Today’s ‘Ask Alex’ has turned out to be nutrient special as we focus on two of the most important nutrients – iron and vitamin D.
My doctor has told me that I need to increase my iron, but don’t eat red meat…how can I do that?
Firstly, what is iron used for and why is it important?
Iron is important for our energy, neurotransmitter synthesis, the formation of haemoglobin and it increases our resistance to stress and disease. In other words…it does A WHOLE LOT.
The recommended daily dietary intake for men/women under 50 years is 18mg/day and over 50 years is 8mg/day.
For teenage girls, iron is off particular importance due to the onset of menstruation, large growth spurts and subsequent expansion of blood volume, all of which increase an individuals iron requirements. The requirements are not often met by an increased dietary intake, hence, we are seeing more and more girls experiencing low iron stores and the symptoms that come with it.
Those who do a lot of running can also be at risk of iron deficiency. Foot strike leading to haemolysis and organ movement can all lead to excess iron losses within the body.
Deficiency of iron can present as fatigue, irritability, pallor, heart palpitations, constipation, shortness of breath, feelings cold, anaemia, foggy brain and/or decreased attention span and more.
It is important to note that red meat is not the be all and end all for iron. In fact, there are many sources of iron that trump red meat. Lets explore a few.
- Dried apricots (3 = 5mg)
- Cooked amaranth (100g = 13mg)
- Lentils (1/2 cup cooked = 4mg)
- Cooked quinoa (1 cup = 4mg)
- 100g lean beef = 3mg
- Cooked spinach (1/2 cup = 3mg)
- Prune juice (1 cup = 3mg)
- Chia seeds (15g = 2.5mg)
- Cashews (30g = 2mg)
- Chicken (1 cup cooked = 1.3mg)
- Brown rice (1 cup cooked = 1mg)
- Egg (1 large = 1mg)
- Soy milk (250ml = 1mg)
- Tuna (100g = 1mg)
- Pumpkin and sunflower seeds (1Tbs = 1mg).
As shown above, lean beef provides less iron than other sources, but it still a significant source.
There are also some specific inhibitors to be aware of with iron.
Calcium, from both supplements and dairy sources, can reduce iron absorption, although its mechanism is only suspected to be short term, thus long term supplements are unlikely to effect iron status to any major extent.
Phytates interfere with iron absorption in a dose-dependent fashion. Polyphenols also inhibit iron absorption, thus it is suggested that tea is consumed in between meals as opposed to with meals. Other sources of polyphenols include raspberries, dark chocolate, rye bread, plums and red grapes.
Lastly, vitamin A also helps to mobilise iron from storage sites within the body, so a vitamin A deficiency may exacerbate an iron deficiency.
If you think you may be iron deficient or want some guidance on how to increase iron in your diet, it is always best to consult your healthcare practitioner or a nutritionist, like myself, who can help guide you on how to do so.
What does vitamin D do?
Vitamin D has been gaining more popularity in recent time as scientific research has begun linking it to some major health conditions.
Vitamin D, aka cholecalciferol, acts as both a fat-soluble vitamin and a hormone. Yes, I know what you’re thinking, it is super smart and talented!
Vitamin D is produced endogenously meaning that when the skin is exposed to ultraviolet rays from sunshine, vitamin D synthesis is triggered from cholesterol in the skin.
Vitamin D obtained in this manner or from food/supplements is biologically inactive, hence it must undergo two hydroxylation’s so that the body can use it.
The first hydroxylation occurs in the liver and forms calcidiol and the second occurs in the kidney with the help of magnesium, forming calcitriol.
Vitamin D in involved in the absorption and metabolism of calcium, phosphorous and magnesium and the regulation of zinc and iron. More specifically, vitamin D promotes the gut’s absorption of calcium and helps maintain adequate concentrations of serum calcium and phosphorous to enable good bone health. Vitamin D insufficiency can result in thin, brittle or misshapen bones, decreased muscle function and quality and can also predispose to illness such as rickets (soft bones and enlargement of joints) in children and osteomalacia in adults (adult version of rickets). Calcium and vitamin D work in harmony to prevent osteoporosis in older individuals.
Vitamin D also plays a role in teeth formation and health, cell growth and differentiation, immunity and cardiovascular and reproductive health. It also helps support the stability of our nervous systems, is needed as part of the insulin secretion process and ensures blood pressure regulation.
Vitamin D deficiency is more common in elderly persons with a reduced ability to synthesis the vitamin in the skin as well as reduced mobility to get outside. It also is seen more in housebound/bedbound/officebound individuals, alcoholics, obese individuals (because of a reduced ability to store vitamin D in fat), individual with a darker skin colour, individuals with liver diseases/kidney disease/crohn’s/coeliac and those using certain medications such as heparin, steroids and anticonvulsants.
Symptoms of vitamin D insufficiency include rickets and osteomalacia (as described above), muscle twitching/weakness/pain and the softening of teeth. A low intake of vitamin D has been linked to poor bone health and associated illnesses such as osteoporosis and arthritis, autoimmune illnesses such as diabetes, mental health implications such as depression and foggy brain, cardiovascular implications such as heart attack, stroke and hypertension as well as other conditions such as multiple sclerosis, cancer, autism and PMT.
You can also show symptoms if you’ve got vitamin D excess, but these can be linked to countless other illness so testing is pertinent. These include; nausea, fatigue, headache, excessive thirst, dry mouth, polyuria, muscular pain and kidney stones.
The recommended daily intake for vitamin D is 5-15mcg or 200-600IU/day. For those who are sun deprived, you should aim for 25mcg or 1000IU/day.
The best source of vitamin D is sunshine as it is naturally present in very few foods. The foods that it is present in include:
- Cod Liver Oil (1tbs = 1300IU)
- Salmon, canned (90g = 530IU)
- Salmon, cooked (90g = 300IU)
- Sardines (90g = 230IU)
- Mackerel (90g = 200IU)
- Tuna, canned (90g = 200IU)
- Fortified soymilk (250ml = 100IU)
- Fortified cows milk (250ml = 100IU)
- Fortified orange juice (250ml = 100IU)
- Egg (1 = 20IU)
- Swiss cheese (30g = 12IU)
As you can see, aside from cod liver oil, fish (also high in omega 3 and protein, yay for added benefits!) prevails as the best dietary source here. Vitamin D is also available as a dietary supplement.
Again, if you think you may be vitamin D deficient, experiencing an excess or want some guidance on how to increase your intake, it is always best to consult your healthcare practitioner or a nutritionist, like myself, who can help guide you on how to do so.
Sources:
Derbyshire, E 2012, ‘Strategies to improve iron status in women at risk of developing anaemia.’, Nursing Standard, vol. 26, no. 20, pp. 51–57.
Kouris, A 2012, Food Sources of Nutrients; A Ready Reckoner of Macronutrients, Micronutrients and Phytonutrients, Elsevier, Sydney.