September 29th marks World Heart Day, an opportunity to raise awareness of the impact diet can have on heart health. In Part 2 of our Heart Health Series, we dive into specific areas of your diet and how these may impact your overall heart health.
Mechanisms of Action
In Part 1 we discussed the Portfolio Diet and the Mediterranean Diet - both of these dietary patterns are predominantly plant-based, and this is thought to play a large part on their effect on cardiometabolic health. Fruit and vegetables contain fibre and polyphenols which influence the production of beneficial bacteria: short chain fatty acids (SCFA). SCFA can exert positive influences on the gut microbiome and its functions, which may have protective properties. The relative risk for heart disease is reduced by 8% for every 200g of fruit and veg consumed each day. Following the 5-a-day guidelines could have a positive impact on your risk of heart disease.
According to the Global Burden of Disease study, more than half of diet related deaths are related to diets high in sodium and low in fruit, vegetables, nuts, seeds, and wholegrains. Whilst the evidence isn’t conclusive right now, evidence from observational studies indicates that diets rich in whole grains could be protective against coronary heart disease (CHD), and in contrast diets that are low in wholegrains may increase the risk of obesity and cardiometabolic diseases.
Sodium and salt are terms used interchangeably, but it is sodium which is the vital mineral found in every cell of the body, used to transmit nerve impulses. Sodium is what’s found in food – especially in processed food containing preservatives. Along with chloride, it is a chemical compound making up salt, and sodium chloride is the principal source of sodium in the human diet. A very delicate balance of sodium is required in the body, which regulates the pressure of cells and is related to blood pressure. The amount of sodium you eat or drink has important implications for your health. It’s important to note quantity of salt you eat is related to the amount of sodium but is not the same.
Evidence shows a clear dose response effect of reducing salt intake on lowering blood pressure, a heart disease risk factor. This means that the more that salt intake is reduced, the more that blood pressure decreases. Adults should eat no more than 6g of salt a day (2.4g sodium) – that's around 1 teaspoon. Average salt intakes in the UK are still high and more work is needed to reach the recommend daily intake, interestingly the American heart association is advocating that people move toward an ideal limit of no more than 1.5g per day for most adults. Our advice would be to limit the foods below, common to be high in sodium, to help keep your intake under control. In the kitchen, use herbs, garlic, and onions to boost flavour without salt.
- Cured meats (e.g., cold cuts like ham, turkey chicken, pork pies and bacon)
- Ready-made soups
- Fast and restaurant food
- Frozen dinners & other packaged foods
- Condiments and sauces
How important is dietary fat?
Although controversial at times amongst health professionals, current understanding from evidence suggests there needs to be a focus on foods and dietary patterns, rather than the single fat nutrient alone. Cohort studies have shown associations between diet and CHD risk and that reducing fat intake alone isn’t enough – the food that replaces the fat is important too. For example, replacing 5% of saturated fat energy intake with polyunsaturated fatty acids (PUFAs), monounsaturated fatty acids (MUFAs) or wholegrain carbohydrates is associated with a reduced risk of CHD incidence (Y Li., et al., 2015).
The most recent published PREDIMED trial, investigated the effects of a Mediterranean diet with added nuts, versus a Mediterranean diet with added olive oil, versus a low-fat control diet. Results showed a 30% reduction in CVD incidence over 5.5. years in both Mediterranean diet groups. Strong evidence that a moderate fat diet rich in unsaturated fatty acids is more cardio protective than a low-fat diet. It’s about not eating too much of the wrong types.
Long chain omega-3 fatty acids might be protective, as there is strong evidence to suggest that they can reduce risk of sudden cardiac death and CHD. This is due to factors such as decreased heart rate and blood pressure, improved vascular function, decreased vascular inflammation and decreased triglycerides in the blood. Fish and seafoods contain long chain omega -3 fatty acids and provide other valuable micronutrients such as iodine and selenium. Dietary guidelines are to consume at least 2 portions of fish a week (1 of which should be oily).
Higher total nut consumption is associated with a lower risk of CVD incidence and nut intake has been shown to beneficially modify CVD risk factors such as weight, blood lipids, and inflammation (G. Liu et al., 2019). Of all the food groups, nuts were shown to have the strongest LDL-cholesterol lowering effects in a network meta-analysis of randomised control trails (RCTS) (Schwingshackl L et al., 2018).
For optimal heart health, try to focus on monounsaturated fats and polyunsaturated fats found in almonds, avocados, and good quality vegetable oils like extra virgin olive oil, as well as omega-3 fatty acids from fatty fish. Replacing saturated fats in your diet with unsaturated fats may help improve cholesterol levels. Just one ounce of almonds contains 13 g of unsaturated fat, only 1 gram of saturated fat and absolutely no cholesterol.
- Greater intake of fruit and vegetables, wholegrains, nuts, unsaturated fat, and lower consumption of saturated fat and salt, is supported by evidence for prevention of CVD.
- Combining all these changes together with maintenance of healthy weight (moderating energy intake and adequate physical activity) could have significant impact on lowering your risk of CVD over a long duration - the health impact of only changing one dietary factor over short periods is likely to be small.
- Emphasis should be on making dietary changes rather than worrying about which individual saturated fatty acids are more harmful to your heart and whether we should eat 5, 8 or 10 portions of fruit and veg per day.
Written by Abby Attenborough