Brief cold dips linked to better glucose handling
- Winter swimmers in Susanna Søberg’s study cleared glucose faster after a drink than matched controls.
- Their routine used brief cold dips alongside sauna, so the study cannot isolate cold’s effects.
Eleven minutes of cold-water immersion a week was the dose in a study Susanna Søberg discussed on Huberman Lab. The experienced winter swimmers in her study dipped for one to two minutes at a time, two or three times a week, and also spent 10 to 15 minutes in a sauna per visit.
After fasting for eight hours, the swimmers produced less insulin than matched controls. After drinking glucose, they also cleared it faster: their blood glucose was lower by the two-hour mark. Søberg says repeated cold exposure can activate brown fat, which generates heat, and links the body’s adaptations to improved insulin sensitivity.
The findings don’t show that brief cold dips alone caused the difference. The swimmers chose their routine, and it combined cold with sauna; the study did not compare cold-only exposure with sauna or other routines. Søberg said the results suggest people may not need long or extreme sessions, but they are not proof that the same benefits will follow from a cold plunge alone.
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Essentials: Cold & Heat Exposure for Metabolic Health | Dr. Susanna Søberg • Nov 5
- Repeated cold exposure can increase brown-fat mitochondria and improve heat production, while skin capillaries become better at constricting and the catecholamine response subsides. Søberg links these adaptations to higher metabolism and improved insulin sensitivity.
- Søberg studied experienced winter swimmers who alternated outdoor cold-water immersion with sauna. They swam in water ranging from about 15°C down to 2-4°C and used an approximately 80°C sauna.
- Søberg's winter swimmers had lower insulin production while fasting and cleared glucose faster after a glucose drink than matched controls. Participants fasted before testing, and the glucose curves were compared over the following hours.
- Søberg's study found that a modest weekly routine was associated with metabolic and cardiovascular benefits. She reported lower blood pressure and heart rate after a winter-swimming season, alongside improved insulin sensitivity.
- Søberg's study supports a low weekly dose: brief cold dips and sauna sessions, spread across multiple visits, produced the reported outcomes. She says people do not need prolonged swims or extreme cold to pursue these benefits.
Also discussed on this episode: (10)
Health (5)
- Susanna Søberg says deliberate cold should feel uncomfortably cold: the initial cold shock raises sympathetic activity and catecholamines, often causing faster breathing and gasping that ease with adaptation.
- Søberg explains the post-immersion temperature drop as an afterdrop: blood vessels constrict in cold water, then reopen outside, sending cooled blood back toward the core. Shivering helps restore heat, so it is not inherently a danger signal unless exposure becomes excessive.
- Søberg says the study measured increases in IL-6 and IL-10. She argues that cold and heat may help reduce chronic inflammation, which research links to type 2 diabetes, depression, anxiety, and Alzheimer's disease.
- Søberg recommends ending contrast sessions in the cold so the body must generate heat afterward through brown fat and muscle activity. She says repeated practice can make people warm more easily, and her winter swimmers had warmer skin but also lost heat faster.
- Søberg favors changing temperatures over rigidly pursuing one water temperature or duration. She says water up to 12°C can activate brown fat and argues that repeated shifts between warm and cold challenge the body's temperature regulation.
Biology (4)
- Cold water covers more skin and activates cold receptors faster than walking in cold air. Skin signals reach the hypothalamus, while norepinephrine and direct neural pathways help activate brown fat; shivering muscles also contribute to heat production.
- Søberg describes cold and heat as hormetic stress that can make cells more responsive, including through heat-shock and cold-shock proteins. She compares the cellular challenge to exercise, while warning that excessive exposure can exhaust cells.
- Cold exposure can activate brown fat without a plunge: Søberg cites hand immersion, outdoor cold, cooling vests, and cool-room sleep. In one study, a month sleeping at 19°C increased brown-fat activity and insulin sensitivity; warmer room temperatures reversed the trend.
- In Søberg's own cold-water experiment, brown-fat temperature rose within minutes, measured with infrared thermography near the collarbones. The exposure was brief, showing that the tissue responded rapidly to skin cooling.
Society (1)
- Søberg argues that modern indoor comfort and sedentary routines reduce exposure to natural temperature shifts. She connects that loss of thermal stress to rising obesity, noting that more comfortable lifestyles spread in the 1960s and 1970s and obesity increased in the 1980s.