Liquid fruit hits the bloodstream like an express delivery of sugar. Once fruit is turned into juice, its intact cell walls are ruptured, and the viscous fiber network that once slowed digestion is largely gone. The result is a dense load of free fructose and glucose that the gut can absorb at high speed, pushing blood sugar upward much faster than the whole fruit ever would.
In whole fruit, insoluble fiber and soluble pectin form a physical matrix that delays gastric emptying and glucose diffusion through the intestinal mucosa. That structure lowers the glycemic index and flattens the postprandial glycemic response. Blending or pressing mechanically destroys this matrix, reducing both viscosity and particle size, which increases the surface area for digestive enzymes and accelerates carbohydrate hydrolysis.
Without that buffering fiber, pancreatic beta cells must release insulin more rapidly to keep plasma glucose within a safe range. Repeated sharp spikes in blood glucose and compensatory hyperinsulinemia can strain glucose homeostasis, especially in people with insulin resistance or impaired beta cell function. Juice still carries vitamins and phytochemicals, but it sheds a key protective feature: the structural fiber that once acted as its built‑in metabolic brake.
