Nutrition Advice

Iron

Iron, yes the same stuff 6” nails are made of, is essential for our health. On average a healthy man will have 4 grams and a woman, 2.5 grams of iron in the body. Most of the iron in our bodies is found in the red blood cells enabling them to carry oxygen to our tissues. Iron is also needed in muscles and other organs for energy generation. Iron is stored in the liver and bone marrow. The recommended daily intakes of iron are about 12 mg for men but 18mg for women of childbearing age. Lack of iron can lead to tiredness, anaemia (low blood count), hair and nail changes, and learning problems in children. Iron deficiency is one of the most common nutrient deficiencies in the developed (and less developed) world, especially in women and children.

So, where can we get iron from? As you might know or guess meat (especially red meat) is an important source of iron in the Australian diet. Typically it is better absorbed than iron from plant sources. However, iron deficiency is common in meat eaters as well as vegetarians. So what about plant sources of iron?

Iron is generally less well absorbed form plant sources. Partly this relates to the form of iron found in plant foods, and the presence of other compounds which bind iron and make it less available, such as phytate (in grains and legumes) and tannins. However, consuming vitamin C rich foods at the same time converts the iron into a form more readily absorbed by the body and the phytate content of wholegrain flours is reduced by soaking and fermentation e.g. during bread-making with yeast and especially with sourdough. Moreover when iron deficiency is present, or requirements are increased, absorption is much more efficient.

Rich plant sources of iron include dried fruits such as Australian muscatel raisins, dried apricots, and peaches, treacle, molasses (as opposed to refined sugars which have none), wholegrain cereals, legumes including soy products, green leafy vegetables, parsley, amaranth, nuts and seeds such as pistachio nuts, brazil nuts, un-hulled sesame seeds and linseed. Berry fruits and stone fruits are also good sources and very rich in vitamin C too!

By including a wide variety of iron-rich foods in our diet, and having vitamin C rich foods or juice with meals, we can obtain sufficient iron, along with a range of other essential and health-giving nutrients!

Dr Gisela Wilcox BMedSc(Hons) MBBS(Hons) FRACP MAACB FRCPA

Calcium

Is it all it’s chalked up to be?

What do teeth, bones, eggshells, seashells, chalk and limestone caves have in common? They all contain lots of calcium! And in fact limestone is believed to have come from the shells and outer skeletons of millions of sea animals, which died on prehistoric ocean floors. We have lots of calcium in our bodies too, over a kilogram in fact, mostly (99%) contained in bones and teeth, but that one percent left over is vitally important for the function of nerves and muscles.

So how much calcium do we need? Calcium requirements depend on things like age and stage of life e.g. pregnancy, and overall dietary pattern. Generally, in Western countries the recommended daily intakes (RDI) are about 800-1000mg per day for adults, 1300mg for teenagers, and about 800mg for primary school-age children respectively. Interestingly, recommended intakes in many less developed countries tend to be lower, with the World Health Organization’s RDI being 500mg daily for non-pregnant adults.

Diets rich in fruit and vegetables, as well as getting enough sunshine to make Vitamin D, tend to help the body retain calcium. Soft drinks, excess caffeine, and diets very high in animal protein and salt tend to make the body lose calcium.

What happens if we don’t get enough? Lack of sufficient calcium during growth and development means the bones don’t develop as strongly. This means that in later life, as we lose bone with aging, we have little in reserve, risking fractures from osteoporosis at an earlier age. During adult life we can better maintain the strength of our skeleton if we consume enough calcium to replace what is being lost. If we don’t take in enough calcium, the body will pull calcium out of our bones to keep our nerves and muscles functioning properly. Other health problems that may be associated with chronic lack of calcium include high blood pressure and colon cancer.

Where can we get calcium from? In countries like Australia, dairy products are the major source of calcium but worldwide, this has not been the case for all time or all peoples.

In many parts of the world drinking water is an important source with some mineral waters containing 200-400mg calcium per litre e.g. San Pellegrino, Ferrarelle. Stone age hunters obtained calcium from animal bones, and today, fish with edible bones are a significant source e.g. sardines, with 400mg per 100g can. Plant sources of calcium vary in calcium content and absorbability. Green leafy vegetables such as bok choy, silver beet, kale and spinach have about 200mg per cupful. Almonds, unhulled sesame seeds, walnuts, tofu, black-eyed peas, oranges, blackberries and rhubarb are all useful sources. Calcium is less well absorbed from foods rich in oxalic acid (e.g. spinach, rhubarb) and phytic acid (e.g. whole grains, beans); however the calcium that’s not absorbed may still provide other health benefits in our intestines. Breads, cereals and meat are generally poor sources of calcium, making dairy foods, including the low-fat products, (containing 200-300mg per serving) important in Western diets. Interestingly, wild plants can be very rich sources e.g. dandelions, European nettles, and both the staple non-cereal grains of ancient civilizations of the Americas, and Asian-style vegetables, provide much more calcium than the cereals and vegetables commonly used in Australia today...

Dr Gisela Wilcox BMedSc(Hons) MBBS(Hons) FRACP MAACB FRCPA

Vitamin D

Some of us may remember being given cod-liver oil as children, during the winter months, to ward off coughs and colds. While some may have had it in a capsule, others even developed a taste for the stuff! So what was the reason for it?

After the industrial revolution in Europe, cities became polluted with thick smoke from burning coal. Little natural sunlight penetrated, especially during the winter months. Children growing up in such cities frequently suffered from a condition known as rickets. Their bones were softer than normal and often bent under their body weight, causing deformities such as “bow-legs”. However, it was noted that a teaspoon of cod-liver oil daily could treat and prevent these problems.

Vitamin D is made by the action of gentle amounts of sunlight on the skin, beginning a number of chemical steps by the skin, liver and kidneys, to make a type of cholesterol into a hormone vital for absorption of calcium.

What does it do? Vitamin D triples the amount of calcium absorbed by the body, to make sure enough reaches the bones to make them strong. It also seems to be important for the function of the immune system, to fight infections, and to keep check on excess multiplication of the body’s own cells. Through effects on calcium balance, it ensures there is enough calcium for nerves and muscles to work properly.

Why is it important? Severe lack of vitamin D leads to rickets in children and softening of the bones, known as “osteomalacia” in adults. Muscle weakness and bone aches go along with this. Nursing mothers lacking vitamin D may inadvertently deprive their infants of this essential nutrient. Though generally uncommon, it is more likely in people who totally avoid natural sunlight, or whose skin is mostly covered-up or naturally dark, and don’t consume foods containing vitamin D. However milder degrees of vitamin D deficiency have been associated with osteoporosis, and even muscle weakness and unsteadiness especially in older people. Importantly, treatment with Vitamin D may improve these problems.

Where do we get vitamin D in Australia today? In the past vitamin D deficiency was not believed to be a problem in sunny Australia. Unlike in the US and Europe, it was not thought necessary to fortify our foods with this vitamin. Vitamin D is made in the skin at lower levels of sunlight than those causing sunburn. For fair-skinned people 10-15 minutes per day of summer sun will provide enough vitamin D, so long as a reasonable amount of skin is exposed. However, those with darker skin, having better protection from UV light, need to be in the sun 3-6 times as long to make enough vitamin D. What’s more in the Melbourne winter the sunlight is too weak in June and July to make any vitamin D at all, so vitamin D levels tend to be lowest in the early spring months. Over the last 20 years we’ve been warned to avoid sunburn and stay out of the midday sun to prevent skin cancer. However, we shouldn’t forget that while too much sunlight can be harmful, some natural sunlight is essential for our health. Casual sunlight exposure e.g. from walking to the shops, or cycling to work or school can be enough. If we don’t get our vitamin D from sunlight, some can be obtained from animal foods such as oily fish, eggs, butter, milk or from fortified margarines e.g. Melrose Omega Gold. The recommended daily intake (RDI) for adults is 200-400IU or 5-10 micrograms; however in those with no exposure to natural sunlight e.g. nursing home residents, the requirements may be double this. In these situations a vitamin D supplement may be advisable.

Dr Gisela Wilcox BMedSc(Hons) MBBS(Hons) FRACP MAACB FRCPA