What are anthocyanins?
Anthocyanins are a very large group of water-soluble colored pigments found in various plants, especially flowers and fruits. They are also found in the leaves, stems, and roots of assorted other plants, including foods.
Anthocyanins are types of flavonoids that are formed when their related compounds, anthocyanidins, are coupled with sugars. Sugars can bind at different places on the anthocyanidin molecule. With assorted types of sugars and different binding sites available, many different types of anthocyanins may be formed. In fact, over 600 different anthocyanins have been identified in plants.
The color and stability of the pigment is affected by pH, light, temperature, and its own structure. Acidic conditions make the pigments red, whereas alkaline conditions turn them blue. Diversity of anthocyanins is further increased by the chemical combination of sugars with organic acids. So, from the various potential molecular combinations, the different types of anthocyanins are vast.
Anthocyanins have a variety of functions for the plants that contain them. They serve as antioxidants, protectants from UV-light, and defense mechanisms. They are also used in pollination and reproduction. The colors help attract pollinators, such as bees and hummingbirds. Some anthocyanins also protect plants against some destructive larvae.
Anthocyanins are what makes many foods red, purple, or blue. The amount of anthocyanin found in a food is generally proportional to the depth of color of the skin of the food. The compounds are found mostly in the skin, except for some fruits such as red berries and cherries, which also contain anthocyanins in their flesh.
Plants containing these compounds have been traditionally used as medicine, and natural food colorants, and dyes. More recent research has uncovered various important health properties of these colorful compounds.
Health Benefits of Anthocyanins
Anthocyanins have been found to have potent antioxidant and antimicrobial properties, improve eye and neurological health, and also provide protection against various diseases. Some anthocyanin-rich foods, such as black carrots, red cabbage, and purple potatoes have been considered as functional foods, and are often eaten for the prevention of specific diseases. Anthocyanins have been shown to help ward off diabetes, cancer, cardiovascular disease, obesity, and inflammation.
Antioxidant Effects. Most of the health benefits of anthocyanins are attributed to their antioxidant effects. Antioxidants are critical for health by neutralizing harmful free radical molecules. Free radical molecules are generated in the body through normal metabolism, and also when we’re exposed to toxins of any sort, infections, high blood sugar levels, alcohol, cigarette smoke, excessive or intense exercise, radiation, and more. They are missing an electron and are very unstable. In an effort to gain stability, a free radical will steal an electron from a nearby molecule making themselves stable, while damaging the other molecule in the process. That “robbed” molecule then becomes a free radical, and the process continues until an antioxidant comes along. The antioxidant is able to “donate” an electron to the unstable molecule without itself becoming unstable and turning into a free radical. An antioxidant stops the damaging process.
Free radicals can serve important functions that are essential for health. For instance, immune cells use free radicals to fight infections, destroying viruses, bacteria, and damaged body cells along the way. Then, antioxidants are used to neutralize the free radicals, stopping further damage in the body. The body strives to maintain a balance of free radicals and antioxidants. When free radicals outnumber antioxidants, it leads to a state of oxidative stress, which invites disease.
Excessive free radicals in the body can damage DNA, cell membranes, and other parts of cells. They have been linked to many illnesses, including diabetes, heart disease, cancer, degenerative eye diseases, atherosclerosis, senile dementia, asthma, inflammatory joint disease, and more. Antioxidants stop harmful free radical molecules by the means detailed above. Antioxidants are critical in the body for health and well-being.
The body makes its own antioxidants. However, since the body needs so many antioxidants, it’s also important to obtain them from foods to help the body in its neutralizing efforts. Antioxidants may also be obtained from various foods (especially plant foods), certain vitamins (such as Vitamins C, E, and the Vitamin A precursor, beta-carotene), and minerals (such as zinc and selenium). It is important to note that it is best to obtain antioxidants from food sources, rather than taking very high dosages of supplements because in some cases, such high dosages may actually promote oxidative stress and the formation of free radicals. Foods that are high in antioxidants should be included as a regular part of the diet to help ward off many diseases.
Cardiovascular Disease. Researchers have found that anthocyanins help to relax blood vessels, thereby lowering blood pressure. They also help to prevent excessive blood clotting. Anthocyanins have also been found to improve the blood lipid profiles of healthy subjects by increasing the formation of high-density lipoproteins (HDL), while decreasing the formation of low-density lipoproteins (LDL). Anthocyanins have also been found to lower the risk of non-fatal myocardial infarction (heart attacks). So, including anthocyanin-rich foods in the diet can be an important part of helping to ward off heart disease.
Anticancer Effects. Anthocyanins have been found to suppress tumor growth, inflammation, and angiogenesis (the development of new blood vessels that feed tumors). Such effects have been seen in the deterrence of esophageal, breast, colon, and prostate cancers, as well as leukemia.
Antidiabetic Effects. Anthocyanins have been found to increase insulin sensitivity (reducing insulin resistance), thereby reducing blood sugar levels. The improved lipid profiles, enhanced antioxidant capacity, and reduced insulin resistance promoted by anthocyanins all work together to help ward off Type 2 diabetes. Anthocyanins have also been found to improve kidney function by reducing oxidative stress, lipotoxicity (the accumulation of fats in non-fatty tissue such as the kidneys, liver, heart and skeletal muscle), and angiogenesis in the kidneys of diabetics, helping to protect them from the damaging effects of diabetes.
Visual Effects. Anthocyanins have been found to improve the visual function in patients with glaucoma. They have also been found to improve blood flow to the eyes without increasing intraocular pressure. In another research project, anthocyanins reduced inflammation in photoreceptor cells, helping to improve their functioning. Anthocyanins have been found to improve dark adaptation, so this may be helpful in people with poor night vision. They have also been found to prevent the formation of cataracts in diabetic subjects.
Antimicrobial Properties. Researchers found that anthocyanins protected cell walls from damage due to invasive microbes. Antibacterial activity was demonstrated against a variety of gram-negative bacteria, including Escherichia choli, Staphylococcus aureus, Pseudomonas aeruginosa, Aeromonas hydrophilia, and Listeria innocua. Therefore, anthocyanins can help to protect us from the diseases caused by these harmful bacteria.
Antiobesity Effects. Anthocyanins have been found to slow weight gain and suppress the formation of fatty tissue, while improving the lipid profiles of obese subjects. Researchers also found that anthocyanins reduced blood and urine glucose concentrations in obese subject. So, if you are striving to lose weight, it would be in your interest to include as many anthocyanin-rich foods in your diet as possible.
Neuroprotective Effects. Anthocyanins have been found to protect against inflammation and degeneration of nerve fibers in mouse models and cell studies. These effects offer protection against Alzheimer’s Disease by preserving memory and synaptic nerve transmission function. The enhanced antioxidant effects of anthocyanins were found to provide extra protection against free radical damage and oxidative stress, improving the functioning of nerve pathways. Anthocyanins were also found to provide protective activity by suppressing dopamine-producing cell death commonly found in Parkinson’s disease.
Foods That Contain Anthocyanins
Deeply colored foods with red, purple or blue hues contain anthocyanins. They are particularly high in berries (such as elderberries, chokeberries, bilberries, black raspberries, blackberries, and blueberries).
Anthocyanins are also found in black currants, black olives, goji berries, red cabbage, black plums, cherries, red and black grapes, strawberries, red raspberries, cranberries, black rice, wild rice, purple corn, red onions, red radishes, pomegranates, purple cauliflower, blood oranges, rhubarb, black beans, eggplant, black or purple carrots, and other foods in lesser amounts.
Although they have high nutritional value in their own way, grapefruits, nectarines, peaches, apples and pears contain some, but not appreciable amounts of anthocyanins.
How to Protect Anthocyanins in Foods
Fresh vs Frozen. Researchers have found that anthocyanins in fresh food degrade relatively quickly after being harvested. When fresh and frozen foods were analyzed, they found that frozen foods, such as berries, contained higher amounts of anthocyanins than their fresh counterparts that spent three to ten days in refrigeration after harvest. Since foods are usually processed and frozen quickly after being harvested, if you want to obtain the highest level of anthocyanins in berries, unless you are picking your own or purchase them freshly harvested at a farm market, frozen berries may be a better choice.
Cooking. In a meta-analysis study published in 2014 in Food Research International, researchers compared the anthocyanin levels in foods that were cooked with various methods, including pressure boiling, pressure steaming, conventional steaming, microwaving, and baking. They found that foods cooked with moist heat methods tended to lose the most anthocyanins. The greatest loss of anthocyanins occurred when foods were pressure-steamed.
Dry-heat methods of cooking, such as microwaving and baking, tended to increase the concentration of anthocyanins in the foods tested. Anthocyanins were increased the most when foods were microwaved.
Based on the results of the above studies, if you must cook a food that is high in anthocyanins, baking or microwaving the food may be your best options for preserving as many anthocyanins as possible. When consuming fresh anthocyanin-rich foods, such as berries, use them as quickly as you can after purchase. When consuming frozen foods such as berries, to obtain the most anthocyanins, use them frozen, or allow them to thaw naturally or very briefly in the microwave.
Julia W. Klee (Judi) began her journey enjoying “all things food” in elementary school when she started preparing meals for her family. That love of food blossomed into a quest to learn more and more about health and wellness as related to nutrition. She went on to earn a BS Degree in Food and Nutrition, then an MS Degree in Nutrition. She has taught nutrition and related courses at the college level to pre-nursing and exercise science students. Her hunger to learn didn’t stop upon graduation from college. She continues to research on a regular basis about nutrition as it relates to health. Her hope is to help as many people as possible to enjoy foods that promote health and wellness.