What happens to your body when you eat too much sugar?
A high-sugar diet may increase the risk of weight gain, obesity, cancer, and potentially accelerate tumor growth.
Nutritionist Tran Pham Thuy Ha from the Nutrition Department at Tam Anh General Hospital in Hanoi explained that among the three macronutrients—carbohydrates, proteins, and fats—carbohydrates are utilized by all cells in the body because they easily break down into glucose. Glucose serves as the primary fuel that provides energy for cells.
Normal cells age and are replaced by new ones, but abnormal cells continue growing, forming benign or malignant tumors. Initially, small tumors obtain oxygen and nutrients from nearby blood vessels. As they grow, they create new blood vessels to receive more oxygen and nutrients.
Malignant (cancer) cells divide and multiply rapidly, consuming large amounts of energy and requiring significant glucose, even under low-oxygen conditions (a phenomenon known as the Warburg effect). Dr. Hoa cited research showing that cancer cells consume glucose 50 to 100 times more than normal cells.
Although no evidence proves that sugar directly increases tumor size, it may indirectly influence growth. The body regulates blood glucose levels through insulin and other hormones. All energy-providing foods—carbohydrates, proteins, and fats—can convert into glucose, enabling tumors to access glucose from these sources along with other nutrients for division.
However, consuming excessive sugary foods, especially refined sugars and high-glycemic-index foods, over time can lead to overweight and obesity. This results in hormonal imbalances and increases the risk of malignant tumor formation.
Overweight and obesity also raise the risk of insulin resistance, where the pancreas releases insulin in response to high blood sugar, but the body's cells fail to absorb glucose efficiently. This leads to chronic high blood sugar and insulin levels, stimulating the production of insulin-like growth factor 1 (IGF-1), which promotes malignant tumor proliferation.
Additionally, high blood sugar and insulin levels contribute to inflammation as fat cells release inflammatory adipokine proteins. Chronic inflammation can lead to the formation and progression of abnormal cells. A diet high in refined sugars also increases oxidative stress, damaging DNA and raising the risk of malignant tumors.
"Many people mistakenly believe that completely cutting out sugar will limit tumor growth," Dr. Hoa said, clarifying that no evidence supports the idea that sugar-restricted diets reduce disease risk.
It is impossible to "starve" tumors without affecting healthy cells. On the contrary, a strict low-carbohydrate diet can harm health since carbohydrates are a primary energy source. Cancer patients on restrictive diets may experience rapid weight loss and nutrient deficiencies, which can slow recovery and increase postoperative complications.
Everyone, including cancer patients, should consume sugar in reasonable amounts based on their condition. Instead of refined sugars, herbal spices like cinnamon, bay leaves, and cloves can be used in dishes and beverages. Limiting refined sugars in sweetened drinks, sodas, candies, ice cream, and processed foods is also recommended. Developing a habit of reading ingredient labels before consuming foods is helpful.
A balanced diet should emphasize fiber from vegetables, fruits, and whole grains. Opting for whole grain bread or brown rice instead of white bread or white rice, and eating whole fruits instead of drinking juice, is preferable. Incorporating anti-inflammatory foods like fatty fish (such as salmon and mackerel), olive oil, turmeric, ginger, and green tea is also beneficial. Pairing these dietary habits with regular exercise and a healthy lifestyle can help reduce malignant tumor growth.
Cancer patients or individuals with benign tumors should consult their doctor or nutritionist to create an appropriate dietary plan.
