Heart disease and food

Heart disease is the leading cause of death in Australia, and elevated blood cholesterol levels are a significant risk factor for this disease. Coronary heart disease is a condition characterised by a narrowing of the arteries. Fatty deposits or plaques, found in atherosclerosis, cling to the artery walls and clog one or both of the coronary arteries triggering a blood clot. Much as you would if you cut yourself, the body's defence to a damaged blood vessel is to clot. If a blood clot forms too quickly or is unable to break down, this will block blood flow. A heart attack occurs when a blood clot blocks the blood vessels of the heart resulting in impeded flow of blood altogether and oxygen deprivation damages or kills the heart cells. When arteries become damaged and narrowed by atherosclerosis they also become twitchy and more prone to spasm. The result is an even higher risk of blockage than the extent of damage would suggest.

Food is directly involved in many of the risk factors for coronary heart disease. Attention to diet is one of the most important preventative measures a person can take.

Risk factors for heart disease
The build-up of fatty deposits in the coronary arteries is caused by a number of factors, including cigarette smoking, sedentary lifestyle and a family history of the disease. Food related risk factors include:
A diet high in saturated and trans fats
Obesity
High blood pressure or hypertension
Uncontrolled diabetes.
Elevated homocysteine?

Cholesterol levels and dietary fats
Cholesterol is a type of fat that is crucial to many metabolic functions. There are two types of blood cholesterol. Low density lipoprotein (LDL) silts up the arteries, while high density lipoprotein (HDL) reduces blood cholesterol levels. Saturated and trans fats in the diet generally tend to increase LDL cholesterol in the blood. Common sources of saturated fats include animal products (such as meat fat, beef, lamb, chicken skin and full-cream dairy foods) and processed foods like pastries and biscuits.

Trans-fatty acids (and saturated fats), such as elaidic acid, are formed when mono-unsaturated or polyunsaturated vegetable oils are hydrogenated and hardened to form margarines or the even harder vegetable fat and shortening used by the food industry. They also occur naturally in small quantities in some meats, butter and dairy products.

Obesity and food
Overweight and obese people usually have diets high in fat, particularly saturated fat. A person who carries the bulk of their body fat around their stomachs ('apples') are at greater risk of heart disease than someone whose body fat tends to settle around their bottom, hips and thighs ('pears'). 'Apples' are also more likely to develop high blood pressure and diabetes. As men tend to be 'apples', they are generally at a greater risk of developing heart disease than women.

High blood pressure
Blood pressure is the amount of force exerted on the artery walls by the pumping blood. High blood pressure, or hypertension, means that blood is pumping harder than normal through the arteries. Some of the factors that contribute to pushing up the blood pressure are food related, and include:
Being overweight or obese
Drinking large amounts of alcohol on a regular basis
A diet high in salt and low in potassium
A diet high in saturated fat.

Diabetes, heart disease and food
Uncontrolled diabetes can damage the artery walls and contribute to coronary heart disease. People who are obese are more likely to develop diabetes than those of normal weight. Australian Aborigines and Torres Strait Islanders experience much higher rates of diabetes than other Australians, even at lower body weights.

Elevated homocysteine?
Homocysteine is an amino acid ( a building block of protein) formed from another amino acid called methione which we consume from food. Homocysteine is toxic to blood vessels (damages the cells lining the inside of the arteries, and interferes with clotting factors) so the body converts it to the amino acids taurine and cysteine withe the help of 3 vitamins - folate, vitamin B6 and vitamin B12. If the diet lacks these vitamins then homocysteine levels rise potentially increasing the risk of blood clots, heart attack and stroke. To date most studies have reported an "association" between elevated blood homocysteine and heart disease - which does not prove cause and effect.
Since homocysteine is lowered by B vitamins, especially folic acid, trials of folic acid, B12 and B6 were commenced to prevent heart attacks and strokes. Studies reported in 2006 (one study included 9000 people) have shown that giving these vitamins to reduce homocysteine levels does not give any benefit and suggested that if given with B12 might instead increase some cardiovascular risks. These studies suggest that homocysteine may not be a risk factor at all or it may simply be a 'marker' for something else. more..

Elevated homocysteine levels can be caused by vitamin B12 deficiency due to impaired absorption of B12 caused by gastric atrophy (damage to the lining of the stomach). B12 deficiency leads to anemia and, if not corrected in time, will permanently damage the nervous system. Folic acid supplements will correct the anemia (which can serve as a warning sign before nerve damage develops), but they do not prevent the damage. For this reason, people over 50 who take folic acid supplements should also take at least 25 micrograms of vitamin B12 per day, a dose large enough to enable adequate amounts to be absorbed. Most people over age 50 should probably take B12 supplements anyway, because gastric atrophy is common as people age.

References:
Toole JF et al. Lowering homocysteine in patients with ischemic stroke to prevent recurrent stroke, myocardial infarction and death: the Vitamin Intervention for Stroke Prevention (VISP) randomized controlled trial. Journal of the American Medical Association 2004;291:565-575

BØnaa KH et al. Homocysteine lowering and cardiovascular events after acute myocardial infarction. New England Journal of Medicine 10.1056/NEJMoa055227

HOPE 2 Investigators. Homocysteine lowering with folic acid and B vitamins in vascular disease. New England Journal of Medicine 10.1056/NEJMoa060900

Foods that prevent heart disease
There is no specific 'magic' food that can decrease a person's risk of developing heart disease. The diet has to be addressed overall, not just tweaked here and there. There is strong evidence that plant food is associated with a decreased risk of heart disease - especially wholegrain cereals, legumes nuts, fruits and vegetables. Studies involving supplements of nutrients or phytochemicals have not shown these to be effective in reducing risk of heart disease. The foods that best protect against heart disease include:
Oily fish - such as mackerel, sardines, tuna, salmon which contains omega-3 fatty acids. This type of fat lowers the levels of both LDL cholesterol and triglycerides (fats). It also improves blood vessel elasticity and thins the blood, making it less likely to clot and reduce the risk of blocking blood flow. Fish oils act further to stabilise heart function during a crisis and to prevent vasospasm or 'twitchy' blood vessels (which can increase the risk of blockage)..
Variety of oils - Both polyunsaturated and mono-unsaturated fats can lower blood cholesterol levels, but polyunsaturated fats appear to have a larger impact. A study on 18 young, healthy men published in Dec 2000 in the Journal of Lipid Research reported that plasma cholesterol, triglycerides, and LDL cholesterol were 10-20% higher on the olive oil enriched diets than on the canola or sunflower enriched diets. The study suggests that a certain amount of omega 3 and omega 6 polyunsaturated fat is needed in the diet and that monounsaturated fat should not be consumed in unlimited amounts. Low density lipoprotein cholesterol (LDL) is considered the 'bad' cholesterol. This is because it can stick to artery walls, causing atherosclerosis, which increases the risk of coronary heart disease and stroke. Studies into LDL cholesterol have suggested that oxidation is an important step in the development of atherosclerosis. It seems that mono-unsaturated fats reduce the capacity of LDL cholesterol to oxidise, which may explain the protective properties of olive oil. However, extra virgin olive oil also contains around 40 antioxidant phytochemicals, including the phytoestrogens called lignans. Antioxidants have been associated with reduced oxidation of LDL cholesterol, so perhaps these phytochemicals are the factors responsible for the health benefits. In one study, extra virgin olive oil was found to prevent the most LDL oxidation compared to other varieties.

Once a fatty meal is eaten, it takes the liver around six to 12 hours to scour dietary fats from the blood and change them into compounds such as LDL and HDL (high density lipoprotein) cholesterol. There is evidence that this six to 12 hour period may be a crucial contributing factor in atherosclerosis. Mono-unsaturated fats like olive oil and short-medium chain saturated fatty acids found in coconut products are cleared from the blood much faster than longer chain saturated fats (found in greater amounts in animal foods), and this reduces the window of opportunity for the development of atherosclerosis. Mono-unsaturated fats also help to prevent the blood from becoming sticky after a fatty meal and forming dangerous clots which can increase the risk of stroke.
Garlic - a compound in fresh garlic called allicin has been found in some studies to lower blood cholesterol.
Fruits and vegetables - there is further confirmation from two recent studies that eating antioxidants in the form of fruit and vegetables as opposed to supplements offer much greater protection against cardiovascular disease; the studies concluded that antioxidant vitamins as supplements can't be recommended as a first line of prevention. A study reported in the Lancet 2002 reported that eating 5 serves of fruit and vegetables daily can help to lower blood pressure and increase the levels of antioxidants in the blood that will be expected to reduce cardiovascular disease in the general population. Fruit and vegetables are also important sources of folate which helps lower the blood levels of the toxic amino acid homocysteine which is known to increase the risk of heart disease.
Fibre from whole grain cereals - offers greater protection against the risk of heart attack than the fibre from fruits and vegetables. Only a minor part of this protective effect can be explained by the cholesterol lowering effect of soluble fibre. A study conducted on postmenopausal women found that eating at least one serve of wholegrains daily reduced the risk of heart and blood vessel disease by almost 30% compared to those who rarely ate wholegrains. Good sources include oatbran, barley, seed husks, flaxseed and psyllium. Whole grain cereals contain omega 3 plant fats, magnesium and phytoestrogens which are known to play a role in protecting against the development of heart disease. Ceraals are also an important source of folate which helps lower the blood levels of the toxic amino acid homocysteine which is known to increase the risk of heart disease.
Legumes and soy - a study in the US in 2001 showed that eating several serves of legumes per week significantly reduced the risk of heart disease by about 20%.
Abstract:http://archinte.ama-assn.org/issues/v161n21/abs/ioi10003.html
In 2000, the US Food & Drug Administration concluded that eating 25g of soy protein daily, as part of a diet low in saturated fat and cholesterol, could significantly reduce the risk of developing heart disease. Soy protein has been shown to lower LDL cholesterol levels, especially if blood cholesterol levels are high. Two to three serves of soy foods are recommended daily to provide heart health benefits. Furthermore, legumes, especially soy, contain phytoestrogens such as isoflavones. They also protect the heart by acting like antioxidants, preventing LDL cholesterol becoming oxidised which turns it into a form which clogs up arteries. They also help to keep blood thin and prevent it from clotting and help to maintain the elasticity of blood vessels to promote blood flow.
Nuts/seeds - unfortunately, nuts were given a 'bad' name in the 1970's because of their energy density and lack of information about their phytochemical content. As a result they were not recommended for people with coronary heart disease or people trying to lose weight. In the meantime, several studies have shown that nuts can protect against heart disease, but still need to be consumed in moderation by overweight people. In 30,000 people, a handful of nuts twice per week was associated with 20% less coronary heart disease (CHD) incidence and 5 times/week with 50% less CHD. They can also help lower blood lipids and reduce the oxidation of LDL, probably due to their high content of vitamin E, omega 3 fatty acid, and other phytochemicals, including phytoestrogens. Nuts are also high in the amino acid arginine. Research has shown that arginine is a dietary precursor of nitric oxide, which helps to keep blood vessels relaxed; it may also help to prevent blood clot formation. The folic acid content of nuts may help lower blood homocysteine levels; high levels have been linked to increased coronary heart disease risk. Copper and magnesium found in nuts may also be protective against coronary heart disease
Walnuts have also been shown to improve blood vessel health more.....
Tea - some evidence suggests that the antioxidants contained in tea can help to prevent the build-up of fatty deposits in the arteries and may act as anti-blood clotting agents, as well as improving function of the blood vessels by improving dilation to allow increased blood flow. A US study reported in 2002 that drinking at least one cup of tea a day halves the risk of suffering a heart attack, regardless of any other risky behaviours. A Dutch study found that the risk of heart attack was 40% lower in tea drinkers with a daily intake greater than 375ml/day.
Red wine - may offer similar protective factors to tea, due to high levels of antioxidants and may increase HDL (good) cholesterol levels. However, alcohol tends to increase blood triglyceride (fat) levels and blood pressure. A high alcohol intake is also a risk factor for heart disease.
Foods containing vitamin E - some studies indicate that vitamin E helps to reduce blood cholesterol. This is thought to be because it acts like an antioxidant and prevents damage to the blood vessel walls. Good sources of vitamin E include avocados, dark green vegetables, vegetable oils and wholegrain products. However, it may not be the vitamin E itself that is protective in these foods. There may be other compounds that offer protection. It is advisable to eat foods that contain vitamin E, rather than taking supplements, to ensure that you receive the greatest protective benefits.

General recommendations
To substantially reduce your risk of developing coronary heart disease, dietary recommendations include:
Cut back on saturated and trans fats by avoiding fried fast food and some processed foods containing vegetable shortening.
Choose a variety of oils (e.g extra virgin olive oil, canola, peanut, soy) and foods containing "natural" (unrefined) fats (e.g nuts, seeds, avocado, olives, soy, fish).
Switch to low fat or non-fat dairy products.
Increase the amount and variety of plant foods consumed e.g eat more vegetables, fruits and wholegrain foods.
Eat a legume (pulses) meal a couple of times a week e.g baked beans, lentil soup, tofu burgers. Try to include more soy foods in your diet, daily if possible, like soy milk or soy linseed bread.
Have a handful (9-15nuts) of a variety of nuts on most days of the week, especially walnuts and almonds (in place of treats like biscuits, cakes, chips). This advice also applies to patients trying to lose weight. Combining nuts with low energy dense foods (e.g. vegetables) in meals is a good way to eat them e.g. Asian style dishes. When nuts are consumed as a snack - the temptation to consume more than a handful is probably greater.
Eat oily fish at least once per week.
If you drink alcohol, consume only moderate amounts (less than two drinks per day).
Trim all visible fat from meat.
Remove poultry skin and eat only the meat.

Things to remember
- Diet is an important risk factor in the development of coronary heart disease.
- Food related risk factors include obesity, high blood pressure, uncontrolled diabetes and a diet high in saturated fats.
- A low saturated fat, high fibre, high plant food diet can substantially reduce the risk of developing heart disease.

References
Albert CM et al. Blood levels of long chain n-3 fatty acids and the risk of sudden death. New Eng J Med 2002; 346: 1113-8.

Geleijnse J et al. Inverse association of tea and flavonoid intakes with incident myocardial infarction; the Rotterdam Study. Am J Clin Nutr 2002; 75: 880-886.

John JH et al. Effects of fruits and vegetable consumption on plasma antioxidant concentrations and blood pressure: a randomised controlled trial. Lancet 2002; 359: 1969-1974.

Setchell & Cassidy. Dietary isoflavones: Biological effects and relevance to human health. J Nutr 1999; 129: 758S-767S.

Trichopoulos et al. Evidence -based nutrition. Asia Pac J Clin Nutr 2000; 9 Supp: S4-9

Jacobs et al. Wholegrain intake may reduce the risk of ischemic heart disease death in post-menopausal women: the Iowa Women's Health Study. Am J Clin Nutr 1998; 68: 248-57.

Fraser GE. Nut consumption, lipds and risk of a coronary event. Asia Pac J Clin Nutr 2000; 9 Supp: 28-31

Liu et al. Fruit and vegetable intake and risk of cardiovascular disease: the Women's Health Study. Am J Clin Nutr 2000; 72: 922-28.

Anderson et al. Meta-analysis of the effects of soy protein intake on serum lipids. N Engl J Med 1995; 333: 276-82.

Bazzano LA, He J, Ogden LG, Loria C, Vupputuri S, Myers L, Wheiton PK. Legume consumption and risk of coronary heart disease in US men and women, NHANES I Epidemiological Follow-up Study. Arch Inter Med 2001; 161: 2573-78.

Article co-authored by Better Health Channel
(Australian -Victorian Government website)

Last Updated: April 2004s