What are AGEs, and why blood sugar matters beyond energy

When I first started looking into my PCOS, I thought blood sugar was mostly about energy: the 3pm slump, the crash after a bowl of pasta. Then I came across glycation, and it changed how I think about food.

Sugar that sticks

When there's glucose in your blood, some of it attaches to proteins without any enzyme controlling the process. This is called glycation. At first the bond is loose and reversible. But over time, some of those sugar-protein links rearrange into stable, permanent compounds called advanced glycation end products, or AGEs.

Why AGEs matter

• They stiffen tissues. AGEs can cross-link proteins like collagen, making skin, blood vessels and joints less elastic. That's one reason they're linked to ageing.
• They drive inflammation. Cells have a receptor, called RAGE, that reacts to AGEs and switches on inflammatory signals.
• They're tied to diabetes complications. When blood sugar stays high for long periods, more AGEs form, and they're involved in damage to the eyes, kidneys, nerves and blood vessels [1].

The HbA1c connection

If you've ever had an HbA1c blood test, you've already met glycation. HbA1c measures how much glucose has stuck to haemoglobin in your red blood cells. That's the early, reversible stage, not AGEs themselves, but it shows how much glycation has been going on over roughly the last two to three months.

The PCOS link

Women with PCOS tend to have higher levels of AGEs in their blood than women without it, and this shows up in lean women with PCOS too, not just those with insulin resistance or a higher weight [3, 4]. Researchers think AGEs may play a part in the ovulation and hormone problems that come with PCOS, though this is still being worked out.

What makes more of them

Higher blood sugar, and blood sugar that stays high for longer, both increase glycation. So does getting older. AGEs also come from food: browning, grilling, frying and charring create them, through the same reaction that gives toast and seared meat their flavour [2].

So should you stop browning food?

No. Only around 10% of the AGEs in food are absorbed [5]. That said, there's some evidence it's worth not overdoing it. In one small trial, women with PCOS who switched to a lower-AGE diet for two months saw better insulin sensitivity and hormone markers [6].

The easy wins are the same habits good cooks use anyway:

• Golden, not charred. Browning is fine; blackened edges are where AGEs pile up.
• Marinate in something acidic. Lemon juice or vinegar before cooking cuts how many AGEs form in meat [2].
• Mix up your methods. Steaming, poaching, simmering and stewing make far fewer than frying or grilling.

What this means for how I eat

Cooking is one lever. The other, and the one this whole site is built around, is what your own blood sugar does after you eat. That doesn't mean fearing every rise: glucose going up after a meal is normal and healthy. What matters is the bigger pattern: how high it goes and how long it stays there. So I keep the carbs, and pair them with protein, fat and fibre so the rise is gentler.

This is general information, not medical advice. If you have diabetes, PCOS or another condition, speak to your GP or care team about what's right for you.