FOOD FOR THOUGHT
| EVIDENCE-BASED NUTRITION—Amy B. Locke, MD, Instructor, Department of Family Medicine, University of
Michigan Medical School, Ann Arbor
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| Main source of nutrition information: United States Department of Agriculture (USDA); industry support important
USDA goal (creates conflict of interest); “for decades, the USDA recommendations have not been supported
by evidence”; new pyramid still does not reflect best available evidence
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 | Main drawbacks of USDA pyramid: continuing emphasis on meat and dairy consumption; paucity of information on
various types of fats and carbohydrates; “lean protein” recommended but not described; bottom line—USDA pyramid
not reliable source of information; Harvard School of Public Health and University of Michigan have better
pyramids, but progress with any pyramid difficult without attention to exercise and portion control, as well as type
of food consumed
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| Fats: “low fat is so 90s”; good evidence shows that substituting carbohydrate for fat produces rise in triglyerides, decrease
in low-density lipoprotein (LDL) and high-density lipoprotein (HDL), but no impact on cardiovascular disease; however,
replacing trans fats and saturated fats with “good fats” associated with decreased LDL, increased HDL, lower risk for
cardiovascular disease; tell patients to cut down on bad fats, rather than reducing all dietary fat; Nurses Health Study—
found that eating large amount of trans fats related to increased risk for cardiovascular disease (CVD), while increasing
mono- and polyunsaturated fats associated with decrease in CVD; total fat and dietary cholesterol made no difference in
CVD outcomes; saturated fat—essential, but should not comprise >10% of daily calories (increases risk for CVD);
cholesterol—found in all animal fats; body makes its own, even if patient consumes little; dietary cholesterol not necessarily
bad; trans fat—linked directly to CVD; increases LDL, decreases HDL, and increases lipoprotein (a) [Lp(a)] and
tri-glycerides; reduces endothelial function; may promote insulin resistance and diabetes; goal should be to eliminate
from diet; trans fats are liquid oils partially solidified (hydrogenated) to prolong shelf life; products with <0.5 g trans fat
per serving can say 0 g on label; may add up if multiple portions consumed; good fats—polyunsaturated fats (eg,
omega-3, omega-6 fats); monounsaturated fats (eg, olive oil); most oils are mixtures of fat types; in one study, people
with history of heart disease who consumed 1 g omega-3 fats daily for 3.5 yr had 25% decrease in myocardial infarctions
(MIs) and 33% decrease in sudden death; ratio of omega-3 to omega-6— in typical American diet estimated at 1:15,
1:20, or 1:40; large quantity of omega-6 fats may be proinflammatory and prothrombotic, may lead to vasospasm, vasoconstriction,
and contribute to allergic or inflammatory disorders, and to cancers; encourage patients to consume more
monounsaturated fats (rich in omega-3) rather than polyunsaturated fats (rich in omega-6); also recommend grass-fed
beef and enriched eggs; limit corn oil and other oils high in omega-6 fatty acids
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| Carbohydrates: recent dogma states simple carbohydrates bad, but complex carbohydrates acceptable; however,
body quickly changes simple starches to glucose; glycemic index—measure of speed with which body breaks
down food into glucose; higher glycemic index means faster breakdown; reference food 50 g white bread; glycemic
load—more accurately predicts impact of food on body; eg, white potatoes and carrots have high glycemic index,
but carrot has much more fiber, so 1 lb of carrots required to have same increase in blood glucose as one potato;
high glycemic load associated with increases in triglycerides, C-reactive protein, risk for diabetes, risk for CVD,
and decrease in HDL; study—consumption of meal with high glycemic index associated with 80% more snacking
among obese teenaged boys; also higher serum insulin and epinephrine and lower serum glucagon
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| Foods with low glycemic index: whole grains (grinding whole wheat until very fine increases glycemic index, although
other nutritional benefits persist); fruits and vegetables (other than potatoes, which have high glycemic index)
should comprise at least 50% of every meal; soluble fiber—found in apples, beans, and other fruits and
vegetables; reduces CVD, LDL, and blood pressure (BP) and improves insulin sensitivity; insoluble fiber—found
in, eg, whole grains, cucumbers, tomatoes
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| Protein: quality important (should be lean); diets higher in protein relative to carbohydrate associated with less CVD,
decreased LDL and triglyceride, and increased HDL; however, no CVD benefit to very low-carbohydrate diets (eg,
Atkins diet), due to increase in bad fats and low-quality protein
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| Milk: high in saturated fat and calories; 75% of world’s population cannot fully digest milk; other ways of adding calcium
to diet; heavy consumption also associated with elevated risk for ovarian and prostate cancers
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| Dietary recommendations: in Lyon Diet Heart Study, Mediterranean diet (increased whole grains, fruits, vegetables,
and fish; limited red meat consumption; butter and cream replaced with canola and olive oils and special margarine;
moderate alcohol) associated with >70% decrease in cardiovascular mortality and 60% decrease in all-cause
mortality, compared to people on standard recommended post-MI diet; no change in serum cholesterol
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| Case 1: woman 45 yr of age; eats plenty of whole grains and variety of vegetables; asks whether she should take multivitamin;
answer—increasing evidence that vitamins help prevent chronic disease; vitamins B6 , B12 , D, and E,
and folate most important; may be good idea for most patients, but cannot replace nutrients found in food (think of
as safety net); recommended daily allowances may not be adequate, but megadosages not recommended (eg, high
doses of vitamin A may promote fractures)
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| Case 2: man 59 yr of age; wants to know how to decrease risk for recurrent diverticulitis; coworker advised him to
stop eating seeds and nuts; answer—fiber prevents constipation; only recommendation for reducing diverticular
disease; also reduces CVD and diabetes; no effect on colon cancer; minimum recommendation 20 to 35 g/day; best
sources include whole grains, vegetables, legumes, and whole fruits instead of juice
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| Case 3: man 65 yr of age; has 2 drinks/day; wife says he should stop; answer—>100 prospective trials associate moderate
drinking (2 drinks/day for men, 1 drink/day for women) with reduction in many illnesses, including CVD,
stroke, diabetes, and peripheral vascular disease; possible increased risk for breast cancer; benefits observed with all
forms of alcohol
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| Case 4: woman 36 yr of age with elevated triglycerides; wants to know how to lower triglyceride level; answer—
decrease foods with high glycemic index, increase intake of good fats
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| Case 5: man 42 yr of age; asks if eating eggs healthy; answer—Nurses Health Study showed that eating 1 egg/day
had no effect on serum cholesterol; acceptable for most people to eat eggs in moderation; diabetics should limit to 2
to 3/wk
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| Case 6: patient asks about health effects of various spices; fresh garlic—processed garlic may not provide same benefits;
immune stimulant; antibacterial, antiviral, and antifungal; decreases LDL and BP; has antiplatelet effect; 2 to 5 g/
day recommended; others—turmeric (antioxidant and anti-inflammatory; level B evidence for efficacy in dyspepsia);
green tea (antioxidant; associated with decreased gastric cancer and BP); dark chocolate (shown to decrease LDL and
improve mood; ≤7 oz/wk
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| FAD DIETS—Andrea Garber, PhD, RD, Assistant Professor, Division of Adolescent Medicine, University of California,
San Francisco, School of Medicine
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| Trends behind obesity epidemic: according to USDA food disappearance data, men averaged 168 more calories/day
in 2000 than in 1970 (translates into 17 extra pounds of fat per year); increase for women, 335 calories/day (35 lb/yr);
take-home message—“we’re eating way too many calories”
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| Sources of excess calories: mostly carbohydrate; possibly consequence of emphasis on low-fat diets during 1980s; from
1990 to 1995, daily calorie intake among teenage boys increased by 275 calories; of those, 228 come from carbohydrate;
main source sugary soft drinks (intake among teenage boys increased 41% over that period); one 20-oz bottle of
soda per day translates into 26 lb of fat per year
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| Low-fat diets: “holy grail” of weight-loss diets in 1970s and 1980s; supported by good science; high-fat high-calorie
diets promote fat storage; however, low-fat diets of 1980s allowed simple sugars, did not distinguish between good
and bad fats, and were hypocaloric
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| Women’s Health Initiative: 48835 postmenopausal women 50 to 79 yr of age; largest study ever of low-fat diets;
spanned ≈8 yr; dietary goals 20% fat (“extremely low”), 5 fruit and vegetable servings and 6 grain servings daily;
hypothesis—low-fat diet would protect against breast and colorectal cancers and CVD; results—at 7.5 yr, women
on low-fat diet had lost 1.9 kg (4.2 lb), compared to controls; no difference in rate of cancer or incidence of CVD;
problems—20% fat too low for most participants to achieve and maintain (chances best with plant-based diet); subjects
probably underreported consumption; trial did not include younger population (may have seen greater effect);
nevertheless, negated notion of low-fat diet as cure-all
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| Current advice: emphasize heart-healthy fats, avoid unhealthy ones, especially trans fats (“almost every food that
comes out of a bag has trans fats”); choose lean meats and plant proteins
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| Low-carbohydrate diets (“the Atkins backlash”): concept originated by William Banting in 1860; Atkins diet
permits only 20 g carbohydrate/day (1 slice whole-grain bread); no milk allowed; salad and green vegetables provide
what carbohydrate there is; high-fat diet does produce spike in fat metabolism; theoretically, in absence of glucose,
body converts fat to ketones, which contain calories and are excreted in urine; compared to low-fat diet, produces better
weight loss at 3 and 6 mo, but at 1 yr, difference insignificant; however, HDL higher and triglycerides lower than
with low-fat diet (no difference in total cholesterol and LDL after 3 mo); both diets improve BP and insulin resistance;
compliance better on Atkins diet; works because followers eat fewer calories, stay on diet longer than people
on other kinds of diets; no evidence linking weight loss to ketosis or carbohydrate restriction itself
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| Current advice: might serve as a “kick start”; could help to limit “carbs” (eg, candy, sugar, sodas, white bread, chips);
urge patients to consume 5 fruits and vegetables and 3 servings milk or other high-calcium food each day
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| Low-glycemic index diets: examples include South Beach, Sugarbusters, and Zone (to some extent); diets emphasize
fruits, vegetables and low-fat dairy and meats, so are low in saturated fats; most include olive and canola oils;
glycemic index system for classifying foods according to content of sugar and available carbohydrates; high-glycemic
index foods include sugars, starches, and some fruits; low-glycemic index foods—whole grains, legumes, vegetables,
and some fruits; produce slower digestion and absorption of carbohydrates, leading to slower and lower rise
in blood glucose than high-glycemic index foods (affects satiety); low-glycemic index foods also lead to slower rise
in insulin; high-glycemic index foods—associated sharp rise in blood glucose, followed by insulin spike, subclinical
hypoglycemia, and suppression of glucagon
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| Importance of glucagon: mobilizes fatty acids from adipose tissue several hours after eating to mitigate hunger between
meals; suppression of glucagon leads to suppression of fatty acid release, with subsequent sharp rise in epinephrine
and growth hormone (stress response to hunger); result sharp rise in hunger; studies of children and adolescents show
that low-glycemic index diet improves insulin sensitivity, minimizes weight gain and cardiovascular benefits
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| Summary on low-glycemic index diets: may reduce hunger and limit snacking between meals; consistent with advice
to eat more whole grains and vegetables while limiting starches and sugars
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| Comparison of 4 popular diets: randomized, controlled trial comparing Atkins, Zone, Ornish and Weight Watchers;
participants were 160 adults (mean body mass index [BMI] 35); all diets produced significant weight loss; amount lost
significantly related to self-reported adherence; take-home message—let motivated patients choose best diet for them;
effect on CVD risk—all diets reduce LDL/HDL ratio by 10%; no significant effect on triglycerides, BP, fasting blood
glucose; cardiovascular benefits proportional to amount of weight lost; low-carbohydrate diets effectively lower triglycerides,
diastolic BP, blood glucose, and insulin; raise HDL (short-term); low-fat diets raise LDL and triglycerides;
study—21 obese nondiabetic women placed in metabolic ward on either low-fat or low-carbohydrate diet (both low in
calories); insulin-sensitive patients (fasting insulin <10 µIU/mL) lost almost twice as much weight on low-fat diet as on
low-carbohydrate diet; reverse true for insulin-resistant patients (fasting insulin >15 µIu/mL); conclusions—low-carbohydrate
diets better for patients with metabolic syndrome; patients’ metabolic profile may profoundly influence their response
to given diet; diet should be tailored to individual patient; cut calories; offer low-carbohydrate or low-glycemic
index diet to patients with metabolic syndrome profile (high total cholesterol, especially high LDL, and insulin resistance)
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| Best nutrition advice: single best nutrition book Eat, Drink, and Be Healthy, by Walter Willett, MD; eat more healthy
fats, and more fruits, vegetables, and whole grains; choose low-fat dairy products; minimize red meat, full-fat dairy
products, processed foods and refined starches; avoid juice and soda
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| Healthy plate: 25% should be whole grains; include protein at every meal (helps maintain between-meal satiety); combined
with fat to delay gastric emptying, lowers meal’s glycemic index; 50% of plate should contain fruits and vegetables; include
good (essential) fats (eg, olive oil, canola oil)
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| Questions and answers: how does “Froot Loops” breakfast compare to none at all?—none probably better metabolically,
but not recommended; have at least one source of protein (handful of nuts or trail mix; yogurt; peanut butter
on apple); what is difference between saturated fat and trans fat?—saturated fat found in lard; highly atherogenic;
trans fat starts as polyunsaturated oil then hydrogenated to solidify at room temperature; probably more atherogenic
than naturally saturated fat; what to feed thin child or adolescent who eats only sweets?—emphasize whole grains,
fruits, vegetables, and lean meats for all family members, with extra servings of whole grains for thin children
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Suggested Reading
Cornier MA et al: Insulin sensitivity determines the effectiveness of dietary micronutrient composition on weight
loss in obese women. Obes Res 13:703, 2005; Dansinger ML, Schaefer EJ: Low-carbohydrate or low-fat diets for
the metabolic syndrome? Curr Diab Rep 6:55, 2006; Ebbeling CB et al: Effects of a low-glycemic load vs low-fat
diet in obese young adults: a randomized trial. JAMA 297:2092, 2007; Foster GD et al: A randomized trial of a low-
carbohydrate diet for obesity. N Engl J Med 348:2082, 2003; Gardner CD et al: Comparison of the Atkins, Zone,
Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women: the A
to Z Weight Loss Study: a randomized trial. JAMA 297:969, 2007; Howard BV et al: Low-fat dietary pattern and risk
of cardiovascular disease: the Women’s Health Initiative Randomized Controlled Dietary Modification Trial. JAMA
295:655, 2006; Hu FB et al: Types of dietary fat and risk of coronary heart disease: a critical review. J Am Coll Nutr
20:5, 2001; Hu FB, Willett WC: Optimal diets for prevention of coronary heart disease. JAMA 288:2569, 2002;
Kris-Etherton P et al: AHA Science Advisory: Lyon Diet Heart Study. Benefits of a Mediterranean-style, National
Cholesterol Education Program/American Heart Association Step I Dietary Pattern on Cardiovascular Disease. Circulaton
103:1823, 2001; Lopez-Garcia E et al: Consumption of trans fatty acids is related to plasma biomarkers of inflammation
and endothelial dysfunction. J Nutr 135:562, 2005; Schaefer EJ et al: The effects of low-fat, high-
carbohydrate diets on plasma lipoproteins, weight loss, and heart disease risk reduction. Curr Atheroscler Rep 7:421,
2005; Warren JM et al: Low glycemic index breakfasts and reduced food intake in preadolescent children. Pediatrics
112:e414, 2003; Willett WC: Low-carbohydrate diets: a place in health promotion? J Intern Med 261:363, 2007;
Yancy WS Jr et al: A low-carbohydrate, ketogenic diet versus a low-fat diet to treat obesity and hyperlipidemia: a
randomized, controlled trial. Ann Intern Med 140:769, 2004.
Educational Objectives
| The goal of this program is to review current knowledge and recommendations on nutrition and weight loss in order
to improve patient health. After hearing and assimilating this program, the listener will be better able to:
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| Describe the shortcomings of the food pyramid developed by the United States Department of Agriculture.
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| Explain why trans fats should be avoided.
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| Discuss the importance of a food’s glycemic index.
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| Compare the benefits of low-fat and low-carbohydrate diets for weight loss.
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| Identify the best candidates for a low-carbohydrate or low-fat diet.
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Faculty Disclosure
In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty members to disclose relevant
financial relationships within the past 12 months that might create any personal conflicts of interest. Any identified
conflicts were resolved to ensure that this educational activity promotes quality in health care and not a proprietary business
or commercial interest. For this program, the faculty reported nothing to disclose.
Acknowledgements
Dr. Locke spoke at Update in Integrative Medicine: News You Can Use in Caring for Common Health Conditions,
held March 29-30, 2007, in Ann Arbor, MI, and sponsored by the Department of Family Medicine, University of Michigan
Medical School, University of Michigan Integrative Medicine, and Office of Continuing Medical Education. Dr. Garber
was recorded at the Annual Review of Family Medicine, held February 4-6, 2007, in San Francisco, and sponsored by
the University of California, San Francisco, School of Medicine. The Audio-Digest Foundation thanks the speakers and
the sponsors for their cooperation in the production of this program.
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