Most of us have experienced that difficult time of day when energy dips, concentration wanes and our stomach grumbles for food.
But for some people, the effects of too little sugar in the bloodstream are more debilitating - headache, shakiness, weakness, rapid heartbeat, anxiety, confusion, blurred vision - and can occur without warning.
Hypoglycemia is the medical term for low blood sugar (glucose). It can be a concern for people with diabetes taking certain blood sugar-lowering medications, but it can also affect those who aren't diabetic.
While diet isn't the underlying cause of hypoglycemia, altering what you eat - and when you eat - can prevent your blood sugar from dropping too low if you're susceptible to the condition. Common mistakes such as missing meals, skimping on protein and fibre, indulging in sugary foods and drinking alcohol can trigger symptoms of hypoglycemia.
Normally, blood glucose levels range from four to six millimoles per litre of blood before eating and rise to five to eight millimoles in the two hours following a meal. When your blood glucose rises after eating, the pancreas releases insulin, the hormone that moves glucose from the blood to the body's cells where it is needed for energy.
If your meal supplies more glucose than your body needs at one time, the extra is stored in your liver and muscles as glycogen. When your blood glucose begins to fall between meals, your pancreas releases glucagon, a hormone that pulls blood sugar back up by signalling your liver to release glucose from glycogen.
Adrenalin and cortisol, hormones released by your adrenal gland, also help keep blood glucose levels up.
In hypoglycemia, blood sugar isn't pulled back up and symptoms, which vary from person to person, can occur.
In diabetics taking glucose-lowering medications, hypoglycemia can happen because of an excessive dose of insulin or certain diabetes medications, skipped or delayed meals or snacks, increased exercise or excessive alcohol. (Drinking alcohol, especially on an empty stomach, can cause delayed hypoglycemia up to 14 hours later in people with Type 1 diabetes.)
Two types of hypoglycemia can occur in people without diabetes: reactive and fasting. Fasting hypoglycemia occurs when a person hasn't had anything to eat or drink for eight or more hours. It's usually related to an underlying illness, hereditary hormone or enzyme deficiencies, taking certain medications or binge drinking (alcohol interferes with your liver's attempts to raise blood glucose).
More common is reactive hypoglycemia, which happens when blood glucose drops abnormally low within one to four hours after eating a meal.
The causes of most cases of reactive hypoglycemia remain unclear. Some scientists speculate that certain people are more sensitive to the body's normal release of adrenalin, which can cause symptoms of anxiousness, sweating, rapid heartbeat and faintness. Other research suggests that a deficiency of glucagon - the hormone that protects from low blood sugar - may be the culprit.
How do you know if your afternoon energy slump is reactive hypoglycemia? If your blood glucose is less than four millimoles per litre and your symptoms disappear when food is eaten, hypoglycemia is probably the cause.
A sudden, acute episode of hypoglycemia can be treated by eating or drinking some form of sugar - candies, glucose tablets, fruit juice, table sugar, honey - to restore blood glucose to normal. (If you take diabetes medication, speak to your health care provider about properly treating low blood sugar.)
Ideally, the goal is to prevent hypoglycemia from happening in the first place. The following strategies can help to ensure glucose enters your bloodstream at a steady pace throughout the day. (If you have diabetes, ask your dietitian for a meal plan that helps manage your blood sugar level.)
EAT EVERY TWO-THREE HOURS
To prevent a fall in blood glucose, eat every two to three hours. That means not skipping meals and including snacks midmorning, midafternoon and sometimes before bed. Carry snacks with you to avert a hypoglycemic episode.
CHOOSE LOW-GI CARBS
Meals and snacks should include carbohydrate-rich foods with a low glycemic index (GI) which means they're digested slowly and, as a result, converted to blood glucose gradually rather than quickly.
Foods that quickly boost blood glucose - sweets, sugary drinks, refined starchy foods - result in an outpouring of insulin, which can trigger blood sugar to fall prematurely.
Low-GI foods include bran cereals, large-flake and steel-cut oatmeal, stone ground whole wheat, pasta, milk, yogurt, soy beverages, apples, pears, oranges, dried apricots, nuts, seeds and legumes.
Ensuring meals and snacks include a source of protein also helps moderate swings in blood glucose. Lean meat, poultry, fish, low-fat cheese, eggs, tofu, nuts and yogurt are digested more slowly than carbohydrates and help sustain blood glucose longer after eating.
INCREASE SOLUBLE FIBRE
Adding soluble fibre to meals and snacks can help prevent hypoglycemia by delaying stomach emptying and the absorption of glucose into the bloodstream.
Good sources of soluble fibre include oatmeal, oat bran, psyllium-enriched breakfast cereals, flaxseed, barley, legumes, sweet potatoes, citrus fruit and strawberries.
LIMIT CAFFEINE AND ALCOHOL
Caffeine in coffee, tea, cola and chocolate stimulates the production of adrenalin and can worsen symptoms of reactive hypoglycemia.
Alcohol can cause a low blood sugar reaction all by itself, especially when consumed on an empty stomach. If you drink, limit your intake to one or two drinks a day and always consume with food.
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is lesliebeck.com.