Health Q&A: postural hypotension and dietry calcium

Dr David Roche / 08 July 2013

Saga Magazine's GP advises a sporty chap on the likely causes of his light-headedness, and gives some diet and lifestyle tips to a reader who is at risk of developing osteoporosis.

What's making me feel light-headed

Question: I’m a 68-year-old man who enjoys swimming 3km and doing three 50km cycle rides every week. During the day I feel fine. However, in the evening, after resting, I often get very light-headed when I stand up. I have to hold on to something while it passes – usually after about 10 seconds. Occasionally I feel close to blacking out, but in the morning I’m okay again. I take 2.5mg Lisinopril and simvastatin, but both my blood pressure and cholesterol are normal.

Answer: This is most likely to be due to ‘postural hypotension’: a transient low blood pressure for a few moments when you first stand from sitting or lying. Typically it is more marked the longer you have been resting. As you stand up, your body systems need to adjust your blood pressure upwards to maintain blood flow to the brain. If blood flow is not maintained, you will feel initially light-headed, followed by a blackout if there is a significant delay in the blood pressure rise.

These symptoms are increasingly common as you get older; it takes a little longer for the reflexes involved to produce the changes required. It is also commoner with drugs such as Lisinopril, so you should check with your GP that you really need this drug, especially if your blood pressure is consistently normal. Meanwhile, you should get up slowly and carefully after resting and, if the light-headedness does not resolve quickly, then lie down promptly to avoid a blackout.

How can I increase my dietary calcium intake?

Question: I have been advised that I am at risk of developing osteoporosis. Rather than taking vitamin D and calcium supplements, I am trying to increase my calcium intake by diet. I’ve been told nuts and seeds are good for this, but have now read they are high in phytates, which block calcium from being absorbed. I’d appreciate your opinion on this.

Answer: Nuts and seeds are high in phytates and although phytates are known to bind to calcium, the effect is not thought to be significant unless you eat a great deal of them. Phytates are chemicals which, in the plant world, carry the element phosphorus. They cannot be digested by humans and so pass through the intestines without being absorbed. In the gut they bind to calcium and other minerals such as zinc and magnesium, so that these pass through unabsorbed, too. There is no evidence that this has a significance in a normal balanced diet so, unless your diet is unusual, you do not need to be concerned. Dairy products are a good source of calcium and low-fat versions contain as much calcium as the original. Vitamin D can be obtained from fish, eggs and some cereals: remember it needs to be activated by exposing your skin to sunlight. If you wish to avoid drug therapy you will need to concentrate on these food types and hope for some summer sun.

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