During an endurance run (1,000 km in 20 days) it was investigated whether an ovo-lacto-vegetarian diet (OLVD) could cover the nutritional requirements of endurance athletes. A regular western diet (RWD) was used as reference. Both diets were offered with an energy content of 4,500 kcal per day and an energy percentage of carbohydrate:fat:protein of 60:30:10. The runners were divided into two dietary groups according to their usual dietary habits. The results of the 55 participants who completed the race show that runners from both groups had the same intake of energy, carbohydrate, fat and protein. Runners of the OLVD group consumed more dietary fiber and polyunsaturated fatty acids as well as less cholesterol. With the exception of sodium chloride and cobalamin, the intake of the calculated minerals and vitamins was higher in the OLVD and exceeded the official recommendations. This study shows that an OLVD with a high nutrient density is adequate to cover the nutritional requirements of endurance-athletes. The intake and absorption of iron should be monitored closely in all diet groups.