DEFINING A HEALTHY DIET: PART 3 - EVIDENCE BASED, HEALTH CONDITION DIETS

Medically Reviewed by Dr. Sony Sherpa, (MBBS) - September 16, 2024

This article forms part 3 of a health and wellness series on diet.

Part 1 discusses dietary guidelines and components.

Part 2, Part 3, Part 4 & Part 5 reviews 24 popular diet plans across 7 major dietary categories.

Part 6 concludes the review, debunking common dietary myths and summarizing key findings.

Evidence-Based Diets

The following diets rose to popularity based on evidence regarding major food groups and the effects of focusing on specific proportions of nutrients.

4. Paleo Diet

The Paleo Diet is an abbreviation for the Paleolithic Diet, which is based on the diets of our hunter-gatherer ancestors from the Paleolithic Era^[1]. This is a part of the Stone Age and spans between 2.5 million and 10,000 years ago. It is believed that this diet was the one that we were designed to eat as humans.

The diet has been recreated with the help of archeological remains of hunter-gatherers and their tools, as well as studies of modern-day tribal people and their activities. The Hadza tribe is one of the most extensively studied tribes, as well as one of the potentially oldest, originating near the supposed “birthplace” of mankind (according to fossil records) in central Africa.

The Paleo Diet is a rather broad term, as people of the Paleo Era would have consumed anything they could locally forage or hunt. Fire and stone tools facilitated minimal refinement of natural whole foods and cooking. Foraged produce common to the paleo diet of prehistoric humans include wild varieties of tubers, seeds, nuts, legumes and flowers. Barley and other wild grains may have been found, dried and beaten into simplistic flours. Fruits such as berries may have been consumed, as well as a wide variety of herbs, weeds, and unspecified plant foods.

Contrary to the conventional idea of a caveman, the hunter-gatherer diet was predominantly plant-based with a limited meat intake. This is perhaps due to meat scarcity, the time and effort involved in hunting, and the wider availability of plant-based foods in the environment. It is estimated that meat only took up to 3% of the hunter-gatherer diet. Nutritious insects were also likely to be consumed, as well as insect products like honey and honeycomb. Small fish and shellfish are believed to have been staples of coastal hunter-gatherer communities.

Dairy products and other refined foods, including cooking oil, table salt and extracted sugars, were not consumed. It is unknown if fermented foods were consumed; however, fermentation is a natural occurrence and may have been an occasional addition to the diet. Eggs are not likely to have been a frequent part of the Paleo Diet but may have also been eaten when found.

In general, experts agree that a Paleo Diet averages a macronutrient intake consisting of 35% fats, 35% carbohydrates, and 30% proteins. This figure is just an estimate but not a strict dietary rule as this contradicts natural principles of adaptation.

Paleo Diet principles often emphasize additional healthy lifestyle input, such as plenty of exercise, getting enough sunlight and participating in as many natural activities as possible.

Advantages

While the Paleo Diet has shown the below results in some studies, more research is required before firm conclusions can be drawn. Many of the below benefits may be achieved by decreasing refined foods and increasing whole food intake.

Potential benefits of consuming a properly formulated Paleo Diet include:

• May help to lower the risk of type 2 diabetes and the development of insulin resistance in some cases^[2],but not more than other health diets tested.
• Associated with an improved fasting glucose, lipid and cholesterol profile. These improvements were shown to be markedly better than similar improvements seen while following other healthy diet plans^[3].
• May contribute positively towards maintaining blood pressure.
• Improves digestive and gut health.
• Enhances metabolism and reduces the risk of metabolic diseases^[4].
• May help to promote weight loss and to maintain a healthy BMI.
• Theoretically, protects against cellular damage and excessive inflammation^[5].
• May increase satiety when compared to other popular diet plans, such as the Mediterranean Diet^[6].
• The Paleo diet is noted to be more micronutrient-dense than other diets, including Mediterranean and vegetarian diets. ^[7]

It is interesting to note that in trials, those following the Paleo Diet yielded results without strict dietary portioning and while opting for foods of their preference that would have been available to them as hunter-gatherers.

Disadvantages

A Paleo Diet is prone to the following pitfalls:

• There are no strict definitions of the Paleo Diet, and many interpretations make use of foods that are refined, such as “paleo-friendly” cooking oils. This defies the diet’s intention.
• Adhering to a genuine Paleo Diet is very difficult for most people.
• There is limited evidence to support the benefits, and many claims have been exaggerated based on poor clinical trials.^[8]
• Paleo Diets may promote iodine deficiency^[9].

​5. DASH diet

DASH is an abbreviation for Dietary Approaches to Stop Hypertension, which highlights the aim of the DASH diet plan. Since its creation in 1998, numerous scientific studies have been carried out on the DASH diet that highlights its effectiveness^[10]. It has reigned alongside the Mediterranean Diet as one of the best diets for health promotion.

The diet was designed based on research on factors that affect blood pressure. There is an emphasis on consuming fresh fruits and vegetables, beans, nuts, seeds, whole grains, lean meat, eggs, fish and low-fat dairy products, as well as using these whole foods to increase micronutrient intake.

Magnesium, calcium, potassium, protein and fiber are core nutritional constituents of the diet. Foods of particular importance increase these nutrient levels and include bananas, oranges, and spinach for potassium; dairy and leafy vegetables for calcium; and whole grains, leafy vegetables, nuts and seeds for magnesium. Leafy green vegetables, nuts and seeds are rich in all the nutrients that the diet aims to increase, including protein and fiber.

Processed foods are restricted, involving low sugar, salt and refined oil use – all other types of refined foods are typically avoided on the DASH diet. Oils are classically healthy oils consisting of non-hydrogenated, cold-pressed vegetable and seed oils, fish oils, or oils found within oily produce (e.g., avocados and nuts). These are consumed in low amounts as well.

A daily serving example while following the DASH diet includes^[11]:

• 5 servings each of fresh fruits
• 5 servings of vegetables
• 7 servings of carbohydrates (includes grains and legumes as well as fruit and vegetables)
• 2 servings of low-fat dairy
• 2 or fewer servings of lean meat products
• 2-3 weekly servings of nuts and seeds

Advantages

The main benefit of the DASH diet is that it promotes lower blood pressure, helps maintain stable blood pressure, and potentially reduces the risk of hypertension, even in healthy people.

Other benefits that have been investigated include:

• Decreases the risk of cardiovascular disease, gout, heart failure, type 2 diabetes, weight gain and obesity.
• Helps to enhance digestion and may potentially lower the risk of colorectal cancer.
• May promote optimal liver function.
• Lowers all-cause mortality and promotes longevity.
• Potentially improves bone mineral density^[12].
• May help to enhance hormonal health and regulate testosterone in women with PCOS^[13].

Disadvantages

Disadvantages of DASH include:

• The DASH diet may be troublesome for those with chronic kidney disease due to the higher intake of potassium, phosphorus and protein.
• Those on medications for chronic liver disease ought to avoid the DASH diet as it may promote subsequent kidney disease.^[14]
• Adherence to the DASH diet tends to be low.

6. MIND diet

The MIND diet combines aspects of the Mediterranean and the DASH diet in order to enhance mental health. MIND is an abbreviation for Mediterranean-DASH diet Intervention for Neurological Delay.

Those who designed this diet merely looked at where the two diet plans intersected with nutrients or foods that serve to enhance neurological function. They then derived a list of foods to include plenty of in the diet and a list of foods to avoid. On the MIND diet, one may follow a combination of Mediterranean and DASH diet principles, as long as their diet is tailored to these two food lists.^[15]

MIND Diet Recommendations include:

• A daily serving of green leafy vegetables and a serving of at least one other low-starch vegetable
• 3 daily servings of whole grains
• 2 or more servings of berries every week
• 5 or more servings of a variety of nuts ought to be consumed each week
• 4 or more servings of beans each week
• 2 or more servings of poultry per week
• 1 or more servings of fish per week, 1 of which needs to be fatty
• Switch to olive oil for cooking
• 1 glass or less of wine daily

NOTE: The weekly servings are meant to be spaced out across the week.

The MIND diet restricts the following foods:

• Consume 1 tb sp or less daily of either butter or margarine.

Research indicates that good quality butter may help to enhance brain health, whereas margarine is associated with poor outcomes.

• 3 or less servings of red meat per week
• 1 or less servings of cheese per week
• 1 or less servings of fried foods per week
• 4 or less servings of refined desserts (incl. pastries, ice cream, candy, cake, cookies, etc)

Advantages

There have been several clinical trials that have shown that the MIND diet is as effective as it sets out to be. Larger scale trials are currently being carried out to verify some of the below benefits^[16].

Advantages of the MIND diet include:

• Potentially reducing the risk of acquiring a few neurological diseases associated with aging, including Parkinson’s Disease and its symptoms (parkinsonism)^[17] and Alzheimer’s Disease^{[18] [19]}.
• Slowing the onset and progression of neurological symptoms seen in Parkinson’s Disease^[20] and dementia.
• May help to improve cognition and slow the progression of cognitive decline in aging individuals^[21].
• Preliminary evidence suggests it may lower the risk of age-related cognitive decline^{[22] [23]}.
• In one study, those on the MIND diet who consumed a higher level of nuts and fruits and who completely avoided fast food or heavily fried foods showed a reduced risk of depression.^[24]
• High adherence to the diet may lower the risk of acquiring breast cancer by as much as 50%.^[25]
• May reduce the severity and frequency of migraines in susceptible individuals^[26].

Disadvantages

Disadvantages of the MIND diet include a composite of those seen for both the Mediterranean and DASH diets. The main ones derive from low to moderate adherence and a failure to implement the diet correctly. This diet ought not to be consumed by those with chronic kidney disease.

7. Mayo Clinic Diet

The Mayo Clinic Diet is a very popular commercial diet plan developed by medical professionals, the first iteration of which has been around since the late 1940s^[27]. In 2017, a revised edition was published based on new research, as well as several other versions of the Mayo Clinic Diet that have been tailored for those with specific health conditions.

The aim of the Mayo Clinic Diet is to facilitate weight loss and promote a healthy BMI in order to improve overall health and well-being. This is achieved through increased physical activity, improved nutrition intake, and facilitating a commitment towards healthy habits and lifestyle approaches.

The diet emphasizes consuming fruits and vegetables in larger quantities than other foods, with these foods forming the foundation of the Mayo Diet food pyramid. In the conventional food pyramid, fruits and vegetables are secondary contenders to grains in terms of portion sizes. The Mayo Clinic Diet food pyramid inverts this, making grains the next category. The rest of the pyramid matches a more conventional approach to nutrition, with protein and dairy having equal standing, fats (including from seeds and nuts) to be consumed in lesser amounts, and sugar-heavy foods to be had in moderation.

The Mayo Clinic Diet is a great place to start for someone with an average health profile to improve their eating habits. It does more than just offer a solution for improving nutrition, helping to lay down a new way of thinking and relating to concepts of health and well-being.

In the first phase, one commits to assessing their lifestyle in order to exchange 5 unhealthy habits for 5 healthy ones. An additional 5 habits are added to this list. In this way, one is able to evaluate for themselves the effects of unhealthy habits vs healthy ones and take responsibility for their well-being. It also helps one adjust to a healthy eating pattern. The second phase resembles phase 1, yet it expands one’s knowledge of how to further tailor one’s diet and lifestyle for the best results in the long run.^[28]

One can purchase the full diet plan from the Mayo Clinic’s website for more information.

Advantages

The Mayo Clinic Diet provides the following advantages:

• Easy to follow with practical guidelines on making the transition towards leading a healthier lifestyle^[29].
• Improves overall health and well-being, particularly in those who lead an unhealthy lifestyle prior to the program.
• May lower the risk of cardiovascular diseases and improve bone mineral density due to the greater consumption of healthy foods.
• Promotes weight loss and optimal BMI.

Disadvantages

The Diet is prone to the following disadvantages:

• May be pricey.^[30]
• There have been few clinical trials dedicated to testing the precise effects the Mayo Clinic Diet has on health and well-being. However, the clinic itself has proven the effectiveness of the diet, generating its own successful results with patients^[31].
• Not suitable for individuals with pre-existing health conditions.

8. Raw Food Diet

A raw food diet describes precisely what the diet entails: consumption of only raw foods. The aim of a raw food diet is almost always to increase nutritional status, lower inflammation and enhance gut health.

Generally, a raw food diet revolves around a high intake of plant-based foods that one can safely eat raw, including fruits, leafy greens, edible roots and bulbs, sea vegetables, herbs, spices, legumes, peppers, nuts, seeds, and grains. Strictly cold-pressed oils are usually permitted, yet they may not have been heated over 39˚C (102˚F) during processing. The same can be said of oil-based supplements.

In some versions of the diet, limited intake of raw meat and raw dairy products is permitted; however, a raw food diet is typically carried out in a vegetarian or vegan manner.

Advantages

There is very limited research attesting to the benefits of consuming a raw food diet.

Advantages may include:

• High in digestive enzymes and nutrients, which promotes optimal digestive function, nutrient absorption and improved micronutrient status^[32].
• May promote increased energy levels.
• Facilitates rapid weight loss in overweight people.
• Shows results as a short-term intervention, but not as a long-term plan.
• Higher consumption of raw fruits and vegetables is associated with improved cognition and mental status.^[33]

Disadvantages

NOTE: Due to some of the potential long-term disadvantages associated with consuming a raw food diet, it should not be done on a long-term basis.

Disadvantages of consuming a diet based purely on raw foods include:

• Low adherence.
• May result in a build-up of oxalates (from leafy veg) and phytates (from grains), which would be contraindicated for those with osteoporosis, arthritis, chronic fatigue, nutritional deficiencies and digestive issues. Research indicates that eventually consuming raw foods high in these nutrients results in changes in the microbiome, which help degrade the anti-nutrients and promote nutritional uptake.
• Ingesting raw animal meat products increases the risk of food poisoning.
• May cause a deficiency in B vitamins, particularly B12^[34].
• Limited evidence suggests that consuming a raw food diet may increase the risk of early menopause^[35].
• Long-term consumption of a strict raw food diet may result in being under-weight.
• Should be avoided by those with severe digestive issues as it may increase gas, bloating and other digestive symptoms for the first week or two.

Well-Known Diets Designed for Specific Health Conditions

Several of the below diet plans are often integrated into other healthy diet plans for optimal synergy.

Those with specific allergies, sensitivities or disease-related concerns may choose to adopt the applicable restrictions in line with the below dietary guidelines in order to enhance their well-being.

9. Autoimmune Protocol Diet (Elimination Diet)

Elimination diets have been used for decades to enhance the treatment outcomes of many kinds of autoimmune conditions^[36]. It is observed that those with autoimmune diseases tend to be more sensitive to what they consume on a regular basis, with certain types of foods prone to trigger an inflammatory immune response. As a result, even if the condition is systemic, those with autoimmune diseases tend to have frequent digestive complaints.

The AIP Diet incorporates principles of success from the Paleo Diet and a standard elimination diet. There is a building body of evidence that these dietary approaches may help to improve upon typical digestive symptoms for those with autoimmune conditions.^[37]

The diet demands cutting out foods that may trigger the immune system and including foods that promote optimal gut health.

There are generally two phases: the elimination phase and the reintroduction phase.^[38]

During the elimination phase, the participant will be asked to cut out all processed foods as well as foods that are high in proteins that have been associated with triggering an inflammatory immune or gut response. These include nuts, seeds, dairy, eggs, grains, legumes, nightshades, caffeine, alcohol, and, in some cases, all animal products and fruits.

Generally, this means consuming a very clean, hypo-allergenic diet consisting of a wide variety of vitamin-rich fruits, leafy green vegetables, herbs, spices, brightly colored root vegetables like beets and carrots, squashes, and fermented foods. Vegetables are emphasized more than fruits, and it is advisable to consume fruit in moderation. In some iterations, wild game, fish, organ meat and poultry are permissible as long as they are consumed in moderation and the source is wild or free-range and grass-fed.

The reintroduction phase requires the participant to conduct their own investigation on foods they wish to re-incorporate back into their diet plan. Only one new food may be reintroduced at a time for optimal results, after which one needs to wait a few days and observe. It is important to keep a record of the reintroduced food, as well as of any inflammatory symptoms that arise within 5-6 days of consuming the previously omitted food. It helps to be aware of other stressors (e.g., infection, psychological stress, sleep loss) that occur within that time period when making an assessment, as these may also be potential triggers.

Advantages

Advantages of an AIP diet include:

• Adherence is associated with gene switches that are conducive to well-being, and that detract from autoimmunity.
• Facilitates gut regeneration.
• Helps the participant to assess the impact of their diet on their symptoms and make healthier decisions based on their own observations.
• May help to lessen the severity of digestive symptoms.
• May promote an optimal dietary pattern in the long run.

Disadvantages

This diet is relatively safe to follow and is not known to cause adverse outcomes.

Disadvantages include:

• May be difficult to implement and follow.
• Not everyone is able to single out potential dietary triggers or differentiate them from other triggers.

10. Low FODMAP diet

A low FODMAP Diet is a diet low in specific dietary sugars, with the name standing for the low-fermentable oligosaccharide, disaccharide, monosaccharide, and polyol (FODMAP) diet. These sugars are associated with irritating symptoms in those with IBS and other inflammatory gut conditions.

Those who benefit from a low FODMAP diet tend to have an unbalanced gut microbiome, with an overgrowth in certain types of bacteria that are typically the source of gut irritation. FODMAPs are prebiotics that serve as a major food source for gut bacteria. For this reason, this diet is not suitable as a long-term diet plan as it excludes many foods that are required for optimal nutrition^[39].

Some versions of the diet apply an elimination diet approach to FODMAP foods, enabling the participant to see which high FODMAP foods are able to trigger their symptoms^[40].

Advantages

Benefits of the low FODMAP diet include:

• Reduces bloating, gas and associated abdominal pain.
• May help lessen the severity of symptoms^[41] and improve overall well-being^[42] for those with IBS.

Disadvantages

A low FODMAP diet has the following pitfalls:

• May detract from microbial diversity in the gut, which negatively impacts digestive health in the long run.
• Not as thorough as an autoimmune elimination diet in terms of identifying dietary triggers.
• Evidence to support its efficacy is preliminary^[43].

11. Gluten-Free Diet

A gluten-free diet is a diet that avoids all gluten. This diet often serves as the main treatment plan for individuals with celiac disease or non-celiac gluten sensitivity who are extremely allergic to gluten. Those with nonceliac gluten sensitivity may only be gluten intolerant some of the time^[44]. A gluten-free diet may additionally benefit individuals with digestive issues and is sometimes recommended as a short-term dietary modification when experiencing digestive complaints.

Gluten is an extremely complex group of proteins, made up of more than 28 unique proteins. Some iterations of a gluten-free diet advocate merely avoiding all gliadin. Gliadin is one of the most complex proteins found in gluten, and compared to the other gluten proteins, it has one of the largest associations with triggering gut inflammation.

Limited research suggests that many more people are gluten intolerant than previously thought^{[45] [46]}. Those with mild gluten intolerance may still be able to consume fermented sources of gluten, such as sourdough bread. Minimally refined sources of gluten may also be better tolerated.

Advantages

The only real advantage of a gluten-free diet is that it minimizes exposure to gluten, which avoids allergic responses in susceptible individuals. It poses no benefit for individuals who have a good tolerance towards gluten.

Disadvantages

Disadvantages include:

• An increased food cost.
• An increased risk of nutritional deficiencies^{[47] [48]}.

12. Low GI diet

A low glycemic index (GI) diet plan is a diet aimed at controlling blood sugar levels by consuming low-GI foods. GI stands for Glycemic Index and refers to a food reference list that suggests the impact of various foods on blood sugar levels. Foods are given a number from 0 to 100, with 100 being the same GI score as pure glucose. Dates may be one of the few foods with a GI higher than 100.

Foods with a higher glycemic index are more likely to spike blood sugar levels and promote the increased release of insulin.^[49]

A low-GI diet may be indicated for those with diabetes and other metabolic conditions.^[50]

Advantages

All the advantages of consuming a low-GI diet only arise within the context of adequate nutrition. Almost all refined foods are avoided as they are high on the glycemic index, which is already associated with enhanced well-being.

Potential advantages of a low-GI diet include^[51]:

• Improving post-prandial blood sugar levels.
• Promoting a balanced blood lipid and cholesterol profile.
• May reduce the risk of coronary heart disease.
• Promotes healthy weight loss.
• May help maintain healthy blood pressure^[52].

Disadvantages

Consuming a low-GI diet is prone to the following disadvantages:

• Avoiding potentially healthy foods that happen to have a high GI.
• Evidence is lacking that a low-GI diet is effective without an emphasis on adequate nutrition.
• Studies purporting the positive benefits of consuming a low-GI diet are often misleading as the diets are based on other beneficial health principles^[53].
• This type of diet may lower microbial diversity in the gut.
• Low adherence^[54].

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