Healthy diet in adults

from Uptodate, Healthy diet in adults by Graham A Colditz, MD, DrPh, Jan 4, 2013 and https://www.eatforhealth.gov.au/

Caloric Balance

• Importance: Maintaining a balance between caloric intake and energy expenditure is crucial for sustaining a healthy body weight. Overnutrition, leading to overweight and obesity, is linked to an increased risk of cardiovascular disease, type 2 diabetes, hypertension, certain cancers, and other serious health conditions.
• Recommendations:
  • For individuals with a normal BMI, caloric intake should match energy expenditure.
  • Total daily energy expenditure (TDEE) can be estimated based on age, sex, weight, and activity level.
  • Patients should use tools like food diaries or 24-hour dietary recalls to assess caloric intake.

2. Macronutrients

Macronutrients are the primary sources of energy, and the proportion of these nutrients in the diet is key to health.

Carbohydrates: 45-65% of Total Caloric Intake

• Types: Simple vs. complex carbohydrates and whole grains vs. refined grains have differential effects on health.
• Glycemic Index: Carbs with a high glycemic index (like white bread, white rice) can raise blood sugar rapidly, contributing to an increased risk of type 2 diabetes, cardiovascular disease, and certain cancers. Low glycemic index foods (like vegetables and whole grains) are preferred.
• Added Sugars: Limit to no more than 25% of total caloric intake. Excess sugar consumption is linked to obesity, metabolic syndrome, and dental health issues.

Proteins: 10-35% of Total Caloric Intake

• Variety: A healthy diet should include a variety of protein sources such as lean meats (poultry), fish, eggs, beans, peas, soy products, unsalted nuts, and seeds.
• Protein Types: Red meat and processed meats are linked with higher risks of cardiovascular disease and cancer. White meats (e.g., chicken, fish) are associated with lower health risks.
• Fish: Consuming oily fish (like salmon, mackerel) 1-2 times per week is encouraged, as they provide beneficial omega-3 fatty acids, which have been linked to a reduced risk of heart disease.

Fats: 20-35% of Total Caloric Intake

• Saturated Fats: Should make up less than 10% of total calories. These fats, found in fatty meats, butter, and full-fat dairy products, contribute to increased cholesterol levels and heart disease risk.
• Trans Fats: Should be minimized as much as possible. These are found in processed foods like margarine and certain baked goods and are strongly associated with heart disease.
• Healthy Fats: Replace saturated and trans fats with unsaturated fats (monounsaturated and polyunsaturated fats) found in olive oil, nuts, seeds, and fatty fish. These can reduce the risk of coronary heart disease.
• Cholesterol: Dietary cholesterol intake should be less than 300 mg/day. Elevated cholesterol levels, particularly LDL cholesterol, are associated with a higher risk of coronary heart disease.

3. Fiber

• Recommended Intake: 25 g/day for women and 38 g/day for men, or 14 g per 1000 kcal consumed.
• Sources: Fiber is found in fruits, vegetables, whole grains, and legumes.
• Benefits: Increased fiber intake is associated with:
  • Cardiovascular Health: High fiber diets lower the risk of coronary heart disease and stroke by improving blood lipid levels, reducing blood pressure, and controlling blood sugar.
  • Diabetes Management: Fiber helps control blood glucose levels, making it particularly beneficial for individuals with type 2 diabetes.
  • Cancer Prevention: Though evidence is mixed, higher fiber intake may reduce the risk of colorectal cancer.
  • Overall Mortality: Higher fiber consumption is linked to a reduction in all-cause mortality, particularly in those with cardiovascular risk factors.

4. Micronutrients

Essential nutrients needed in smaller quantities include vitamins and minerals.

Sodium

• Recommended Intake: Less than 2.3 g/day (approximately 6 g of table salt).
• Health Impact: Excess sodium is a major risk factor for hypertension and cardiovascular diseases. Reducing sodium intake can lower blood pressure and reduce the risk of cardiovascular events.

Calcium and Vitamin D

• Calcium Recommendations: 1000-1200 mg/day depending on age and sex. Essential for bone health and prevention of osteoporosis.
• Vitamin D Recommendations: 400-800 IU/day, increasing with age. Necessary for calcium absorption and bone health.
• Sources: Dairy products, fortified foods, and supplements if dietary intake is inadequate.

Folate

• Importance: Folate (vitamin B9) is crucial for DNA synthesis and erythropoiesis. For women of reproductive age, folic acid supplementation (0.4 mg/day) is recommended to prevent neural tube defects in pregnancy.

5. Food Groups

A balanced diet should include a variety of food types to provide all the essential nutrients.

Fruits and Vegetables

• Recommended Intake: At least 5 servings per day.
• Benefits: Rich in fiber, vitamins, and minerals, fruits and vegetables are associated with a lower risk of cardiovascular diseases, certain cancers, and overall mortality.
• Specifics: Cruciferous vegetables (e.g., broccoli, cabbage) and vitamin C-rich fruits are particularly beneficial.

Grains

• Recommended Intake: At least half of grain consumption should be whole grains (e.g., brown rice, whole wheat bread).
• Benefits: Whole grains are high in fiber and contribute to better glycemic control and weight management. Refined grains (white bread, white rice) have been linked to weight gain and higher risk of chronic diseases.

Dairy

• Recommended Intake: 3 cups/day for adults on a 2000 calorie diet.
• Benefits: Dairy provides calcium, vitamin D, and protein. Low-fat or fat-free dairy products are preferable to reduce saturated fat intake.
• Health Impact: Whole-fat dairy products may increase cholesterol levels, but the association between dairy intake and cardiovascular disease is not strong.

Meat and Protein-Rich Foods

• Recommended Intake: 150g/day for adults on a 2000 calorie diet.
• Healthy Sources: Lean meats (e.g., chicken, turkey), seafood, eggs, legumes, and nuts are preferred.
• Red and Processed Meats: These should be limited as they are linked to higher risks of cardiovascular disease and cancer.

6. Beverages

Alcohol

• Moderation: Limit to 1 drink/day for women and 2 drinks/day for men.
• Health Impact: Moderate alcohol consumption is linked to a reduced risk of cardiovascular disease, but excessive intake increases the risk of cancers (especially breast and colorectal cancers).

Sweetened Beverages

• Recommendation: Discourage consumption of soft drinks and sweetened fruit juices (cordials, fruit drinks, vitamin waters, energy and sports drinks) due to high sugar content and their association with weight gain and metabolic disorders.
• Substitution: Encourage water as the primary beverage for hydration.

7. Other Considerations

• Multivitamins and Supplements: May be necessary in specific populations (e.g., folic acid in women of reproductive age, vitamin D in older adults).
• Physical Activity: Integral to energy balance, regular physical activity is recommended to complement dietary management
• Limit intake of foods containing added salt
  • Read labels to choose lower sodium options among similar foods.
• Limit intake of foods containing saturated fat
  • Limit intake of foods high in saturated fat such as many biscuits, cakes, pastries, pies, processed meats, commercial burgers, pizza, fried foods, potato chips, crisps and other savoury snacks.
  • Replace high fat foods which contain predominantly saturated fats such as butter, cream, cooking margarine, coconut and palm oil with foods which contain predominantly polyunsaturated and monounsaturated fats such as oils, spreads, nut butters/pastes and avocado.
  • Low fat diets are not suitable for children under the age of 2 years.

Diets for Weight Loss

1. Types of Diets for Weight Loss

• Low calorie diets: Focus on reducing total daily caloric intake. This is commonly achieved by portion control and avoiding high-calorie, low-nutrient foods. These diets generally aim for a calorie deficit to promote weight loss.
• Low fat diets: These diets restrict fat intake, usually to less than 30% of daily energy, with the aim of reducing overall calorie intake and improving cardiovascular health. Some concern exists that low-fat diets might lead to increased carbohydrate consumption, but studies have shown this doesn’t necessarily lead to weight gain.
• Low carbohydrate diets (e.g., Atkins diet): Focus on reducing carbohydrate intake while increasing fats and proteins. Low-carb diets like the Atkins diet are thought to promote fat metabolism (ketosis) and stabilize blood sugar levels, but long-term effects on cardiovascular health remain under study.
• High protein diets: These diets increase the proportion of protein intake while reducing fats and carbohydrates. They are often designed to promote muscle retention during weight loss and to improve satiety.
• Portion-controlled diets: Focus on regulating the quantity of food consumed rather than specific food types. These are effective in reducing overall caloric intake and can be customized to various types of foods or meal plans.

Note: These diets are primarily studied for weight loss rather than long-term maintenance of normal weight. Studies have not clearly identified which is the most effective for long-term weight maintenance.

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2. Lack of Evidence in General Populations

• Few well-designed randomized trials compare these diets in general populations, especially outside of overweight or obese individuals.
• Cultural dietary patterns and the variability in dietary habits make it difficult to determine a universally “optimal” diet.
• Most evidence on diet effectiveness is based on short-term weight loss rather than long-term health outcomes.

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3. Commonly-Used Diets for Health Maintenance

• The following diets are commonly used to maintain health rather than focus on weight loss. They offer various health benefits, such as lowering blood pressure, improving cholesterol levels, and reducing the risk of cardiovascular diseases.
• Low-fat diet
• Vegetarian diet
• Dietary Approaches to Stop Hypertension (DASH) diet
• Mediterranean diet

These diets are associated with various health benefits and are often chosen based on patient preference and adherence rather than for weight loss alone.

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Low-fat Diet

• Mechanism: Reduces fat intake to <30% of total energy, focusing on fruits, vegetables, whole grains, and lean proteins. Reduces consumption of high-fat foods like butter, full-fat dairy, and fried foods.
• Key Studies:
  • The Women’s Health Initiative Dietary Modification Trial (48,835 postmenopausal women) found that women on a low-fat diet lost weight and maintained it better than those in the control group, without any caloric restriction goals. After 7.5 years, the difference was 0.4 kg. This shows that fat reduction alone can lead to modest weight loss without promoting weight gain from increased carbohydrate consumption .
• Health Benefits: Helps reduce LDL cholesterol levels and improve heart health. Although effective for weight loss, it’s also associated with reductions in coronary heart disease and stroke risk.

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Vegetarian Diet

• Types:
  • Macrobiotic: Focuses on whole grains, legumes, and seaweed, with occasional white meat or fish.
  • Semi-vegetarian: Includes occasional meat or fish.
  • Lacto-ovovegetarian: Includes eggs and dairy but excludes meat.
  • Lactovegetarian: Includes dairy but no eggs or meat.
  • Vegan: Excludes all animal products, including eggs and dairy.
• Health Outcomes:
  • Lower incidence of obesity, coronary heart disease, hypertension, and type 2 diabetes. A meta-analysis of observational studies indicated that vegetarian diets can reduce the risk of cardiovascular disease .
  • Long-term adherence to a lactovegetarian diet is associated with better health outcomes compared to vegan diets, as vegans may lack key nutrients like vitamin B12 and vitamin D .
• Nutritional Concerns:
  • Vitamin B12 deficiency: Common in strict vegan diets, as B12 is mostly found in animal products. Supplementation is recommended.
  • Vitamin D and Calcium: May be inadequate, leading to risks of osteoporosis and fractures in vegans who exclude dairy .

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DASH Diet (Dietary Approaches to Stop Hypertension)

• Mechanism: Focuses on high intake of fruits, vegetables, and low-fat dairy, combined with reduced intake of sodium and saturated fats. Recommended for those with or at risk of hypertension.
• Health Benefits:
  • Lowers blood pressure in both normotensive and hypertensive individuals. When combined with sodium restriction, the DASH diet has been found to lower blood pressure as effectively as some antihypertensive medications .
  • Reduces the risk of stroke and heart disease, particularly when combined with exercise and weight management.
• Key Components:
  • 4–5 servings of fruits and vegetables daily
  • 2–3 servings of low-fat dairy
  • <25% of daily energy from fat
  • Low sodium intake (<2.3 g/day of sodium recommended)

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Mediterranean Diet

• Mechanism: Emphasizes high intake of fruits, vegetables, whole grains, legumes, nuts, seeds, and olive oil as the primary fat source. Fish and poultry are included in moderate amounts, while red meat is limited.
• Health Benefits:
  • A meta-analysis of 12 cohort studies involving over 8 cohorts found that adherence to a Mediterranean diet significantly reduces all-cause mortality, cardiovascular disease, cancer mortality, and incidence of neurodegenerative diseases like Parkinson’s and Alzheimer’s .
  • Reduced risk of cardiovascular disease and stroke, as well as improvements in metabolic health and weight management, are observed in Mediterranean diet followers.
• Key Components:
  • High in unsaturated fats (especially from olive oil)
  • Rich in fiber, vitamins, and minerals
  • Low intake of processed and red meats

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Conclusion

These diets — low-fat, vegetarian, DASH, and Mediterranean — have varying mechanisms, but they share common themes of high nutrient density, increased intake of plant-based foods, and reduced intake of saturated fats. The choice of diet often depends on personal preference, cultural influences, and the individual’s ability to adhere to the diet in the long term.