Small gains still mean seconds off your PB... What are the best/ most beneficial vitamins for triathletes? The obvious answer is a multivitamin, but if you follow a healthy diet you could end up taking too much of one or more vitamins. So avoid multivitamins that contain more than 200% percent of the RDA for any single nutrient. For us Brits, at this time of year, vitamin D (the sunshine vitamin) is a must to help keep bones, teeth and muscles healthy. Why is having a strong core important? In short, it helps to improve strength and efficiency in all three sports. Whether it’s swim, bike or run, your core acts as a stabilising point from which all your power is generated. If your core isn’t strong, other areas will overcompensate, which is when injury can occur.