Nutrition: Calories, Fats, Proteins and Carbohydrates (Part I)

Nutrition: Calories, Fats, Proteins and Carbohydrates

Part One

By Ladislav P. Novak, Ph.D.

Courtesy John Eagle Honda, North Dallas LIVING WELL Magazine 

All efforts to achieve weight loss, stronger muscles, establish good health habits, etc., would decline slowly year by year if you didn’t put a determined break on your appetite simultaneously. In other words, energy intake must equal energy output. The energy in is measured in calories taken in each day in the form of foods and beverages. The energy out is the amount of calories needed for basal metabolism-sustain vital body functions like breathing, heart rate, waste removal, cell growth and cell repair. All this accounts for up to 75% of the calories burned daily. A second amount of calories is needed for physical activity and third for digestion and absorption of food (about 105 of daily calories). The rate the body burns calories when at rest is called resting metabolic rate (RMR). This RMR differs and is assumed to be genetically determined.

How many calories per gram, as sources of energy should be memorized to maintain optimal weight:

1 gram of carbohydrate = 4 calories

1 gram of protein = 4 calories

1 gram of fat = 9 calories

The recommended caloric intake for 50-60 year old men is about 2,200 cal/day. For 60-70 year old men, about 1,800 cal/day. For women of the same age categories – 1,500 cal/day and 1,200 cal/day. Increase in weight will require increase of caloric intake.

The final step in controlling body weight is caloric balance. Caloric intake must equal caloric expenditure. When you gain weight you are in a positive caloric balance and conversely, if you lose weight you find yourself in a negative caloric balance. During that period the body fat is drawn upon to supply the missing calories not supplied by the diet. Weight reduction plans are based on this principle to successfully attain ideal body weight. Sensible reduction requires persistence. Remember that you did not put all that weight on in one month, did you?

Digestion and Absorption of Proteins – Protein molecules must be broken down to their individual amino acids, which are absorbed from intestinal track into the blood.

Protein Quality – Amino acids from animal sources are best absorbed, about 90%. Eighty percent from legumes (kidney bean, soy bean, pea, lentil, black-eyed pea, etc.), and 60-80% from grains. The highest utilization of proteins comes from egg white (100%), fish (83%), beef (80%), milk (70%), rice (67%), and corn (56%).

The Protein RDA – for healthy older adult males around 70 grams per day while for older females 50 grams per day (2.5 oz and 1.8 oz).

The Control System of Digestion – The hypothalamus in the brain has very sensitive receptors to glucose (simple sugar), which are activated by the level of glucose in the blood, which is almost exclusive fuel for the control of the nervous system. For example, after exercise receptors of the hypothalamus are stimulated, the satiety center activates contraction of the stomach and we experience a sensation for food.

Recommended Dietary Allowances (RDA) – Proteins – 15%, Carbohydrates – 55%, Fats – 30% (saturated – 10%, monounsaturated – 10%, polyunsaturated – 10%)

Carbohydrates are a major source of energy. Our brain utilizes glucose only and therefore the daily intake of 300-400 grams = 10.5-14.0 ounces. All starches we eat are broken down to glucose by enzymes. Sources of starches are numerous such as cereal grains, potatoes, rice, etc. Our body stores a little glucose as glycogen in muscles which gives us about 1000-1250 calories for activity. Liver stores about 124-156 grams providing a reserve of 500-600 calories of glucose in the blood to offset tiredness and fatigue. Hunger pangs are immediately felt by center for hunger and satiety (hypothalamus), which stimulates nerve endings in the stomach and urgency to eat restores glucose level to normalcy. However, heavy dinners (steak, baked potato, butter, corn, carrots) fill all the cells in the body with glucose. Liver cells are filled in glycogen and thus the extra energy is stored in the fat cells – they enlarge. And if more calories are eaten compared to calories used for activity OBESITY DEVELOPS.

Dietary fiber occurs in all plant-derived foods (vegetables, fruits, grains, etc.). Their non-digestible residue helps to prevent constipation, hemorrhoids, diverticulitis, and colon cancer. Insoluble fiber is available in brown rice, wheat bran, legumes, seed fruits, etc. Water soluble fiber is barley, oat bran, rye, seeds. It helps lower cholesterol in the blood and prevents atherosclerosis, heart attacks and strokes. RDA – 25-40 grams/day (1.0 oz – 1.5 oz). Caution: Excess of fiber carries water out of the body and may cause dehydration.

The Lipids – Fats and Oils. Since 1 gram of fat provides us with 9 calories, removing most of the fat from your plate will change the calories you consume. However, fats are useful. They are the main storage of energy from food used for activity, specifically muscular work. Fat carries fat-soluble vitamins – A, D, E, K. Fat under the skin insulates our body from extreme temperatures. Fat surrounds vital organs as a safe shock absorber. Fat slows digestion and provides greater feeling of satiety.

Saturated vs. Unsaturated Fats. Saturation refers to the number of hydrogens a fat chain is holding. From animal fats all carbons are filled with hydrogen by very stable single bonds – saturated fat. Fish or plants have one hydrogen missing in their fat – monounsaturated fat oleic acid. If two or more hydrogens are missing such fat is called polyunsaturated (safflower oil, sunflower oil, soybean oil, corn oil). Health care providers recommend limiting saturated fats and use for cooking mono- or poly-saturated fats. Cholesterol + saturated fats raises a serious question of atherosclerosis while vegetable fats seem to promote lowering blood cholesterol. Similar effect comes from consumption of anchovies, herring, sardines, mackerel, salmon, tuna (fresh), halibut, bass, rainbow and sea trouts.

Endogenous cholesterol made by our liver is a part of bile, necessary for digestion of fats, for sex and adrenal hormones (estrogen, androgens and progesterone). 7-Dehydrocholesterol found in our skin enables our body to manufacture vitamin D when exposed to sunlight. Deficiency in elderly of both genders has been report in the news.

Exogenous cholesterol is included mostly in dietary saturated fat. Examples – egg yolk- 273 mg., 3 oz. beef – 80 mg, 3 oz chicken – 63 mg. The danger of high cholesterol should be checked in your regular visit to your physician – ask for your Blood Lipid Profile.

What is a desirable blood lipid profile?

Total cholesterol – below 200 mg/100 ml of blood,

Triglycerides(fat) below 150 mg /100 ml of blood,

High density lipoproteins – HDL (good cholesterol) – males 28-68 mg and females 34-78mg / 100 ml of blood.

Low density lipoproteins – LDL (bad cholesterol) below 130 mg for both genders. Higher HDL – low risk of coronary heart disease, high risk with high LDL.

Proteins differ from carbohydrates and fats because they contain nitrogen atoms. Proteins are made from amino acids – about 22 different ones. Eight of these must be provided in our diet and are called essential amino acids. The rest can be made by our body from precursors, non-essential amino acids. Essential amino acids are important because they make new cells and synthesize new proteins in the body.

  1. Growth and Maintenance – New tissues are built, growth of embryo, bleeding, surgery, scars that heal wounds, new hair and nails, replacement of outer skin cells, etc. For this growth of new cells, essential amino acids must be constantly supplied from food.
  2. Enzymes – Thousands help to release energy from food quickly.
  3. Hormones – These are secreted and released into the blood by endocrine glands, which influence metabolism. For example, if there is high glucose in the blood, the pancreas releases “insulin” to control the glucose. If there is low glucose concentration in the blood, the pancreas releases “glycogon” from the liver and into the blood.
  4. Antibodies – These are formed in response to foreign particles that invade our body (bacteria, viruses, toxins). Antibodies recognize this invasion and form antibodies that inactivate the foreign protein-body develops Immunity.
  5. Fluid and Electrolyte Balance – Proteins help to regulate the quantity of fluids inside and outside the cells. A cell must contain a constant amount of fluid. Too much, and the cell ruptures. Too little and the cell shrinks and metabolism would be impaired. Proteins attract water, which is important for maintenance of blood volume. Sodium and potassium play an important role as well.
  6. Acid-Base Balance – Our body constantly produces acids and bases, which must be carried by the blood to the kidneys to be excreted. This role is accomplished by proteins in the blood by their buffering activity to act on either acid or base. Excessive acidosis or alkalosis can cause coma and death.
  7. Energy – Only in a few cases such as starvation or anorexia would proteins be used for energy.

Keep watch for my next article “Nutrition: Part II” in the summer issue of LIVING WELL Magazine where I present minerals and vitamins.

Author Ladislav P. Novak, Ph.D., Professor Emeritus, Southern Methodist University, Dallas, TX 75275. Email: lnovak@mail.smu.edu

 John Eagle Honda, located at 5311 Lemmon Ave., Dallas, TX 75209 may be reached at 888-343-7677.