Nutritional Recommendations for the

Physically Active PersonChapter 7

Part 3

Nutritional Status

Inadequate nutrition◦ Lethargy◦ Early fatigue◦ Irritability◦ Poor training and competitive performance◦ Increased incidence of injury◦ Infection ◦ Excessive weight fluctuations

A low-carbohydrate diet rapidly compromises energy reserves for vigorous physical activity or regular training.

Carbohydrate Intake

Training diet for physically active◦ Adequate refueling day to day◦ Recover between daily sessions

Multiple workouts◦ Nutritional strategies

> 90 min – CHO becomes limiting factor

Nutritional Status

Optimum diet for most sports◦ CHO contributes 60-70% of total energy intake

After each bout of exercise◦ Sufficient CHO to replenish glycogen stores

Maximize subsequent performance

Position Stand

CHO – after exhaustive exercise◦ 50 g every 2 h◦ Moderate and high glycemic foods◦ Goal – 600 g in 24 h

Position Stand (cont)

Recommendations 6-10 g CHO/kg BM/day

Endurance training 10 g CHO/kg BM/day

This is quite a bit of food 70kg person = 2800 kcal of CHO

CHO Intake

Tour de France◦ 6 h per day◦ 12-13 g/kg body weight/day◦ Close to 4000 kcal of CHO/day

CHO Intake

More recently◦ 1.0-1.8 g/kg BM/hr◦ Feedings every 15-60 min◦ Still over 3000 kcal of CHO/d

CHO Intake

Highest rates of glycogen storage◦ First hour post exercise◦ Activation of glycogen synthase

Glycogen depletion ◦ Exercise-induced insulin sensitivity

Permeability of muscle cell to glucose◦ Storage rates

7.7 mmol/kg/wet weight/h (first 2 h) 4.3 mmol/kg/ww/h

Timing of CHO Intake

Exercise enhances energy metabolism Exercise increases total energy expenditure

◦ Is there an increased need, deficiencies of vitamins?

◦ Do athletes have normal vitamin status?◦ Do athletes require vitamin supplements?

Exercise Effects on Vitamin Needs

B complex◦ Coenzymes in reactions during catabolism

Fat, CHO, protein◦ Vitamin B6 or Thiamin

Vitamin C◦ Negligible effects on endurance

Vitamin E◦ Deficiencies impair muscular function◦ No benefit with excess consumption

Vitamins and Performance

50 years of research Fail to support vitamin supplements to improve

performance aerobic and anaerobic exercise

Vitamins and Performance

Daily supplements of vitamin C 500-1500 mg of per day

May reduce infections Glutamine

Fuel for the immune system Supplementation reduces the risk of infection

Vitamins and Performance

Most often occur in:• Vegetarians • Groups with low energy intake • Elimination of one or more food groups • Individuals who consume

Processed foods Simple sugars - low micronutrient density

Vitamin-Mineral Deficiencies

Contain doses at least 10 and up to 1000 times the RDA

Excess vitamin C = kidney stones Excess vitamin B6 = liver disease and nerve

damage Excess riboflavin (B2) = impaired vision Excess niacin = vasodilatation and

inhibition of fatty acid mobilization during exercise

Megavitamins

Folate = trigger an allergic response Excess vitamin E = headache, fatigue,

blurred vision, gastrointestinal disturbances, muscular weakness, and low blood sugar

Excess vitamin A = toxic to the nervous system

Excess vitamin D = damages kidneys

Megavitamins

Aerobic exercise metabolism increases the production of free radicals.

Antioxidants:• ß-Carotene • Vitamin C• Vitamin E• Selenium, copper, manganese, and zinc • Coenzyme Q10

Antioxidants

Vitamin E deficient animals◦ Reached exhaustion earlier

Sufficient Vitamin E◦ Reduced oxidative damage to muscle fibers

Vitamin E

Vitamin E

Innate ◦ Skin and mucous membranes◦ Body temperature◦ Specialized defenses

Natural killer cells, diverse phagocytes, and inflammatory barriers

Immune System

Immune System

Continuous barrier◦Protection ◦Dead cells on outside

The Skin

Acquired immune system Specialized B (bone)- and T (Thymus)-lymphocyte

cells. B cells

Produce antibodies T cells

Cytokines and toxic granules

Exercise Immunology

Theoretical Model

Moderate exercise• A bout of moderate exercise boosts natural

immune functions and host defenses for up to several hours.

Exercise Intensity and the Immune System

Exhaustive exercise• A prolonged period of exhaustive exercise (and

other forms of extreme stress or increased training) severely impairs the body’s first line of defense against infection.

Exercise Intensity and the Immune System

Exercise Intensity and Risk of Infection

Excessive sweating Loss of body water and related minerals.

Mineral loss Replaced with well-balanced meals.

Single-mineral supplementation Potential adverse consequences.

Minerals

Strenuous exercise may increase excretion of the following four trace elements: • Chromium• Copper• Manganese• Zinc

Trace Minerals and Exercise

Energy intake needs to be balanced with energy expenditure.

Regular moderate-to-intense physical activity Increase daily energy intake to match their higher

level of energy expenditure.

Exercise and Food Intake

Many athletes, particularly females, do not meet energy intake recommendations. Active women (20-60 miles/wk)

35 kcals/kg BM Discrepancies in reported kcals and activity? Active become more sedentary when not

exercising Increased metabolic efficiency

Expend less energy

Exercise and Food Intake