Sunshine and coronary heart disease
Part 1: Worldwide heart disease patterns
Throughout the medical literature about coronary heart disease, you can read about a number of 'paradoxes' — examples of populations who apparently had 'unhealthy' lifestyles but did not suffer from the heart disease 'healthy eating' dictocrats would predict. While I might suggest that it was evidence that their high-fat diet protects them, there may also be another reason: if one looks at disease patterns across the world, it is clear that there is a lot less cardiovascular disease at the equator than there is in higher latitudes. The evidence is persuasive that this is because of the amount of sunlight — and the vitamin D that is made with it.
Anyone who has travelled in Italy will know that most Italians love the sun. As a consequence, most Italians have healthy vitamin D levels in summer,[1] and the death rate from cardiovascular disease is relatively low. An Italian proverb states: 'Where the sun does not go, the doctor does'.
In France the numbers of deaths from heart disease are much lower in the South and West than in the North and East. Dr. Marie Chapuy, found that vitamin D levels in the blood of healthy adults in France follow a similar regional trend: mean blood levels the sunnier and drier South and West are more than double those in the colder, wetter North.[2]
The Northern Ireland paradox also fits this paradigm.[3] Belfast has four times the rate of heart deaths compared to Toulouse, despite having similar heart disease 'risk factors'. But Belfast is at 54oN and has 257 rainy days per year. Toulouse is 11o closer to the equator and has only 74 rainy days per year.
The effect of polyunsaturated fats
Similar effects are seen in other 'paradoxical' countries. Despite its 'protective' consumption of polyunsaturated fats, Israel has a high death rate from heart disease.[4] But despite Israel being a sunny country, Jews, particularly orthodox ones, cover up in the sun and suffer from vitamin D deficiency.[5,6] The same is true of Moslems who cover up almost all of their bodies: Average vitamin D levels among healthy adults in Lebanon, are dangerously low.[7]
To compound this, 'healthy' mono- and polyunsaturated fats reduce the bioavailability of vitamin D;[8] saturated fats do not.
In Greece, there were quite remarkable large differences in blood cholesterol levels in both men and women at different altitudes in spite of similar diets.[9] Those who lived at high altitude, where the atmosphere is thinner had much higher levels of vitamin D than those living at sea level.
References
1. Romagnoli E, Caravella P, Scarnecchia L, et al. Hypovitaminosis D in an Italian population of healthy subjects and hospitalized patients. Br J Nutr 1999; 81: 133-7.2. Chapuy MC, Preziosi P, Maamer M, et al. Prevalence of vitamin D insufficiency in an adult normal population. Osteoporos Int 1997; 7: 439-43.
3. Evans AE, Ruidavets JB, McCrum EE, et al. Autres pays, autres coeurs? Dietary patterns, risk factors and ischaemic heart disease in Belfast and Toulouse. QJM 1995; 88: 469-77.
4. Yam D, Eliraz A, Berry EM. Diet and disease — the Israeli paradox: possible dangers of a high omega-6 polyunsaturated fatty acid diet. Isr J Med Sci 1996; 32: 1134-43.
5. Mukamel MN, Weisman Y, Somech R, et al. Vitamin D deficiency and insufficiency in Orthodox and non-Orthodox Jewish mothers in Israel. Isr Med Assoc J 2001; 3: 419-21.
6. Hochwald O, Harman-Boehm I, Castel H. Hypovitaminosis D among inpatients in a sunny country. Isr Med Assoc J 2004; 6: 82-7.
7. Gannage-Yared MH, Chemali R, Yaacoub N, Halaby G. Hypovitaminosis D in a sunny country: relation to lifestyle and bone markers. J Bone Miner Res 2000; 15: 1856-62.
8. Bouillon R, Xiang DZ, Convents R, Van Baelen H. Polyunsaturated fatty acids decrease the apparent affinity of vitamin D metabolites for human vitamin D-binding protein. J Steroid Biochem Mol Biol 1992; 42: 855-61.
9. Grimes DS, Hindle E, Dyer T. Sunlight, cholesterol and coronary heart disease. QJM 1996; 89: 579-89.
