The jump in nutrient absorption is no small effect. When researchers tried feeding people a healthy salad of spinach, romaine, carrots, and tomatoes along with a source of fat, there was an impressive spike in carotenoid phytonutrients in their bloodstream over the next eight hours. With a fat-free dressing, carotenoid absorption flatlined down to negligible amounts; it was as if they’d never eaten the salad at all.23 Similarly, adding some avocado to your salsa may triple the amount of fat-soluble nutrients that make it into your bloodstream (in this case, the lycopene in the tomatoes).24 It doesn’t take much. Just three grams of fat in an entire hot meal may be sufficient to boost absorption.25 That’s just a single walnut or a spoonful of avocado or shredded coconut. Snack on a few pistachios after a meal, and you’re all set. The greens and the source of fat just have to end up in your stomach at the same time.
Another way to remove bitterness from greens is to blanch or boil them, but unfortunately this works by leaching some of the healthy compounds into the cooking water.26 If you’re making soup, that’s not a problem, because the nutrients aren’t destroyed as much as they are displaced. If the cooking liquid is poured off, however, you could be losing some nutrition. But even if 50 percent of these healthy compounds go down the drain, if the decreased bitterness motivates you to eat twice as many greens, problem solved! Whenever I’m boiling pasta, for example, I’ll add a bunch of fresh greens to the pot a few minutes before I’m ready to drain the pasta. I know I’ll be losing some nutrients when I pour off the cooking water, but it’s worth it to me for the convenience of throwing everything into one pot and getting my family to eat even more greens.
Try to incorporate greens into as many meals as possible. I put just about everything I eat on a bed of greens. That way, the greens take on the flavor of the rest of the dish. However, if you want to eat cooked greens “straight,” you can try adding lemon juice, flavored vinegars, chilli flakes, garlic, ginger, low-sodium soy sauce, or caramelized onions. I personally like mine hot, sweet, smoky, and salty. I use hot sauce for heat, balsamic glaze for sweetness, and both smoked paprika and liquid smoke. For saltiness, I used to be fond of a soy sauce substitute called Bragg Liquid Aminos until I got more serious about cutting down my sodium intake. The best sodium-free salt substitute I’ve been able to find is something called Table Tasty. (What’s with these names?)
There are whole grocery aisles full of prepared sauces with which you can experiment. Most have added salt, oil, or sugar, so I try to reserve them for exceptionally healthy foods. Mixing yellow- and red-light foods together (like dipping your fries and McNuggets in barbecue sauce) may just add insult to injury, but I wouldn’t eat half as many baked rosemary sweet-potato fries if I weren’t dipping them in hot-sauce-spiked ketchup. And if there were ever an excuse to dip out of the green-light zone, it would be for green, leafy vegetables.
During my bachelor days, I would regularly order Chinese food for delivery—usually broccoli and garlic sauce (hold the white rice). Then I’d throw brown rice or quinoa along with dried lentils into my rice cooker and steam or microwave a pound of greens. By the time the delivery arrived, everything was ready and I would just mix it all together and have more than enough for leftovers.
You can also find prepackaged pouches of Indian food online or at Indian or natural foods markets. Again, I’d use them as sauces rather than eat them as a meal in themselves. My favorite is spinach dal—that way, I’m eating greens in a greens sauce! That’s like the kale-pesto principle: Use one green (basil) to make the other green (kale) taste better.
The Health Benefits of Vinegar
Vinegar may be one condiment that’s good for you. Randomized, controlled trials involving both diabetic and nondiabetic individuals suggest that adding two teaspoons of vinegar to a meal may improve blood sugar control, effectively blunting the blood sugar spike after a meal by about 20 percent.27 So adding vinegar to potato salad or to rice (like the Japanese do to make sushi rice) or dipping bread in balsamic vinegar may blunt the effects of these high-glycemic foods.
We’ve known about the antiglycemic effect of vinegar for more than twenty-five years, but we’re still not sure of the mechanism.28 Originally, it was thought that vinegar slowed stomach emptying, but even consuming vinegar outside of meals appears to help. Type 2 diabetics consuming two tablespoons of apple cider vinegar at bedtime, for example, were found to wake up with better blood sugars in the morning.29 Consuming pickles or vinegar pills does not seem to have the same effect.30 Do not, however, drink vinegar straight, as it can burn your oesophagus,31 or in excess—250 ml a day for six years (that’s 500 liters!) was discovered to be a bad idea.32
Vinegar may also help with polycystic ovary syndrome (PCOS), improve arterial function, and help reduce body fat. A daily tablespoon of apple cider vinegar restored ovarian function within a few months in four out of seven women with PCOS.33 A tablespoon of rice vinegar was found to acutely improve artery function in postmenopausal women. We’re not sure why, but the acetate from the acetic acid in vinegar may lead to improved nitric-oxide production (see here).34 Such an effect would be expected to help with hypertension, and indeed there is a study purporting to show blood pressure benefits from a tablespoon of vinegar a day.35
Despite folk wisdom to the contrary, vinegar does not appear to be an effective treatment for head lice,36 but it may help with weight loss. A double-blind, placebo-controlled (but vinegar company-funded) study was performed, in which obese subjects consumed daily vinegar drinks with either one or two tablespoons of apple cider vinegar, or a placebo drink that tasted like vinegar but contained no acetic acid. Both vinegar groups lost significantly more weight than the control group. Though the effect was modest—about four pounds over a three-month period—CT scans showed the vinegar groups’ subjects lost a significant amount of their “visceral” fat, the abdominal fat that is particularly associated with chronic disease risk.37
There are all sorts of flavorful, exotic vinegars to explore these days, including fig, peach, and pomegranate. I encourage you to experiment and find ways to incorporate some into your diet.
Salad Days
Having a big salad every day is a great way to burn through the Daily Dozen. To a base of mesclun greens and rocket, I add tomato, red bell pepper, beans, and barberries, along with toasted nuts if I’m using a fat-free dressing. My current favorite dressing recipe is a Caesar spin-off shared by Dr. Michael Klaper from the TrueNorth Health Center:
2 tablespoons almond meal
3 cloves crushed garlic
3 tablespoons dijon mustard
3 tablespoons nutritional yeast flakes
2 tablespoons white miso
3 tablespoons lemon juice
80 ml water
Blend and enjoy! (If you have a high-speed blender, you could probably use whole almonds instead of meal.)
Baby spinach may have higher levels of phytonutrients than mature spinach leaves,38 but what about real baby spinach—so-called microgreens, the seedlings of vegetables and herbs? A nutritional analysis of twenty-five commercially available microgreens found they did have significantly higher nutrient densities. For example, red cabbage microgreens have a sixfold higher vitamin C concentration than mature red cabbage and nearly seventy times the vitamin K.39 But they’re eaten in such microquantities that even the healthiest upscale restaurant garnish probably isn’t going to do much for you.
If, however, you want to grow your own, you could have rotating trays of microgreens that you snip off with scissors for probably the healthiest salad out there. (On a lecture tour, I once stayed with someone who did just that, and I’ve been jealous ever since.) Microgreens are the perfect plants for the impatient gardener—fully grown in just one to two weeks.
The One Green to Avoid
Although greens are the healthiest of foods, there’s one green I caution against eating: alfalfa sprouts. Over a dozen years, twenty-eight outbreaks of Salmonella food poisoning linked to sprouts have been documented in the United S
tates, affecting 1,275 people.40 Of course, Salmonella-tainted eggs sicken an estimated 142,000 Americans every year,41 but that doesn’t make it any less tragic for those hospitalized and killed in “sproutbreaks.” Alfalfa sprout seeds have all sorts of microscopic nooks and crannies where bacteria from manure-contaminated irrigation water can hide. So even home-sprouted alfalfa seeds should not be considered safe.
I will never forget a presentation I gave in Boston. It was in a game show-style format in which contestants from the audience tried to rank, from healthiest to unhealthiest, the foods I’d brought with me. There was a lively cacophony of conflicting advice shouted from the crowd. You can imagine the groans when I revealed that alfalfa sprouts—a quintessential health food—belonged way at the top on the foods-to-avoid list.
Later that night, I was stuck with the sprouts after all the healthier and yummier items had been given away as prizes. I had just told my audience not to eat them—but I hate wasting food. In a do-as-I-say-not-as-I-do moment, I added them to my salad that night. Yes, they had been sitting in the car all day and on stage for hours. Yes, they were at the top of my game show’s list of foods you should not eat. But, what were the odds that that one particular package was contaminated? I went back to work the next day at the New England Medical Center emergency room—not as a physician but as a patient with Salmonella food poisoning.
So other than the dreaded alfalfa sprout, greens truly are the healthiest foods on the planet. You simply can’t do better in terms of nutrition per calorie. Explore, innovate, taste test, play, and teach your palate to enjoy them. Whether you sneak them into a refreshing smoothie, incorporate them into sauces and dressings, use them as a base for main dishes, or eat them straight in a big, vibrant salad—just do it. Your body will thank you with every bite of greens you take.
Other Vegetables
Dr. Greger’s Other Favorite Vegetables
Artichokes, asparagus, beetroot, peppers, carrots, sweetcorn, garlic, mushrooms (button, oyster, portobello, and shiitake), okra, onions, purple potatoes, pumpkin, sea vegetables (arame, dulse, and nori), snap peas, squash (delicata, summer, and spaghetti squash varieties), sweet potatoes/yams, tomatoes, and courgette
Serving Sizes:
60 g raw leafy vegetables
50 g raw or cooked nonleafy vegetables
125 ml vegetable juice
7 g dried mushrooms
Daily Recommendation:
2 servings per day
The mammoth Global Burden of Disease Study identified the typical American diet as the primary cause of Americans’ death and disability1 and inadequate vegetable intake as our fifth-leading dietary risk factor, nearly as bad as our consumption of processed meat.2 The Union of Concerned Scientists estimates that if the nation increased its consumption of fruits and veggies to meet the dietary guidelines, we might save the lives of more than one hundred thousand people a year.3
You should eat more fruits and vegetables as if your life depended on it, because maybe it does.
Garden Variety: Diversifying Your Vegetable Portfolio
Perhaps the least controversial advice in all of nutrition is to eat more fruits and vegetables, which is to say eat more plants, since the term vegetable basically just means all parts of the plant that aren’t fruit. There are root vegetables like sweet potatoes, stem vegetables like rhubarb, pod vegetables like peas, and even flower vegetables like broccoli. (It isn’t called cauliflower for nothing.) We’ve already talked about the leaf vegetables in the greens section. If dark-green, leafy vegetables are the healthiest foods around, then why branch out to other parts of the plant? (Pun intended!) Yes, you’re supposed to eat the rainbow, but didn’t we just learn that green leaves have an entire spectrum of colors hidden inside?
Unlike more generic compounds like vitamin C, which is broadly available in various fruits and vegetables, other nutrients are not so evenly distributed. Just as certain fruits like citrus offer unique nonpigment phytonutrients not found in other fruits, different vegetables contribute different compounds. White cauliflower, lacking antioxidant pigments, doesn’t appear to have much to offer at first glance, but because it belongs to the cruciferous family, it’s one of your healthiest options. Similarly, white mushrooms may look pretty drab, but they can provide myconutrients not found in the entire plant kingdom.
We now know that certain phytonutrients bind to specific receptors and other proteins in the body. I talked about the Ah “broccoli receptors” in chapter 5. There are also effectively green-tea receptors in your body—that is, receptors for EGCG, a key component of green tea. There are binding proteins for the phytonutrients in grapes, onions, and capers. Recently, a cell surface receptor was even identified for a nutrient concentrated in apple peels. These specific proteins may not be activated, though, unless you eat specific foods.4
The different phytonutrient profiles may then result in different clinical effects. For example, drinking tomato juice can rescue the immune function of study subjects crippled by two weeks of fruit and vegetable deficiency, but carrot juice apparently cannot.5 Even different parts of the same vegetable can have different effects. One of the reasons certain tomato products appear to be protective against heart attacks6 is because the yellow fluid surrounding the seeds concentrates a compound that suppresses platelet activation.7 (Platelets are what help trigger the blood clots that cause heart attacks and most strokes.) Aspirin has a similar effect, but it doesn’t work in everyone and can increase bleeding risk—two limitations that the tomato compound may be able to overcome.8,9 But if you only consume tomato sauce, juice, or ketchup, you may be missing out10 since the seeds are removed during processing. So when picking out tinned tomato products, choose whole, crushed, or chopped tomatoes instead of tomato sauce, purée, or paste.
Different plants may also affect the same part of the body in different ways. Consider mental function, for instance. In a study of dozens of fruits and vegetables, from raspberries to swedes, certain plants appear to shore up specific cognitive domains. For example, the consumption of some plant foods was associated with better executive function, perceptual speed, and semantic (fact-based) memory, while the consumption of others was more consistently associated with visual-spatial skills and autobiographical memory.11 In other words, you may need to build up a portfolio of many fruits and vegetables to cover all your bases.
One of the reasons studies may underestimate the protective effects of plant foods is that they tend to measure quantity of fruit and vegetable consumption rather than quality of fruit and vegetable consumption. People are more likely to eat bananas and cucumbers than blueberries and kale. But variety is important too. Half the fruit servings in the United States are taken up by just five fruits—apples and apple juice, bananas, grapes, orange juice, and watermelon—and most vegetable servings are from tinned tomatoes, potatoes, and iceberg lettuce.12
In one of the few studies that looked specifically at the diversity of fruit and vegetable consumption, the variety of intake was an even better predictor of decreased inflammation in the bodies of middle-aged adults than the absolute quantity of consumption.13 Even after removing the effects of quantity, the addition of two different types of fruits and vegetables per week has been associated with an 8 percent reduction in the incidence of type 2 diabetes.14 These kinds of data led the American Heart Association to add a recommendation in their latest dietary guidelines to also eat a variety of fruits and vegetables.15 It’s an important addition; otherwise, a big bag of crisps or one head of iceberg lettuce could technically fulfill or exceed your recommended nine servings a day.
It’s better to eat a whole orange rather than take a vitamin C pill, since the pill deprives you of all the other wonderful nutrients in the oranges themselves. The same principle applies when you don’t diversify your fruit and vegetable consumption. By only eating apples, you also miss out on oranges’ nutrients. You don’t get the limonoids in citrus, like limonin, limonol, or tangeretin, though you may get more m
alic acid (from the Latin malum, meaning apple). When it comes to the unique phytonutrient profile of each fruit and vegetable, it’s like comparing apples to oranges! That’s why you should mix it up.
In a sense, though, all fruits are just fruits, whereas vegetables can be any other part of the plant. Roots may harbor different nutrients than shoots. For this reason, it may be even more important to get in a variety of vegetables, so you can benefit from all parts of the plant, as one large cancer study of nearly half a million people did indeed find.16 “Because each vegetable contains a unique combination,” a recent review concluded, “a great diversity of vegetables should be eaten . . . to get all the health benefits.”17 Variety is not only the spice of life; it may prolong it as well.
Eating Better to Look Better
We’ve all heard of the proverbial golden glow that’s often equated with health, vitality, and youth. But instead of using a sunbed to achieve a more golden hue, you can do it with a bed of greens.
There are certain animals who use diet to increase their sexual attractiveness. Great tits, distinctive olive-and-black songbirds ubiquitous throughout Europe and Asia, tend to prefer carotenoid-rich caterpillars, which make their breast plumage brighter yellow, to become more attractive to potential mates.18 Can a similar phenomenon be found in humans?
Researchers took digital photographs of African, Asian, and Caucasian men and women and asked others to manipulate the skin tone of their faces with a dial until they reached what they perceived to be the healthiest-looking color.19 Sure enough, both men and women preferred the yellow “golden glow” that can be achieved through “dietary carotenoid deposition in the skin.”20 In other words, by eating the yellow and red pigments in fruits and vegetables, like beta-carotene in sweet potatoes and lycopene in tomatoes, men and women may be able to naturally acquire more of a golden and rosy glow. Researchers decided to put it to the test.
How Not to Die Page 41