Best Dx/Best Rx: Diet and Exercise

Diet and Exercise

Harvey B. Simon, M.D., F.A.C.S. Harvard Medical School

Dietary Recommendations
Vitamins
Essential Minerals and Trace Elements
Exercise
Best References

Dietary Recommendations

General Dietary Guidelines for Healthy Adults

Eat more vegetable products than animal products
Eat more fresh and homemade foods than processed foods
< 30% of calories should come from fat, < 10% from saturated fat (< 7% for those with atherosclerosis, diabetes, hyperlipidemia, or obesity), and the remainder from unsaturated fat in vegetables, fish, legumes, and nuts
Limit cholesterol to < 300 mg a day (< 200 mg for those with atherosclerosis, diabetes, hyperlipidemia, or obesity)
Eat ≥ 30 g of fiber a day
55%–65% of calories should come from complex carbohydrates
10%–15% of calories should come from protein
Limit sodium to < 2,300 mg a day
Obtain 1,200–1,500 mg of calcium a day from food or supplement
Eat ≥ 6 servings of grain products a day
Eat 3–5 servings of vegetables and legumes a day
Eat 2–4 servings of fruit a day
Eat two 4 oz servings of fish a week
Eat ≤ two 4 oz servings of red meat a week
Chicken and turkey should be eaten in moderation with skin removed
Eat ≤ 1 egg yolk a day, including those used in cooking and baking
Use vegetable oils, preferably olive and canola oils, in moderation
Have ≤ 2 alcoholic drinks a day
Adjust caloric intake and exercise level to maintain a desirable body weight
Avoid fad diets and extreme or unconventional nutrition schemes
Avoid untested nutritional supplements, including megavitamins, herbs, food extracts, and amino acids

Alcohol

Calorie-dense
Low to moderate consumption substantially reduces the risk of coronary artery disease, peripheral vascular disease, and all-cause mortality
Protective doses: 1–2 drinks a day (5 oz of wine, 12 oz of beer, or 1.5 oz of spirits is the equivalent of one drink)

Caffeine

Can trigger migraines in sensitive individuals
Withdrawal can precipitate headaches or depression in habitual consumers
Can cause anxiety, insomnia, and gastroesophageal reflux
Brewed coffee may increase blood cholesterol levels, but filtered coffee does not
Consumption should be discouraged in pregnancy

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Vitamins

Sources and Recommended Daily Allowances for Nonpregnant Adults

A (retinol, retinoic acid)
- Liver, dairy products, eggs; dark-green and yellow-orange vegetables (carotenoids)
- Men, 3,000 IU or 900 µg; women, 2,333 IU or 700 µg
B₁ (thiamine)
- Grains, legumes, nuts, poultry, meat
- Men, 1.2 mg; women, 1.1 mg
B₂ (riboflavin)
- Grains, dairy products, meat, eggs, dark-green vegetables
- Men, 1.3 mg; women, 1.1 mg
B₃ (niacin, nicotinic acid)
- Meat, poultry, fish, grains, peanuts; synthesized from tryptophan in foods
- Men, 16 mg; women, 14 mg
B₆ (pyridoxine)
- Meat, poultry, fish, grains, soybeans, bananas, nuts
- Men: 19–50 yr, 1.3 mg; 50 yr and older, 1.7 mg
- Women: 19–50 yr, 1.3 mg; 50 yr and older, 1.5 mg
B₁₂ (cobalamin)
- Meat (especially liver), poultry, fish, dairy products
- 2.4 µg
Folic acid
- Vegetables, legumes, grains, fruit, poultry, meat
- 400 µg
Biotin
- Many foods
- 30 µg
Pantothenic acid
- Many foods
- 5 mg
C (ascorbic acid)
- Fruits, green vegetables, potatoes, cereals
- Men, 90 mg; women, 75 mg
D (calciferol)
- Fortified dairy products, fatty fish, egg yolks, liver
- < 50 yr, 200 IU; 50–70 yr, 400 IU; > 70 yr, 600 IU
E (a-tocopherol)
- Vegetable oils, wheat germ, nuts, broccoli
- 15 mg
K
- Leafy green vegetables (K₁), intestinal bacteria (K₂)
- Men, 120 µg; women, 90 µg

Supplements

Women of childbearing age, the elderly, and people with suboptimal nutrition should take a single multivitamin tablet daily
Strict vegetarians and those > 60 yr should take the RDA of vitamin B₁₂
Multivitamin supplements can avert vitamin D deficiencies, particularly in the elderly
Antioxidants with zinc can slow the progression of age-related macular degeneration
Discourage use of megadose vitamins

Essential Minerals and Trace Elements

RDA for Healthy Adults

Macrominerals

Sodium: no RDA; recommended daily maximum amounts:
- AHA: 2,400 mg
- Dietary Guidelines for Americans 2005: 2,300 mg
- Institute of Medicine: 1,500 mg
- Substantially lower intake may be beneficial in hypertension, congestive heart failure, cirrhosis, nephrotic syndrome, etc.
Calcium
- < 50 yr, 1,000 mg
- ≥ 50 yr, 1,200 mg
Phosphorus: 700 mg
Magnesium
- Men, 350 mg; women, 280 mg
Potassium: 1,700–5,100 mg

Trace Elements

Iron
- Men and postmenopausal women, 8 mg
- Premenopausal women, 18 mg
- Pregnant women, 27 mg
Chromium
- Men: 19–50 yr, 35 µg; ≥ 50 yr, 30 µg
- Women: 19–50 yr, 25 µg; ≥ 50 yr, 20 µg
Copper: 900 µg
Fluoride
- Men, 4 mg; women, 3 mg
Iodine: 150 µg
Manganese
- Men, 2.3 mg; women, 1.8 mg
Molybdenum: 45 µg
Selenium: 55 µg
Zinc
- Men, 11 mg; women, 8 mg
Cobalt: required in small amounts as a component of vitamin B₁₂

Exercise

Effects

Protective effects against coronary artery disease, hypertension, stroke, type 2 diabetes mellitus, obesity, anxiety, depression, osteoporosis, and cancers of the colon and breast
Increases insulin sensitivity of muscle
Improves glucose tolerance in diabetic patients
Increases serum levels of HDL cholesterol
Reduces blood levels of C-reactive protein and other inflammatory markers
Endurance exercise produces improvements in mood, self-esteem, and work behavior in healthy people and in patients undertaking cardiac rehabilitation
Increases functional status and decreases mortality in the elderly

Isotonic Excercise

Shortening of muscle fibers with little increase in tension (swimming, bicycling, running)
Increases muscle endurance
Lowers total peripheral resistance, but heart rate and cardiac output rise; systolic blood pressure rises substantially, diastolic pressure changes little, resulting in a small increase in mean arterial pressure
Imposes a volume load on the heart
Enhances endurance and can produce adaptive cardiovascular changes in healthy individuals and cardiac patients

Isometric Exercise

Increase in muscle tension without a significant change in fiber length (handgrip exercises, pushing or pulling against a fixed resistance, holding a heavy weight)
Increases total peripheral resistance; systolic and diastolic blood pressure rise substantially, with relatively little increase in stroke volume or cardiac output
Places a pressure load on the heart
Increases muscle strength and bulk
Produces minimal cardiovascular conditioning; circulatory demands of intense isometric work can be hazardous to patients with heart disease
Unsupervised isometric exercising should be avoided by patients with cardiovascular disease; with appropriate precautions, it can be safe for selected cardiac patients and can produce favorable effects on muscular function and blood pressure

Preexercise Evaluation

Careful history and physical exam with particular attention to the following:
- Family history of coronary disease, hypertension, stroke, or sudden death
- Symptoms suggestive of cardiovascular disease
- Cigarette smoking, sedentary living, hypertension, diabetes, obesity
- Physical findings suggestive of pulmonary, cardiac, or peripheral vascular disease
- Musculoskeletal health
Screening tests for apparently healthy individuals
- Complete blood count
- Urinalysis
- Blood glucose level
- Serum cholesterol level
- Creatinine level
- Valsalva maneuver
- Isometric handgrip
- ECG not required for asymptomatic, low-risk patients
- Exercise testing useful for detecting exercise-induced arrhythmias, establishing maximal heart rate for exercise prescription, and determining work capacity
Evaluation of patients with known or suspected cardiovascular abnormalities
- Pulmonary function tests
- Exercise ergometry
- Holter or telemetric monitoring during exercise
- Echocardiography

Exercise Advice for Patients

Get a medical check-up before beginning a formal exercise program
Warm up before each exercise session; cool down afterward with 10 min of stretching and light calisthenics
Start slowly and build up to 30 min of moderate to intense exercise or 45–60 min of mild to moderate exercise
Begin with aerobic-type exercise; later, add stretching exercises for flexibility and low-resistance weight training for strength
Exercise daily if possible; alternate harder workouts with easier ones
Dress comfortably
Use good equipment, especially good shoes
Do not eat during the 2 hr before you exercise, but drink plenty of water before, during, and after exercise, particularly in warmer weather
Do not ignore aches and pains that may signify injury
Do not exercise if you are feverish or ill
Learn warning signals of heart disease, including chest pain or pressure, disproportionate shortness of breath, fatigue, sweating, erratic pulse, light-headedness, indigestion
Consider getting instruction or joining a health club

Prescribing Exercise

Healthy persons
- Exercise without supervision
Patients with ischemic heart disease or other significant cardiovascular abnormalities
- Medically supervised, graded exercise programs or mild exercise
  - Walking, bicycling, with appropriate precautions
Physical exertion contraindicated for patients with the following conditions:
- Decompensated congestive heart failure
- Complex ventricular irritability
- Unstable angina
- Significant aortic valve disease
- Aortic aneurysm
- Uncontrolled diabetes
- Uncontrolled seizure disorders
Most health benefits of regular exercise can be attained by 30–45 min daily of moderate exercise at intensities well below the aerobic-intensity level (gardening, walking)
Aerobic fitness can be developed and maintained in healthy adults with 3–5 exercise sessions a week
Sedentary persons and those with cardiopulmonary disease must initiate training at lower intensities and shorter durations and build up gradually
Brisk walking, jogging, swimming, cross-country skiing, skating, bicycling, vigorous singles racket sports provide good conditioning
Doubles tennis, golf, bowling, baseball are much less desirable for aerobic fitness but can still make important contributions to health
Activities requiring sudden bursts of intense isometric activity, such as weight lifting, provide little cardiovascular conditioning and are contraindicated for patients with hypertension or heart disease
Contact sports cannot be recommended for health
Swimming is particularly desirable for patients with musculoskeletal problems or exercise-induced asthma
Walking and bicycling are ideal for older people or those starting from a low level of fitness
Educate patients about safety

Best References

American Heart Association:

Dietary Guidelines for Healthy Americans:

http://www.americanheart.org/presenter.jhtml?identifier=4561

AHA Dietary Guidelines:

http://circ.ahajournals.org/cgi/content/full/102/18/2284

Exercise and Fitness:

http://www.americanheart.org/presenter.jhtml?identifier=3004541

HHS/USDA Dietary Guidelines for Americans: http://www.healthierus.gov/dietaryguidelines

Institute of Medicine, Dietary Reference Intakes: Applications in Dietary Planning: http://www.iom.edu/CMS/3788/4003/4733.aspx

May 2006