There are no foods that you shouldn’t eat in the morning. A common concern is that eating a banana on an empty stomach in the morning will cause magnesium and potassium to enter the blood, upsetting the balance. However, there is no evidence to support this claim. One banana contains 300 mg of potassium, and 30 mg of magnesium, a smaller amount compared to potassium. However, eating a banana on an empty stomach is not enough to disrupt the body’s electrolyte balance. According to the Korean Nutrient Intake Standards, the recommended potassium intake is 3,500 mg per day. Eating a banana for breakfast is only one-tenth of your daily potassium intake. If you’re a healthy person with normal kidney function, this shouldn’t be enough to upset your body’s electrolyte balance. Therefore, you can eat a banana in the morning on an empty stomach.

People also often raise concerns that drinking milk on an empty stomach may not be a good idea, saying calcium and casein stimulate the secretion of stomach acid. The same goes for sweet potatoes, tangerines, tomatoes, and coffee. However, all foods stimulate the secretion of stomach acid. Protein-rich drinks, such as milk, stimulate acid secretion even more. In fact, it’s even more concerning if food enters the stomach through the esophagus and doesn’t stimulate the gastric acid.

If you can't digest the lactose in milk, you may feel gassy or sick after drinking milk on an empty stomach. However, this doesn't hinder the body's absorption of other nutrients, such as protein. Generally, lactose intolerance is not a significant issue for most individuals, up to 5 grams or half a glass (100 ml) of milk per day. Consumption alongside other foods may increase lactose tolerance as it gets diluted. Many individuals can tolerate up to 12 grams of lactose or a large glass of milk daily.

Moreover, lactose-intolerant individuals may experience the added benefit of a reduced risk of type 2 diabetes when they consume milk. This finding stems from a study published in January 2024 in the journal Nature Metabolism, which analyzed six years of data from 12,653 Hispanics enrolled in the UK Biobank. The study revealed that individuals who consumed substantial amounts of milk, even if lactose intolerant, exhibited a lower body mass index (BMI) and a 30 percent decreased risk of type 2 diabetes compared to non-consumers. Conversely, for those without lactose digestion issues, there was no observed association between milk intake and reduced risk of diabetes.

Certainly, these findings do not establish a definitive cause-and-effect relationship. However, researchers speculate that lactose might have positive effects on appetite regulation, insulin secretion, and liver fat reduction by promoting the growth of beneficial gut bacteria such as bifidobacteria and increasing the production of short-chain fatty acids. In simpler terms, when a lactose-intolerant individual consumes moderate amounts of milk, the unabsorbed lactose in the small intestine can serve as a prebiotic in the large intestine, nourishing beneficial bacteria. Given that humans are omnivores, maintaining a balanced diet is considered a healthier approach than being selective in food choices.

Jeong Jae-hoon is a food writer and pharmacist. He covers a variety of subjects, including trends in food, wellness and medications. This column was originally published in Korean in Joongang Ilbo on Feb. 29, 2024. – Ed.