On the keto diet? Ditch the cheat day: Just one dose of carbohydrates can damage blood vessels -- ScienceDaily"Since impaired glucose tolerance and spikes in blood sugar levels are known to be associated with an increased risk in cardiovascular disease, it made sense to look at what was happening in the blood vessels after a sugar hit." For their test, the researchers recruited nine healthy young males and had them consume a 75-gram glucose drink before and after a seven-day high fat, low carbohydrate diet. The diet consisted of 70 per cent fat, 10 per cent carbohydrates and 20 per cent protein, similar to that of a modern ketogenic diet. "We were originally looking for things like an inflammatory response or reduced tolerance to blood glucose," says Durrer. "What we found instead were biomarkers in the blood suggesting that vessel walls were being damaged by the sudden spike in glucose." Little says the most likely culprit for the damage is the body's own metabolic response to excess blood sugar, which causes blood vessel cells to shed and possibly die. "Even though these were otherwise healthy young males, when we looked at their blood vessel health after consuming the glucose drink, the results looked like they might have come from someone with poor cardiovascular health," adds Little. "It was somewhat alarming."