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Important health numbers: Sept'12

Body mass index, blood pressure and blood sugar levels... all health topics that can be linked to important health numbers - but do you know what those numbers are? Our experts were back to help you find out on Tuesday 11 September, with Dr Sarah Jarvis on hand to discuss everything from abnormal blood sugar levels to the risks of high blood pressure and the importance of staying within a healthy BMI range.

Having been a partner at her medical practice for 22 years, Sarah Jarvis is a GP with a particular interest in cardiology - and sits on the advisory board of the British Journal of Cardiology and the patient services board of the cholesterol charity Heart UK, so was more than happy to answer a wide range of your questions. Here's what she had to say:

Fionad asked: Hi Dr Jarvis - what are the signs of abnormal blood sugar levels?

Dr Sarah Jarvis: Hi, Fiona D. high blood sugar can be a sign of diabetes or 'pre-diabetes'. There are two different kinds of diabetes - in type 1 diabetes blood sugar can become extremely high, especially before diagnosis, and can lead to dramatic weight loss, feeling extremely unwell or even coma. It also causes the same symptoms as the lesser levels of raised blood sugar more commonly seen in type 2 diabetes - feeling generally tired and slightly under the weather, feeling thirsty all the time, needing to pass water often including at night, sometimes getting recurrent minor infections like boils and thrush, and possibly losing a bit of weight.

Low blood sugar is mostly seen as a side effect of some treatments for diabetes - most commonly insulin. Symptoms include feeling shaky, sweating, tingling in the lips, going pale, heart pounding, confusion and irritability. if untreated, severe low blood sugar or 'hypo' can cause loss of consciousness

Hungry_Healthy_Happy asked: Hi Dr Jarvis. I am just wondering how you feel about BMI and why do you think the health world focuses on it so much? Personally, I don't like how much of a focus there is on BMI when it comes to weight loss, as it doesn't take into account muscle. I know plenty of people who are classed as overweight (by BMI), despite being very healthy, fit and muscular.

Dr Sarah Jarvis: Dear Hungry-Healthy-Happy, I'm afraid that our apparent obsession with BMI is for good reasons. The 'ideal' BMI levels are based on actuarial tables which look at life expectancy for millions of people, and which show that your best chance of a long, healthy life comes hand in hand with an 'ideal' BMI of 20-25. Being overweight (BMI 25-30) increases the risk of long term health conditions; being obese (BMI 30-40) increases that risk further and by the time your BMI is over 40, the likelihood is that you will die from a directly obesity related disease. Having said that, these days we also take waist circumference into account.

Much of the damage to health from being overweight or obese comes from intra-abdominal fat - not fat under the skin, but deep inside your stomach. Being an 'apple' rather than a 'pear' increases your risk of heart attack and diabetes significantly. Even with the treatments we have available today, the potential dangers of poorly controlled diabetes are very high. Being overweight also increases your risk of several cancers. Not happy news, but there's no doubt that keeping your weight to the ideal range and your waist size down is important for your health

the_salt_girls! asked: Hi Dr Jarvis! Just how dangerous is having high blood pressure?

Dr Sarah Jarvis: Dear 'the salt girls' - high blood pressure is a major risk factor for stroke in particular, but also increases your risk of heart attack. Try an experiment - go to http://www.patient.co.uk/doctor/cardiovascular-risk-calculator, log in your age, gender, smoking status and cholesterol (if you know it - otherwise, just try a cholesterol of 6 and an HDL cholesterol of 1.2). Then plug in a high blood pressure - say 160/100, and see what your risk of heart attack or stroke (that's the 10 year risk at the bottom) is. Then use all the same figures but substitute a 'normal' blood pressure of 120/80 and see what it does to your risk. On the one hand it's scary stuff, but on the other hand it shows just how much benefit you can get from keeping your blood pressure under control. Diet and lifestyle will make a big difference, but if your blood pressure is still high it is important to take tablets if your doctor recommends, and to keep going unless she advises you otherwise

David_Bojangles asked: Hi Dr Jarvis, is alcohol bad for blood sugar levels?

Dr Sarah Jarvis: Dear David, Yes, alcohol is definitely bad for blood sugar levels in many respects. If you have diabetes (and even, to an extent, if you don't) excess alcohol hugely increases the risk of low blood sugar or 'hypo' - if you've drunk too much alcohol you're less likely to notice the early warning signs and be able to take action to avoid your blood sugar dropping lower. Severe low blood sugar, which can cause loss of consciousness, seizures or even brain damage, is clearly bad news. People with diabetes are advised to limit their alcohol to 2 units a day for women or 3 units a day for men.

Peter_D asked: Hello. I generally try to stick to a healthy diet but I do eat too many processed foods. I find it nearly impossible to keep track of my salt intake. Can you tell me is everyone at risk of high blood pressure etc from salt or is it something where only some are at risk? Thanks

Dr Sarah Jarvis: Dear Peter D. You're quite right to highlight that processed foods are often very high in salt - so too are seemingly innocuous foods like bread and even breakfast cereals, although the food industry has been working with health experts in recent years to try and reduce some hidden sources. If you have high blood pressure already, it's very important to keep your salt intake under control. If your blood pressure is borderline, high salt intake can push it up enough to be worryingly high. If you have normal or low blood pressure, high salt intake isn't likely on its own to put your blood pressure up to worrying levels. However, it's really important in the longer term to try and tackle your salt tooth. As you get older, your small arteries (called arterioles) get naturally stiffer, increasing your risk of high blood pressure and pretty much everyone reaches the stage in life where a high salt intake will be bad for them.

the_salt_girls!: 'Salt tooth' - great term! I think I know lots of people with one of those!

Cerpin_Taxt asked: Hi, Dr Jarvis. I've heard that BMI can be massively skewed by a person's height, with taller people more likely to have a much higher BMI. Is there any truth in this?

Dr Sarah Jarvis: Dear Cerpin, BMI is based on a relationship between your height and your weight, so height shouldn't make a difference - it's a fairly accurate reflection of your height to weight ratio compared to the ideal for someone of your height. I'm afraid the comment about it being skewed against tall people may have been someone tall trying to justify getting bad news about their need to lose weight!

the_salt_girls! asked: Yikes. It looks as if you are still at risk even if your blood pressure is not high though, should everyone think about getting their blood pressure as low as possible?

Dr Sarah Jarvis: Dear salt girls, you've raised a really interesting point. It certainly won't do you any harm to have blood pressure that is on the lower end of normal - the only exceptions are people whose blood pressure is unusually low because they've lost a lot of blood or because they have medical conditions affecting their hormone levels. As a rule, otherwise the worst that will happen is that you'll feel lightheaded if you stand up to quickly. However, as you get older, something called 'the j shaped curve' applies - the more you drop your blood pressure from high levels the lower your risk of stroke or heart attack, until you get to very low levels where dropping the blood pressure further can do more harm than good. I stress that this doesn't apply to everyone - for instance, in people with chronic kidney disease, a blood pressure below 120/70 might actually harm them, while in a 20 year old I would hope it was naturally in that region.

the_salt_girls!: Thanks Dr Jarvis that is really helpful. We know all about how to reduce your salt intake and would be happy to point people in the right direction if they're having any difficulties!

Hungry_Healthy_Happy asked: Yes - I understand why BMI is important in the fact that obesity is a big problem and many health problems are associated. But, with there being so much focus on it, it can lead people who are not overweight to think that they are overweight. For example, a very muscular man, would have a high BMI, as a lot of their weight would be muscle, but they would not be unhealthy.

Dr Sarah Jarvis: Dear Hungry-healthy-happy - the old 'muscle weighs more than fat and rugby players all have high BMIs' argument! I hear this all the time from my patients and of course you're absolutely right. If someone is extremely athletic, and has a very high proportion of muscle, they may well be in the overweight category if we only look at BMI. However, they are highly unlikely also to have a raised waist circumference. Interestingly, a more extreme version of the sportsman argument is that sumo wrestlers are hugely overweight using BMI but if you do scans of their stomachs, they have very little intra-abdominal fat (the kind that puts you at risk of heart attack, stroke and diabetes). However, the moment they stop exercising their risk of heart attack and stroke skyrockets

Alan asked: Hi, my BMI is always on the line somewhere between healthy and overweight. I try to keep my weight down and it's not increased over the years, but neither has it gone down. I notice you mention that waist/ stomach size is a risk factor. To be honest all my adult life my belly has always been like this even though I don't carry excess body fat elsewhere e.g. in my limbs or my bottom. Would exercise help this/ lessen the risk or is it a dietary thing?

Dr Sarah Jarvis: Dear Alan, well done for trying to keep your weight down. I assure you I'm human and I am only too aware how tough it can be! Many people (like you from the sound of it) naturally tend to accumulate any excess weight around their midriffs - that's what we mean by 'apples'. It may seem unfair, but two people with identical BMIs can have very different risks of heart attack or diabetes if one is an apple and the other a pear. The good news is that if you're overweight and you reduce your weight by 10%, you can not only cut your 'bad' LDL cholesterol by 15% and increase your 'good' HDL cholesterol by 8%, you can reduce the amount of intra-abdominal fat by up to 30% - so it really is worth keeping up the battle! I'm sure you'll be aware that the best way to do this, and to protect your heart, is with a combination of diet and regular aerobic exercise

Sarah_jane asked: Hi, how often should you get your blood pressure checked? I am 25 should i be getting mine checked regularly? My parents suffer a bit with high BP, is this something i should be worried about? Am i likely to get it - is it hereditary?

Dr Sarah Jarvis: Hi, Sarah Jane, that's a much more complicated question than you might think. People whose parents have high blood pressure often end up having high blood pressure themselves, but in fact in most cases it's more down to the fact that they tend to 'inherit' a tendency to the sort of unhealthy lifestyle which makes you prone to high blood pressure than any direct genetic link. There are a few exceptions - sometimes people of Afro-Caribbean origin can have a strong family history of very high blood pressure. getting older is the single biggest risk factor for getting high blood pressure (probably in the UK in the order of 50% of over 50s, 60% of over 60s and 70% of over 70s have high blood pressure). Other risk factors include being overweight and having a high salt diet, as we've mentioned already. Regular aerobic exercise (the kind that makes you mildly out of breath - everything from jogging through cycling to Zumba!) can reduce your blood pressure.

If you're taking medication that can increase your blood pressure or where high blood pressure can increase the risk of complications (the oral contraceptive pill or medicines for mental health problems are examples) you need your blood pressure checking at least once a year. If you have other medical conditions like diabetes you'll also need regular checks. Otherwise at your age you certainly don't need it checking more than every 5 years if you're in good health and have never had high blood pressure

Gezzalinko asked: Hi, I am just reaching that mid 40's point in my life, although I don't look it may I say... and due to my lifestyle, young family and hectic working hours, my BMI is, as you can guess, is continually categorising me as overweight. However, I still try to do regular exercise and swim at least 3 times a week and so I consider myself to be physically fit. I have tried to keep my weight down and it has hovered around the same place for several years. I eat reasonably healthy, but as you can guess I am tempted with the odd visits to Greggs on occasion. What do you recommend as ways to control my weight and get me into that safe normal weight category?

Dr Sarah Jarvis: Dear Gezzalinko, you have my sympathy. Your intentions are clearly good but it can be really difficult to fit a healthy diet and exercise regime into a very busy schedule. I'm afraid there are no quick fixes. It can be tempting to miss breakfast, but in fact that can be completely counterproductive as the evidence shows that you may be more hungry ny mid-morning, and tempted to 'fuel up' on the sort of high fat, empty calorie snacks that you can buy from the vending machine or keep in your office. A healthy breakfast, ideally with a 'slow burn' form of carbohydrate and some low fat protein, can keep your concentration levels up while reducing the urge to snack unhealthily. The world is full of fad diet book but if I had to sum them up in one word, it would be 'don't'! The vast majority of fad diets don't result in long term weight loss.

Alcohol can be a deceptively high source of calories - it has almost as many calories as pure fat - and you may find it easier to incorporate daily small changes to your exercise tally than try and set aside time for formal exercise. For instance, getting off the bus/tube one stop earlier every day; taking the stairs rather than the lift etc. It's amazing how these small changes add up, but you need to make a conscious effort to do them every day for several weeks before they become part of your routine. If you do crave the odd really unhealthy food (and I'm afraid I have very little good to say about processed pies!) don't tell yourself you'll never eat one again, but rather set yourself a day in the week when you can have one, but only one day and only one pie.

Emily asked: Whilst I was on holiday this year I went for a Turkish bath, during which i sat in a boiling hot sauna and then plunged into a pool of very cold water, apparently this is meant to be good for blood pressure - is this true? If so can you explain how?

Dr Sarah Jarvis: The rationale for the effect of this sort of temperature change on blood pressure is that in extreme heat your heart rate increases and your blood vessels on the skin surface dilate to allow heat to escape by evaporation. The opposite happens when you go into a very cold environment. Unfortunately the effects are very unpredictable and I certainly wouldn't describe it as being good for your blood pressure - in some cases blood pressure can go up rather than down. If you're otherwise healthy it's unlikely to be bad for you, but doctors would normally advise anyone with high blood pressure to avoid this kind of sudden change of temperature because of the effect in can have on your heart.

Nakamura asked:
Hi. Can you tell me is it true that a glass of red wine now and then can help cholesterol levels? Generally my diet is healthy and I generally avoid anything with hydrogenated vegetable oil in it.

Dr Sarah Jarvis: Dear Nakamura, There has been increasing interest in 'flavonoids' found in red wine and a possible heart-protective effect. However, it's worth bearing in mind that if there is a benefit, you will get it all from a single glass and drinking more than this doesn't offer any further protection and may carry health risks. The benefits seem to be most strong for men over the age of 40 and women past the menopause. I'm delighted to hear that you avoid hydrogenated fats - by this, I assume you're referring to super-heated oils which can cancel out all the 'heart-healthy' benefits from oils high in polyunsaturated and monounsaturated fats. Rape seed oil has a particularly good profile in this respect, and because it has a high 'smoke point' it shouldn't lose its benefits if you use if for cooking. Olive oil has a lower smoke point but is also a good balance in terms of the kind of fats it contains

A Twitter user asked: We have received a question via twitter: How much salt can we actually consume within a day? I have no idea how much I intake throughout the day, should I be taking note?

Dr Sarah Jarvis: Adults should eat no more than 6g of salt a day. It can be really difficult to keep track, as about 3/4 of the salt we eat is 'hidden' in foods like ready meals and bread. Preserved food like salami, smoked meats, bacon; salted snacks and crisps; soups, sandwiches and ketchups or sauces can all add up. It really is worth getting into the habit of looking at the salt content on packaging - as a rule of thumb, a 'high salt' food has more than 1.5g salt (sometimes written as 0.6g sodium) per 100g, and a low salt food has less than 0.3g salt (0.1g sodium) per 100g

Sam asked: Hi Dr Jarvis. i was wondering if you could advise. my brother is type 1 diabetic and has taken insulin for many years. I recently spoke to him and his doctor has prescribed him 40mg of statins daily. is this for any reason. he is 44. I'm not an medical expert, but isn't that a high dosage if he were to be on them? many thanks

Dr Sarah Jarvis: Dear Sam, Type 1 diabetes is a very different condition from type 2. Changing your diet, weight and lifestyle can dramatically reduce your risk of getting type 2 diabetes, while these factors don't have any proven impact on type 1 at all. However, like people with type 2 diabetes, people with type 1 diabetes are at significantly higher risk of heart attack or stroke than other people with no long term medical conditions. Statins can greatly reduce your risk of heart attack and stroke, and we generally recommend that anyone at really high risk of heart attack or stroke takes them. The strength of statins varies, but 40mg of simvastatin and atorvastatin - the most commonly prescribed statins - are absolutely standard. Unless there's a compelling reason, such as taking other medications which might interact (your brother's doctor would have taken that into account) I almost always prescribe the 40mg dose

Sam asked:
Another quick question. Is it possible to feel that you might have high blood pressure? are there any signs and symptoms someone should look out for?

Dr Sarah Jarvis: Dear Sam, One of the biggest problems with high blood pressure is that unless it's dangerously high, it pretty much never causes symptoms, even though it's hugely increasing your risk of heart attack and stroke. One of the reasons some of my patients believe they can feel when their blood pressure is high is that these days many people have home blood pressure monitors. If you feel generally unwell, your blood pressure is likely to go up. You feel unwell, you check your BP, it's high - hey presto, you assume the high blood pressure is the cause rather than the side effect of feeling unwell. You can never rely on knowing how high your blood pressure is - that's why we recommend that people get checked every so often, especially as they get older. With exceptionally high blood pressure you can get a headache, but this really is the exception rather than the rule

fionad asked: Hi Dr Jarvis - I sometimes feel faint and dizzy when I don't eat regularly (e.g. at times I am rushing about and have to have a late lunch). Could this be blood sugar related?

Dr Sarah Jarvis: Dear Fionad, your blood sugar could be low if you haven't eaten. If you don't have another medical condition like diabetes it's probably still within the normal range (and unlikely to be at all dangerous) but it can certainly affect your concentration and make you feel a bit lightheaded. It's worth making sure you keep a healthy snack or two of slow release carbohydrate (nuts or oatcakes are good examples) if you're going to be too busy to eat. It may also be because you're dehydrated - if your blood pressure is naturally low, being dehydrated can also make you feel a bit faint.

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