A British study involving 165 healthy nonsmoking adults (aged 40–70) has found that a diet based on UK health guidelines could reduce risk of a heart attack or a stroke by up to a third, compared to a traditional British diet

The predicted risk of cardiovascular disease over the next 10 years for the participants was estimated to be about 8% in the men and 4% in the women. Participants followed their diets for 12 weeks. Those on the modified diet ate oily fish once a week, more fruit and vegetables, replaced refined with wholegrain cereals, swapped high-fat dairy products and meats for low-fat alternatives, and restricted their intake of added sugar and salt. Participants were asked to replace cakes and cookies with fruit and nuts and were also supplied with cooking oils and spreads high in monounsaturated fat.

The average body weight in the group on the modified diet fell by 1.3 kg; that in the control group rose by 0.6 kg. Waist circumference was 1.7 cm lower in the dietary group compared to the control group. There were also significant falls in systolic blood pressure/diastolic blood pressure (4.2/2.5 mm Hg for daytime and 2.9/1.9 mm Hg for night time) and average heart rate. Cholesterol fell by 8%. High-sensitivity C-reactive protein (a marker for inflammation) was 36% lower. There was no significant change in markers for insulin sensitivity. Much of the fall in blood pressure could be accounted for by the drop in sodium.

http://www.eurekalert.org/pub_releases/2015-03/kcl-hdr031715.php

Reidlinger, D. P., Darzi, J., Hall, W. L., Seed, P. T., Chowienczyk, P. J., & Sanders, T. A. (2015). How effective are current dietary guidelines for cardiovascular disease prevention in healthy middle-aged and older men and women? A randomized controlled trial. The American Journal of Clinical Nutrition, 101(5), 922–930. http://doi.org/10.3945/ajcn.114.097352