This blog provides free general information for anyone who is seeking to understand more about nutrition and micronutrients, not intended as a medical consult. Please seek appropriate medical (physician specialising in nutritional medicine) and dietician advice for an individual assessment and management.
The 5 food groups (macronutrients) are:
- Vegetables, legumes (beans)
- Grain (cereal)
- Protein (lean meats, poultry, fish, eggs, nuts, seeds)
- Dairy (milk, yoghurt, cheese)
Micronutrients are the small quantities of other nutrients required for normal body physiological functions. Commonly these include:
- Acetic, citric, lactic, malic, choline, taurine
- A (retinol)
- B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (panthothenic acid), B6 (pyridoxine), B7 (biotin vitamin H), B8 (ergadenylic acid), B9 (folate/folic acid), B12 (cyanocobalamin), choline
- C (ascorbic acid)
- D (calciferol)
- E (tocopherol)
- K (phylloquinonone, phytomenadione)
- Carotenoids (alpha, beta, cryptoxanthin, lutein lycopene, zeaxanthin)
- Boron, calcium, cobalt, chromium, copper, fluoride, iodine, iron, magnesium, manganese, molybdenum, selenium, zinc
Many fruits, vegetables, meat and dairy products contain the essential micronutrients, which include vitamins (A, C, E), phytochemicals (beta carotene) and trace minerals (iron, folic acid, magnesium, zinc, phosphorous). Hence it is emphasized that our diet contains a balanced meal from each of the 5 food groups, with emphasis on fresh fruits, vegetables, legumes and seeds, avoiding processed foods and some cereal grains.
Micronutrient and its essential function
Micronutrient and its essential function
The function of some micronutrients (vitamins and minerals) are listed below:
A For growth of healthy skin and hair
Anti-oxidant which helps with the immune function
B6, 9, 12 A role to play in cell repair, energy production, immune system
B9 (folate) For healthy red blood cells and nerve developments in foetus
C Is an anti-oxidant and important for the immune system
Also needed for growth of healthy tissues and wound repair
D Helps the GI tract absorbs calcium, for healthy teeth and bones
E For healthy cardio-vascular system
Is an anti-oxidant
K For normal blood clotting and strong bones
Calcium Maintain the strength of teeth, bones
Needed for muscle contraction, nerve conduction and blood clot
Iron Needed for carrying oxygen in red blood cells
Helps with immune function
Magnesium Needed for cell function and energy production
Helps with maintaining integrity of healthy bones, teeth, muscle
Zinc Helps with the immune system and macronutrient digestion
*Note: Too much of a particular vitamin or trace mineral may have serious adverse effect and can be toxic.
Some of the clinical effects of vitamin and trace mineral deficiencies are listed below:
Vitamin Clinical effects
A (retinol) Dry eyes (xerophthalmia) and night blindness
B1 (thiamine) Beri-beri (Wernicke and Korsakoff)
B3 (niacin) Pellagra
B5 (pantothenic) Numbness (paresthesia)
B7 (biotin) Hair and skin conditions, infertility
B9 (folate) Neural tube defects (in the foetus)
B12 (cobalamin) Megaloblastic anaemia
E (tocopherol Neurological problems
K (phylloquinolone) Blood clotting problems
Minerals Clinical effects
Iron Microcytic anaemia
Calcium Osteopenia and osteoporosis,
Muscle cramps, nerve irritation, cardiac arrythmia
Magnesium Fatigue, nausea, vomiting
Muscle, cramps, seizures, cardiac arrythmia
Potassium Abdominal bloating, pain, constipation
Muscle cramps, cardiac arrythmia
Zinc Slow growth in children
Poor immune function and poor wound healing
Hair loss, impotence, diarrhea
Some micronutrient (vitamin and trace minerals) food sources:
A Carrot, sweet potato, pumpkin, kale
Orange fruits (papaya, mango, cantaloupe, apricots)
Milk, eggs, liver
C Citrus fruits, strawberry, kiwi fruit, guava, tomato
D Eggs yolk, oily fish (salmon, tuna, sardine)
Milk, soy, orange juice
E Green leafy vegetables, vegetable oils
Avocado, nuts, wholegrain
B1 (thiamine) Fortified breads, cereals, wholegrain
Beans, peas, soy food
B2 (riboflavin) Meat, eggs, legumes (peas, lentil), nuts, dairy products
Green leafy vegetables, asparagus, broccoli
B3 (niacin) Red meat, poultry, fish, peanuts
B6 Potato, beans, spinach, seeds, nuts
Red meat, poultry, fish, eggs
B9 (folate) Liver, dried beans, legumes
Green leafy vegetable, asparagus, fortified rice, cereals
B12 Fish, red meat, poultry, yeast extracts (vegemite)
Milk, cheese, eggs
Iron Red meat, fish, poultry, bean, lentil
Calcium Milk, yoghurt, cheese, tofu
Brocolli, kale, chinese cabbage
Magnesium Legumes, nuts, seeds, wholegrains
Green leafy vegetables
Potassium Banana, plum, orange juice, potatoes, vegetables
Zinc Oysters, red meat, poultry
Beans, nuts, wholegrains, dairy products
*Note: Beta-carotene (in orange coloured fruits and vegetables) can be converted into vitamin A in the body.
*Note: Water soluble vitamins (B, C) can’t be stored in the body, they are required from food sources daily. Fat soluble vitamins (A, D, E, K) may be lost with fat malabsorption (steatorrhoea), which may occur with long limb gastric bypass or other medical conditions.
*Note: Natural sunlight exposure helps the body to produce vitamin D.
*Note: Healthy bacteria (normoflora) in the colon can produce vitamin K.
Damaging chemicals termed free radicals are the normal by products of oxidation, a part of normal cell function in the human body. When oxygen is metabolised, new unstable molecules are released (free radicals) and they can damage cell DNA and cell membranes.
The effects of free radicals may include damage to:
- Lens of the eyes, which leads to blindness.
- Joints, which leads to arthritis.
- Nerve and brain cells, which leads to Parkinson’s or Alzheimer’s disease.
- Hasten the ageing process.
- Increase the LDL cholesterol and coronary artery plaque formation, which leads to angina or heart attack.
- Cell DNA damage, which may increase the risk of cancer.
Antioxidants are chemical compounds that can be found in foods that can neutralise these free radicals. Plant foods (fruits, vegetables, nuts and wholegrains) are rich sources of antioxidants and are recommended by nutritionist. These foods contain vitamins (A, C, E), minerals (copper, zinc, selenium) and phytochemicals (lycopene, anthocyanins).
Studies indicate that anti-oxidant lycopene (from tomatoes) may be associated with a reduction in prostate cancer risk, lutein (from spinach and corn) may be associated with a lower risk of lens degeneration or blindness and flovonoids (in tea) may be associated with a lower risk of coronary artery disease.
Some examples of anti-oxidants include:
- Vitamin A from liver, sweet potatoes, carrots, milk, egg yolks
- Vitamin C from oranges, blackcurrants, kiwifruit, mangoes, strawberries, broccoli, spinach, capsicum
- Vitamin E from avocado, nuts, seeds, wholegrains, vegetable oil
- Zinc from seafood, fish, offals
- Allium from leeks, onions, garlic
- Anthocyanins from grape, berries, eggplant
- Beta carotene from apricots, carrots, mangoes, pumpkins, spinach, parsley
- Catechins from tea, red wine
- Copper from seafood, lean meat, milk, nuts
- Cryptoxanthins from red capsicum, pumpkin, mangoes
- Flovonoids from green tea, citrus fruit, red wine, apple, onions
- Indoles from cruciferous vegetables (broccoli, cabbage, cauliflower)
- Isoflavonoids from milk, soybeans, tofu, lentils, peas
- Lignans from bran, sesame seeds, wholegrains, vegetables
- Lutein from green leaft vegetables
- Lycopene from tomatoes, watermelon, pink grapefruit
- Manganese from seafood, lean meat, milk, nuts
- Polyphenols from thyme, oregano
- Selenium from seafood, lean meat, wholegrains
Although some anti-oxidants supplements are available for purchase, they are not routinely recommended after bariatric surgery. However taking some vitamin and mineral supplements are recommended and at the same time, these supplements also have an anti-oxidant effect.
A much better alternative to daily or periodic supplements is to ensure adequate quantities and varieties of fresh vegetables, fruits, nuts and grains are consumed in our diet every day.
Fruits (6 types):
Citrus: orange, mandarin, grapefruit, lime
Stone fruit: plum, cherry, apricot, peach, nectarine
Berries: strawberry, raspberry, blueberry, kiwi fruit, passion fruit
Melons: watermelon, honeydew, rock melon (cantaloupe)
Tropical: banana, mango, pineapple, paw paw
Other: apple, pear, dates, fig, grape, avocado, tomato
- Tomatoes contain seeds and are considered a fruit (from a compound ovary).
- A simple fruit is developed from one plant ovary.
- Aggregate fruit is developed from multiple ovaries combined into one; examples are strawberry, raspberry, dewberry and blackberry.
- Multiple fruits can be formed from a cluster of flowers; examples are pineapple, fig and mulberry.
Vegetables (6 types):
Green leafy: lettuce, spinach, silverbeet
Cruciferous: cabbage, cauliflower, broccoli, brussel sprouts
Marrow: cucumber, zucchini, pumpkin
Root: potato, sweet potato, yam
Stem: asparagus, celery
Allium: onion, garlic, shallot
In general for fruits and vegetables:
- Red ones (tomato, watermelon) contain lycopene, which may help in prevention of heart disease and prostate cancer.
- Green ones (spinach, kale) contain lutein and zeaxanthin, which may help in preventing eye disease related to aging.
- Blue/purple ones (blueberry, eggplant) contain anthocyanine, which may have some anti cancer properties.
- White ones (cauliflower) contain sulforaphane, which may have some anti cancer properties.
Some common tree nuts:
Almonds (many varieties)
Brazil nut, butternut
Pecan, pine nut, pistachio
- Almond and cashew are actually seeds, not nuts.
- Peanuts are really legumes, not nuts.
In general all plants have seeds (plant embryo). Beans, nuts, seeds and grains are all part of the same seed family. But we commonly refer to a seed as the embryonic plant covered in a seed coat (an ovule with an embryo) and a grain as the fruit of the grassy crops (fusion of seed coast and fruit).
Included in the grain family are cereal grains, pseudo cereal grains, grain legumes and oil seeds.
- Cereal grains come from grass. Examples of cereal grains are wheat, barley, corn, millet, rice, rye, sorghum and oats.
- Pseudocereals are seeds or come from a non grass family. Examples of pseudo cereals are buckwheat, amaranth, quinoa and chia.
- Legumes are seeds, examples listed below.
- Oilseeds are small seeds that can be eaten (examples include chia, poppy, flax, sunflower, mustard, sesame) or consumed as oil (safflower, canola/rapeseed).
Note grains in their raw form are toxic to humans. Also grains may not have a lot of nutritional value, they are often fortified with vitamins and minerals. Although whole grains are better than refined grains (white flour and processed foods), it does not necessary mean that grains are a healthy food group.
Gluten is found in wheat (durum, spelt, kamut, semolina and others) and in susceptible individuals, this may lead to gluten insensitivities or Coeliac’s disease. Gliadin antibodies may be detected in some people with similar intolerance to wheat. Some people suggest that gliadin may stimulate appetite, responsible for obesity. Note cereal grains such as corn, millet, rice and oats does not contain gluten.
Grains may be associated with inflammatory bowel disease , irritable bowel syndrome and inflammatory conditions. Grains does not have the same health benefits as nuts and seeds, hence for weight reduction as well as improvements in health, it is generally advisable to minimize grain consumption (e.g. high GI index carbs or breads).
Some common seeds:
Soy: soy beans, bean curd (tofu)
Legume flours: flours from chickpea (besan), lentil and soy
Fresh beans and peas: green peas, green beans, butter beans, broad beans, snow pea
Dried beans and peas: haricot bean, red kidney bean, chickpea, lentil
*Note: Eat raw/fresh fruits and vegetables whenever possible but legumes must be cooked, to aid digestion and to eliminate harmful toxin.
The exception are tomatoes, when cooked there are greater levels of carotenoids (especially lycopene) released.
Refer to the section below for the proposed health benefits of soya beans.
Beware of certain legumes, fruits and vegetables:
Some foods must be cooked:
- Raw lima beans contain limarin.
- Raw kidney beans contain phyto haemagglutinin.
- Raw cassava (manioc or yucca) contains cyanide, which can kill.
- Raw almond contain cyanide.
Some seeds are not to be eaten:
- Seeds (from cherry, apricot, peach, plum) contain cyanide and their leaves, which contain oxalic acid.
- Seeds from apple contain cyanide.
- Large quantities of nutmeg, which contain myristicine, a psychoactive drug and hallucinogen.
Some leaves are not to be eaten:
- Rhubarb leaves (has some unknown toxin).
- Tomato leaves and vines, which contain alkaloid poisons and atropine.
- Potato stem and leaf contain glycoalkaloid.
- Also avoid sprouting potatoes, which contain solanine.
Avoid these potentially very poisonous foods:
Some mushroom (toadstool)
Puffer fish or blow fish (fugu or its liver)
Castor bean/oil (contain ricin)
*Note: avoid peanuts (a legume, not a nut) or tree nuts (almond, Brazil, cashew, chestnut, hazelnut, macadamia, pecan, pinenut, pistachio, walnut) in those with the nut allergy. Peanut allergy is type 1 hypersensitivity, a potentially fatal immune (IgE) mediated anaphylaxis reaction causing mast cells to release histamine and other vasoactive chemical substances. Tree nut allergy has a range of symptoms from mild to severe anaphylaxis. Some people have allergies to both peanuts and tree nuts.
Avoid over consumption of vitamin or mineral supplements
Excessive levels of fat soluble vitamins (A, D, E, K) and water soluble vitamins (B6) may be toxic. Large folate intake may mask vitamin B12 deficiencies or interact with anti-epileptic medications.
High levels of vitamin A may be harmful to the foetus during pregnancy.
High levels of vitamin B6 may be associated with neuro-toxicity.
High levels of vitamin C may cause diarrhea.
Large intake of fluoride may lead to staining and weakening of teeth.
Large doses of fish oil supplements may increase the risk of bleeding (especially after surgery).
Excessive iron intake may have GIT symptoms (abdominal cramps, nausea, black non smelly stools) or severe systemic symptoms (altered mental state).
After bariatric surgeries, blood tests are usually performed by the general practitioners to monitor for any deficiencies and obviously to advise patient against over zealous consumption of vitamins and minerals in the long term.
Health benefits of nuts
It is recommended that we consume 30g (a handful) of nuts a day to reduce developing the risk of cardio-vascular disease by up to 50% and the risk of death from heart attack by 20%.
Nuts may be associated with:
- The prevention of Type 2 diabetes mellitus
- Reducing the risk for developing Metabolic Syndrome
The benefits may be due to:
- Mono-unsaturated and poly-unsaturated fats, fibres and plant sterols in nuts, which help to reduce cholesterol absorption and blood LDL-cholesterol level.
- Arginine (amino acid) in nuts is converted to nitric oxide in the body, which has vasodilation effects (keeps blood vessels elastic and opened) to reduce atherosclerosis.
- Phytochemical anti-oxidants (flavonoids, resveratrol) and minerals (vitamin E, copper, selenium, zinc, manganese) in nuts may reduce oxidation damage and inflammation.
- Nuts contain a variety of macronutrients (protein), micronutrients (niacin, vitamin B6, E, niacin and folate), fiber and minerals (iron, potassium, magnesium, zinc, calcium, copper, selenium). There is a low level of saturated fats and no cholesterol in nuts.
- But minimize the consumption of coconuts and palm nuts because they do contain a high level of saturated fat.
The Mediterranean diet:
Studies have shown significant beneficial health effect from the Mediterranean diet, which include olive oils, nuts and vegetables.
- Reduced cardiovascular events (myocardial infarction, stroke and sudden death from cardiovascular diseases).
- A 39% reduction in total mortality in an older Mediterranean population at high risk of cardiovascular disease.
- Decrease in body mass index (BMI) of 0.78 and waist circumference of 2.1cm.
- 50% reduction in diabetes incidence (compared to following the low-fat diet over four years).
- 26% reduction in metabolic syndrome.
Dairy products and calcium balance
Milk and milk products is a good source of vitamins (A, B2 (riboflavin), B12 (cyanocobalamin)) and minerals (calcium, zinc, phosphorus, potassium, magnesium). Milk and dairy products (yoghurt and cheese) should be consumed daily as part of a balanced diet. There are controversies whether drinking raw unpasteurized milk is beneficial or harmful to humans but convention dictates that milk should be pasteurized in our modern Westernized society.
Calcium is necessary for:
- normal integrity and strengthening of bones and teeth
- normal muscle function (contraction and relaxation)
- to regulate heart function
- normal blood clotting
- normal enzyme function.
Inadequate calcium in our diet and/or lack of vitamin D may lead to poor bone health (osteopenia, osteoporosis and pathological fracture) and secondary hyperparathyroidism. Calcium deficiency is not uncommon after malabsorption operation such as the long limb gastric bypass.
Types of milk:
- Full cream contains up to 4% fat.
- *Low or reduced fat milk contains 2% fat.
- *Skim milk contains less than 0.15% fat.
- Calcium enriched milk
- UHT (ultra high temperature treated milk) is to improve storage life of the milk.
*Note when fat is removed, often the milk is fortified or have added vitamin A and D to compensate for the natural loss when fat is removed.
Humans need lactase, an enzyme found in the small intestine, to break down lactose (a dissacharide in milk) into glucose and galactose for absorption. When there is inadequate lactase production, excessive amount of lactose end up in the gut without being digested or absorbed, which then becomes available to the colonic bacteria. The clinical consequence is gas bloating, abdominal pain and diarrhoea, all symptoms of lactose intolerance. Lactose free milk (added lactase in milk) is available from supermarkets nowadays for patients who are truly lactose intolerance.
Some dairy products contain small amount of lactose, which may be consumed by those with relative lactase enzyme deficiency. Examples include
- Fermented dairy products (yoghurts, mature cheese such as cheddar, Edam, Swiss, brie, fetta, mozzarella) contain no lactose. Fresh cheese (cottage, ricotta) has low levels of lactose and may be tolerated in small quantities.
- Butter and cream have low levels of lactose but beware the saturated fat contents in these foods.
- Heated milk products (evaporated milk).
- Soy foods are completely lactose free and available with fortified calcium (soy based milk, custard, yoghurt, cheese).
Some children may be intolerant of cow or goat’s milk but this is not lactose intolerance. They may grow out of it eventually. Some people may develop temporary lactose intolerance, for example after gastro-enteritis, dietary iron deficiency or maybe after gastric/bowel surgery, often this resolves with time.
For those with lactose intolerance or vegetarians, other sources of calcium include:
- Edible fish bones (salmon, sardines)
- Hard cheese, yoghurts
- Calcium fortified soy products, rice milk, orange juice
- Almond and Brazil nuts
- Sesame seeds
- Dried fruits (figs, apricots)
- Dark green leafy vegetables (Bokchoy)
The section below discusses the great discoveries made regarding soy bean that has a positive impact on health.
Soy beans can be eaten (as Japanese Edamame) or used to produce soy milk, vegetable oil, bean curd and fermented products such as miso soup, soy sauce, bean paste and tempeh.
- Soy bean oil contains the beneficial omega 3 fatty acids and alpha linolenic acid.
- Soybeans are a source of complete protein, which contains significant amounts of all the essential amino acids. Essential amino acids can’t be synthesized in the body, hence must be provided in the diet. This is obviously an important source of protein for vegans (textured vegetable protein) as well as containing less saturated fats compared to animal protein.
Soy milk is a plant milk produced by soaking dried soybeans and grinding them in water.
Soy milk is a complete protein and has about the same amount of protein as cow’s milk; it can replace animal protein and other sources of dietary fiber, vitamins and minerals. Unlike cow’s milk, soy milk has little saturated fat and no cholesterol.
Soy milk contains little digestible calcium because calcium is bound to the bean’s pulp, which is indigestible by humans. Hence soy milk needs to be enriched with calcium.
Soy products contain sucrose as the basic disaccharide, which breaks down into glucose and fructose. It does not contain galactose (from lactose breakdown). It can be given to children with galactosemia, allergic to pasteurized cow’s milk protein and people who are lactose-intolerant.
Soy milk consumption may be associated with a reduction in LDL-cholesterol and triglycerides, the risk for cardio-vascular disease.
Tofu (bean curd) is made by coagulating soy milk and then pressing the resulting curds into soft white blocks. Tofu has a low calorie count, relatively large amounts of protein, high in iron and is often high in calcium and/or magnesium (depends on the coagulants used). Many different varieties of tofu exist.
Studies have suggested that soy protein actually decrease LDL-cholesterol but the significance or the level of cholesterol reduction is debatable.
Involves a (fungus) fermentation process that binds the soybeans into a cake.
The soy carbohydrates (oligosaccaharides) in tempeh become more easily digestible as a result of the fermentation process.
- Allergy to soy protein may occur. Symptoms may range from mild rashes and swelling to severe anaphylaxis.
- Soy may result in food intolerance presenting with vomiting and diarrhoea.
- Soy should be avoided in people with gout because the purine in soy makes gout worse.