23 April 2015
Rainbow of Flavonoids
Juliet Blankespoor explains all the delicious benefits of a flavonoid-rich diet in this highly informative handout from the Southeast Women’s Herbal Conference 2014.
Imagine a bowl overflowing with color: garnet cherries aside crimson and golden raspberries, blueberries the color of a summer sky, resting against the blush of rose petals. Juicy and alluring, tempting you with vibrancy that promises fresh sweetness. Our intuition is fine-tuned to spot vitality and nutritional density. Humans are naturally drawn to bright colors in our food—the invention of food coloring testifies to this phenomenon. There are a wide variety of compounds lending their color to food; flavonoids are some of the most researched and widely represented colorful phytochemicals in the plant world. It is refreshing to dive deep into the well of tradition and science, both of which describe the medicinal virtues of these tasty treats.
Flavonoids, also known as bioflavonoids, are the largest family of plant phenolic compounds, with over 4,000 identified types. Lisa Ganora writes in Herbal Constituents, “The basic structure of a flavonoid consists of two phenolic rings, with varying numbers and kinds of substituents, joined in the middle by a central pyran ring. Flavonoids are found in commonly ingested fruits, vegetables and beverages, and exhibit virtually no toxicity when ingested in their whole food form.” Although I have two years of college chemistry under my belt, I must confess to a certain lazy glazy interpretation of her first sentence, but I can easily grasp the second sentence. Continuing along that vein, I will present the medicinal qualities of flavonoids without a lot of chemistry explanations, mostly because I haven’t the fortitude.
Plants produce flavonoids for a number of reasons. Flavonoids act as pigments in flowers and fruits, helping to attract pollinators and fruit dispersers respectively. They also protect plant tissues against damage from ultraviolet radiation. Interestingly, some flavonoids play an important role in legumes (Fabaceae) in the communication with their symbiotic nitrogen-fixing bacteria.
Flavonoids have become a buzzword in the popular media during the last decade, resulting in more Americans incorporating more berries into their diet. Frozen wild blueberries have found themselves in the freezers and cereal bowls of everyday citizens across the land. Flavonoids are generally anti-inflammatory, anticarcinogenic, antioxidant, and cardioprotective. Many recent studies have focused on the neuroprotective qualities of flavonoids, including the prevention of age-related mental and motor function decline.
Some flavonoids, such as quercitin, are anti-allergenic through inhibiting mast cell degranulation, or rupture. Mast cells release histamine and other inflammatory compounds upon rupturing, thus a stable mast cell means less histamine, and therefore less inflammation. Quercitin is found in red onions, dill, lovage, capers, buckwheat, sorrel and watercress.
Recent studies on strawberries and blackberries have demonstrated their marked antibacterial properties. Ellagic acid, which is found in many berries, including raspberries, cranberries, and strawberries, has been shown to minimize lung damage from pollutants such as tobacco. Finally, berries are being touted as an excellent food for moderating metabolic diseases and obesity; blood sugar is more slowly absorbed into the bloodstream and lipids are more poorly absorbed when berries are consumed with other foods.
Many herbalists, including myself, recommend adding flavonoid-rich foods to the diet, helping to alleviate inflammation in atopic allergies, such as asthma, hayfever, and eczema. Other inflammatory conditions, such as arthritis, tendonitis, COPD, and ulcerative colitis, also benefit from a high flavonoid diet. The cardiovascular benefits of colorful foods are well documented—flavonoids, such as anthocyanins, help to lower cholesterol levels and reduce the inflammatory processes that instigate atherosclerosis. A general recommended dosage is one cup of fresh berries daily, or the equivalent in the form of frozen or dried berries, jam, solid concentrate, or wine.
One of the most well-known and studied benefits of flavonoids is their antioxidant potential: To understand how antioxidants work, it is important to first grasp the chemistry of free radicals. A free radical is an atom or molecule with an unpaired electron in its outer shell. Stable atoms and electrons have paired electrons; the presence of an unpaired electron creates imbalance or instability. Without an electron partner, an atom or molecule is chemically “needy” and will seek an electron “mate” at any cost. The free radical ends up stealing a neighboring molecule or atom’s electron, which then, in turn, creates another free radical. This electron stealing travels from molecule to molecule and is often described as the toppling of a domino chain or a wildfire spreading from treetop to treetop. The electron-stealing cascade is termed oxidative 'stress'.
Free radicals can damage all macromolecules, including lipids, protein, and nucleic acids. What does this mean for our cells? Plasma membranes, enzymes, and mitochondrial and nuclear DNA may be damaged. This can translate to a poorly functioning cell or cell death. Additionally, DNA mutation can induce the beginning stages of cancer. Cell membranes can become inelastic and poorly functioning as oxidative damage “glues” together its components. Free radical damage is associated with over two hundred disorders, including cancer, atherosclerosis, heart disease, strokes, Alzheimer’s disease, schizophrenia, Parkinson’s disease, diabetes, and arthritis. One of the leading theories on the physiology of aging postulates that mitochondrial damage from free radicals is responsible for the aging process. Many animal studies have demonstrated a link between oxidative stress and a shorter lifespan.
Where do free radicals originate? Air pollution, smoking, ultraviolet radiation, and pesticides can all cause the formation of free radicals in animals. However, the majority of free radicals are created inside the body as a byproduct of healthy metabolism. Merely breathing, or living on a planet with oxygen, creates free radicals. In plants, photosynthesis creates free radicals. Cellular respiration naturally creates reactive atoms—when we burn our food we are creating free radicals. Plants and animals have evolved with the challenge of free radicals, and produce antioxidants to reduce oxidative stress. Free radicals are not just an evil entity. For example, our white blood cells use free radicals to destroy bacteria. As with most things in life, balance is imperative –in this case, the balance of free radicals with antioxidants.
Antioxidants are molecules capable of donating an electron to a free radical, effectively stopping the cascade of electron stealing. Due to the special chemical structure of their bonds, antioxidants are capable of greater stability, even with a missing electron, than an average molecule. An everyday molecule will become a free radical itself after donating its electron, but antioxidants possess a super chemical power of stability. Antioxidants also work in tandem to extinguish free radical fires. For example, after Vitamin E extinguishes an oxidative fire by donating an electron to a free radical, Vitamin C comes along and replenishes Vitamin E. The synergistic effect of cooperating antioxidants explains why diets rich in whole fruits and vegetables have been shown to lower cancer rates in population studies. In contrast, isolated antioxidants, in supplemental form, may actually be pro-oxidants, as evidenced by increased mortality rates in those taking isolated antioxidant vitamin supplements!
The body produces its own supply of antioxidants and additional antioxidants are ingested in commonly eaten fruits and vegetables. Selenium, bioflavonoids, and Vitamins A, C, and E are well-known dietary antioxidants. The antioxidant powers of dietary and herbal flavonoids have been widely explored through scientific studies, especially in the field of cancer research. Personally, I am intrigued by why plants produce the compounds that we humans use as medicine. Photosynthesis creates oxidative stress in plant tissues, so plants must produce antioxidant compounds to protect themselves against DNA mutations and other molecular madness. All leafy greens contain ample antioxidants, as plants need to quench the free radicals naturally produced through photosynthesis. We humans also produce a slew of antioxidant compounds to protect our cells and tissues from the free radicals that are naturally produced as part of life. Herbivorous animals, such as Homo sapiens, have an extra armor against oxidative stress—ingesting antioxidant compounds produced by plants.
Sources of flavonoids:
Rather than learning about all the types of flavonoids and their actions on the body, we might instead focus on increasing a wide variety of flavonoid-rich foods into our daily diet. It is helpful to remember that color is a good indicator of most flavonoids’ bioavailability—if a food is still vibrant, than its medicine is also vital. It is good to know that cooking, drying, fermenting, canning and freezing does not, in general, destroy or diminish flavonoids. In fact, freeze-drying berries concentrates flavonoids up to ten times as compared to the fresh berries. When it comes to flavonoids shelf life, the proof is in the pudding—if a food is still bright and vibrant, the flavonoid will generally be intact and bioavailable.
Almost everyone is going to benefit from more berries in their diet. I typically recommend fruit sweetened jams, low-sugar pies and cobblers, smoothies, fruit wines, berries and yogurt, fruit leathers, dried fruit, and high-flavonoid teas. While it is true that most Americans consume too much sugar in their diet, the judicious additions of healthy sweeteners in moderation can often satisfy the sweetest of tooth. Maple syrup, honey, and fruit juices can be added to berries in the creation of medicinal confections! In my mind, if one going to eat a sweet treat, at least it can be medicinal and nutritional, as well as delicious. Additionally, consider adding berries to savory foods such as chutneys, barbeque sauce, and salsas. We add autumn olive berries (Elaeagnus umbellata, Elaeagnaceae) to chili and stew, much as one would add tomatoes to these familiar dishes.
Most berries contain an array of bioflavonoids, all of which are medicinal. Eating a variety of seasonal and local berries, edible flowers, and colorful vegetables is a wonderful way to optimize antioxidants into the diet. It is easy to fall into the pitfall of believing that exotic expensive foods are somehow nutritionally superior to the foods growing in our own backyard. Most places in the temperate world have a steady supply of wild edible berries during the growing season, in addition to cultivated berries.
Common wild edible berries and fruit:
• Raspberries, wineberries, black raspberries, blackberries (Rubus spp., Rosaceae)
• Mulberries (Morus spp., Moraceae)
• Rose hips (Rosa spp., Rosaceae)
• Blueberries (Vaccinium spp, Ericaceae)
• June berries (Amelanchier spp., Rosaceae)
• Autumn olives (Elaeagnus umbellata, Elaeagnaceae)
• Wild cherry and chokecherry (Prunus serotina and P.virginiana, Rosaceae)
• Chokeberry (Aronia spp., Rosaceae)
• Hawthorn (Crataegus spp., Rosaceae)
• Cactus fruit (Opuntia spp., Cactaceae)
• Wild Strawberries (Fragaria spp., Rosaceae)
Article courtesy of:
Juliet Blankespoor, Director
Chestnut School of Herbal Medicine
56 Sluder Branch Rd. Leicester, NC 28748