Reminder: Please bring your questions for the "junk science" unit to class! Write down something you have heard about health which you wonder about. Could it be true or is it not really based on science?
Eat Your Colors!
(All about Phytonutrients)
by Laura Dolson
December 6, 2004
What the heck are phytonutrients? Phyto- means "plant", and phytonutrients, also called phytochemicals, come from plants. Phytonutrients are a relatively recent discovery in the nutrition world, and they are turning out to be quite important. For a long time, we've known that people who eat a lot of vegetables and fruits seem to be healthier in many ways. It was assumed that this is because vegetables and fruits are rich in vitamins and minerals, and this is part of the story. But it turns out that there are hundreds, and perhaps even thousands of other substances that are beneficial to humans that are produced by plants.
How do phytonutrients help us? Most of the benefits attributed to tea in our last lesson come from the fact that it has a high level of certain kinds of phytonutrients. Since there are so many of them, you can imagine that they do a few different things. In plants, they seem to help form a protective shield against the environment, including preventing diseases. They may do similar things for us. They can repair damage to cells, help build our immune systems, and act as antioxidants.
What are antioxidants? All of the work our cells do to keep our bodies going takes place in chemical reactions. Some of the reactions which occur with oxygen create unstable byproducts called "free radicals". In excess, these molecules can interact with other molecules in the cell membrane and other parts of the cell, such as the DNA, and cause damage. Antioxidants can counteract these free radicals and protect the cells from damage. Eating foods containing high amounts of antioxidants can help prevent diseases such as cancer (which happens partly from damaged cell DNA) and heart disease (which happens partly because of cholesterol becoming oxidized and sticking to arteries). Besides phytonutrients, some examples of antioxidants are vitamins C and E, and the mineral selenium.
Why are colors important? Interestingly, a lot of the phytochemicals that are good for us also produce bright colors in vegetables and fruits. This is where the saying "Eat Your Colors" comes from. It's also important to understand that each of these foods contains many different phytochemicals that can take care of different oxidation reactions in our cells. Each of them probably has a slightly different effect in our bodies. This is why it is important to eat a variety of fruits and vegetables.
Can we get our phytonutrients from pills (food supplements)? Because there are so many of these chemicals, and they may work in concert with each other, it doesn't seem to be working out well to give people large doses of one or a few antioxidants in pill form. Studies of single antioxidants sometimes even have negative results. It could be that too much of one antioxidant even has pro-oxidant effects of its own. (When you read negative things about phytonutrients or antioxidants, they are sure to be talking about the pills, not the naturally-occurring ones in food.) Eating a variety of foods high in phytonutrients seems to be the best and only sure way to get their protective benefits.
Which foods are high in phytonutrients and antioxidants? Some of the foods highest in antioxidants are: tea, berries, plums (and prunes), oranges, purple grapes (and raisins), cherries, kiwi fruit, pink grapefruit, dark green leafies like spinach and kale, broccoli, Brussels sprouts, beets, tomatoes, red pepper, and dark chocolate (not milk chocolate).
There are also families of foods that tend to have some of the same protective compounds in them, although there is variation within each family.
The Cabbage Family, also known as cruciferous vegetables. These contain chemicals (sulforaphane, isothiocyanate and idoles, to be exact) that help breakdown cancer-causing compounds. Included are broccoli, Brussels sprouts, cabbage, kale, cauliflower, bok choy, and watercress.
The Allium Family - these vegetables contain compounds that protect DNA. They are onions (all kinds, including green onions), garlic, leeks, shallots, and chives.
The Purple/Red Family - Some of the most powerful antioxidant foods are in this family. Most of the berries (especially blueberries), plums (and prunes), red grapes (including raisins, grape juice, and red wine), cranberries, and pomegranates are in this family. The color in these fruits comes from a groups of chemicals called anthocyanins, which reduce inflammation, protect against cancer, and recent studies show good effects in eyes, arteries, and brains.
The Red Family - Tomatoes and tomato products, watermelon, pink grapefruit. These foods contain lycopene, which studies have shown reduces the risk of several types of cancer. Apricots and pink guavas are also sources of lycopene.
The Deep Orange Family contain fruits and veggies rich in the carotenes. Carrots (of course!), pumpkins, mangos, apricots, cantaloupe, and sweet potatoes are some of the foods in this group. Carotenes help improve communication between cells as well as doing many of the same functions as other antioxidants.
The Yellow-Orange Family contain the citrus fruits as well as peaches, nectarines, pineapple, and papaya. These fruits are rich in vitamin C and flavanoids, another group of antioxidants which help our immune systems.
The Green Family - There are lots of green vegetables, and they vary in which family they belong to. The dark green leafy vegetables are rich in lutein, among other phytochemicals. Others belonging to this family are green beans, avocados, kiwi fruit, green peppers, and honeydew melon.
Not all vegetables and fruits fit easily into families, but most of them have phytonutrient constellations of their own.
Other plant foods rich in various types of phytonutrients are:
Seeds, and Grains (particularly nuts and flax seeds)
For more information on various foods and their health benefits, as well as cooking and serving suggestions, I recommend this site: The World's Healthiest Foods
How many servings of fruits and vegetables should we eat? Current recommendations are 5-9 servings per day, and there is evidence that more is better. Although the U.S. recommendations include potatoes as part of this recommendation, the World Health Organization and many other countries put potatoes in other categories, so as not to take away valuable "color servings" from vegetables and fruits.
What is a Serving? Fruits - One medium-sized piece of fruit, ¾ cup juice, ½ cup cut-up fruit, or ¼ cup of dried fruit are generally recommended as a serving. For vegetables, 1 cup of raw leafy vegetables or ½ cup of other vegetables are considered a serving. But take note! Many vegetables, especially leaves, "collapse" when cooking as the moisture cooks out and cell walls break down. It takes six cups of cooked spinach to make one cup of raw spinach! I feel this should be taken into consideration when deciding on serving sizes, and we should probably eat larger servings of vegetables when raw, especially leafy ones.