DEFINING A HEALTHY DIET: REVIEW OF 24 POPULAR DIET PLANS AND THEIR CONTRIBUTIONS TOWARDS WELL-BEING

Medically Reviewed by Dr. Sony Sherpa (MBBS) - September 13, 2024

At the end of the day, a diet is ultimately what one eats on a continuous basis.

There is a lot of pressure on people to remain healthy, eat well, and be at their best, particularly with regard to productivity. Diets are constantly promoted as one of the primary means to achieve this.

While this understanding means well, there is no fixed diet plan that works for every person on the planet. Rather, the best diet plans have a few key factors in common that enhance health and well-being, in spite of their major differences.

The following dietary review highlights key dietary factors across many types of diets that promote health and well-being. Basic nutritional components of diet are explained, alongside factors that improve the chance of successful dietary outcomes. Lastly, following a comprehensive review of 24 popular diet plans, diet myths and dated perceptions of health are discussed.

Why Go On A Diet?

It’s important to ask this question before attempting to adopt a specific diet plan. Every diet out there is designed with a unique purpose in mind, and that purpose may not be in line with your personal goals.

The most common reason for adopting a diet plan would be to improve health in one way or another. If this is true in your case, then it helps to know precisely what about your health you wish to improve.

For example, many wish to diet in order to lose weight, which is known to directly improve health^[1] as well as lessen the risk of developing related metabolic diseases^{[2] [3]}. However, not all diets designed for weight loss are good for your overall health and may have negative consequences in the long run^[4].

Some diet plans are there to enhance health in general, while others focus on particular aspects of wellness. Unfortunately, generalized diet plans often fall short. This is because there are many factors that can affect which diet may improve one’s health on an individual level. Some of these factors are described briefly below to give a general idea.

Nevertheless, it is still advisable to get professional help before making extreme dietary changes, as these are likely to be based on the limited or biased information found online.

What Makes for a Good Diet Plan?

A good diet plan is one that is nutritious, healthy, and easy to follow. This may mean something unique to every person.

If a diet meets the following indications, it is a sign that it may work for you:

1. Aim. A diet that was designed to achieve a goal that you have in mind is an ideal diet for you. Make sure you have a clear understanding of what you want to achieve by opting for a specific diet plan.
2. Achievability. If you are not able to fulfill the requirements of the diet plan for any reason, then it is pointless to adopt the diet and expect to get the intended results. Low adherence is known to be one of the main barriers to the success of any healthy diet plan. Access to the foods recommended, affordability, and personal preferences are important to consider, as these will determine how well you are able to adhere to the diet.
3. Variety. A diet that offers a wider variety of foods is likely to be more successful than one that severely limits your options. Variety is important in terms of adherence, nutrition, health and fulfillment.
4. Balance. A balanced diet is another important part of choosing a good diet that can improve your health. Any diet that completely does away with an entire food group is considered extreme and likely to cause problems in the long run. Such extreme practices are only truly used by professionals as short-term interventions to reach a specific health goal, often one that is oriented toward achieving a balanced diet in the end.

Nutritional Components of a Balanced Diet

Every official diet plan has been formulated to fulfill the nutritional requirements of a specific health profile. By altering the ratio of nutrients consumed, one can affect their cellular metabolism in numerous ways, which have widespread consequences for health and well-being^[5]. The effect certain nutrient ratios have on one’s health is unique to the individual’s biology.

While it is known that certain nutritional profiles are good for the health profiles of certain types of people, there is still bound to be a substantial amount of variation. This is important to keep in mind when choosing a diet that is appropriate.

The main nutritional components of one’s diet are conventionally broken down into macro and micronutrients. A balance of all nutrient groups is required for optimal health, as is highlighted below.

Macronutrients

Most people have heard of macronutrients and haveg a basic understanding of them. They consist of:

1. Carbohydrates

Carbohydrate is another fancy name for sugar. They consist of simple and complex carbohydrates. Simple carbs are readily absorbed, while most complex carbs get broken down into simple ones during the process of digestion. Simple carbs are mostly simple sugars, while complex carbs mainly consist of complex sugars, starches, and fibers.^[6]

The body uses simple carbohydrates as one of several fuels for cellular energy production. While glucose is one of the main substrates for cellular energy production, glucose is not the only simple carbohydrate used for that purpose. Lactate has recently been shown to be an alternative carbohydrate substrate used for cellular energy production^[7].

Most fruits and vegetables are a composite of carbohydrate types, however, carbs can be found in varying proportions in grains, legumes, pulses, sprouts, nuts, seeds, and dairy products. Refined sugars are carbohydrate extracts from plants and sometimes dairy.

All carbohydrates feed the bacteria in the gut, serving as energy substrates for them as well as the cells of the body. Complex carbohydrates tend to sustain energy production for longer periods of time due to a slower release of nutrients throughout digestion. A healthy blend of carbs is required furthermore to sustain bacterial growth, feeding, and the further digestive processes that occur in the colon near the end of the gastrointestinal tract.

Fiber, especially water-soluble fiber, helps to promote the survival of bacteria in the colon, which maintains optimal nutrient absorption. This is especially true of fats, vitamins, and electrolytes.

Simple sugars and starches are more easily digestible by digestive juices and tend to be broken down in the small intestine. This is why pure sugar tends to increase energy levels almost immediately, while consuming complex carbohydrates often promotes sustained energy levels.

2. Fats

Fats are required for many cellular processes in the body, including being an important component of energy production. We need fats in order to produce cholesterol^[8], which is the base building block of all hormones in the body. Fats are also a vital component of cell walls, non-hormonal cell signals, as well as nerve (myelin sheath) and organ (brown fat) insulation.

Like with carbohydrates, fats are classified according to their density and complexity.^[9] Fat molecules are made up of lipid chains, which become increasingly difficult to break down and absorb the larger molecules. Short-chain and medium-chain fatty acids are readily digestible, while long-chain and very long-chain fatty acids require more work to absorb.^[10]

In addition to the chain length, fats may be saturated or unsaturated. Saturated fats have a molecular structure that is richer in hydrogen ions, and that takes more time to break down during digestion. Unsaturated fats are less “saturated” in hydrogen and are therefore easier to digest. Fats become progressively more saturated during oxidation or heating. Unsaturated fats may become saturated in this fashion^[11], while saturated fats that become overly oxidized turn into trans-fatty acids^[12]. Trans fats are the most difficult fats for the body to process and are often associated with promoting ill health.

It is important to remember that digestion is a process of slow oxidation in which foods get broken down. In the gut, long-chain fats make it to the colon and help to feed the bacteria there, much like fiber does. Trans fats and very long-chain fats are difficult for these bacteria to digest and, as a consequence, tend to produce inflammation^[13] and decreased levels of probiotic bacteria^[14]. A diet too high in saturated fat may cause similar trouble^[15].

These types of fat also influence cholesterol production and maintenance. Unsaturated fat tends to increase high-density lipoprotein (HDL) cholesterol, saturated fat tends to increase low-density lipoprotein (LDL) cholesterol, and trans fat increases LDL while diminishing HDL^[16]. Dietary trends promote increasing unsaturated fat consumption to balance the cholesterol profile associated with the Western diet; however, saturated fats are also required in small amounts for optimal health and well-being.^[17]

Amongst these classifications, there are also many types of fat that serve unique functions in the body. For instance, omega-3, omega-6 and omega-9 fats are all essential for a variety of reasons, including immune function, cellular repair, pain signaling, and more^[18]. If any one of these is overly consumed, issues may arise at the cellular level that detract from health and well-being^[19].

3. Proteins

Protein is often associated with animal products and beans; however, it is a common component of most foods. Similar to other food groups, proteins can be broken down into peptides and polypeptides, the latter of which is more complex, larger, and more difficult to break down during digestion.

Proteins are often harder to digest than any of the other nutrient groups as they are typically dense molecules. In order for protein absorption to take place, both the digestive organs and the gut microbiome^[20] need to be working properly, which partly demands the consumption of the other nutrient groups.

Amino acids are perhaps the most vital of protein nutrients^[21]. They form a substrate for many important proteins that our own cells make in order to function, including DNA, signaling peptides, cellular antioxidants, enzymes, growth factors, nutrient and hormone chaperones as well as intermediate compounds used in energy production. The proteins our cells make often have a mineral component to them as well, as evidenced by selenoproteins, iodoproteins, and heme proteins.

Micronutrients

The smallest things are some of the most underestimated. Nothing could sum this up better than when looking at micronutrients in the diet. These are nutrients that are abundant in all foods in trace quantities. Our cells also require them in trace amounts to sustain optimal function^{[22] [23]}.

Essential micronutrients classically consist of vitamins and minerals; however, there are also plenty of other micronutrients in food that help to promote cellular well-being.

1. Vitamins

Vitamins are vital for our health and are required in order to allow for cells to function properly. The vitamins A, D, K and E are fat-soluble, while Vitamin C and the B vitamins (B1, B2, B3, B5, B6, B7, B9, and B12) are all water-soluble. Many of the water-soluble vitamins can be produced by colonic gut bacteria. The same colonic bacteria are indispensable for extracting and absorbing fat-soluble vitamins.

To highlight their importance, a few functions of essential vitamins are listed below:

• Vitamin A is required for immune function, melanin production, and/or radiation protection in the skin, liver and digestive function, and maintaining vision.^[24]
• Vitamin D is necessary for regulating many pathways at the cellular level^{[25] [26]}. Examples include immune function, energy balance, cellular metabolism, and the production of major hormones such as parathyroid hormone.
• Vitamin E helps to stabilize cellular oxidation^{[27] [28]}, which is a fundamental yet potentially dangerous part of cellular metabolism. It works with Vitamin C in order to promote cellular homeostasis by preventing a buildup of destructive oxygen species^[29].
• Vitamin K is another vital vitamin that serves as a prohormone in many types of cells within the body. It promotes adequate immune function, is required to regulate blood platelets, thins the blood, and works together with vitamin D in order to keep calcium and other essential minerals inside bone tissue. ^[30]
• B vitamins are necessary for facilitating small, yet crucial parts of energy production, as well as many other vital processes such as cellular nutrient absorption, growth, repair, and defense^[31]. The nervous system especially benefits from B vitamins^[32].
• Vitamin C is a primary cellular antioxidant compound, working together with Vitamin E in order to ensure that cells do not overproduce destructive compounds during oxidation. The cells of the brain make more use of vitamin C than any other tissue in the body, using it as a substrate for many vital processes.^{[33] [34]}

2. Minerals

Minerals are perhaps the smallest of all nutrients, in spite of having some of the largest effects on our biology. Much of our biochemistry is governed by the movement of minerals in the form of charged particles known as ions.

There are seven main mineral ions that are absolutely essential for basic cellular function. They are commonly referred to as electrolytes. These include^[35]:

• Sodium and potassium are vital regulators of the heartbeat, as well as the influx and efflux of fluids and other compounds moving in and out of cells.
• Calcium is used to transport electrons within cells, acting as a signaling molecule and an important component of cellular energy production. Neurons are an example of a cell that is dependent on higher levels of calcium in order to transmit electrical information.
• Magnesium and phosphorus regulate the majority of chemical processes within the cell, often acting as vital cofactors for chemical reactions and energy production.
• Chloride serves a few functions at the cellular level, typically pertaining to enzyme formation and maintaining pH.
• Bicarbonate is used to balance pH within the body, typically keeping the action of acids under control.

Aside from electrolytes, many other trace minerals are required for optimal health. Examples include selenium, iodine, manganese, molybdenum, copper, sulfur, zinc, and iron. Many of these are found alongside proteins and other macronutrients in foods.

3. Phytochemicals and Other Beneficial Micronutrients

There are a host of other nutrients found in trace amounts in foods that interact with our biology in a beneficial manner.^{[36] [37]} These compounds are known as phytochemicals and tend to give food sources their flavor and color.

At the cellular level, they may mimic essential cellular signaling molecules, such as hormones^[38], antioxidants^[39] or other nutrients. As a result, they may help enhance health or detract from health, depending on the source and the biology of the organism consuming them.

4. Probiotics

Probiotics are not considered an essential nutrient but are becoming increasingly recognized as an important part of optimizing digestion and nutritional absorption. In this sense, maintaining healthy populations of gut bacteria is an important consideration to make when wanting to improve nutritional status. Furthermore, the bacteria of the gut produce additional nutrients, some of which are already known to be essential, such as vitamins, and others that are being newly discovered as essential for the body.^[40]

Probiotic bacteria tend to grow in the gut based on the availability of nutrients, which is based on what we eat. However, since the advent of antibiotics and mass-produced chemicals with antibiotic-like actions, humanity's gut microbiome has been seeing a decline in bacterial diversity^[41]. This has coincided with the sudden rise in lifestyle diseases and sub-clinical nutrient deficiencies observed in the last couple of decades. Research highlights the role of the gut microbiome in promoting states of either health or disease.^[42]

In this context, consuming a healthy balance of macro and micronutrients may not be sufficient to meet one’s nutritional needs if the microbiome is too depleted of functional bacteria. Probiotics consist of fermented products that contain high numbers of bacterial strains found in the gut microbiome. For the above reasons and more, many experts consider small portions of fermented foods to be an essential component of dietary well-being.

Factors Influencing Personalized Nutrition

The food we eat is not enough to dictate our health, a point that cannot be stressed enough. One’s overall metabolism is affected by more than just their diet^[43].

Our nutrition provides the building blocks that our cells then process, and the net result is the productive output of the cell. This is the overall metabolism of a cell, and it includes the efficiency with which the cell can produce proteins and other compounds (e.g., hormones) to serve vital functions.

Genetics plays a role in dictating certain aspects of cellular function and how cells in all tissues may utilize nutrients in order to function. Many gene sets respond to the environment and change their configuration, leading to subtle metabolic differences. This field of study is known as epigenetics - how the environment influences our genes. In this respect, diet is regarded as a highly influential environmental factor that interacts with our genes - for better or for worse.^[44]

Energy metabolism is a core component of cellular metabolism as it facilitates all cellular activity. The mitochondria govern cellular energy metabolism^{[45] [46] [47]} and have been shown to profoundly affect the majority of operations within the cell^[48]. Unlike any other cellular organ apart from the nucleus, the mitochondria have their own set of genes that dictate their functioning. These are also affected by epigenetic factors.^[49]

Ongoing research into the gut microbiome has revealed that the microbiomes of the gut and of other tissues in the body are a second set of genes that interact with our cells^{[50] [51],} also having an effect on their metabolism^{[52] [53] [54]}. The gut is the largest pool of bacteria we house and the microbes it houses can alter the activity of cells in nearly all systems and tissues.

Environmental factors such as physical activity levels^[55], one’s lifestyle choices, and any physically stressful events (i.e. emotional and/or physical trauma, chronic illness, etc) affect cellular metabolism and influence the required output of cells. For example, factors that may give rise to cellular damage promote the cell to focus on repair processes. This may demand more energy and certain kinds of nutrients or building blocks to achieve.

In this way, the perfect diet is dependent on the metabolic requirements of the person at the cellular level.