In many areas of nutrition and even medicine, it is often believed that taking more than the recommended dose amount of a vitamin, mineral or medicine, will have a better benefit or a faster or longer action. This is not necessarily the case and certainly applies to giving mega doses of vitamins to racing greyhounds.
Whilst, it is reasonably well known that high doses of vitamin A and D can be toxic and have long lasting adverse effects on bone growth, strength and brittleness, for example, large doses of vitamin E and vitamin C are generally considered to be safe with no adverse effect on the performance or speed.
However, studies have shown that these two vitamins, either given separately, or in combination, in large doses, such as a pre-race dose, can actually slow a greyhound’s speed when racing.
Earlier Observations
As I have been a vet involved in greyhounds for over 30 years and particularly interested in nutrition of greyhounds, having contributed to a number of books and presentations on feeding greyhounds based on my own experiences and observations, I became aware of the performance slowing effects of excess doses of vitamin C and also vitamin E in my client’s greyhounds.
Both these vitamins act as important antioxidants in rapidly contracting muscle cells to increase the efficiency of oxygen use and energy production, as well as reduce oxidative damage from free harmful radical, or reactive oxygen species (ROS)formation during intense exercise.
One would presume that giving higher than standard doses would help protect muscle cells against exercise induced oxidative damage. Often trainers would experiment by giving larger doses of Vitamin E, which was and still is, one of the most important vitamins to assist muscle strength and provide antioxidative protection.
It has an important role during exercise when large volumes of oxygen are being transferred from the red blood cells through the fat layers in the muscle cell walls.
However, many trainers reported that in doses over 200 IU vitamin E per day, especially as a pre-race loading dose, many greyhounds seemed to ‘hit the wall’ up the home straight and did not perform to their usual standard.
Of course, there are many other reasons for a poor run on race day, but some trainers linked it to high doses of vitamin E which was recommended by a company selling vitamins.
I also observed a similar reduction in performance when large doses of vitamin C were given in the pre-race period.
I personally recommend a daily supplement of up to 100 IU Vitamin E and 250mg vitamin C to greyhounds in hard training, as it appears to reduce the risk of cramping, muscle soreness and assists overall performance.
However, other greyhound veterinarians and I have found that the popular practice of giving 1000mg vitamin C as a pre-race booster dose on race day did not improve speed or performance and in fact, appeared to reduce speed in the finishing stages of a race.
More recent studies
The effect of high doses of vitamin C has been investigated by researchers working together in Florida and Minnesota in the USA.
A study published in 2002 found that high doses of vitamin C appear to slow racing greyhounds.
It is well known that during intense exercise in athletes, including racing greyhounds, that oxidative stress increases and antioxidant capacity decreases.
Vitamin E acts as the primary antioxidant into protect fats or lipids in muscle cell walls, while vitamin C acts to regenerate vitamin E as its antioxidant capacity is reduced during intense muscular activity as occurs during a race.
Although prior to this study, the benefits of supplementary vitamin C had not been scientifically investigated, although, observations, as outlined above, suggested that high doses were not beneficial.
The Florida/Minnesota study, headed by Dr Richard Hill of the University of Florida in Gainsville, where many research studies have been carried out on racing greyhounds, compared the performance of 5 trained racing greyhounds over a 4 week period.
They were assigned 3 treatments over the trial period, receiving no supplementary vitamin C; 1000mg (1 gram) vitamin C daily after racing and 1000mg as a pre-race dose 60 mins before racing.
The bitches were raced twice weekly over 500metres during the 5 week period.
It was found that the concentration of oxidative markers in the blood was not influenced by supplementing with vitamin C, and it had no affect on the plasma vitamin E concentration.
However, as would be expected, the blood level of vitamin C was higher in the animals which were given the high dose of vitamin C before racing for the 60 minute period after racing.
Race records indicated that the greyhounds supplemented with high doses of vitamin C before racing actually performed on average 0.2 seconds slower, or a distance margin of 3 metres, as compared to non-supplemented greyhounds under similar race conditions and distance.
A number of biochemical explanations can be used to explain the underlying cause of the reduced performance associated with high pre-race doses of vitamin C and even high dose vitamin E.
Indeed the same laboratory found in an earlier study that 100 IU daily doses of vitamin E appeared to have no adverse effect on performance, but mega doses of 1000 IU daily were associated with a loss of form.
Practical Approach
The study does suggest that standard doses of vitamin E up to 100 IU daily and lower doses of vitamin C (I suggest a limit of 250mg vitamin C daily based on my own observations over the years) may be of benefit in protecting muscle cells from oxidative damage during intense exercise and during early training in unfit greyhounds during their first free gallops as part of their speed training.
It is also worth suggesting, that as a trainer, you should add up the total daily intake of these two vitamins from sources in the dry feed, supplements and natural food content.
Vitamin E and vitamin C are likely to be the two vitamins which are low in meat and many other common feeds.
Most dry foods are boosted with these vitamins to provide near the recommended daily intake, although there is likely to be loss during storage prior to being fed to a greyhound in training.
Some brands of supplement claim to contain high levels of these 2 vitamins, but the stability may be affected by the iron and copper content in the formulation.
The best supplements contain protected forms of vitamins and organic bioplex or amino acid chelated trace-minerals to reduce interaction with vitamins and complexing within the formulation during storage.
It is also important to check the total provided by all the supplements in the diet, including the dry food, added antioxidant supplements and performance boosters.
It is wise to use supplements from one company which provides practical pre-race doses and tailors dose rates to avoid excess if all the products are supplemented on a daily basis and especially at higher doses in the pre-race period.
