The Juice Effect: The Top 40 Juices and Their Benefits to Your Health
Carrots can be combined with other fruits and vegetables to make tasty juices. A person can try the following recipes at home:. Carrots contain antioxidants , which may explain their role in cancer prevention. In a review of studies , researchers looked at the effect of eating carrots on the risk for stomach cancer. They concluded that eating carrots was associated with a 26 percent lower risk for stomach cancer. However, they did not specify how many had to be eaten to lower stomach cancer risk.
More controlled studies are needed to confirm this association. More research is needed, but carrot juice may have a future role in leukemia treatment. In one study , researchers looked at the effect of carrot juice extracts on leukemia cells. The carrot juice extracts caused the leukemia cells to self-destruct and stopped their cell cycle. A study of breast cancer survivors looked at the effect of carrot juice on levels of carotenoids, markers of oxidative stress , and markers of inflammation in the blood.
The researchers reported that higher levels of carotenoids in the blood were associated with a lower risk of breast cancer returning. During the study, participants consumed 8 ounces of carrot juice daily for 3 weeks.
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At the end of the study, the women had higher blood levels of carotenoids and lower levels of a marker associated with oxidative stress. Carrot juice is high in vitamin C. Researchers looked at the association between dietary vitamin C intake and chronic obstructive pulmonary disease COPD in Korean adults aged 40 years or older.
They found that people with COPD had significantly lower intakes of multiple nutrients found in carrot juice, including carotene, potassium, vitamin A, and vitamin C, than people without COPD. For people who smoked heavily, the risk of COPD is lower in those who consumed more vitamin C than those who consumed very little. People with weakened immune systems — such as those receiving cancer treatment, pregnant women, young children, and older people — may need to avoid certain foods if there is a risk of these carrying food-borne illnesses.
Fruit and vegetable juices that are freshly squeezed or have not been pasteurized may have a higher risk of carrying germs. The Memorial Sloan Kettering Cancer Center state that people who have been told to follow a low-microbial diet should avoid unpasteurized fruit and vegetable juices unless they are made at home.
According to the U. Freshly squeezed juices, which may be sold at farmers' markets or juice bars, should also be avoided. Carrots contain a type of carotenoid called beta-carotene that the body can convert into vitamin A. Eating large amounts of carotenoids from foods has not been linked with harmful effects.
However, the skin can turn yellow-orange if a person consumes large amounts of beta-carotene for a long time. This effect is called carotenoderma. Carrot juice may offer many health benefits due to the concentrated levels of nutrients it contains. However, carrot juice has less fiber and more sugar than whole carrots.
Fiber is associated with weight management and lowering cholesterol levels. Carrot juice may not be appropriate for everyone, especially pregnant women, young children, the elderly, and people with certain illnesses, depending on how it is prepared.
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Carrot juice in moderation can be included as part of a healthy diet. However, drinking juice is not a replacement for eating whole fruits and vegetables. Article last reviewed by Wed 13 December Most estimates of fruit and vegetable consumption are limited by disagreement on what constitutes a serving of a fruit or vegetable. Dietary fiber intake was particularly low in their analysis.
Common serving sizes of fruits and vegetables contain 1—5 g of fiber.
Most of the fiber in vegetables and fruits is insoluble fiber, except for citrus fruits Table 3. The importance of fiber for the normal function of the digestive system has been long appreciated. As the scientific support for a role for resistant carbohydrates not captured by the crude fiber method such as pectin, glucans, and oligosaccharides was published, additional analytical methods to measure more carbohydrates resistant to digestion and absorption were needed.
Accepted analytical methods to determine dietary fiber were then developed, especially because fiber was included on the Nutrition Facts panel. Nutrition Facts must include total dietary fiber TDF ; insoluble and soluble fiber also may be listed but are not required unless claims are made.
Besides food manufacturers, epidemiologists, scientists, and dietitians need data on the fiber content of foods 8. Yet attempts to define and standardize methods to measure dietary fiber remain contentious. Dietary fiber is essentially the undigested carbohydrates in the diet 9. These carbohydrates may be fermented in the large intestine, although some resistant fibers, such as purified cellulose, escape any fermentation, whereas other fibers, such as inulin or pectin, are completed broken down by bacteria in the colon.
Most analytical schemes to measure dietary fiber are chemical and enzymatic extraction procedures. Because the TDF method does not isolate all undigested carbohydrates, especially short-chain oligosaccharides, other methods have been developed and accepted to quantitate these compounds. Determining the solubility of fiber was an attempt to relate physiological effects to chemical types of fiber 9. Soluble fibers were considered to have beneficial effects on serum lipids and insoluble fibers were linked with laxation benefits. This division of soluble and insoluble fiber is still used in nutrition labeling.
However, despite these commonly used generalizations, scientific evidence supporting that soluble fibers lower cholesterol and insoluble fibers increase stool weight is inconsistent. Many fiber sources are mostly soluble but still enlarge stool weight, such as oat bran and psyllium. Also, soluble fibers such as inulin do not lower blood lipids.
Most fruits and vegetables are concentrated in insoluble fiber, not soluble fiber Table 3. Exceptions to this generalization include cooked potatoes, oranges, and grapefruit. The USDA Nutrient Database includes only total fiber; there are no official databases that include soluble and insoluble fiber.
Lists of content of total, insoluble, and soluble fibers are compilations of data from the USDA, the published literature, and estimated values Often, the values for soluble and insoluble fiber do not add to total fiber or the values for soluble fiber were estimated by subtracting a literature value for insoluble fiber from a USDA value for total fiber. Not surprisingly, there is much discrepancy in the fiber concentrations for fruits and vegetables. Processing can either increase or decrease the fiber content of a fruit or vegetable.
Peeling fruits or vegetables will lower the fiber content A serving of grapefruit without any associated membrane contains much less fiber than a grapefruit serving with membranes 0. Home cooking generally has a negligible effect on fiber content. Cooking, in general, may even increase the fiber content of a product if water is driven out in the cooking process. Baking or other heat treatments e. Fruit juices are not devoid of fiber Table 4. Increasingly, research indicates that additional properties, such as viscosity and fermentability, are important characteristics in terms of the physiological benefits of fiber Table 5.
Viscous fibers are those that have gel-forming properties in the intestinal tract, and fermentable fibers are those that can be metabolized by colonic bacteria. In general, soluble fibers are more completely fermented and have a higher viscosity than insoluble fibers.
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However, not all soluble fibers are viscous e. Fibers, like starches, are made mostly of many sugar units bonded together. Unlike most starches, however, these bonds cannot be broken down by digestive enzymes and pass relatively intact into the large intestine. There, fiber can be fermented by the colonic microflora to gases such as hydrogen and carbon dioxide or it can pass through the large intestine and bind water, increasing stool weight. Although fibers are not converted to glucose, some SCFA are produced in the gut as fibers are fermented. SCFA are absorbed and can be used for energy in the body.
This value is derived from data on the relationship of fiber consumption and coronary heart disease CHD risk, although the IOM also considered the totality of the evidence for fiber decreasing the risk of chronic disease and other health-related conditions.
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Consequently, the IOM fiber recommendations are highest for populations who consume the most energy, namely young males. Fiber recommendations are lower for women and the elderly. Using this method for determining recommended fiber intake for children is problematic e. The past recommendations for children were based on the age plus 5 rule e. Dietary fiber is listed on the Nutrition Facts panel and 25 g of dietary fiber is the recommended amount in a kcal diet. Dietary fiber on food labels includes both dietary fiber and functional fiber.
In the IOM developed the following set of working definitions for fiber To make recommendations for fiber intake, the IOM used prospective cohort studies that linked fiber intakes to lower risk of cardiovascular disease CVD. In establishing the dietary recommended intakes, the IOM 14 recommended an AI level of 14 g of fiber for each kcal of energy consumed for all individuals from 1 y of age throughout the remainder of their lives. Most commonly consumed foods are low in dietary fiber Table 3. Generally, accepted servings of food contain from 1 to 3 grams of fiber per serving.
Higher fiber contents are found in drier foods such as whole-grain cereals, legumes, and dried fruits. Other fiber sources include over-the-counter laxatives containing fiber, fiber supplements, and fiber-fortified foods. The major sources of dietary fiber in the American diets are white flour and potatoes, not because they are concentrated fiber sources but because they are widely consumed 9. Vegetarian diets have been promoted since the 18th century by men and women in search of physical and spiritual health Vegetarian theorists who professed to follow the tenets of the ancient philosopher Pythagoras believed that diet should be part of an ascetic lifestyle.
Vegetarianism was also symbolic of a commitment to health and social reform. Southgate 16 described the nature and variability of human food consumption and the role of plant foods in these relationships. A wide range of plant foods is consumed, including most parts of the plant, such as fruits, seeds, leaves, roots, and tubers. The compositional features of plant foods are summarized Table 6 Fruits have a high water content and low levels of protein and fat.
The protein is concentrated in the seeds and is resistant to digestion in the small intestine and bacterial degradation in the large intestine. Fruits contain mostly sugars and fibers, such as pectin, that are extensively fermented in the large intestine. Certain fruits, especially apples and pears, are concentrated in fructose Free fructose is poorly absorbed and would function similar to dietary fiber, escaping absorption in the small intestine while being fermented in the large intestine.
This results in SCFA production, which is linked to small amounts of energy being absorbed in the colon. Additionally, it explains why apple and pear juices are used to treat constipation in children. Fruits are also recommended as a source of vitamin C and potassium. Traditionally, fruits, as foodstuffs were available for a limited time and, when ripe, were sometimes difficult to collect and transport. When ripe, they have a short period of acceptability before senescence intervenes. Leaves and stems are widely consumed by humans. The protein contents are higher than fruits and they contain low amounts of sugar.
Leaves and stems are bulky to transport and not very stable when stored. Also, some produce secondary metabolites that have bitter or astringent properties and may produce toxic alkaloidal and other compounds such as hemoglutenens. Others produce intestinal enzyme inhibitors, such as lectins, which bind to mucosal surfaces and inhibit digestion, especially that of proteins Roots and tubers are important sources of energy as starch Table 6.
Some roots such as cassava contain toxic secondary metabolites and require soaking in water before they are safe to consume. As foodstuffs, roots, and especially tubers, can be time-consuming to collect but can be stored for long periods. Legumes are higher in protein that other vegetables but contain toxic plant metabolites, including saponins and lectins The wide use of these products was much later in evolution, once foods were cooked in water.
Southgate 16 lists the following as factors determining food choice: It is generally accepted that the preference for sweet tastes is instinctive and the avoidance of bitter tastes would protect against the consumption of plant foods containing toxic alkaloids or other bitter plant constituents. Higher fat diets may have had advantages for satiety and concentration of energy and supported the consumption of foods such as meat or fish. Southgate 16 discussed the selection of dietary mixtures to meet nutrition requirements.
The protein content of fruits is inadequate to support growth and development. Thus, dietary guidance over time has supported the principles of moderation and variety. No food group has all the nutrients needed to support life. By consuming a variety of foods, humans avoided getting toxic doses of any component and also were successful in obtaining the required protein, vitamins, and minerals needed for growth, development, reproduction, and for sustaining life. Historically, the consumption of certain plant foods, fruits, vegetables, and legumes was thought to prevent or curve ailments ranging from headaches to heart disease Early medicine revolved around the prescription of specific foods for certain disorders.
Many of these plant foods are also high in dietary fiber and phytoestrogens, so the later hypotheses often were driven by fiber, carotenoids, phytoestrogens, or other plant chemicals. Of course, determining the relationship between any dietary component and health outcomes is difficult, because diet is a complicated exposure; each day we eat a variety of foods and nutrients and linking any particular food or nutrient to a health or disease outcome is limited. The fiber hypothesis of the s was driven by stories that populations who consumed high-fiber diets had little chronic disease 9.
Although these stories were often entertaining, especially accounts of the large stools associated with these healthy, nomadic people, confounding variables were not considered at the time. Scientific estimates of the intake of fiber in these populations do not exist, although it is generally accepted that the diets were high in poorly digested carbohydrates.
Current scientific thinking demands a more evidence-based review of research support. In the hierarchy of evidence, randomized controlled trails are considered the strongest support for studying dietary risk factors and disease For epidemiologic studies, prospective cohort studies are deemed the strongest study designs to examine diet and disease relationships. Cross-sectional and case-control studies are weaker epidemiologic study designs to determine diet and disease relationships. Intervention trials are strong support for these relationships, especially because in these smaller studies, it is possible to determine the biomarkers of interest in disease prevention.
Dietary data are generally collected with food frequency instruments in epidemiologic studies. Estimates of total, soluble, and insoluble fiber are limited by the poor methods to measure these substances and inadequate databases. In epidemiologic studies, it is possible to count the number of servings of fruits and vegetables consumed daily if there is agreement on what counts as a serving of fruit or vegetable. Of course, fruits and vegetables vary greatly in composition. In the 18th century, botanical definitions were standardized and the definition of a fruit was based on its anatomy, whereas that of a vegetable was based on culinary usage.
Generally, culinary custom dictates which plant foods are considered vegetables or fruits. A drawback of using a culinary definition is the misclassification of botanical fruits, e. Within each category, other classifications can be used. For example, for vegetables, raw, cooked, canned, pickled, leafy green, and legumes are often examined. Fruits and vegetables have also been described as part of a phytochemical group, e. Other challenges of determining exposure to fruits and vegetables are that fruits are often consumed as juices and vegetables are often consumed in mixed dishes such as soups, casseroles, and stews.
Components of fruits and vegetables that have been linked to health outcomes are often placed in different categories Table 7 A wide range of compounds, beyond dietary fiber, have been linked to lower incidence of chronic diseases, especially cancer and CVD. Additionally, there are compounds in fruits and vegetables that have been linked to adverse health events Table 7. Compounds, such as phenols, are listed in both the protective and adverse lists.
Earlier reviews that included cross-sectional studies found stronger support for the protective properties of fruit and vegetable intake and disease prevention. Steinmetz and Potter 20 concluded that the scientific evidence regarding a role for vegetable and fruit consumption in cancer prevention is generally consistent and supportive of current dietary recommendations. Yet Hung et al. They concluded that increased fruit and vegetable consumption was associated with a modest, although not significant reduction in the development of major chronic disease.
Riboli and Norat 25 also concluded that prospective studies provide weaker evidence than do case-control studies of the association of fruit and vegetable consumption with reduced cancer risk. No association was found for total fruits, total vegetables, or total fruits and vegetables. No additional benefit was found in comparisons of the highest and lowest deciles of intake.
Additionally, no associations were observed for green leafy vegetables, 8 botanical groups, and 17 specific fruits and vegetables. They concluded that fruit and vegetable consumption during adulthood is not significantly associated with reduced breast cancer risk. Other recent studies have measured the relationships between fruit and vegetable consumption and health outcomes. They agreed that under rigorous, controlled experimental conditions, fruit and vegetable consumption is associated with decreased blood pressure. In a population-based cohort study in The Netherlands, higher consumption of fruit and vegetables, whether consumed raw or processed, was protective against CHD incidence A systematic review and meta-analysis of fruit and vegetable intake and incidence of type 2 diabetes included 6 studies, 4 of which provided separate information on the consumption of green leafy vegetables You often hear opposing opinions on the topic of juicing.
One camp promotes extreme juicing [where you only consume juice] as a way to cleanse your body for around 10 days. The other camp thinks that juicing should be treated as a handy supplement to your daily diet; allowing you to increase antioxidant intake from an avalanche of vegetables that you wouldn't otherwise consume in one day. Why do we need to increase our antioxidant intake? Surely if we have a good diet, we're already getting what we need? The thought that we can obtain all of our nutritional needs from our diets alone is now somewhat of a long lost dream.
Nutrient levels in the foods we eat are much lower than they once were, thanks in part to over-farmed soil and the often ridiculously convoluted routes to market that some of our fruit and veg undergoes. We also live in increasingly polluted environments, and experience high levels of stress — both of which increase our requirement for antioxidants. The truth is that the Government's 5 a day recommendations only scratch the surface when it comes to optimum antioxidant intake.
Active people should ideally aim for portions of fruit and vegetables per day, predominantly vegetables. But that's impractical, which is where juicing comes in. So why does juicing get a bad rap? Everyone likes to have opinions on the latest dietary 'fad'. A common negative comment on juicing is that it "contains too much sugar and not enough fibre" — which has more than a grain of truth to it, if you are drinking fruit juices without other fibre in your diet [fibre is found in whole foods and slows the release of sugar into the bloodstream].
A nd then there's the accusation that it's "not natural" — ie we should be eating the fruit and vegetables whole because that's how Mother Nature intended it. That way we get a healthy hit of antioxidants — and the fibre that our bodies need to regulate their assimilation. Again, this is informed by sound thinking. Almost definitely — but that doesn't by extension make juicing a bad thing. The truth is that humans alter the state of a lot of ingredients. Of course, food is best consumed in its wholefood state, but we seem to be able to adapt reasonably well when it's processed into something else.
The problem with juicing is that people mistakenly think that all juices are created equal. Downing a litre of concentrated pasteurised orange juice that's depleted of nutrients and enzymes is almost comparable to drinking sugared water. Pasteurised, cheap fruit juices which can happily sit on the shelves for months unchanged offer little to no nutritional content except for a fast release of glucose into the blood stream, which causes an insulin spike, encouraging fat storage. I n contrast, juice containing raw, cold, pressed vegetables and low sugar fruits — think: But it might not taste quite as nice the first few times you try it if your taste buds are used to high sugar fruit juices!