Special Diets: Vegan, Keto, DASH, Prediabetes, and Safety

Choose the Diet You Want to Explore

Select the eating pattern that matches your main interest.

What Is a Special Diet?

A special diet changes a normal eating pattern for a defined purpose.

Special diets can be grouped into several types.

Preference or Values-Based Diets

These may include vegan, vegetarian, religious, cultural, or environmentally motivated eating patterns.

Medical Diets

These may include renal diets, celiac diets, food allergy diets, liver disease diets, diabetes meal plans, or diets used for metabolic conditions.

Therapeutic Diets

These are used as part of treatment under professional care.

Examples may include a medically supervised ketogenic diet for epilepsy or a low FODMAP trial for IBS.

Performance Diets

These may change protein, carbohydrate, calories, hydration, or meal timing to support training and recovery.

Weight Management Diets

These may reduce calories, carbohydrates, fat, meal frequency, or specific foods.

The diet name matters less than whether the plan is safe, nutritionally adequate, and sustainable for the person using it.

Special Diet Comparison Chart

This chart gives a general overview.

It is not a personal recommendation.

How to Choose a Special Diet Safely

1. Define the Goal

Ask what you expect the diet to do.

Possible goals include:

• Manage a diagnosed medical condition
• Follow ethical or religious values
• Improve food quality
• Support sport or muscle
• Manage digestion
• Change body weight
• Reduce blood pressure
• Support pregnancy

A clear goal makes it easier to judge whether the diet is helping.

2. Choose the Least Restrictive Effective Option

Removing more foods does not make a diet more powerful.

Choose the smallest change that can meet your goal.

This protects food variety and reduces nutrient risk.

3. Check Nutrient Coverage

Review:

• Total energy
• Protein
• Fiber
• Vitamin B12
• Iron
• Calcium
• Vitamin D
• Zinc
• Iodine
• Omega-3 fats
• Potassium and phosphorus when medically relevant

4. Review Medicine

A large diet change can affect blood sugar, blood pressure, fluid balance, blood clotting, and medicine timing.

Ask your prescriber or pharmacist whether monitoring or dose changes may be needed.

5. Check Whether the Diet Is Sustainable

A plan should fit your:

• Budget
• Culture
• Schedule
• Cooking skills
• Family meals
• Food access
• Social life
• Health needs

6. Plan a Review Date

Do not follow a restrictive experiment forever without reviewing it.

Check symptoms, energy, bowel habits, weight trends, training, laboratory results, and mental health.

Vegan and Vegetarian Diets

Vegan diets exclude animal foods.

Vegetarian diets vary.

Some include eggs, dairy, or both.

These patterns can support a varied and nutritious diet when they are planned carefully.

Build Meals Around Whole Plant Foods

Useful choices include:

• Beans
• Lentils
• Chickpeas
• Tofu
• Tempeh
• Edamame
• Whole grains
• Vegetables
• Fruit
• Nuts
• Seeds
• Fortified foods

Vitamin B12 Is Essential

Vitamin B12 is naturally found in animal foods.

Plant foods do not naturally contain vitamin B12 unless they are fortified.¹

People following a vegan diet need a reliable source of fortified food, supplements, or professional guidance.

Do not rely on seaweed, fermented vegetables, or unverified natural products as dependable vitamin B12 sources.

Protein

Plant proteins can meet needs when food variety and total intake are adequate.

Combine different sources throughout the day.

You do not need to combine specific proteins in every meal.

Iron

Plant iron is found in beans, lentils, tofu, seeds, whole grains, and fortified cereal.

Vitamin C-rich foods can help the body absorb plant iron.

Do not diagnose iron deficiency from tiredness alone.

Calcium and Vitamin D

Use fortified plant drinks, calcium-set tofu, beans, tahini, almonds, and suitable green vegetables.

Check vitamin D fortification because products vary.

Iodine

Iodine may come from iodized salt, fortified foods, supplements, dairy, eggs, or seafood, depending on the diet.

Seaweed iodine can be very high and unpredictable.

Omega 3 Fats

Walnuts, chia, flaxseed, hemp, and some oils provide ALA omega-3.

Algae products may provide DHA or EPA.

Supplements are not required for every person.

Children, Pregnancy, and Older Adults

These life stages require extra attention to calories, protein, vitamin B12, iron, calcium, vitamin D, iodine, and other nutrients.

Use qualified professional guidance.

Ketogenic and Low-Carbohydrate Diets

A ketogenic diet is very low in carbohydrates and high in fat.

It is different from simply reducing sweets or refined grains.

A moderate low-carbohydrate diet may include more vegetables, beans, fruit, or whole grains than a ketogenic plan.

Possible Reasons People Try Keto

• Weight management
• Appetite management
• Blood sugar goals
• Personal preference
• Medically supervised epilepsy treatment

Nutrition Issues to Review

• Fiber intake
• Vegetable variety
• Micronutrients
• Saturated fat
• Constipation
• Hydration
• Sodium and electrolytes
• Kidney stones
• Blood lipids
• Long-term sustainability

Diabetes Medicine Safety

People using insulin or medicine that can lower blood sugar may need closer monitoring when carbohydrate intake changes.

Do not reduce insulin or another medicine on your own.

FDA-approved prescribing information for SGLT2 medicines identifies factors such as ketogenic eating, missed insulin, illness, surgery, dehydration, and reduced food intake as possible ketoacidosis triggers.⁷

People using an SGLT2 inhibitor should speak with their prescriber before starting a ketogenic diet.

Possible Ketoacidosis Symptoms

Seek urgent medical care for symptoms such as:

• Nausea
• Vomiting
• Abdominal pain
• Deep or rapid breathing
• Severe weakness
• Confusion
• Unusual sleepiness

Ketoacidosis can occur even when blood glucose is not extremely high in people using some SGLT2 medicines.

Who Should Seek Professional Advice First?

• People with diabetes
• People using SGLT2 medicines or insulin
• Pregnant or breastfeeding people
• Children
• People with kidney, liver, gallbladder, or pancreatic disease
• People with an eating disorder history
• People with very high cholesterol or triglycerides

Prediabetes and Diabetes Eating Plans

Prediabetes means blood glucose is above the usual range but not high enough for a diabetes diagnosis.

It raises the risk of developing type 2 diabetes, although long-term lifestyle changes and, for some people, medicine can reduce that risk.

There is no single required prediabetes diet.

NIDDK emphasizes long-term eating and activity changes rather than quick-fix plans.³

Useful Food Priorities

• Vegetables
• Whole fruit
• Beans and lentils
• Whole grains
• Suitable protein foods
• Healthy fats
• Water and low-sugar drinks

Carbohydrate Quality and Portion

Carbohydrates are found in fruit, milk, beans, grains, potatoes, sweets, and sugary drinks.

They do not affect health in the same way.

Food quality, portion, preparation, meal balance, and medicine all matter.

Weight Management

For adults with overweight or obesity, gradual weight loss may reduce type 2 diabetes risk.

Weight loss is not required or suitable for every person.

Focus on sustainable habits rather than rapid loss.

Physical Activity

Regular movement supports blood sugar management and overall health.

Begin with an amount that fits your health and ability.

Medicine and Monitoring

People using insulin or other glucose-lowering medicines may need meal timing and carbohydrate guidance.

Do not fast or sharply reduce carbohydrates without discussing medicine safety.

The DASH Eating Plan

DASH means Dietary Approaches to Stop Hypertension.

It is a flexible and balanced eating plan designed to support healthy blood pressure.

It does not require special branded food.²

DASH emphasizes:

• Vegetables
• Fruit
• Whole grains
• Beans
• Nuts and seeds
• Fish
• Poultry
• Low-fat or fat-free dairy foods
• Lower sodium intake

DASH Is Not a Detox or Short Challenge

It is an eating pattern that can be adapted to culture, budget, and calorie needs.

You do not need to change every meal at once.

Kidney Disease Caution

DASH includes many potassium-rich foods.

This can be useful for many people, but may need adjustment when kidney disease or high blood potassium is present.

Potassium salt substitutes can also interact with kidney disease and some blood pressure medicines.

Pregnancy and Breast-Feeding Nutrition

Pregnancy nutrition is not a weight-loss diet.

It should support the pregnant person and the developing baby.

Needs vary according to health, pregnancy stage, body size, food access, nausea, vomiting, diabetes, and other conditions.

Folic Acid

CDC recommends 400 micrograms of folic acid each day for people who can become pregnant.⁵

Some people require a different amount based on medical history.

Use personal advice from a qualified maternity professional.

Other Nutrients

Pregnancy may require closer attention to:

• Iron
• Iodine
• Vitamin B12
• Vitamin D
• Calcium
• Choline
• Omega-3 fats
• Protein
• Total energy

Food Safety

Pregnant people have a higher risk of serious illness from some foodborne germs.

Choose properly cooked meat and eggs, pasteurized dairy products, and washed produce.

Avoid raw or undercooked high-risk foods and unpasteurized milk products.⁴

Alcohol

There is no safe time for alcohol use during pregnancy, according to CDC guidance.⁵

Pregnancy Nausea

Small meals, bland foods, fluids, and avoiding personal triggers may help some people.

Persistent vomiting can cause dehydration and poor nutrition.

Seek medical care when you cannot keep food or fluids down.

Vegan Pregnancy

Vegan pregnancy requires a reliable vitamin B12 source and careful review of iron, iodine, vitamin D, calcium, protein, omega-3 fats, and total energy.

Use prenatal and dietetic guidance.

Gluten-Free Diets

Gluten is a protein found mainly in wheat, barley, and rye.

A strict gluten-free diet is the treatment for celiac disease.

It may also be used for another diagnosed gluten-related condition.

Test Before Removing Gluten

Do not begin a gluten-free diet before speaking with a doctor when celiac disease is suspected.

Removing gluten can make blood tests and intestinal biopsy results less accurate.⁶

Gluten-Free Does Not Automatically Mean Healthy

Some gluten-free packaged products contain little fibre and may be high in sugar, sodium, or refined starch.

Build meals around suitable whole foods such as:

• Rice
• Potatoes
• Corn
• Quinoa
• Buckwheat
• Beans
• Fruit
• Vegetables
• Eggs
• Fish
• Meat or poultry
• Suitable dairy or alternatives

Cross Contact Matters in Celiac Disease

Small amounts of gluten may be harmful for a person with celiac disease.

Separate preparation and careful label reading may be required.

A registered dietitian can help with a nutritionally complete plan.

Elimination and Low FODMAP Diets

An elimination diet removes one or more foods for a defined reason and period.

It should usually include a planned reintroduction stage.

Permanent restriction without reintroduction can make the diet unnecessarily narrow.

Low FODMAP Diet

A low-FODMAP diet may be used as a structured trial for some people with IBS.

It usually involves:

1. A short restriction phase
2. Planned food challenges
3. A personalized long-term diet

It is not intended as a permanent list of forbidden foods.⁹

Food Allergy Elimination

A diagnosed food allergy requires strict avoidance and an emergency care plan when anaphylaxis is possible.

Food intolerance is not the same as allergy.

Risks of Broad Elimination

• Low calorie intake
• Low fibre
• Nutrient deficiency
• Food fear
• Social difficulty
• Delayed medical diagnosis

Use qualified guidance when several foods or food groups are removed.

High-Protein and Fitness Diets

Protein supports muscle, enzymes, hormones, immunity, and tissue repair.

People who exercise may need more protein than inactive adults.

This does not mean that every athlete needs a very high-protein diet.

Protein Food Sources

• Eggs
• Fish
• Chicken
• Lean meat
• Milk
• Plain yogurt
• Cottage cheese
• Beans
• Lentils
• Tofu
• Tempeh
• Edamame

Do Not Ignore Carbohydrates and Fats

Carbohydrates can support training and recovery.

Dietary fats support hormones, cells, and vitamin absorption.

A high-protein plan should still provide vegetables, fruit, fibre, grains or other carbohydrates, and healthy fats.

Kidney Disease

People with kidney disease may need a personal protein target.

Do not begin a high-protein diet or use protein powder without checking your kidney plan.

Protein Powders

Protein powders are optional.

They may contain added sugar, sodium, potassium, phosphorus, herbs, stimulants, or other ingredients.

Whole foods can meet many people’s needs.

Intermittent Fasting and Time-Restricted Eating

Intermittent fasting changes when food is eaten.

Common patterns include a daily eating window or fasting on selected days.

It is one way to organize meal timing, but it is not necessary for weight management or health.

The full food pattern and long-term adherence still matter.

Possible Problems

• Hunger
• Headache
• Low energy
• Overeating after fasting
• Difficulty exercising
• Medicine timing problems
• Low blood sugar
• Worsening food obsession

Diabetes Safety

People using insulin or medicines that can cause low blood sugar should not begin fasting without medical guidance.

Fasting can raise the risk of low blood glucose when a person continues taking medicine that lowers glucose.⁸

Who Should Avoid Unsupervised Fasting?

• Pregnant or breastfeeding people
• Children and teenagers
• Underweight people
• People with an eating disorder history
• People with frequent low blood sugar
• People who must take medicine with food
• People recovering from illness or surgery

Endometriosis and Diet

Endometriosis is a chronic medical condition. WHO states that there is currently no known cure, although symptoms can be treated with medicine and, for some people, surgery.¹⁰

It can cause pelvic pain, painful periods, pain during sex, digestive symptoms, fertility problems, and other symptoms.

Food cannot diagnose or cure endometriosis.

What the Research Shows

Researchers have studied Mediterranean-style eating, fibre, fats, vegetables, fruit, dairy, gluten removal, and supplements.

Results are mixed, and current evidence does not support one universal endometriosis diet.

Restrictive diets may help a personal symptom but can also create nutrient gaps.

A Practical Starting Pattern

A balanced pattern may include:

• Vegetables
• Fruit
• Beans and lentils
• Whole grains
• Fish
• Suitable protein foods
• Nuts and seeds
• Olive oil and other unsaturated fats

Keep a short symptom record if specific foods appear to cause problems.

Change one factor at a time.

Seek gynecologic care for diagnosis and treatment.

Medical Diets Require Personal Guidance

A medical diet is used to manage a diagnosed condition or treatment.

It should reflect laboratory results, medicine, disease stage, symptoms, and nutritional status.

Kidney Diets

Kidney diets may change sodium, potassium, phosphorus, protein, and fluid.

The plan differs before dialysis, during hemodialysis, and during peritoneal dialysis.

Use the Kidney and Liver Health Foods Hub.

Liver Disease Diets

Fatty liver disease and cirrhosis require different nutrition plans.

People with cirrhosis may need enough protein and calories rather than a detox or fasting plan.

Heart and Blood Pressure Diets

Heart disease, heart failure, high blood pressure, and high cholesterol may require different sodium, fluid, fat, or potassium advice.

Use the Heart Healthy Foods Hub.

Food Allergy Diets

Food allergy diets must remove the allergen while protecting nutrition.

People at risk of anaphylaxis need an emergency plan.

Therapeutic Ketogenic Diets

A ketogenic diet used to treat epilepsy is different from a social media weight-loss diet.

It requires a specialist team and careful monitoring.

Supplements and Special Diets

Restrictive diets often lead people to buy several supplements.

A supplement should correct a real need.

It should not be used to make an unsafe diet appear complete.

Check for Duplicate Nutrients

A multivitamin, protein powder, prenatal product, and fortified drink may contain overlapping nutrients.

Add the amounts before combining products.

Watch High Doses

High doses of vitamin A, vitamin D, iron, iodine, zinc, calcium, potassium, or magnesium may cause harm.

Check Medicine Interactions

Supplements can affect blood clotting, blood pressure, blood sugar, thyroid medicine, antibiotics, and other treatments.

Pregnancy Requires Extra Care

Do not use weight-loss, detox, bodybuilding, or herbal supplements during pregnancy without professional advice.

Signs That a Special Diet May Be Causing Harm

Stop and seek professional advice if a diet causes:

• Fainting
• Severe dizziness
• Repeated low blood sugar
• Persistent vomiting
• Severe diarrhea or constipation
• Rapid unplanned weight loss
• Loss of menstrual periods
• Marked weakness
• Hair loss
• Constant coldness
• Chest pain or palpitations
• Confusion
• Inability to exercise or complete daily tasks
• Food fear or guilt
• Binge eating
• Purging
• Secretive eating
• Social isolation around food

Seek urgent medical help for fainting, confusion, severe breathing difficulty, chest pain, signs of ketoacidosis, a serious allergic reaction, or another medical emergency.

A Four-Step Special Diet Trial

Step One: Write Down the Goal

Use one clear goal that can be reviewed.

Examples include improving blood pressure, following vegan ethics, or identifying an IBS trigger.

Step Two: Build a Complete Plan

Plan meals, snacks, protein, fibre, key nutrients, and suitable supplements before removing foods.

Step Three: Track Useful Outcomes

Track only what relates to your goal.

This may include symptoms, blood pressure, blood sugar, bowel habits, energy, training, or laboratory results.

Step Four: Review and Personalize

Keep the changes that help.

Reintroduce foods that do not need to remain restricted.

Seek professional help when the diet is medical, complex, or difficult to maintain.