Nutrition

“Leave your drugs at the chemist’s pot if you can heal your patient with food.”Hippocrates

Introduction to Nutrition

Nourishment:• Provision of energy and building materials essential for

growth and survival

Nutrition: • Study of food and nutrients, their actions, interactions and

balance in relation to health and disease

• Overall role of nutrition is to supply appropriate substrates to cells of various tissues for moment to moment function

Introduction to NutritionNutrient:• a substance that nourishes• macronutrients ( protein, carbohydrate, fats)• micronutrients (vitamins, minerals, trace

elements)

Essential nutrient:• a nutrient required for survival (species specific)

Conditionally essential nutrient• one that may become essential under certain

conditions

Nutrients in question include, among other things:

• oxidizable energy sources used for production of useful chemical energy carriers such as ATP

• amino acids required for protein synthesis, as precursors for purines & pyrimidines and other specialized molecules

• vitamins required for a variety of specific cell functions

• inorganic compounds such as calcium, phosphorus, iron, etc.

Nutrient Functions

• Structural

• Muscle, bone, cytoskeletal

• Functional

• enzymatic reactions, transport, synthesis, degradation, energy

metabolism… LIFE!

• Chemical

• toxicity, pharmacologic properties- includes phytochemicals,

“functional foods”

Nutrition and Health and Disease: Evolution of Guidelines

_ Historically, dietary restrictions were related to religious practices and law.

_ Late 1800’s: Germ theory of disease: contaminated foods could act as vectors.

_ Early 1900’s: Vitamin theory of disease: substances missing from diet contributing to disease.

Nutrition and Health and Disease: Evolution of Guidelines

_ Post WW2: Framingham, Twin Cities, 7 Country studies: evaluated diet and life style risks for development of cardiac disease: – Link between dietary excess and development

of chronic disease

Nutrition and Disease• Obesity• Type II diabetes• Atherosclerotic cardiovascular disease• Hypertension• Cancer• Dental carries• Osteoporosis• Anemia• Infection• Pregnancy outcomes• Pediatric growth and development

Nutrition and Disease

• Chronic diseases: Diabetes, Cardiovascular disease, Hypertension, Stroke and Cancer

_ Prevalent: 7 out of 10 who die each year die from chronic disease- more than 1.7 million.

_ Costly: 75% of the nation’s $1.4 trillion medical care costs.

_ Preventable

Dietary Reference Intakes

Dietary Reference Intakes (DRI)• Reference values for meeting needs for

essential nutrients and energy • Determined by Food and Nutrition Board of the

National Academy of Sciences • Firmly established on basis of experimental

evidence

• Designed to prevent impairment of health from nutritional inadequacy which is directly related to diet and to which susceptibility is universal

RDA - DRI

• Defined as the amounts of nutrients considered sufficient to meet the physiological needs of practically all healthy persons in a specific group (age and gender based) and the amount of food sources of energy needed by members of that group

• Designed to prevent nutritional deficiencies

which lead to specific pathological conditions

• Focus now on indicators of nutritional sufficiency

and on levels which may prevent chronic disease

RDA/ DRI’s• deal mainly with quantities of micronutrients and

protein needed daily

• do not deal with non-nutrients and nutrients that are not essential

• specific values are given for different age-sex groups

• serve as standards for establishing health policy

• Terminology - Dietary Reference Intake (DRI) has “replaced” the term RDA in United States & Canada

DRI includes• Estimated Average Requirement (EAR) - intake at

which risk of inadequacy is 50% (EAR is evidence-based)

• Recommended Dietary Allowance (RDA) - intake at which risk of inadequacy is 2 - 3%

• RDA set relative to EAR: RDA = EAR + 2SDEAR

• Tolerable Upper Limit (UL) - highest level of daily intake likely to pose no risks of adverse effect to almost all persons in general population

• Adequate Intake (AI) - set for those nutrients without enough evidence to develop RDA, no consistent relationship to EAR or RDA

DRI Example: Calcium_ Infant 0-6 months: 210 mg_ Infant 6-12 months: 210 mg_ Child 1-3 y: 500 mg_ Child 4-8 y: 800 mg_ Males/Females 9-13, 14-18 1300 mg_ Males/Females 19-30, 31-50 1000 mg_ Males/Females 51-70, >70 1200 mg_ Pregnancy same as age group_ Lactation same as age group

New Macronutrient Guidelines and DRI’s announced recently (Sept. 2002)

For ages >19 years old (% of total calories)

• Carbohydrates: 45 - 65% • Fats: 25 - 35%• Protein: 10 - 35%• Fiber: 25-38 g per day • Essential fatty acids: -3’s new • Increased exercise recommended:

• 60 minutes per day of moderate activity for children and adults

DRI’s and Food Labels

_ Daily Values for nutrients listed on food labels as required by FDA

_ Reference Daily Intake for vitamins and minerals

_ Uses RDA’s for 18 y/o male (highest RDA) except for iron (19-30 y/o female)

Dietary Guidelines

Dietary Guidelines

• Differ from DRI in several aspects• Much more general than DRI• Primarily deal with quantities of certain foods

and nonessenteial dietary components (e.g., fiber, cholesterol, saturated fat, etc.) and proportions and types of energy sources judged desirable in healthful diets

Dietary Guidelines

• advice on selecting foods to achieve nutritionally adequate diet

• deal mainly with proportions of energy-yielding nutrients in diet

• include advice on consumption of such non-nutrients as fiber and cholesterol

• recommendations are general, without specification for different segments of the population

Dietary Guidelines

• are health policy proposals• directed toward prevention of chronic diseases

for which diet is a potential modifying factor and to which susceptibility is highly variable

• evidence mainly indirect from observations between diet and disease incidence

Consensus Dietary GuidelinesCirculation 100:450 (1999)

_ The Unified Dietary Guidelines: American Cancer Society, American Dietetic Association, American Academy of Pediatrics, National Institutes of Health and

American Heart Association.

Consensus Dietary GuidelinesCirculation 100:450 (1999)

• Saturated fat < 10% of calories

• Total fat < 30% of calories

• Polyunsaturated fat < 10% of calories

• Monounsaturated fat < 15% of calories

• Cholesterol < 300 mg/day

• Carbohydrates > 55% of calories

• Total calories to achieve and maintain desirable weight

• Salt intake limited to < 6 g/day

Consensus Dietary GuidelinesCirculation 100:450 (1999)

_ The consensus panel concluded that for many individuals the recommendations could best be achieved by following U. S. Dietary Guidelines and Food Guide Pyramid

USDA Food Guide Pyramid

Fats, Oils & Sweets USE SPARINGLY

Meats, Poultry, Fish,

Dry Beans, Eggs & Nuts 2-3 SERVINGS

Milk, Yogurt & Cheese Group 2-3 SERVINGS

Vegetable Group 3-5 SERVINGS

Fruit Group 3-5 SERVINGS

Bread, Cereal, Rice & Pasta Group

6-11 SERVINGS

USDA Food Pyramid (1992)

Nutrition and Your Health:

Dietary Guidelines for AmericansUSDA & USDHHS 5th ed., May 2000

Aim for Fitness• Aim for a healthy weight

• Be physically active

Build a Healthy Base• Let the Pyramid guide your food choices

• Choose a variety of grains daily, especially whole

grains

• Choose a variety of fruits and vegetables daily

• Keep food safe to eat

Choose Sensibly• Choose a diet that is low in saturated fat and

cholesterol and moderate in total fat

• Choose beverages and foods to moderate your

intake of sugars

• Choose and prepare foods with less salts

• If you drink alcoholic beverages, do so in

moderation

Criticism of USDA Food Guide Pyramid

Benefits are well documented

Ignores critical differences in types of fat. Saturated and trans fatty acids should be minimized, but monosaturated and polyunsaturated fats may be beneficial

Misleading. Two or three servings of meat per day may be unhealthy

Whole grain & minimally processed products should be emphasized

Low-fat products are preferable. Calcium supplements are effective substitutesfor preventing fractures

Importance is well documented. Greens and dark orange vegetables should be included. Even more frequent servings may be beneficial.

USDA Food Pyramid as annotated by W. C Willet in Science 264 : 532 - 537 (1994)

From Willett, Walter C., Eat, Drink, and Be Healthy, Fireside, New York (2001)

Willet Food Guide Pyramid

Revision of Food Guide Pyramid

_ Currently underway, expected 2005_ Areas expected to be addressed

– Portion sizes: are currently not consistent with portion sizes typically consumed or stated on food labels as required by FDA

» Most problematic with grains/starches

» Pyramid suggests 6-11 servings per day, counting 1 serving as 1/2 small bagel

How are we eating?

Percent of People Meeting Recommendations for: Total Fat ( 30% Kcal); Saturated Fat (<10% Kcal); and

Fruits and Vegetables ( 5 servings a day). (1989-91)

A few comments on

Obesity and Comorbidities

A few comments on obesity

• The most serious nutritional problem in the United States and the industrialized world is the marked increase in obesity

• The problem is extending to less developed countries.

• It is growing at epidemic rates in adult populations

• Also occurring at alarming rates in children

*

¶

Notes: *For adults Overweight includes Obese & Extremely obese¶All values for children are for Overweight

For 1976 - 1980, 47% of adults were overweight (15% were obese)

Obesity and comorbidity risk

Table 2. Increased Risk of Obesity Related Diseaseswith Higher BMI

DiseaseBMI of25 or less

BMI between25 and 30

BMI between30 and 35

BMI of35 or more

Arthritis 1.00 1.56 1.87 2.39Heart Disease 1.00 1.39 1.86 1.67Diabetes (Type 2) 1.00 2.42 3.35 6.16Gallstones 1.00 1.97 3.30 5.48Hypertension 1.00 1.92 2.82 3.77Stroke 1.00 1.53 1.59 1.75

Source: Centers for Disease Control. Third National Health and Nutrition Examination Survey. Analysis byThe Lewin Group, 1999.

U.S. NIH revised weight guidelines: 1994 and 1998

• Guidelines apply equally to men & women

• Guidelines do NOT allow for weight gain in middle age

• Revisions made in response to mounting evidence that increases in weight associated with increased risk of premature death from heart disease, diabetes, and certain cancers

• At each height, proposed guidelines recommend weights that translate to a Body Mass Index (BMI) of 18.9 - 24.9

• In medical literature, BMI is calculated by BMI = Weight(kg)/[Height(m)]2

• Current research suggests that obesity-related health problems begin to mount at BMIs above 25

U. S. National Institutes of Health obesity

guidelines (June, 1998)

BMI• Underweight < 18.5• Normal 18.5 - 24.9• Overweight 25 - 29.9• Obese (Class I) 30 - 34.9• Obese (Class II) 35 - 39.9• Obese (Class III) > 40

In this unisex version:

• weights at lower end of range recommended for persons with low ratio of bone to fat

• weights at upper end of range advised for those with more muscular physiques

• most of us fall into the 1st category, thus DHHS-NIH suggest that we aim for lower end of range

Conversion factors:

• Weight (lb) x 0.454 kg/lb = Weight (kg)

• Height (in)/39.4 = Height (m)

Conflicting Nutritional Advice

Nutrition Recommendations

_ Nutrition science is a rapidly growing field of study, many new and sometimes conflicting findings and advice reported in popular press.

_ “Guidelines” often influenced by special interest groups.

_ Consumer behavior is greatly influenced by multi-billion dollar food industry.

Recent info on consumer confusion and negativism about nutritional advice

• J. Am. Dietitics Assoc (01/01/01) Reported survey results on conflicting advice about “healthy diet”

• >40% were tired of hearing about foods they should or should not eat

• ~40% thought that dietary guidelines be taken with “a grain of salt”

• 70% said government shouldn’t tell people what to eat