Basic Description
Vitamin C may be the most familiar of all of the nutrients. Although most adults would be hard pressed to name a good food source of biotin or riboflavin, most everyone can name citrus fruits good sources of vitamin C. It is also a commonly used nutritional supplement, with many outsized claims for its clinical efficacy.
The first use of modern scientific methods to assess disease treatment was when the British navy used foods containing vitamin C (although the vitamin itself would remain undiscovered for nearly two centuries) to prevent scurvy among sailors. You could make a good case that this nutrition experiment is among the most important scientific findings in human history.
Though most of us are familiar with vitamin C and can name foods that contain it, it is to this day a common nutrient deficiency. This is a shame because so many tasty and easy-to-prepare foods deliver large amounts of this nutrient.
Of the World's Healthiest Foods, a staggering 29 rate as excellent sources of vitamin C. Six of these contain a full day's requirement of vitamin C in a single serving. We also rate 13 very good and 14 good sources of the vitamin. This should give you plenty of variety with which to build a menu plan that easily exceeds your vitamin C goal.
Role in Health Support
Protection Against Free Radicals
Vitamin C is probably best known in the modern world as an antioxidant. This is a word that we use frequently but is surprisingly hard to understand or define. If we define free radicals as a smoldering fire creating damage to body structures, then antioxidants are best described as a fire extinguisher, able to neutralize these radicals, and dispose of them without creating any damage along the way.
Dietary vitamin C has been shown to fit this description well. Some of the items possibly protected by dietary vitamin C include the lens of the eye, cholesterol in the blood stream, and DNA in your cell nucleus.
One interesting application of vitamin C as an antioxidant is its ability to reduce iron into a state that is better absorbed in the intestine. Including vitamin C-rich foods in recipes with your best iron sources can potentially be a way to enhance iron absorption.
Collagen
Vitamin C is required to produce collagen, a protein that plays a critical role in the structure of our bodies. Collagen is the framework for our skin and our bones, and without it, we would quite literally fall apart.
This is exactly what we see with severe vitamin C deficiency, or scurvy. People who have this condition lose teeth, bleed easily, and lose the strength of their bones. Luckily, it doesn't take much vitamin C to prevent this problem. As we've known for more than two centuries, a single lime per day should be enough.
Brain Health
Vitamin C is necessary to make certain neurotransmitters. These neurotransmitters are the signals that carry thoughts, feelings, and commands around our brains.
In particular, we need vitamin C to produce serotonin, the neurotransmitter that is affected by the most commonly used medications for depression. While we are not suggesting that vitamin C from foods or from supplements would have a similar effect to drug therapies for depression, we do recommend including fresh fruits and vegetables in the diet regularly as part of an overall mood support strategy.
Summary of Food Sources
Our best food sources of vitamin C have a single thing in common: they are all plant foods. Even though many—even most—animals make vitamin C in their bodies, only plants make it to the degree that they provide a rich source of the nutrient when eaten.
Probably most of you associate citrus fruits with vitamin C. This is not a myth—all of our listed citrus fruits (orange, grapefruit, lime, and lemon) are excellent sources of vitamin C.
Many non-citrus fruits are highly rated sources, as well. Papaya, strawberries, pineapple, kiwifruit, cantaloupe, and raspberries are also excellent vitamin C sources. Cranberries, blueberries, and watermelon are examples of very good sources, while apples, pears, and bananas are in the good category. You should expect almost any fresh fruit to be a good or better source of dietary vitamin C.
In addition, many vegetables contain vitamin C. All of the greens on our website are excellent sources of vitamin C. We are big fans of green leafy vegetables as sources of many nutrients and encourage their inclusion in daily diets. Our 3-Minute Swiss Chard is an easy and tasty recipe to get you started.
Many of the cruciferous vegetables are excellent sources of vitamin C. These foods have many potential health benefits and are the focus of many of our recipes. Some of the other vegetables that are very good to excellent sources of vitamin C are technically fruits, including tomatoes, bell peppers, and squash.
Some spices even make significant contributions to overall vitamin C intake. Just 2 tablespoons of parsley contain 13% of your daily requirement.
In case you are feeling lost in the flurry of good vitamin C sources, let's take a step back and make this easy. If you are getting two to three servings of fruit per day, and three to five servings of vegetables, you are almost certainly getting enough dietary vitamin C. If you find yourself worried, make sure you get a serving of fresh green leafy vegetables daily, as this will get you half way to the requirement in one sitting.
Nutrient Rating Chart
Introduction to Nutrient Rating System Chart
In order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the World's Healthiest Foods that are either an excellent, very good, or good source of vitamin C. Next to each food name, you'll find the serving size we used to calculate the food's nutrient composition, the calories contained in the serving, the amount of vitamin C contained in one serving size of the food, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration's "Reference Values for Nutrition Labeling." Read more background information and details of our rating system.| World's Healthiest Foods ranked as quality sources of vitamin C | ||||||
|---|---|---|---|---|---|---|
| Food | Serving Size | Cals | Amount (mg) | DRI/DV (%) | Nutrient Density | World's Healthiest Foods Rating |
| Papaya | 1 medium | 118.7 | 168.08 | 224.11 | 34.0 | excellent |
| Bell Peppers | 1 cup | 28.5 | 117.48 | 156.64 | 98.9 | excellent |
| Broccoli | 1 cup | 54.6 | 101.24 | 134.99 | 44.5 | excellent |
| Brussels Sprouts | 1 cup | 56.2 | 96.72 | 128.96 | 41.3 | excellent |
| Strawberries | 1 cup | 46.1 | 84.67 | 112.89 | 44.1 | excellent |
| Pineapple | 1 cup | 82.5 | 78.87 | 105.16 | 22.9 | excellent |
| Oranges | 1 medium | 61.6 | 69.69 | 92.92 | 27.2 | excellent |
| Kiwifruit | 1 2 inches | 42.1 | 63.96 | 85.28 | 36.5 | excellent |
| Cantaloupe | 1 cup | 54.4 | 58.72 | 78.29 | 25.9 | excellent |
| Cauliflower | 1 cup | 28.5 | 54.93 | 73.24 | 46.2 | excellent |
| Kale | 1 cup | 36.4 | 53.30 | 71.07 | 35.1 | excellent |
| Cabbage | 1 cup | 43.5 | 51.60 | 68.80 | 28.5 | excellent |
| Bok Choy | 1 cup | 20.4 | 44.20 | 58.93 | 52.0 | excellent |
| Grapefruit | 0.50 medium | 41.0 | 44.03 | 58.71 | 25.8 | excellent |
| Parsley | 0.50 cup | 10.9 | 40.43 | 53.91 | 88.7 | excellent |
| Turnip Greens | 1 cup | 28.8 | 39.46 | 52.61 | 32.9 | excellent |
| Beet Greens | 1 cup | 38.9 | 35.86 | 47.81 | 22.1 | excellent |
| Mustard Greens | 1 cup | 36.4 | 35.42 | 47.23 | 23.4 | excellent |
| Collard Greens | 1 cup | 62.7 | 34.58 | 46.11 | 13.2 | excellent |
| Raspberries | 1 cup | 64.0 | 32.23 | 42.97 | 12.1 | excellent |
| Swiss Chard | 1 cup | 35.0 | 31.50 | 42.00 | 21.6 | excellent |
| Tomatoes | 1 cup | 32.4 | 24.66 | 32.88 | 18.3 | excellent |
| Lemons and Limes | 0.25 cup | 13.4 | 23.61 | 31.48 | 42.2 | excellent |
| Spinach | 1 cup | 41.4 | 17.64 | 23.52 | 10.2 | excellent |
| Asparagus | 1 cup | 39.6 | 13.86 | 18.48 | 8.4 | excellent |
| Sea Vegetables | 1 TBS | 10.8 | 12.16 | 16.21 | 26.9 | excellent |
| Fennel | 1 cup | 27.0 | 10.44 | 13.92 | 9.3 | excellent |
| Thyme | 2 TBS | 4.8 | 7.68 | 10.24 | 38.0 | excellent |
| Sweet Potato | 1 medium | 180.0 | 39.20 | 52.27 | 5.2 | very good |
| Winter Squash | 1 cup | 75.8 | 19.68 | 26.24 | 6.2 | very good |
| Green Peas | 1 cup | 115.7 | 19.56 | 26.08 | 4.1 | very good |
| Blueberries | 1 cup | 84.4 | 14.36 | 19.15 | 4.1 | very good |
| Cranberries | 1 cup | 46.0 | 13.30 | 17.73 | 6.9 | very good |
| Watermelon | 1 cup | 45.6 | 12.31 | 16.41 | 6.5 | very good |
| Green Beans | 1 cup | 43.8 | 12.13 | 16.17 | 6.7 | very good |
| Summer Squash | 1 cup | 36.0 | 9.90 | 13.20 | 6.6 | very good |
| Carrots | 1 cup | 50.0 | 7.20 | 9.60 | 3.5 | very good |
| Plum | 1 2-1/8 inches | 30.4 | 6.27 | 8.36 | 5.0 | very good |
| Garlic | 6 cloves | 26.8 | 5.62 | 7.49 | 5.0 | very good |
| Basil | 0.50 cup | 4.9 | 3.82 | 5.09 | 18.8 | very good |
| Dill | 0.50 cup | 1.9 | 3.78 | 5.04 | 47.5 | very good |
| Romaine Lettuce | 2 cups | 16.0 | 3.76 | 5.01 | 5.6 | very good |
| Potatoes | 1 medium | 160.9 | 16.61 | 22.15 | 2.5 | good |
| Avocado | 1 cup | 240.0 | 15.00 | 20.00 | 1.5 | good |
| Onions | 1 cup | 92.4 | 10.92 | 14.56 | 2.8 | good |
| Banana | 1 medium | 105.0 | 10.27 | 13.69 | 2.3 | good |
| Apple | 1 medium | 94.6 | 8.37 | 11.16 | 2.1 | good |
| Pear | 1 medium | 101.5 | 7.65 | 10.20 | 1.8 | good |
| Beets | 1 cup | 74.8 | 6.12 | 8.16 | 2.0 | good |
| Leeks | 1 cup | 32.2 | 4.37 | 5.83 | 3.3 | good |
| Apricot | 1 whole | 16.8 | 3.50 | 4.67 | 5.0 | good |
| Celery | 1 cup | 16.2 | 3.13 | 4.17 | 4.6 | good |
| Cucumber | 1 cup | 15.6 | 2.91 | 3.88 | 4.5 | good |
| Peppermint | 2 TBS | 5.3 | 2.42 | 3.23 | 10.9 | good |
| Cilantro | 0.50 cup | 1.8 | 2.16 | 2.88 | 28.2 | good |
| World's Healthiest Foods Rating | Rule |
|---|---|
| excellent | DRI/DV>=75% OR Density>=7.6 AND DRI/DV>=10% |
| very good | DRI/DV>=50% OR Density>=3.4 AND DRI/DV>=5% |
| good | DRI/DV>=25% OR Density>=1.5 AND DRI/DV>=2.5% |
Impact of Cooking, Storage and Processing
The same thing that makes vitamin C so important—its ability to protect against free radical damage—also makes it very prone to damage. It is degraded by heat, oxygen, and storage. In fact, the relative instability of vitamin C in foods presents a compelling argument in favor of fresh food dietary approaches like the ones we advocate at World's Healthiest Foods.
The vitamin C content of food starts to decline as soon as it is picked. Keeping food cool and intact will slow this process, but not arrest it. For example, broccoli stored at room temperature will lose almost 80% of its vitamin C content over a six-day period.
Keeping your produce cool will reduce the rate of vitamin C loss. Cut spinach leaves lose all of their vitamin C at room temperature over six days. If kept refrigerated, they will retain about half of the original amount. Similarly, apples kept in cold storage will lose about half of their vitamin C in the first month, then will lose comparatively little over the next several months.
Unlike many nutrients that are degraded by light, vitamin C content may in fact be enhanced by it, at least in green vegetables. This is because the light exposure keeps some of the plant energy production alive, even after it is picked. For instance, cold stored romaine lettuce will lose about a quarter of its vitamin C in cold storage during a week when kept dark. If it is exposed to a moderate amount of light (about 10 to 25% of the intensity of direct sunlight) during this period, it won't lose any at all.
Long-term storage of vegetables will cost a significant amount of vitamin C. Kept frozen for a year, kale will lose half its vitamin C or more. Canning is even more detrimental, with 85% of the original vitamin C lost over the same year.
Cooking will reduce some vitamin C from foods, but the amount of degradation will vary widely by cooking method. For example, basket-steaming broccoli for 15 minutes will reduce the vitamin C content by nearly one quarter. But if you cook that same broccoli in the microwave, you'll have almost no vitamin C when it is finished. For this reason (among others), we recommend steaming as one of the healthiest ways to prepare most vegetables.
Risk of Dietary Deficiency
The risk of dietary deficiency of vitamin C is substantial in the United States. According to data collected over 2003 and 2004, the average adult male and female both eat just a couple of milligrams more than the recommended daily intake level for vitamin C. Worse yet, about 7% of the population shows clear biochemical evidence for vitamin C deficiency.
The risk of deficiency of vitamin C goes up as income goes down, attesting to the problem we have nationally in providing fresh food across the economic spectrum. We also see the risk of vitamin C deficiency go up as body weight increases.
This is a shame because it is so easy to obtain a full day's supply of vitamin C. We feature a large number of recipes on our site that contain more than double the recommended amount. The seven days in our Healthiest Way of Eating sample menu contain between 365% and 741% of the daily recommendation.
For many foods, we put together a menu that spreads the intake across multiple meals, adding up small amounts to meet a daily need. For vitamin C, it can be as easy as this—eat a serving of bell peppers. Or if you prefer, eat a serving of broccoli. This will cover your vitamin C needs for an entire day.
In case you get tired of bell peppers or broccoli, rest assured that other fruits and vegetables can be nearly as good. In fact, you could pretty much grab any fruit we list on our site at random, along with a serving of greens, and again hit your daily recommendation for vitamin C.
At the risk of oversimplifying, if you are eating multiple servings of fresh fruits and vegetables every day, you are getting enough vitamin C. If you are not, you may be at risk for deficiency.
Other Circumstances that Might Contribute to Deficiency
Since smoking increases free radical damage, smokers will need more dietary vitamin C. The National Academy of Sciences recommends that smokers get an extra 35 mg of vitamin C every day, about the amount found in one-half of a medium orange.
Relationship with Other Nutrients
Vitamin C increases the absorption of iron (especially the iron found in plant foods) and may help those at risk for iron deficiency stay out of deficit. Although some sources suggest that this should be supplemental vitamin C, the nutrient derived from food will do this, too. For those at risk of iron overload, you may need to be careful about combining foods rich in iron with those rich in vitamin C.
Antioxidants in foods tend to work together in important and synergistic ways to provide protection against free radical damage. The most well-known of these connections is that between vitamin E and vitamin C. Specifically, vitamin C helps to protect vitamin E in people, such as smokers, who have chronic overproduction of free radicals.
Similarly, we see the flavonoid class of plant-based antioxidants helping to make the free radical protection from vitamin C that much stronger. This is great news, given that the foods that are most flavonoid-rich also tend to be among our better vitamin C sources. This synergistic protection is but one of many potential explanations for why the health benefits of plant-based diets cannot be replicated by nutrient supplements.
Risk of Dietary Toxicity
The National Academy of Sciences has established a Tolerable Upper Intake Level (UL) of 2000 mg per day for adults. While it is plausible that in rare situations—particularly with a rich intake of citrus juices—an individual could be above this UL from foods alone, we are not aware of any evidence to suggest that vitamin C intake from foods ever is responsible for toxicity symptoms.
People who supplement with large amounts of vitamin C often will experience gas and diarrhea as a result. There is some evidence to suggest that intakes of vitamin C beyond the UL may also be linked to increased risk of kidney stones.
Disease Checklist
- Common cold
- Scurvy
- Capillary fragility
- Asthma
- Gingivitis
- Gout
- Musculoskeletal injury
- High blood pressure
- Seasonal allergies
- Smoking
Public Health Recommendations
In 2000, the Food and Nutrition Board of the National Academy of Sciences released a set of Dietary Reference Intakes (DRI) for vitamin C that included a range of Recommended Dietary Allowances (RDA) by age and gender. These are summarized in the chart below. Note that the recommendations for infants under age one are Adequate Intake (AI) standards. The RDAs and AIs are as follows.
- 0-6 months: 40 mg
- 6-12 months: 50 mg
- 1-3 years: 15 mg
- 4-8 years: 25 mg
- 9-13 years: 45 mg
- 14-18 years, female: 65 mg
- 14-18 years, male: 75 mg
- 19+ years, female: 75 mg
- 19+ years, male: 90 mg
- Pregnant women, 14-18 years: 80 mg
- Pregnant women, 19+ years: 85 mg
- Lactating women, 14-18 years: 115 mg
- Lactating women, 19+ years: 120 mg
The 2000 DRI report also included a Tolerable Upper Intake Level (UL) for vitamin C of 2000 mg for adults. Although the report does not draw a distinction between dietary vitamin C and supplements, it would be very hard to routinely go above this UL from food alone. Reflecting this, the published reports of symptoms related to excessive vitamin C intake that we have seen were all triggered by use of supplements.
According to the DRI, smokers require extra vitamin C, and should add 35 mg to their daily RDA from the chart above. You'd find those 35 mg in a single serving of beet or mustard greens.
The Daily Value (DV) of vitamin C that you'll see on food labels is 60 mg. This is one of a very few examples of a DV recommendation that is less than the newer RDA standard.
References
- Bruno RS, Ramakrishnan R, Montine TJ, et al. Alpha-tocopherol disappearance is faster in cigarette smokers and is inversely related to their ascorbic acid levels. Am J Clin Nutr. 2005;81:95-103.
- Carr AC, Frei B. Toward a new recommended dietary allowance for vitamin C based on antioxidant and health effects in humans. Am J Clin Nutr 1999;69:1086-107.
- Felicetti E, Mattheis JP. Quantification and histochemical localization of ascorbic acid in 'Delicious,' 'Golden Delicious,' and 'Fuji' apple fruit during on-tree development and cold storage. Postharvest Biol Tech 2010;56:56-63.
- Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academy Press; 2000;284-324.
- Frei B, Birlouez-Aragon I, Lykkesfeldt J. Authors' perspective: What is the optimal intake of vitamin C in humans? Crit Rev Food Sci Nutr 2012;52:815-29.
- Korus A, Lisiewska Z. Effect of preliminary processing and method of preservation on the content of selected antioxidative compounds in kale (Brassica oleracea L. var. acephala) leaves. Food Chem 2011;129:149-54.
- Pellegrini N, Chiavaro E, Gardana C, et al. Effect of different cooking methods on color, phytochemical concentration, and antioxidant capacity of raw and frozen Brassica vegetables. J Agric Food Chem 2010;58:4310-21.
- Raseetha S, Leong SY, Burritt DJ, et al. Understanding the degradation of ascorbic acid and glutathione in relation to the levels of oxidative stress biomarkers in broccoli (Brassica oleracea L. italica cv. Bellstar) during storage and mechanical processing. Food Chem 2013;138:1360-9.
- Sanhueza C, Ryan L, Foxcroft DR. Diet and the risk of unipolar depression in adults: systematic review of cohort studies. J Hum Nutr Diet 2013;26:56-70.
- Zhan L, Hu J, Ai Z, et al. Light exposure during storage preserving soluble sugar and L-ascorbic acid content of minimally processed romaine lettuce (Lactuca sativa L. var. longifolia). Food Chem 2013;136:273-8
- Source; http://www.lenntech.com/vitamins/vitamin-c.htm
No comments:
Post a Comment