Iron
Iron has many essential roles. It’s needed for growth and development, for making haemoglobin, a protein in red blood cells that carries oxygen from the lungs to all body cells. About 75 per cent of the body’s iron is found in haemoglobin but iron also plays a role in activating some enzymes, and synthesising collagen, neurotransmitters and some hormones.
Monthly menstrual blood loss means women need much more iron than men. Pregnancy also increases needs. Men need much less iron but if their level is low, further medical tests are essential to check for any bleeding from the intestine. Low iron levels can also be a sign of undiagnosed coeliac disease.
In foods, iron exists in two main forms: haem and non-haem. Haem iron is found only in animal-based foods. Good sources include red meat (especially kangaroo), fish and other seafood (especially oysters and mussels) and chicken (especially thigh and leg meat). With the exception of eggs, non-haem iron is in plant foods, with good sources being legumes, wholegrains, vegetables, nuts, tofu and seeds.
Vegetarians can easily meet their iron needs if their daily diet includes these healthy choices. When the body needs more iron, it also increases its absorption of non-haem iron, especially if foods that contain vitamin C are consumed at the same meal. This is yet another reason to include fruit or vegetables at each meal.
Spinach has long been touted as a top source of iron. That’s true, but spinach also contains oxalic acid, which stops its iron being absorbed, although it doesn’t affect the vitamins, antioxidants and other plant compounds. The oxalic acid in spinach has no effect on our ability to absorb iron from other foods at the same meal.
Iron deficiency is common throughout the world, especially where people lack sufficient food. In countries like Australia, there’s no more iron deficiency in vegetarians who have a healthy diet than in those who consume meat. It’s true that iron levels may be a little lower in vegetarians, but they’re still within the normal range. And more is not better with iron levels.
The good news in pregnancy and also for children who may be fussy eaters, is that the body can absorb more iron, especially non-haem iron, when more is needed.
Symptoms of low iron levels include extreme fatigue, restlessness and inability to concentrate, but don’t be tempted to self-diagnose such symptoms as being due to insufficient iron. They may be due to other reasons. The most common genetic disorder in Australia, haemochromatosis, is a problem caused by the body absorbing too much iron. It occurs in about one in every 200 people and its symptoms often mimic those of iron deficiency. If someone with this condition takes iron, it can damage the pancreas, liver and heart. Even for those without haemochromatosis, excess iron acts as a pro-oxidant.
Always get a blood test to identify iron levels before taking a supplement.
Calcium
Calcium is best known for its role in building and maintaining strong bones and teeth. It also activates enzymes throughout the body, plays a role in regulating blood pressure, and helps muscles to contract, nerves to send messages and blood to clot appropriately.
Vitamin D helps the absorption of calcium – another reason to expose a little skin (forearms will do) to sunlight for short periods.
Both men and women tend to lose calcium from their bones with age. This begins around age 30 but accelerates when oestrogen levels fall in women at menopause and can result in brittle bones and osteoporosis.
Weight bearing exercise is vital for calcium to be deposited into bones and the denser bones are at age 25, the less likely osteoporosis will develop.
Extreme thinness can exacerbate osteoporosis. This may occur from eating too little or exercising too much. If a young woman is so thin that her periods stop, the loss of bone that usually occurs at menopause will begin and result in extremely fragile bones.
High quantities of calcium are found only in a few foods. Milk, yoghurt and cheese are rich sources and canned sardines or other fish with edible bones are also excellent sources. Tofu, plant-based ‘milks’ and tahini (sesame seed paste) have varying quantities. Some vegetables (purple broccoli and Asian greens score very well), fruit (dried figs win this category) and soy beans add valuable amounts of calcium.
All ages need calcium, with the highest recommended intakes for 13 and 18 year-olds, women over 50 and men over 70.
It’s not difficult to meet our calcium needs from the daily diet. Those who are lactose-intolerant rarely have any problem with small amounts of milk (the intolerance is not an allergy). Most cheeses have very little lactose and the bacteria that thicken natural yogurts partially digest lactose and usually cause no problems.
With tofu and dairy alternatives, always check the calcium listed on the label, as it varies. For example, calcium in tofu can range from 60 to 500 mg/100g.
Those with osteoporosis may need a supplement. These rarely cause problems, although high doses of calcium carbonate can provoke constipation. However, if you take various medications, check the compatibility of any supplement with your doctor.
Magnesium
Like calcium, magnesium is an important component of bones, with about 60 per cent of the body’s magnesium content found in bones. Magnesium is also essential for all the body’s reactions involving the release of energy from ATP (adenosine triphosphate – the primary energy carrier), giving it a vital role in the body’s ability to use proteins, fats and carbohydrates. It also has a vital role in muscle contraction and controlling blood glucose levels.
Fortunately, magnesium is widely distributed in foods. Good sources include seeds (especially pepitas and chia), nuts, peanut butter, potatoes, legumes, wholegrains (especially brown rice and oats), yoghurt, milk, green vegetables and bananas.
Deficiencies are rare because if the intake is limited, the kidneys ensure that excretion is minimised. Major problems are usually only seen in chronic alcoholism when there may be vomiting, weakness, personality changes, abnormal heart rhythms, seizures and cramps.
There is no simple way to assess magnesium levels in the body and some supplement sellers exploit this, often claiming their products will help problems such as cramps or fatigue. In the absence of other symptoms of chronic alcoholism, cramps are unlikely to be caused by a lack of magnesium. The most likely causes are forgetting to drink enough water or engaging in unfamiliar exercise.
High doses of magnesium actually interfere with magnesium absorption. And as discussed last month, many magnesium supplements also contain hazardous levels of vitamin B6 that can cause peripheral neuritis and damage to the nerves in hands and feet.
Next month: sodium, potassium, iodine and fluoride.
Dr Rosemary Stanton OAM, Nutritionist
