This blog provides free general information for anyone who is seeking to understand more about nutrition and macronutrients (dietary carbohydrate, protein and fats), not intended as a medical consult. Please seek appropriate medical (physician specialising in nutritional medicine) and dietician advice for an individual assessment and management.
- Fats mentioned in this blog refer to dietary fats and not body fat.
- Similarly triglycerides and cholesterol refer to the dietary form and not serum cholesterol or triglyceride or the body stores of fat.
The 5 food groups (macronutrients) are:
- Vegetables, legumes (beans)
- Grain (cereal)
- Protein (lean meats, poultry, fish, eggs, nuts, seeds)
- Dairy (milk, yoghurt, cheese)
Extra information about:
- Australian Guide to Healthy Eating is available on the website eatforhealth.gov.au
- Nutrition news on website nutritionaustralia.org
- Australian Dietary Guidelines (2013) on nhmrc.gov.au/guidelines-publications/n55
We need fats as part of our macronutrient in our diet as a source of energy.
- Fat provides more calories (9kcal/g) (37kJ/g) than other macronutrient.
- Too much high-fat meal has the potential to contribute to excess energy, morbid obesity, chronic inflammation and increases cardio-vascular risk factors.
- Traditional dietary guidelines recommend that 20-35% of our calories come from fat and specifically <10% comes from saturated fats.
Fat are necessary for normal body physiological function.
- Fat is needed for cell membrane formation and synthesis of steroid hormones.
- It is needed for absorption of fat soluble vitamins (A, D, E, K and carotenoids).
- In general saturated fats and trans fats adversely affect our health but the omega 3 poly-unsaturated fats are beneficial.
- Essential fatty acids (certain omega 3 and omega 6 poly-unsaturated fats) cannot be synthesized in the human body and needs to come from an external dietary source.
- In summary we should consume more omega 3, less omega 6 fatty acids and avoid trans fat.
Dietary lipids include triglycerides, sterols and phospholipids.
- Triglycerides are the most abundant type of dietary lipid and how our health can be affected by fats relate to the triglyceride fatty acid composition (whether it is saturated, mono-unsaturated or poly-unsaturated).
- Although sterols and phospholipids (e.g. cholesterol) comprise a small proportion of total dietary lipids, they are also an important part of our diet.
Types of triglycerides:
- Saturated fats mainly come from animal sources (meats, dairy, egg yolks) and some plant (coconut oil and palm oil) used commonly in the take-away food industry.
- Mono-unsaturated fats are found mainly in olive oils, canola oils, nuts (peanut, hazel nut, cashew, almonds), seeds and avocados and small amounts in meats.
- Poly-unsaturated fats are found in plant/vegetable oils (such as soybean, sunflower, corn and safflower oil), fish, seafood, nuts (walnuts, Brazil nuts) and seeds.
Essential poly-unsaturated fatty acids:
- Linoleic acid (omega 6 fatty acid) and alpha-linolenic (ALA) (omega 3 fatty acid) are essential fatty acids because they cannot be synthesized in the body. Many people also have a limited ability to synthesize the important long-chain omega 3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from ALA. Hence some nutrition experts consider EPA and DHA to be essential.
Omega 6 fatty acids (including the essential linoleic acid) are found in the common plant oils (sunflower, safflower, corn and soybean oil), nuts and seeds.
Omega 3 fatty acids can be found in both plant and animal source.
- The essential ALA is found in flaxseeds, pumpkin seeds, walnuts and canola oil.
- EPA and DHA are found in fish (salmon, sardines, mackerel, herring and tuna).
More importantly it is the balance between omega 3 and omega 6 intake that is important for good health.
- Typical Western diets tend have an excess of omega 6 over omega 3 fatty acids.
- Ideally the ratio of omega 6:omega 3 is no more than 3:1 but in many Western diet the ratio is 10-20:1 or more.
Chemistry of unsaturated fats:
The shape of carbon chains in unsaturated fatty acids is either cis or trans. Most naturally occurring unsaturated fatty acids are cis and very small amount of trans can be found in cow’s milk and meat.
The majority of trans fatty acids in our diet are hydrogenation of oils from processed foods. Examples are processed baked goods (cakes, cookies, crackers, pies) and a significant amount from margarine.
Trans fat are also found in milk, cheese, beef and lamb but in small quantities. Trans fat contents are increased significantly during the process of baking (pies, pastries, cakes, biscuits, buns). it is the trans fat that are produced from food manufacturing (processed foods) that we should be concerned about, not the small amounts in in natural foods (low fat dairy products and lean meats).
Dietary fats and the effects on health
- The consumption of excess dietary fats (especially saturated fats) combined with a Western society sedentary lifestyle is associated with morbid obesity. Fat stored is less likely to be oxidized and increases further fat stores.
- In individuals with certain genetic predisposition, high levels of saturated fats and trans fats, will lead to elevated cholesterol and triglycerides in the blood, increase the risk of acute myocardial infarcts and premature deaths.
- Higher fats intake may be associated with insulin resistance and an increase in Type 2 diabetes mellitus.
- Fatty meals tend to increase circulating inflammatory cytokines and oxidative stress in the body, leading to chronic inflammation and damage to vascular endothelial tissue. Omega 6 poly-unsaturated fatty acids arachidonic acid leads to the production of prostaglandin E2 and leukotriene B, promoting inflammation. On the contrary omega 3 (EPA and DHA) has anti-inflammatory function and has been shown to reduce blood CRP levels.
To lose weight and reduce cardio-vascular risk factors we should consume a diet that is low in saturated animal fats and trans fat because fat is more easily absorbed in the intestine and it produce more calories than protein and carbohydrates. Also fat does not create a fullness sensation (satiation) the same as protein.
Saturated and trans fatty acids have been shown to have adverse effects on serum lipids and cardio-vascular morbidity and mortality (heart attacks and sudden deaths).
Omega 3 fatty acids on the other hand may have protective effects and is beneficial to reduce cardio-vascular risk factors. Some nutrition experts recommend that we have oily fish twice a week or have fish oil supplements (when the fish source is suspected to have high concentration of environmental contaminants).
Advice from a lot of dieticians include following the bariatric food pyramid:
- Increase variety of fresh fruit, vegetables and wholegrain foods.
- Have fresh protein food (nuts, beans, fish, chicken without the skin and lean meat), avoiding deep fried or barbequed meat whenever possible and limit processed or fatty meats (salami, sausage).
- Choose low fat milk or dairy products (yoghurts, cheese) instead of the full fat variety.
- Choose foods that are high in fiber.
- Avoid sugar based drinks or desserts and alcohol.
Olive oil is a major component of the Mediterranean diet, the beneficial effects which include reduced cardio-vascular risk factors and increased life expectancy.
The mechanism of action may include a reduction in LDL cholesterol and triglyceride, elevation of HDL cholesterol as well as anti-inflammatory and antioxidant effect (because of the phenolics compounds in olive oil). Olive oil may also be associated with reduction in certain cancer risks (breast, colon, lung, ovarian).
Note that the health benefits are really when olive oil is used as a substitute for other types of dietary fats or oils, not in conjunction with other types of saturated animal fats or vegetable oils. In other words, don’t use olive oil to barbeque or deep fry meats or proteins.
Different types of olive oil are sold:
- Extra virgin olive oil is the premium grade, made from first cold pressing of the olives with no chemicals used in the process.
- Virgin olive oil is from the second cold pressing of olives or from second grade olives with no chemicals used in the process.
- Pure (non virgin) olive oil is from subsequent pressing of the second grade olives. The oil undergoes a refining process involving heat, chemical solvents, high pressure and filtration treatments. A small quantity of extra virgin olive oil is added into this mixture to give it the desired flavour.
- Light and extra light olive oil is from the last pressing of olives, more refined than the above types.
The unrefined (virgin) grades offers the best health benefits, colour and flavour of natural olive oil with minimal processing by heat or chemical treatments.
Palm oil is derived from the red pulp of palm trees. Palm oil and coconut oil are sources of saturated fats from plant sources, which is unusual because saturated fats are usually derived from animal food sources. Palm oil has palmitic acid (saturated fats), also oleic acid (mono unsaturated fats) and a high beta carotene content (hence the red colour).
Palm oil is used for cooking in many countries because it is relatively cheaper than other vegetable oils. It is also used as a substitute for butter and hydrogenated trans fat. But beware the food labeling of food that does not have butter or trans fat because they may contain palm oil, which may not have the same beneficial health effects as olive oil, especially when there is no conclusive or definitive evidence that palm oil reduces cardio-vascular risk factors.
Because palm oil needs to be oxidized or processed, harmful benefits have been observed. Some studies even suggest that consumption of palmitic acid or palm oil may increase cardio-vascular diseases, LDL cholesterol and apo-lipoprotein B.
Protein are derived mainly from animal sources (fish, poultry, meat, eggs, dairy products) and plant sources (beans, legumes, seeds, nuts, grains, soy). It is preferred that people choose the fat free or low fat variety of milk, yoghurt and cheese.
20 different amino acids (peptide bonds) of various lengths and combinations form the many proteins. The amino acids that cannot be synthesized in the body are essential amino acids, there are 9 essential amino acids for humans.
- In general animal sources, soy products and quinoa contain all the essential amino acids but other plant sources may lack some amino acids.
Strict vegans need a mixture of cereals and legumes to provide them with the needed amino acids.
- Examples of cereals include buckwheat, oats, rye, millet, maize (corn), rice, wheat, bulgar, sorghum, amaranth, and quinoa.
- Examples of legumes include soybeans, lentils, kidney beans, white beans, mung beans, chickpeas, cowpeas, lima beans, pigeon peas, lupines, wing beans, almonds, Brazil nuts, cashews, pecans, walnuts, cotton seeds, pumpkin seeds, sesame seeds and sunflower seeds.
- Root and tubers (yams, cassava and sweet potato) and some fruits are very poor sources of protein.
Like fats and carbohydrates, proteins are essential for life.
- Protein is the major structural component of all cells in the body, especially muscle, body organs, hair and skin (protein are needed to build muscles and for tissue repair).
- Proteins are part of cell membranes (glycoproteins).
- Protein is needed to form red blood cells (haemoglobin).
- Amino acids are used to form nucleic acids, co-enzymes, hormones and neuro-transmitters for immune response, cellular repair, stress response (adrenaline) and cell signalling.
- Protein also provides energy (4 kcal/g) (16kJ/g) when the fuel source from lipids and carbohydrates are low. It is recommended that 10-35% (or maybe 15-25%) of calories come from dietary protein.
- Proteins cannot be stored in the body, amino acids enters the liver, nitrogen is converted into ammonia, which is converted to urea, which are excreted by the kidneys. Excessive protein consumption may be associated with calcium excretion in urine and the formations of kidney stones.
- When there is an excess of protein consumption, amino acids can also be converted into glucose and ketones.
The amount of dietary protein needed depends on body weight, age and health.
- In times of illness and stress, increased protein intake is necessary (this is termed conditional amino acids).
The Recommended Dietary Intake (RDI) of protein (g/kg of body weight) is:
- For adult men 0.84g/kg
- For adult women 0.75g/kg
- For pregnant women 1g/kg
The Australian Dietary Guidelines recommendations for the protein intake (from the sources listed above) are:
- Men (19-50 years of age) have 3 serves a day
- Men (aged over 51 years) have 2.5 serves a day
- Women (aged 19-50 years) have 2.5 serves a day
- Pregnant women have 3.5 serves a day
- Women (aged over 51 years) 2 serves a day
Examples of a standard serve are (in uncooked weight):
- 90-100g of lean meat (beef, lamb, veal, pork, goat, kangaroo)
- 100g of lean poultry (chicken, turkey)
- 100-115g of fish
- 2 large chicken eggs
- 150g (1 cup) of beans, lentils, chickpeas
- 170g tofu
- 30g of nuts, seeds, peanut or almond butter
Cow’s milk is usually 80% casein and 20% whey protein.
Whey protein has a very high concentration of branched chain amino acids, which are believed to be beneficial to athletes and individuals trying to achieve optimal lean muscle mass (increase the bioavailability of carbohydrate to the muscles) and prevent muscle protein breakdown during exercise.
Whey protein also promotes satiety (feeling full after a meal), better than a meal that contains carbohydrate and fats.
People who have a healthy balanced diet do not require protein supplements. Although they are sometimes prescribed for endurance athletes (aerobic exercise) and body builders (resistance training) because it is important for muscle protein metabolism and peak performance, the supplements are not necessary in many situations.
- Examples of processed protein powders include casein, whey, egg, rice and soy.
Maintaining muscle mass is particularly important for the elderly, during illness and periods of starvation or extreme weight loss.
- From about 50 years of age, people begin to lose skeletal muscle mass, this is known as sarcopenia, made worse by poor dietary protein intake and lack of exercise or sedentary behaviour.
- For this group the consumption of more lean meat in the diet is encouraged.
- Egg yolks are very high in cholesterol, hence for a normal person it is recommended to have less than 4 eggs a week.
In contrast for endurance athletes and body builders with a well balanced diet, they do not need extra protein intake or supplements.
- The excess of protein in fact may do more harm, producing higher levels of toxic ammonia, putting more strain on the kidney to excrete urea and possibly leads to calcium loss and bone demineralization.
- It is sufficient and more beneficial to have a glass of milk or a tub of yoghurt after aerobic exercises or resistance training.
Caution against very high protein diets
- Note that muscle growth is related to exercise and not dietary protein intake. It is a misconception that body builders need high protein diet between 200 to 400g a day (5g/kg body weight) or more than 5 RDI.
- Fad diets that are very high in protein and low in carbohydrate may be harmful. Due to inadequate glucose from dietary carbohydrate, the body obtains its glucose source from muscle breakdown and this leads to the build up of ketones and reduced body metabolism.
- Often high protein meals from animal sources are also high in cholesterol, saturated fats and trans fat (depends on the cooking method), which adversely affect the cardio-vascular risk factors.
- The liver and kidney needs to work harder to eliminate the excess protein byproducts, which may be associated with water loss (dehydration), calcium loss (reduced bone mineral density) and the formation of kidney stones, gallstones and uric acids (gout).
Natural sugars are derived from either sugar cane or sugar beets.
Some sugars are from maple tree sap, palm sugar or sweet sorghum.
- Monosaccharides include glucose and fructose.
- High fructose corn syrup is not sucrose and is added in a lot of American soft drinks.
- Dissacharides include sucrose and saccharose, which comes in the crystalline forms or liquid (syrup).
Artificial sweeteners are 160 to 700 sweeter than natural sucrose. The common ones include:
- Aspartame (Nutra Sweet and Equal)
- Sucralose (Splenda)
Natural sweetener has recently been sold as well:
- Stevia is derived from natural food (plant source).
Most of the increased calorie in our food consumption is related to the increase in sugar or caloric sweetener consumption.
Beverages such as fruit juice/drinks, carbonated soft drinks, energy drinks, coffee/tea drinks and alcohol have a high concentration of sucrose or high fructose corn syrup.
Foods such as desserts (cake, puddings, cookies, pies) cereals, breads, snacks, salad dressings have added sugar or fructose syrup.
Foods that contain carbohydrates include bread, breakfast cereals, rice, pasta, legumes, corn, potato, fruit, milk, yoghurt, sugar, biscuits, cakes and lollies. Carbohydrates are mostly broken down to monosaccharide (glucose). With the concurrent release of insulin from the pancreas, glucose will enter the cells to be utilized (burned) as fuel to produce energy. Excess may be stored as glycogen in liver and muscle cells.
High glycemic index (GI) foods (sweets, potato) are broken down quickly, enter the blood stream and cause a rapid rise in blood insulin and insulin release.
Low GI foods (oats) break down slowly, glucose enters the blood stream gradually and not cause the rapid peaks and subsequent falls in blood glucose.
The glycemic load (GL) is calculated by multiplying the GI with the amount of carbohydrates (grams) in each serve of food. People with insulin resistance or diabetes mellitus should have a carb restriction (low GL) and avoid high GI foods.
Examples of carbohydrates:
- Low GI (<55): soy products, beans, fruit, milk, pasta, grains, porridge, lentils
- Medium GI (55-70): orange juice, honey, basmati rice, whole meal bread
- High GI (>70): potato, white bread, short grain rice
There are controversies regarding low carb diet for weight loss. Certainly it is potentially harmful when these low carb diet contain larger proportion of saturated fats with a deficit in micronutrients (thiamine, folate, calcium, magnesium, iron, potassium, vitamin A, B6 and E), fibre, anti-oxidants and phytonutrients. Examples of low carb foods include beef, chicken, fish, eggs, non starchy green vegetables and fats (oils, butter, mayonnaise).
The theory is that a low carb diet is calorie (or kilojoules) restriction. The body does not have adequate glucose as a fuel source, hence glycogen stores (in liver, muscle cells) are broken down back to glucose. When the glycogen stores are depleted the body will use the fat stores, leading to ketosis.
There are no specific recommendations regarding carbohydrates intake, much of it is usually common sense:
- Choose carbohydrate foods in the right portions (appropriate GL and avoid excess calorie intake)
- Have a meal with a mixture of high and low GI foods
- Have a variety of fresh fruits, vegetables and legumes and less potato, refined grain or concentrated sugar
- Choose whole meal bread over white bread
- Choose a breakfast cereal based on oats, barley or bran
- Combine a low carb diet (calorie restriction) with foods that provide a good protein source (lean meat, fish, chicken without the skin, nuts, legumes) and fats from plant source (olive oil, canola oils) rather than animal fats.