Are you a little low? Failure to match energy intake with requirements is a possible cause of that ‘low blood sugar’ feeling.

The symptoms of such low blood glucose (or hypoglycaemia, as it is medically termed), include: irritability; faintness; tremor; hunger and anxiety. However, it is not known whether such women experience true (biochemically defined) hypoglycaemia or whether their symptoms are caused by some other factor. Hypoglycaemia, especially following a meal, is rare in otherwise healthy women.

Reporting in the British Journal of Nutrition (2), scientists from the University of Nottingham conducted a study on 30 healthy, non-obese women (aged 19-49 years) who reported symptoms they thought were due to hypoglycaemia on one or more occasions each week, plus 18 symptom-free controls. The women took finger-prick blood samples and measured their blood glucose three hours after breakfast and lunch and also recorded their diet and physical activity levels for a week. Women who reported experiencing hypoglycaemia also took blood glucose measurements whenever they felt symptoms.

Women who reported symptoms of hypoglycaemia after a meal had significantly lower blood glucose compared to women in the control group (4.7 vs 5.1mmol/L). Furthermore, blood glucose was significantly lower than controls when symptoms were being experienced (4.2 mmol/L). Biochemically, hypoglycaemia is defined by a blood glucose of 3.0mmol/L. or less; only seven out of 30 women reporting symptoms of hypoglycaemia actually had a blood glucose indicative of hypoglycaemia, suggesting that other factors may be causing symptoms. However, the observation that glucose values were significantly lower on occasions when symptoms were noted suggests some alteration in glucose balance in these women.

Sugar has been anecdotally cited as a cause of ‘reactive hypoglycaemia’ (blood glucose levels falling a few hours after a meal). In this study, there was no difference in sugar intake between the two groups. Fat and protein intakes were lower on days when women experienced symptoms of hypoglycaemia. Some common starchy foods, such as wholemeal bread or potatoes, raise blood glucose to a similar or greater extent to table sugar (sucrose).

Researchers, Ian Macdonald and Elizabeth Simpson from the University of Nottingham, point out that symptoms associated with hypoglycaemia after eating, such as tremor, anxiety, irritability and feeling faint are also seen in women with other conditions.

Exploring reasons for the symptoms of reactive hypoglycaemia; researchers suggest that energy imbalance may play a role in the aetiology.

On days when women experienced symptoms of hypoglycaemia they tended to be more physically active, when compared with the control group, and their reported energy intake did not meet predicted energy requirements. As exercise increases insulin sensitivity, the combination of increased physical activity and a mismatch of energy intake with needs, leads to a lower blood glucose and may be a contributing factor to hypoglycaemia.

Therefore, if you experience symptoms of reactive hypoglycaemia it appears important to match energy intake with requirements on a daily basis, especially if you are physically active.