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Last Updated Saturday July 29 2017 12:06 AM IST

Matters of the Heart | Can high sugar intake increase blood pressure?

Dr Roy John Korula
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Sugar Photo: Getty Images

One out of every three Indian adults in urban areas has high blood pressure. In the rural areas, it is only about one in ten.

If you're among them, some of the recommendations your physician probably gave you included reducing your weight, changing your lifestyle (reduce your stress), do some exercise, and to cut back on salt. And of course quit smoking, and limit your alcohol intake.

Eating too much of commercially available processed salt leads to fluid retention and high blood pressure. But there is conflicting evidence about eating less salt to prevent heart attacks, strokes or death. Eating less salt works for some people. This may be because natural occurring salt may not be as dangerous as processed salt. Also potassium deficiency (potassium relaxes the blood vessels and lowers blood pressure) may also contribute to high blood pressure. A combination of too much salt, and too little potassium probably compounds the damage.

Salt Photo: Getty Images

But did the physician tell you about sugars too? I think not. You see most doctors neglect to tell patients about the correlation between high blood sugars and blood pressures.

In the mid-seventies, the greatly influential Sugar Association in the USA used tobacco-style gag-and-muzzle tactics, to dismiss uncomfortable, distressing and troubling evidence, that sugars were the problem of increasing obesity and heart disease. Instead, wooing and funding dieticians, nutritionists, health advisors and doctors from major US universities, they deflected, diverted and distracted from the evidence that showed a close relationship linking sugar consumption to high blood cholesterol, triglycerides and heart disease. They published these subtly manipulated studies, in highly respected medical journals, and without disclosure of their clear conflict of interest. These skewed publications helped shape public opinion and influenced the prevailing belief, that the only requirement of reduce heart disease was to reduce dietary cholesterol and substitute polyunsaturated fats for saturated fats.

Cholesterol test Photo: Getty Images

“Repeat a lie often enough and it becomes the truth”, is a law of propaganda often attributed to the Nazi Joseph Goebbels.

In actuality, the research by the Sugar Association showed them that if people ate low fat diets, their consumption of sugars would increase by more than a third.

Many people with diabetes have switched over to a high protein, low (or zero) carbohydrate diet to control their sugars. These diets mainly consist of fresh vegetables and fruits, fat-free meat, fish, whole (not refined) grains, low fat diary products, and a low salt content. The important thing is that it does not contain processed foods (high in salt and sugars), sugary foods, pasta, rice and refined flours.

Protein diet Photo: Getty Images

And just like diabetes do, maybe that the best thing you can do for your high blood pressure also, is also to mainly eat this type of diet – a high protein, low carbohydrate diet, low in starch, sugars and fructose. It is highly likely, that not only the restriction of salt, but importantly, the restriction of sugars helps lower blood pressure.

Diabetes Photo: Getty Images

In a recent review in the journal Open Heart, the authors make a case for the fact that the high consumption of added sugars (particularly fructose) in the US diet may be more strongly and directly associated with high blood pressure than the consumption of salt. High sugars in the food produce multiple detrimental effects on the heart like increasing the heart rate, increasing the oxygen demand and oxygen consumption of the heart, increasing blood pressure, and contributes to inflammation and the metabolic syndrome (obesity, hypertension, high cholesterol, increased Body Mass Index (BMI) and insulin resistance).

One of the ways excess sugars leads to high blood pressure is related to your body producing too much insulin and leptin in response to a high-carbohydrate (i.e. high sugar) diet.

Leptin the "satiety hormone", is a hormone made by fat cells that inhibits hunger. Leptin is opposed by the actions of the hormone ghrelin, the "hunger hormone". Both hormones act on receptors in the brain to regulate appetite to achieve energy homeostasis. In obesity, a decreased sensitivity to leptin occurs, resulting in an inability to detect satiety despite high energy stores.

In a previous communication, I had emphasised the fact that people are not fat, because they eat too much, but that they eat too much because they are fat.

After a meal high in sugars, there is an outpouring of insulin in response to the sugar spike. The feedback system that tells the body to stop producing insulin is a little delayed. So there is a relative fall of blood sugar some time after the meal, causing leptin (the hormone that tells the individual he or she is hungry) to be secreted, causing the individual to eat again. But persistent and prolonged levels of high insulin levels, in response to high carbohydrate diets, causes the body to become resistant to insulin (and leptin).

Insulin helps store magnesium in the cells. But if your insulin receptors are blunted and your cells grow resistant to insulin, you can't store magnesium and it passes out of your body through urination. Magnesium stored in your cells relaxes muscles and blood vessels. If your magnesium level is too low, your blood vessels will be unable to fully relax, and this constriction raises your blood pressure.

Fructose, found in sodas, fruit juices, sports drinks, and processed foods causes the liver to turn some of this excess sugar into fat, which is deposited in the liver itself. This itself can lead to Non Alcoholic Fatty Liver Disease (NAFLD). Eating fresh fruit (with its fibre) reduces the absorption of fructose by as much as 30%, as opposed to drinking its fresh juice.

Fruit juice Photo: Getty Images

Fructose also elevates uric acid, which drives up your blood pressure by inhibiting the nitric oxide in your blood vessels. (Uric acid is a by product of fructose metabolism. In fact, fructose typically generates uric acid within minutes of ingestion.) Nitric oxide helps your blood vessels dilate, and maintains their elasticity. So nitric oxide suppression leads to increases in blood pressure.

Too much sugars not only make you fat, but make you sick.

So any series of recommendations, or plan of action adapted to address high blood pressure also needs to include measures to normalize both your insulin/leptin sensitivity and uric acid levels.

Bitter gourd juice Photo: Getty Images

Present guidelines recommend that your total sugar consumption should be 5% of your total calorific intake. So if you are eating a 2000 calorie diet, your sugars should not be more than 100 calories – about 25 grams daily – about 6 teaspoons. (Each teaspoon has about 4 grams of sugar, and each gram has 4 calories.)

If you're diabetic, and have high blood pressure, heart disease, or other chronic diseases, you'd be wise to limit your sugars to 15 -20 grams or less daily, until your condition has normalized.

Diabetes Photo: Getty Images

But don’t underrate or downplay the importance of losing weight, doing exercise, changing your lifestyle (in terms of stress and anger management), cutting out smoking, and restricting alcohol intake to control your hypertension.

The significance of meditation and prayer also cannot be underrated or undervalued.

These are all equally, if not more important than just diet control.

(The author is a former head of the department of cardiothoracic surgery at Christian Medical College and Hospital, Vellore. He is currently the chief administrative of icer, and head of the cardiothoracic surgery department at Pushpagiri Heart Institute, Tiruvalla.)

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