Berries are small fruits with a sweet taste and a high content of vitamins and minerals. Berries include gooseberries, chokeberry, bilberry, blueberry, lingonberry, blackberry, raspberry, white currant, red currant, black currant, wild strawberry, strawberry, grape, and cranberry.

Berries are characterized by a high content of polyphenols, terpenes, glycosides, and ascorbic acid. Among the polyphenols, the largest group are flavonoids, especially anthocyanins and quercetin. Flavonoids are characterized by high biological activity and determine various ways of influencing cellular metabolism.

Antioxidant function

Flavonoids exhibit antioxidant activity through various mechanisms:

• Capturing/neutralizing free oxygen radicals and their reactive forms (ROS – reactive oxygen species) – is essential in inflammation.
  • Free radicals are atoms or molecules that have unpaired electrons and, therefore, easily bind to other structures and lead to their damage.
• Inhibition the ROS production in cells by inhibiting the enzymes (xanthine oxidase, membrane NAD (P) H oxidase, myeloperoxidase) involved in ROS formation.
• Chelating metal ions, i.e., copper and iron, and thus inhibiting the formation of reactive hydroxyl radicals.
• Protection of some antioxidants against oxidation, e.g., ascorbate (vitamin C) in the cytosol and α-tocopherol (a component of vitamin E) in biological membranes.
• Inhibition of free radical reactions in non-enzymatic and enzymatic peroxidation of lipids by reducing the activity of enzymes, e.g., phospholipase and lipoxygenase.

Anti-inflammatory function

Flavonoids, including, e.g., quercetin, inhibit the activity of enzymes such as lipoxygenase (LOX) and cyclooxygenase (COX), which are involved in the synthesis of pro-inflammatory prostaglandins and leukotrienes from arachidonic acid. Consequently, the influx of leukocytes is inhibited, the tone of blood vessels is improved, and the inflammatory reaction is reduced.

Anti-allergic function

Flavonoids, especially quercetin, which is found in, e.g., blueberries, inhibit the proliferation of lymphocytes, inhibit the synthesis of IgE, IgG, IgM, and IgA antibodies, and also inhibit the release of histamine from mast cells.

Which diseases are conducive to consuming berries rich in flavonoids?

Cancers

• Flavonoids, especially anthocyanins, induce apoptosis of human oral cancer cells (tested in vitro).
• They inhibit the growth of cervical cancer neoplastic cells.

Cardiovascular diseases

• They increase the antioxidant capacity of plasma
• They cause a decrease in total cholesterol and LDL fraction
• They are the source of essential unsaturated fatty acids EFA – e.g., black currant seed oil
• Flavonoids (especially rutin) and vitamin C make the blood vessels more flexible and strengthen by inhibiting the activity of hyaluronidase (an enzyme that breaks down hyaluronic acid). As a result, vessels are less permeable and brittle

Diabetes

• Flavonoids stimulate insulin synthesis in pancreatic β cells and inhibit glucose synthesis in hepatocytes. As a result, blood glucose levels drop.
• Flavonoids can slow down the absorption of glucose in the intestine.
• Flavonoids are inhibitors of the enzyme (aldose reductase) that catalyze sorbitol synthesis deposited in the eyeball. Thanks to this, they protect people suffering from diabetes against cataracts.

Atherosclerosis

• Flavonoids reduce the inflammation of blood vessels and inhibit the influx of leukocytes to the inflammatory area.
• They reduce the number of reactive oxygen species that oxidize the LDL cholesterol fraction, thus preventing the formation of atherosclerotic plaques.

Thrombosis

• Flavonoids make it difficult for platelets to stick together
• They inhibit the activity of COX and phosphodiesterase enzymes

The power of berries and the prevention of skin aging

“Aging” cells accumulate in the epidermis and dermis in the process of chronological aging. This process is enhanced by various cellular disorders, including DNA damage and mitochondrial dysfunction. The aging of the dermis and epidermis can also be induced by external factors that damage DNA (e.g., X-rays, UV radiation, and cigarette smoke). “Aging cells” secrete specific pro-inflammatory cytokines, chemokines, and growth factors. This phenomenon is known as the secretory aging phenotype (SASP). SASP can lead to chronic local or generalized inflammation and changes in the structure and function of tissues.

UVA and UVB radiation activates the SASP genes, i.e., IL-1, IL-6, and MMP, and reduces the expression of the growth factor TGF-β, thereby decreasing the synthesis of type I collagen, leading to skin thinning and wrinkle formation.

Aging is also associated with changes in the skin’s immune system – decreased number of Langerhans cells, decreased antigen-specific immunity, and an increased population of T regulatory cells. These changes result in reduced immunity and increased susceptibility to cancer and infection.

The action of flavonoids in the process of inhibiting skin aging

Apigenin

Apigenin can inhibit the mTOR signal pathway, the dominant mechanism by which this flavonoid inhibits the development and progression of skin cancer. It also has antioxidant and anti-inflammatory properties and can restore normal skin function (e.g., DNA repair and viability of human keratinocytes and skin fibroblasts) after sun damage. Apigenin reduces the secretion of several SASP factors (e.g., IL-6 and IL-8) in human fibroblasts. It also inhibits the production of the IP10 protein secreted by aging fibroblasts. IP10 and other chemokines promote the Th1 cell response to cell damage. Apigenin inhibits the activity of the metalloproteinase MMP-1- in this way protects the skin against degradation of the collagen matrix caused by UVA and UVB radiation. Moreover, it induces the synthesis of type I and III collagen de novo in skin fibroblasts in vitro.

Fisetin

Fisetin has strong senolytic properties (removes aging cells) in vitro and in vivo. Fisetin inhibits the inflammation caused by tumor necrosis factor TNF-α and keratinocytes damages caused by hydrogen peroxide. It also can reduce UVB damage by inhibiting the production of reactive oxygen species (ROS) and the MAPK/AP-1/MMP signaling pathway. Fisetin prevents collagen degradation and the inflammatory response in human skin fibroblasts.

Quercetin

Quercetin blocks the UV-induced expression of COX-2 cyclooxygenase and the MMP-1 metalloproteinases, thus preventing collagen degradation in human skin and skin fibroblasts. This flavonoid reduces the number of aging cells induced by stress and inhibits the aging-related secretion of the inflammatory mediators IL-8 and interferon-β. Moreover, it has senolytic properties – it eliminates aging fibroblasts in vitro.

One of the most recent in vitro studies shows that anthocyanins extracted from blackcurrant increase the levels of ECM extracellular matrix components, such as collagen and elastin, in human skin fibroblasts.

What about skin disorders?

Due to their antioxidant, anti-inflammatory, and fiber properties, Flavonoids are also helpful in treating certain skin ailments resulting from metabolic disorders, including acne vulgaris and rosacea.

How do berries affect skin appendages, especially hair?

There are several mechanisms, confirmed by research, by which berries can act as a hair loss suppressant and prevention:

• They stimulate hair growth by activating hair follicle cells by up to 20% and promoting the expression of type 17 collagen. Hair loss may be associated with a decreased level of type 17 collagen; hence increasing its level may reverse the effects of hair loss. Additionally, berries stop hair loss by inhibiting the enzyme 5α – reductase. This enzyme converts testosterone into dihydrotestosterone, which has a destructive effect on the hair follicles, leading to baldness.
• The aromatic compound in raspberries – raspberry ketone – has a structure similar to capsaicin. Capsaicin activates sensory neurons, leading to the peptide release related to the calcitonin gene and further out of IGF – 1. The insulin-like growth factor is involved in the development and maturation of hair follicles. Research shows improved hair growth in people using raspberry ketone topically.
• Berries stimulate hair growth by influencing the signal pathway mechanism: JAK – STAT – Janus Activated Kinases – Signal Transducter and Activator of Transcription. Some forms of hair loss are associated with the inability of hair follicle cells to transform from the telogen phase to the anagen phase. Studies show that inhibition of the JAK-STAT pathway with an inhibitor facilitates the transition of follicle cells from the telogen phase to the anagen phase. Blueberries, blackberries and strawberries are rich in bioactive compounds – ellagitannins, which act as a JAK inhibitor, thus stimulating hair growth.  

Is it worth eating blueberries? The answer is simple – it’s worth it !!!

The studies conducted so far suggest that both topically and systemically, flavonoids have many advantages. However, no convincing clinical studies confirm the efficacy and safety of flavonoids in treating skin lesions and skin disorders resulting from the aging process.

Nevertheless, the supply of berries and other vegetables and fruits is recommended due to the rich source of various flavonoids that can act comprehensively and synergistically. Consuming different flavonoids positively affects both our intestinal microbiome and the skin condition.