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 as good sources of vitamin C. It is also a commonly used nutritional supplement.
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.
Despite the familiarity of the U.S. public with vitamin C and the popularity of vitamin C supplements, food intake of vitamin C by the average U.S. adult is not much higher than the Dietary Reference Intake (DRI) level. For men in the U.S. twenty years and older, this average is 96 milligrams per day, and for women in the U.S. twenty years and older, it is 82 milligrams per day. (The DRIs for these two groups are 90 milligrams and 75 milligrams, respectively.) So even though U.S. adults are averaging adequate intake of vitamin C intake from their food, the amount is not as high as some people might expect given widespread familiarity and interest in vitamin C.
Of the World's Healthiest Foods, a staggering 27 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 14 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.
Vitamin C is probably best known as an antioxidant. This is a word that we use frequently but don't always stop to think about in terms of its meaning. Antioxidants are forms of molecules that help keep chemical reactions in our body in check. In particular, antioxidants help prevent excessive activity on the part of free radical molecules. (Free radicals are forms of molecules that tend to be very reactive, and too many free radicals in the wrong place at the wrong time can do damage to our cells and tissue.) Vitamin C and other antioxidants help prevent that damage. Damage to the lens of the eye, damage to molecules circulating around in our bloodstream, and damage to genetic material (DNA) in our cells are all examples of damage that have been shown to be prevented under certain circumstances by vitamin C.
One interesting application of vitamin C as an antioxidant is its ability to transform 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.
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 would usually be enough. (However, as described earlier, we have dozens and dozens of great food choices that will give us as much vitamin C as a single lime!)
Vitamin C is necessary to make certain neurotransmitters. These neurotransmitters are the signals that carry thoughts, feelings, and commands around our brains and throughout our nervous system.
In particular, we need vitamin C to produce serotonin, a hormone that plays a critical role in wide variety of body systems, including the nervous system, endocrine system, immune system, and digestive system. Many of our moods, daily bodily rhythms (including sleep-wake cycles), and experiences of stress and pain have serotonin included as a factor in their occurrence. Some of the most commonly used prescription medications for depression (SSRIs, or Selective Serotonin Reupdate Inhibitors) also target this hormone. While we are not suggesting that dietary intake of vitamin C will automatically improve the quality of any experiences described above, we do recommend that you include vitamin C-rich foods on a daily basis as part of your overall well-being.
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, very good, or excellentsource 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. Very good sources of vitamin C in the vegetable group include summer and winter squash, green beans, and carrots.
Our Herbs and Spices can also be very helpful in boosting your vitamin C intake. One WHFoods serving of parsley, for example, provides you with over half of our WHFoods recommended daily amount of vitamin C!
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, since this amount will provide you with over one-third of the requirement in one sitting.
|World's Healthiest Foods ranked as quality sources of|
|Bell Peppers||1 cup||28.5||117.48||157||98.9||excellent|
|Brussels Sprouts||1 cup||56.2||96.72||129||41.3||excellent|
|Kiwifruit||1 2 inches||42.1||63.96||85||36.5||excellent|
|Bok Choy||1 cup||20.4||44.20||59||52.0||excellent|
|Turnip Greens||1 cup||28.8||39.46||53||32.9||excellent|
|Beet Greens||1 cup||38.9||35.86||48||22.1||excellent|
|Mustard Greens||1 cup||36.4||35.42||47||23.4||excellent|
|Collard Greens||1 cup||62.7||34.58||46||13.2||excellent|
|Swiss Chard||1 cup||35.0||31.50||42||21.6||excellent|
|Lemons and Limes||0.25 cup||13.4||23.61||31||42.2||excellent|
|Sea Vegetables||1 TBS||10.8||12.16||16||26.9||excellent|
|Sweet Potato||1 cup||180.0||39.20||52||5.2||very good|
|Winter Squash||1 cup||75.8||19.68||26||6.2||very good|
|Green Peas||1 cup||115.7||19.56||26||4.1||very good|
|Blueberries||1 cup||84.4||14.36||19||4.1||very good|
|Cranberries||1 cup||46.0||13.30||18||6.9||very good|
|Watermelon||1 cup||45.6||12.31||16||6.5||very good|
|Green Beans||1 cup||43.8||12.13||16||6.7||very good|
|Summer Squash||1 cup||36.0||9.90||13||6.6||very good|
|Carrots||1 cup||50.0||7.20||10||3.5||very good|
|Plum||1 2-1/8 inches||30.4||6.27||8||5.0||very good|
|Garlic||6 cloves||26.8||5.62||7||5.0||very good|
|Basil||0.50 cup||4.9||3.82||5||18.8||very good|
|Dill||0.50 cup||1.9||3.78||5||47.5||very good|
|Romaine Lettuce||2 cups||16.0||3.76||5||5.6||very good|
Density>=7.6 AND DRI/DV>=10%
Density>=3.4 AND DRI/DV>=5%
Density>=1.5 AND DRI/DV>=2.5%
The same thing that makes vitamin C so important—its ability to protect against free radical damage—also makes it very prone to damage by heat, oxygen, and storage over time. In fact, the relative instability of vitamin C in foods presents a compelling argument in favor of fresh food dietary approaches like the one we advocate at World's Healthiest Foods.
The vitamin C content of food will start to decline as soon as it is picked, even though this decline can be slowed down and minimized by cooling and retention of the food in its whole form. But a fresh, vitamin C-rich vegetable like broccoli—if allowed to sit at room temperature for 6 days—can lose almost 80% of its vitamin C. That potential vitamin C loss is one of the reasons it is so important to store broccoli (and all other vitamin C-rich foods) according to the methods that we describe in our individual food profiles. All of our food profiles include sections on How to Select and Store, and for each food we provide you with exact storage times and conditions that will help minimize nutrient loss from each food.
Long-term storage of vegetables can cost a significant amount of vitamin C. Kept frozen for a year, kale can lose half its vitamin C or more. Canning is even more detrimental, with 85% of the original vitamin C lost over the same year.
While cooking will lower the amount of vitamin C in most foods, but the amount of vitamin C lost will vary widely by cooking method. For example, basket-steaming broccoli for 15 minutes will reduce the vitamin C content by nearly one quarter. That's one of the reasons why our WHFoods method for steaming broccoli never lasts longer than 5 minutes!
As described earlier, the average dietary intake for vitamin C in the United States is just above the Dietary Reference Intake (DRI) level for both adult men and adult women. From this standpoint, U.S. adults aren't at significant risk for vitamin C deficiency. However, average total calorie intake in the U.S. also tends to be too high, and while we may be doing okay in terms of our average vitamin C intake, we may also be overeating in order to do so. Whole, natural foods—especially fresh vegetables—can play a major role in providing ample vitamin C without increasing the risk of overeating. It's one of the reasons we recommend this food group so highly.
At the risk of oversimplifying, if you are eating multiple servings of fresh fruits and vegetables every day, you are very likely to be getting enough vitamin C.
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.
Vitamin C can increase the absorption of iron (especially the iron found in plant foods) and may help lower the risk of dietary iron deficiency. You'll sometimes see us recommending the additional of a vitamin C-rich food to meals and recipes for this reason.
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.
A great example of vitamin C and flavonoids in a whole, natural food is fresh oranges. In this fruit, most of the vitamin C is found in the watery orange-colored portions, while many of the flavonoids are found in the white-colored linings and section dividers. (This distribution of vitamin C and flavonoids in oranges is one of the reasons that it can be helpful to consume the "pulp" along with the juice if you decide to consume a processed juice version of this food.)
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.
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 hard to routinely go above this UL from food alone.
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.
We adopted 75 milligrams per day—the DRI for adult women 19 years and older—as our WHFoods recommended daily intake level for vitamin C.