Blood sugar (glycaemia)
The level of glucose (sugar) in the blood, finely regulated by hormones, whose stability is essential for energy, mood and long-term metabolic health.
Blood sugar (glycaemia) is the concentration of glucose in the blood, normally kept at around 1 g/L when fasting. It is constantly regulated by a play of hormones (insulin, which lowers it, and glucagon, which raises it) to stay within a narrow range, because too high and too low are both problematic.
The blood sugar rollercoaster: beyond fasting values, what matters for everyday wellbeing is the swings in blood sugar after meals:
- A meal of fast sugars (sweets, fizzy drinks, white flour) causes a spike in blood sugar, followed by a large release of insulin that makes blood sugar drop, sometimes below where it started (reactive hypoglycaemia)
- This drop triggers cravings, tiredness, irritability, difficulty concentrating and a desire for sugar, restarting the cycle
This « rollercoaster » explains the 11 am or mid-afternoon slump, the cravings and some of the mood swings. Stable blood sugar means steadier energy and mood.
The rise of glucose sensors (CGMs): a recent phenomenon, as continuous sensors (originally for people with diabetes) are now being used by people without diabetes who are curious to see the impact of their meals in real time. This has popularised « glucose smoothing » strategies. A caveat: in healthy people without diabetes, the real usefulness is debated (the body regulates well), but it is an interesting educational tool.
Evidence-backed strategies to smooth blood sugar:
- Meal composition: combining carbohydrate with fibre, protein and fat slows absorption
- Order of foods: starting with vegetables and protein and finishing with starchy foods reduces the spike (convincing studies)
- Favour complex carbohydrate and low-GI foods, and avoid liquid sugars
- Resistant starch (starchy foods cooked then cooled)
- Move after eating: a 10 to 15 minute walk after a meal clearly reduces the spike (muscle takes up glucose)
- Vinegar before a carbohydrate-rich meal dampens the spike (emerging data)
Blood sugar and long-term health: chronically high blood sugar (even at « pre-diabetic » levels) gradually damages blood vessels, promotes inflammation and glycation (the « caramelisation » of proteins, linked to ageing) and leads to diabetes. Stabilising your blood sugar is an investment in your health.
In practice: most people need neither obsession nor a sensor. Simple principles (balanced meals, order of foods, a walk after eating, limiting fast sugars) are enough to avoid the rollercoaster and its drawbacks.