Functional Foods and Nutraceuticals: Biochemical and Safety Insights

Introduction

Functional foods are items that provide benefits beyond essential nutrition [1]. They can be foods with naturally occurring bioactive (e.g. turmeric), foods fortified with bioactive (e.g. probiotic dairy) or modified items with additional nutritive values (e.g. golden rice). They are non-specific biological therapies with extraordinary health benefits with role of stimulant sometime to increase immunity levels.

In 1984, the concept of ‘functional foods’ was formally introduced by a research team led by Professor Soichi Arai at the University of Tokyo under the “Systemic Analysis and Development of Functional Foods” project, which was funded by the Ministry of Education, Science and Culture (MESC) of Japan. In 1991, Japan’s Ministry of Health and Welfare announced “Foods for Specified Health Uses (FOSHU),” the world’s first policy to legally permit the commercialisation of functional foods. Its first product, hypoallergenic rice, was approved in 1993 and made headlines in Nature News: “Japan explores the boundary between food and medicine” [2].

Functional foods contain bioactive compounds that aid in metabolism and other molecular processes. They are introduced as part of a regular diet and may contain compounds like polyphenols, fatty acids, carotenoids, and vitamins. They interact with various metabolic pathways to enhance homeostasis and regulate functioning, thus preventing diseases.

Nutraceuticals, conversely, are concentrated forms of bioactive substances extracted from food. In 1989, Dr Stephan L. DeFelice (M.D) coined the term ‘Nutraceutical’ by combining ‘nutrition’ and ‘pharmaceutical’. As the term suggests, these food derivatives are consumed as supplements to provide therapeutic effect. They are available in various formulations, such as tablets, capsules, powders, and syrups. According to the modern concepts, the personalised nature of nutrition is vital in view of tailored dietary recommendations, dependent on diverse responses to functional elements approaches are well aligned with hygienic and health goals. These functional foods must be prepared, marketed and used in compliance to regulatory guidelines.

Biochemistry of Bioactive Compounds

Bioactive substances provide benefits through complex physiological interactions between compounds and various physiological processes, such as enhancing enzymatic activity, antioxidation, and strengthening the immune system. The following are some of the many perks of incorporating nutraceuticals and FFs into a daily regime.

Antioxidant Properties: ROS are free radicals produced naturally during cellular metabolism. Production of ROS can increase through UV exposure, smoking and pollution. Its accumulation over time leads to damage of cells and tissue. Excess ROS can cause damage by oxidating bases of nucleic acids and cause mutation. Lipid peroxidation, the effect of lipid oxidation, is said to be one of the causes of neurodegenerative diseases like Alzheimer’s and Parkinson’s disease. Furthermore, ROS accumulation also results in damage to cardiovascular functioning and triggers cancer cell production by promoting metastasis.

Many compounds from FFs and nutraceuticals possess antioxidant properties. They combat oxidative stress by neutralising reactive oxygen species by donating an electron to the free radicals and converting them into more stable, i.e., less reactive molecules. Certain enzymes (e.g. glutathione) reduce ROS by breaking it down to hydrogen peroxide. Antioxidants protect lipids from oxidation [3].

Anti-inflammatory Benefits: Inflammation is an immune response towards invading particles like pathogens, damaged cells or other irritations. It aims to protect by removing the causal stimulus and initiate healing.

Various cytokines, enzymes and pro-inflammatory molecules (e.g. histamines and prostaglandins) contribute to inflammation by promoting vasodilation and increasing permeability in blood vessels. This allows immune cells and plasma proteins to arrive at the site of infection and initiate inflammation, phagocytosis and tissue recovery.

However, chronic inflammation leads to various diseases. ROS are produced as an immune response during inflammation, excess of which can cause tissue damage. Excessive inflammation also contributes by:

• Progression of CVD by causing plaque formation
• Promoting neurodegenerative diseases (like Parkinson’s disease) by causing neuroinflammation
• Increasing insulin resistance and contributing to Type 2 diabetes and obesity Bioactive compounds like curcumin act as an anti- inflammatory agent by downregulating the production of pro-inflammatory cytokines, thus helping to control inflammation. Prostaglandins are produced by the action of enzymes called cyclooxygenases (COX-1 and COX-2). Nonsteroidal anti-inflammatory drugs (NSAIDs), like aspirin, reduce inflammation by targeting COX-2 [4]. Certain antioxidants, like sulforaphanes (found in cruciferous plants), are also known to control inflammation.

Modulation of Gut Microbiota: Gut microbiota is known to aid metabolism and comprises various microorganisms, primarily bacteria, fungi, and viruses. These organisms help break down complex elements (e.g., dietary fibres) that are not digested by enzymes. Moreover, these organisms contribute to the synthesis of various vital vitamins (e.g. B12). Some of these organisms are known to synthesise neurotransmitters like dopamine and serotonin, linking metabolism to cognitive health.

A healthy gut biome is essential for the proper functioning of metabolism. The imbalance of these organisms in the gastrointestinal tract leads to a condition called ‘dysbiosis’. It is commonly caused by consuming highly processed foods, antibiotic usage and infection. It can lead to irritable bowel syndrome (IBS), obesity and type 2 diabetes. It can also lead to the weakening of the intestinal barrier and lead to a phenomenon known as ‘leaky gut’, where the permeability of the intestine increases, allowing toxins and pathogens to cross the barrier and enter blood flow [5].

Various bioactive can help enhance gut health. Prebiotics and probiotics are some of the most prominent and effective compounds beneficial for gut microbiota. Prebiotics contain non-digestible fibres, which selectively stimulate the activity of gut bacteria and increase their population. Probiotics contain live microorganisms which restore the biome balance when consumed in adequate amounts.

Cardiovascular Health: Cardiovascular disease (CVD) refers to a group of disorders that impact the heart and blood vessels. It is one of the leading causes of. Although various factors, like genetics and environmental factors, influence CVD, it is primarily experiencing a rise due to poor lifestyle.

The majority of CVDs are caused by high cholesterol, LDL, and hypertension. These lead to plaque formation, narrowing the walls and reducing blood flow. When the artery carrying blood to the brain is blocked, it leads to brain stroke. Hypertension, or high blood pressure, damages arteries and reduces blood circulation. Obesity also increases the risks of CVDs by increasing blood pressure. Deposition of fat occurs around the heart and blood vessels, which can obstruct blood flow, leading to brain stroke and heart attack. Similarly, insulin resistance developed in an obese individual and diabetic patient leads to high blood sugar and increased fat deposits around arteries. This deems them at high risk of CVDs.

Neuroprotection and Cognition: Neurodegenerative diseases like Parkinson’s disease and Alzheimer’s are proven to have a correlation with oxidative stress, mitochondrial damage and neuroinflammation. These factors affect neurons and deteriorate them over time, leading to cognitive and motor dysfunctions, and memory loss. Bioactive compounds, which help reduce the above factors, have shown potential in preventing neurodegeneration. Compounds like omega-3 and curcumin have been reported to be beneficial for cognitive health as they provide protection against ROS damage and inflammation [6].

Cancer Prevention: When a normal cell undergoes genetic mutation and grows uncontrollably, it gives rise to cancer cells. Some of these cells succeed in evading mechanisms of the immune system and lead to the formation of tumours. This mutation is triggered by various factors like inflammation, oxidation and genetic modifications. Defects in tumour suppressor gene (e.g. TP53), which functions in apoptosis of cancer cells, prevent it from producing necessary proteins, leading to uncontrolled growth of cells. Oncogenes responsible for cell growth turn into cancer-causing cells through genetic faults. Antioxidants help prevent tumour formation by neutralising ROS, which causes DNA damage and genetic instability, leading to mutations. Anti-inflammatory compounds prevent cytokine formation in neurons involved in cancer progression [7]. Sulforaphane (present in broccoli) can induce apoptosis and is considered for therapy against tumours [8].

Ageing: Ageing is a natural phenomenon influenced by multiple factors, such as genetics, lifestyle, and environment. It is characterised by a decrease in physiological functions and susceptibility to diseases caused by the accumulation of cellular damage. Collagen protein is responsible for structural integrity and is present in skin, tendon, cartilage, and bone. This protein is degraded over time as a result of senescence.

Proper diet and lifestyle can regulate ageing by decreasing cellular damage. Bioactive compounds that aid in oxidative stress and inflammation help reduce cellular injury and slow senescence. Telomere metabolism is also closely related to oxidation status. As a result, antioxidants and anti-inflammatory agents can slow down the shortening of telomeres, which is a hallmark of ageing. Polyphenol compounds like flavonoids inhibit collagen degradation by reducing inflammation. Collagen production can be induced by consuming compounds which stimulate fibroblast (cells that contribute to collagen production). Geroprotectors like metformin (medication for Type 2 Diabetes) are studied in geroscience as a possible drug for longevity [9].

Bioactive compounds present in FFs and nutraceuticals are derived from various sources from plants and animals. In the following section, we will discuss the participation of various biological actives that contribute to health.

Polyphenols: Polyphenols are plant-derived compounds which are secondary metabolites of all vascular plants. It is characterised by one or more hydroxyl rings over a benzene ring, which gives it the ability to scavenge ROS. Apart from having exceptional antioxidation properties, polyphenols are anti-inflammatory, anti-allergenic and cardioprotective. It can increase cellular glucose metabolism by inducing the expression of GLUT1, and can be used as a therapeutic agent in diabetes treatment. Being equipped with multiple functions makes polyphenols a great therapeutic and functional compound.

• Flavonoids
• flavanols (e.g. catechin, theaflavin)
• flavonols (e.g. quercetin, kaempferol)
• flavones (e.g. luteolin, apigenin)
• isoflavones (e.g. daidzein, genistein)
• flavanones (e.g. eriodictyol, hesperetin)
• anthocyanidins (e.g. cyanidin, delphinidin) Natural sources: Fruits (berries, apples, citrus fruits), vegetables (onion, broccoli, spinach, legumes), nuts (walnut, peanut, almonds), beverages (tea, wine) and cocoa.

Phenolic Acids: These are compounds derived from cinnamic acid and benzoic acid.

• hydroxybenzoic acid (e.g. gallic acid, salicylic acid)
• hydroxycinnamic acid (e.g. caffeic acid, coumaric acid) Natural Sources: fruits (blackberries, grapes, pomegranates), vegetables (spinach, broccoli, radish), nuts (walnuts, hazelnuts, almonds), beverages (coffee, tea), and beans (black and white).

Stilbenes: Used in the manufacturing of dye. The most popular functional compound of this subclass is resveratrol (found in grapes, berries, cocoa, and peanuts), which is produced by plants as a secondary metabolite in response to injury or pathogen attack. This bioactive is widely proven for its multifactorial properties, including antioxidation, cardiovascular benefits, anti-inflammatory properties and anti-ageing effects [10].

Lignans have phytoestrogen properties, which lower breast cancer and menopausal symptoms in females. Predominantly found in flax seeds, lignans decrease the risk of CVD and osteoporosis [11].

Fatty Acids (Primary sources are fish and nuts)

• MUFAs (monounsaturated fatty acids): Increases level of HDL [12].
• PUFAs (polyunsaturated fatty acids): Predominantly found in flax seeds One of the few compounds that crosses the blood-brain barrier and induces cognition by reducing neuroinflammation [13]. These contribute as structural FAs for the integrity of cells and neural functions. Despite its functions, mammals lack a system to synthesise PUFAs. **
• Linoleic acid (omega-6): Essential component of ceramide. Moderate intake can reduce LDL-C. Arachidonic acid (omega-6 FA) is a precursor for many lipid metabolites
• Linolenic acid (omega-3): Omega-3 FA, primarily EPA and DHA, participates in various functions, including transportation of compounds to and fro BBB., Supplementation during pregnancy leads to improved cognition in children. HDL** is predominantly known as ‘good cholesterol’ as function to reverse cholesterol transport (RCT) [14].

Carotenoids: Pigment found in red, yellow and orange fruits with antioxidative properties.

• Carotene
• α-carotene: Precursor of vitamin A, which produces collagen (structural protein). It also reduces ROS and supports eye and skin health. It can be found in carrots, pumpkins and sweet potatoes.
• β-carotene: Precursor to vitamin A and ROS scavenger. Found in green leafy vegetables, carrots and sweet potatoes.
• Lycopene: Found predominantly in tomatoes, it is a potent antioxidant and modulates gene expression to promote DNA and apoptosis. Xanthophyll: Yellow pigment which possesses antioxidative properties and support eye health by acting as natural blue-light filters. These are sourced from algae and seafoods.
• Primary xanthophyll (lutein, zeaxanthin, β-cryptoxanthin)
• Secondary xanthophyll (astaxanthin and canthaxanthin) Fiber: It is a complex carbohydrate which is non- digestible. It helps regulate blood sugar. Prebiotics are fibres which additionally stimulate gut microbiota. **
• Soluble Fibres (e.g. oats): Water soluble and regulate hunger.
• Insoluble Fibres (e.g. legumes): Insoluble in water and help food move through the system Vitamins
• Vitamin A** derives retinoic acid, which shows anti- ageing properties by stimulating collagen production.

Also vital in optical health as it indirectly produces retinal, a critical component for vision. Examples: Fish, eggs, carrot.

Vitamin B Complex • Thiamine (B1): It metabolises carbohydrates. Examples: Whole grains. • Riboflavin (B2): Precursor for coenzymes involved in energy production and metabolism. Examples: Eggs • Niacin (B3): Part of coenzyme NAD (essential in multiple cellular processes). Example: Chicken • Pantothenic acid (B5): Involved in synthesis of coenzyme A. Example: Avocado • Pyridoxine (B6): Involved in glycogenolysis and gluconeogenesis. Example: Poultry. • Biotin (B7): Catalyse carboxylases involved in metabolism of amino acids, FAs and glucose. Examples:

Eggs • Folic acid/ Folate (B9): Crucial in RBC production and nucleic acid synthesis as a cofactor. Examples: Broccoli • Cyanocobalamin (B12): Essential in neural functions and forms RBCs alongside B9. Examples: lean meat • Vitamin D • Ergocalciferol (D2): Synthesised by plants. Promotes bone health by regulating calcium and phosphate metabolism. Example: Mushrooms • Cholecalciferol (D3): Synthesised by animals. Promotes calcium absorption. Example: Exposure to UVB rays is enough for self-production. • Vitamin E: Potent antioxidant and protects lipids from oxidation, supporting health and immunity [15]. Example: Sunflower seeds. • Vitamin K: Coenzyme in blood clotting. Example: green leafy vegetables.

Minerals

• Macro minerals: Includes calcium, magnesium, potassium, sodium, phosphorus, sulfur and chloride required for proper metabolism functioning and various processes. Sources are milk, leafy vegetables, banana, meat and sea salt.
• Trace minerals: Includes iron, zinc, copper and manganese. Example: Leafy vegetables, seafood and whole grains. **
• Glucosinolates (found in cruciferous vegetables like broccoli and cabbage) are sulphur-containing phytochemicals.
• Sulforaphane is a potent bioactive with multifaceted effects, from anti-cancer to neuroprotection. A study on Parkinson’s disease concluded that treatment with sulforaphane prevents cell death of neural tissue [8].
• Probiotic are live bacteria beneficial for gut microbiome. They support pre-existing microbiota to enhance metabolism. Examples: yogurt.
• Diarylheptanoid (Polyphenol)
• Curcumin:** This bioactive compound found in turmeric display potent therapeutic properties. It scavenges ROS as an antioxidant and exhibit anti-inflammatory effects by inhibiting NF-κB pathway and other proinflammatory processes Table 1. It is therapeutic as anti-cancerous as it induces apoptosis and metabolism of cancer cells. It prevents neurodegenerative diseases by preventing plaque formation of β-amyloid. It is known to help control CVD by reducing C-reactive protein (risk factor for CVD) [16].