Whether you’re a fan of a crisp, refreshing green juice or a velvety vegetable smoothie, here’s what you need to know about these two delicious, health-supporting beverages.
Green juices and smoothies are an easy – and tasty – part of a Nutritarian diet. But while either will help you ramp up your intake of raw leafy greens and other veggies, there are a few things to remember: Don’t go overboard on the fruit. Do be aware of calorie density (more on this later). And don’t substitute them for your daily main dish salad.
Supporting satiety and healthy blood glucose levels
Whether you call it a blended salad or a green smoothie, this mix of leafy greens, fruit and nuts and/or seeds is an excellent, portable morning meal. It contains all the fiber from the greens and fruit, plus fat from the nuts or seeds to keep you full and limit the rise in blood glucose from the fruit.
On the other hand, a vegetable juice with a small amount of fruit, depending on size, may be as calorie-dense as the smoothie, but will not be a satisfying meal on its own. For this reason, if you have a substantial amount of weight to lose, I wouldn’t recommend juicing too often (in addition to your meals) because it will likely add too many extra calories without the feeling of satiety and compromise your weight loss efforts.
Whether you’re making a smoothie or a juice, remember to put the focus on the vegetables, not the fruit, to limit calorie density and glycemic effects.
Intermittent fasting
If you do have weight to lose, a green juice can be used in place of a meal as part of an intermittent fasting program that reduces calorie intake dramatically a few days per week. A juice provides a rich source of nutrients in place of lunch or dinner on low-calorie days, and a smoothie works as a satiating, greens- and berries-packed breakfast.
Even if you don’t have weight to lose, episodic restriction of calories to extend the overnight fasting period enhances the body’s ability to heal and repair. The body has natural detoxification and repair mechanisms that kick in when we are in the fasting state. Occasionally replacing dinner with a vegetable juice is a great way to achieve this.
Micronutrient content and availability
Blending and juicing both disrupt the mechanical structure of plant cells, which increases the accessibility of many micronutrients. Many beneficial micronutrients – carotenoids, polyphenols, and folate for example – are often bound to structural components or large molecules within the plant cell like fiber, proteins, and starches. Processing, heating, and chewing break down these cellular structures to increase the availability of the bound micronutrients; however, many may not be accessible for our absorption by chewing alone. Blending increases our likelihood of absorbing these nutrients. Some micronutrients – those that are bound to fiber within the plant cell – may be removed with the fiber by juicing, and therefore be more available via blending than juicing.1
With green smoothies, you are adding nuts or seeds as a healthful fat source. Although blending alone increases the accessibility of carotenoids, since the presence of fats is known to increase carotenoid absorption from leafy greens,1,2 it is likely that nuts and seeds in a smoothie could increase absorption further.
Green juices pack in extra nutrients using a quantity of vegetables that would be difficult to eat in one sitting, or even in a smoothie. You can get two pounds of vegetables into one glass of juice. This lets you quickly increase the level of phytochemicals in your tissues or simply increase your intake of carotenoids, isothiocyanates, and other beneficial phytochemicals.
For those who have nutrient absorption problems, gastrointestinal conditions, or other medical conditions, vegetable juices (especially cruciferous vegetables) are often useful as a supplement to a healthful diet, providing additional beneficial nutrients to promote healing. For people with gastrointestinal issues, juicing can be a good way to rest the digestive system while maintaining a high intake of these beneficial nutrients.
Guidelines for juicing and blending
- A green smoothie can be a meal substitute, while a vegetable juice is better viewed as a supplement to add extra leafy green-derived nutrients to a healthful diet.
- Limit smoothies and green juices to one per day
- It is important to chew some vegetables every day, so eat a raw salad daily.
- Juices should be made up of one-third green cruciferous vegetables (such as kale, collards, and/or bok choy), one-third non-cruciferous green vegetables (such as lettuce, cucumber, and/or celery), and one third high-antioxidant flavorful vegetables (carrots, beets).
- Having a green juice occasionally instead of dinner can help you practice episodic caloric restriction and increase the body’s time in heal and repair mode.
- Maximize the nutritional value and limit glycemic effects of both smoothies and juices, by using mostly leafy greens and other vegetables and adding only a small amount of fruit for flavor (such as half of a green apple or 1 cup of berries in a juice).
- Don’t juice spinach, parsley or Swiss chard because of their oxalic acid content (which limits calcium absorption).
Sources
1. Food microstructure affects the bioavailability of several nutrients
2. Carotenoid bioavailability is higher from salads ingested with full-fat than with fat-reduced salad dressings as measured with electrochemical detection
Originally printed on Dr. Fuhrman’s blog. Reprinted with permission from Joel Fuhrman, MD.
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Joel Fuhrman, M.D. is a board-certified family physician, seven-time New York Times bestselling author and internationally recognized expert on nutrition and natural healing, who specializes in preventing and reversing disease through nutritional methods. Dr. Fuhrman coined the term “Nutritarian” to describe his longevity-promoting, nutrient dense, plant-rich eating style. For over 30 years, Dr. Fuhrman has shown that it is possible to achieve sustainable weight loss and reverse heart disease, diabetes and many other illnesses using smart nutrition. In his medical practice, and through his books and PBS television specials, he continues to bring this life-saving message to hundreds of thousands of people around the world.
