximum nutritional benefit. We’ve already seen that powdered mustard seeds love cruciferous veggies, but that’s just the tip of the broccolini. Let’s examine how to increase intake of iron, vitamin D, and other fat-soluble vitamins by smart combining.

Iron

To get enough iron, eat iron-rich foods like leafy greens, chickpeas, tofu, lentils, and oats with foods high in vitamin C. If you eat a plant-based diet, you’re getting the non-heme form of iron, which isn’t as bioavailable as the heme iron found in animal tissue. The vitamin C increases the absorption and bioavailability of iron in the body. Examples include lentil soup with a squeeze of lemon juice, cooked oats with fresh strawberries, and sauteed spinach with red peppers. There’s also some evidence that foods high in beta-carotene can also aid in nonheme iron absorption.

Garlic and onions also increase the availability of nonheme iron when eaten with iron-containing foods. No, I’m not going to give you a recipe for oatmeal with cinnamon and freshly sliced raw garlic on top. Now that I’ve said it, maybe it will be a viral TikTok sensation by next week! But you can benefit from this effect by eating savory grains with cooked or raw onion and garlic dishes.

There are also foods that inhibit iron absorption, including foods containing high concentrations of calcium (some leafy greens and soy foods), tannins (found in coffee and tea), and unsoaked grains or beans (that phytate again).

Vitamin D

Vitamin D is one of the most important nutrients that many of us need more of. Since it’s produced by the body when sunlight hits the skin, those of us with mostly indoor lives are at risk of deficiency. It’s crucial for calcium absorption and is an important nutrient for our immune systems. Research has shown that low levels of vitamin D are associated with poor COVID-19 outcomes. To get your vitamin D from sources other than the sun, you may need to supplement. 

Vitamin D is a team player — it needs vitamins K1 and K2 to do its job of regulating calcium metabolism for bone and heart health, and K2, in particular, seems to boost absorption of D. K2 is another nutrient that’s easy to be deficient in, unless you’re a fan of natto. If you’re not familiar, natto is a fermented soybean dish that’s a breakfast staple in Japan, and provokes very strong opinions ranging from love to, well, not love. Since these vitamins spend a lot of their time and energy shuttling calcium around the body, you want to make sure you’re getting sufficient calcium along with your D and Ks. Some examples of calcium, D, and K combos include tempeh with low oxalate leafy greens and mushrooms, or broccoli with tahini sauce.

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