Sugar, carbohydrates and balancing blood sugar levels
You may well be wondering what sugar and blood sugar levels have to do with heart disease. A lot! Unfortunately over the years ultra low fat diets have been touted as being the major players in the protection against heart disease, this led many people to eat diets that were high in sugar and/or high in (non-vegetable and fruit) carbohydrates. Many low-fat foods contain ample amounts of added sugar and are often highly refined/processed. Previously (see posts dated 8th September and 9th September) I mentioned the importance of providing the body with a steady supply of energy and preventing blood sugar imbalances in order to prevent fatigue. Well, balanced blood sugar levels also seem to be incredibly important in preventing heart disease (and don’t just affect diabetics as you may well have thought). Simply lowering the total amount of fat in the diet is unlikely to improve fat (lipid and cholesterol) profiles or reduce coronary heart disease (CHD) risk (1).
Foods that release sugar quickly into the bloodstream have what is known as a high Glycaemic Index (GI), meals that favour a spike in blood sugar levels are said to have a high Glycaemic Load (GL). To identify foods with a high glycaemic index that will contribute to increasing the GL of a meal please view the website The Glycemic Index, there you will find a database where you can search for specific foods and find out more about GI and health.
Unbalanced blood sugar levels following a meal (post-prandial dysmetabolism) can cause havoc in the body. A high post-meal blood sugar level can lead to damaging free radicals (reactive oxygen molecules) being released which are a risk for atherosclerosis (damage to blood vessels) and metabolic syndrome (a big risk factor for heart disease). The high blood sugar can lead to internal inflammation, dysfunction in the lining of the blood vessels and may also lead to an increase in triglycerides (blood fats) – all risk factors for heart disease (2,3). A recent review paper(3) looked at how the current western diet, which favours meals that cause spikes in blood glucose, can be improved in order to exert immediate favourable changes in post-meal glucose dysregulation. The authors found that:
“Specifically, a diet high in minimally processed, high-fiber, plant-based foods such as vegetables and fruits, whole grains, legumes, and nuts will markedly blunt the post-meal increase in glucose, triglycerides (blood fats), and inflammation”. Additionally they found that lean protein, fish oil, weight loss and exercise also prevent post-meal glucose spikes.
Eat healthy fats to protect the heart.
You guessed it, I am going to talk about omega 3 fatty acids and fish oils again! Omega 3 fatty acids are essential to the body and so following a fat-free diet really isn’t clever for health reasons.
Raised triglyceride (fat) levels in the blood are a risk for CHD, they often occur in conjunction with accumulation of central body fat, blood sugar and insulin problems and raised levels of what is known as SDLDL cholesterol (small dense low density lipoprotein cholesterol) a very destructive type of cholesterol. Together these risk factors for CHD are known as the metabolic syndrome (or syndrome X). Metabolic syndrome is present in about 25% of the UK middle aged population and its’ importance as a risk for CHD development is now well established (4). Raised blood fat levels can be lowered by losing weight and eating a diet that prevents blood sugar fluctuations, as mentioned above.
Another way of reducing blood fat levels is by including oily fish (e.g. salmon, mackerel and sardines), a rich source the healthy omega 3 fats (EPA and DHA), in the diet or taking fish oil supplements. Trials have confirmed the blood fat (triglyceride) lowering effects of fish oils. In one study(5) supplementation with 3g/d reduced post-meal triglyceride rises by 26% and reduced fasting triglyceride levels by 35%. Fish oils and consumption of oily fish also seem to provide many other benefits for CHD, there is evidence that they can, reduce blood pressure, prevent blood clotting, prevent abnormal heart beats (arrhythmias), reduce inflammation and reduce constriction in blood vessels – all factors that may reduce CHD risk (6,7).
Very recently a study(8) found that the low risk of heart disease in the Japanese population may well be due to their high intakes of omega 3 fatty acids from fish oils. Another large study (9), released only a few weeks ago, has found that an omega 3 fatty acid supplement reduced death and admission to hospital for all cardiovascular reasons in people with existing heart problems. If you are vegetarian/vegan another recently published study paper (10) has found that flaxseed oil, a vegetarian oil rich in the omega 3 fatty acid alpha-linolenic acid, could be protective against heart problems and heart attacks.
If you do not regularly consume oily fish (at least twice per week) you may wish to consider a fish oil supplement providing around 250mg of EPA and 250mg of DHA daily. For vegetarians a flaxseed oil supplement providing around 500-700mg of alpha linolenic acid could be considered.
While a lot of emphasis has been placed on the need to avoid saturated fat in the diet (red meat, diary, eggs), there is mounting evidence (e.g. 11,12,13) to suggest that the fats known as ‘partially hydrogenated’ and ‘trans fatty acids’ are more of a risk factor for CHD. These fats, found in many fast foods, baked goods, processed foods and margarine are associated with an increased risk of heart disease, it makes sense to avoid such ‘trans’ fatty acids.
Please look after your heart. Eat healthy foods which are minimally processed and include plenty of fruits and vegetables into your daily meals, try to incorporate some form of exercise (walking counts) into your day, try and quit the cigarettes if you are a smoker and don’t let stress rule your life. If you have any concerns regarding symptoms then speak to your GP. Take some time to look at the British Heart Foundation website and become heart health aware!
(1)Hu FB & Willett WC. 2002. Optimal diets for prevention of coronary heart disease. JAMA. 288(20):2569-78.
(2)Livesey G et al. Glycemic response and health–a systematic review and meta-analysis: relations between dietary glycemic properties and health outcomes. Am J Clin Nutr. 87:258s-268s
(3)O’Keef JH et al. 2008. Dietary strategies for improving post-prandial glucose, lipids, inflammation, and cardiovascular health. J Am Coll Cardiol. 51(3):249-55.
(4) Griffin BA & Fielding BA. 2001. Postprandial lipid handling. Curr Opin Clin Nutr Metab Care. 4:93-98.
(5) Minihane, AM. et al. 2000. ApoE polymorphism and fish oil supplementation in subjects with an atherogenic lipoprotein phenotype. Arterioscler Thromb Vasc Biol. 20:1990-1997.
(6) Kris-Etherton PM et al. 2003. Fish consumption, fish oil, omega 3 fatty acids, and cardiovascular disease. Circulation. 106:2747-2759
(7) Nordoy A et al. 2001. n-3 Polyunsaturated Fatty Acids and Cardiovascular Diseases. Lipids. (Suppl)36:S127-S129
(8)Sekikawa A et al. 2008. Marine-Derived n-3 Fatty Acids and Atherosclerosis in Japanese, Japanese-American, and White Men: A Cross-Sectional Study. J Am Coll Cardiol. 52:417-424
(9)GISSI-HF 2008. Effect of n-3 polyunsaturated fatty acids in patients with chronic heart failure (the GISSI-HF trial): a randomised, double-blind, placebo-controlled trial. The Lancet. E-Pub ahead of print August 2008 DOI:10.1016/S0140-6736(08)61239-8
(10)Campos H et al. 2008. -Linolenic Acid and Risk of Nonfatal Acute Myocardial Infarction. Circulation. E-Pub before print July 2008. doi: 10.1161/CIRCULATIONAHA.107.762419
(11) Ascherio A. 2002. Epidemiologic studies on dietary fats and coronary heart disease. Am J Med. 30;113 Suppl 9B:9-12.
(12)Ascherio A & Willett WC. 1997. Health effects of trans fatty acids. Am J Clin Nutr. 66:1006s-1010s
(13) Oomen CM et al. 2001. Association between trans fatty acid intake and 10-year risk of coronary heart disease in the Zutphen Elderly Study: a prospective population-based study. Lancet. 357(9258):746-51.
Written by Ani Kowal