Diet and Skin: What the Evidence Supports

Few topics attract as many confident claims as food and skin. Some links between diet and skin are well supported, some are plausible but unproven, and some are myths that keep circulating. Sorting them by the strength of the evidence makes it easier to decide what is worth changing.

Reasonably good evidence

High-glycemic diets and acne. Foods that raise blood sugar quickly, such as white bread, sugary drinks and many processed snacks, appear to make acne worse in some people. In a 2007 Australian trial, young men who switched to a low-glycemic diet for 12 weeks had noticeably fewer acne lesions than a comparison group. The American Academy of Dermatology describes the link as real but modest.

Deficiencies show up in the skin. Severe shortages of certain nutrients cause recognizable skin problems: easy bruising and slow wound healing with vitamin C deficiency, a scaly rash around the mouth and hands with zinc deficiency, and cracked corners of the mouth with some B-vitamin deficiencies. These are uncommon with a varied diet but more likely with restrictive eating or certain medical conditions.

Some evidence, still debated

Dairy and acne. Several large observational studies have found that people who drink more milk, especially skim milk, report more acne. Observational studies can't prove cause, and cheese and yogurt show weaker or no links. Cutting dairy for a few weeks to see whether it helps is reasonable; cutting it permanently without replacing calcium and protein is not.

Omega-3 fats. Small trials suggest fish oil may reduce inflammatory acne or ease eczema in some people, but results are inconsistent.

Weak or no evidence

• "Drink more water for clearer skin." Severe dehydration affects the skin, but for people who already drink normally, studies of extra water have found small and inconsistent effects on skin hydration and none on acne.
• "Detox" juices and cleanses. The liver and kidneys remove waste products. No juice speeds that up, and very low-calorie cleanses can leave the skin looking duller.
• Chocolate. A few small studies have linked chocolate to more breakouts, possibly through sugar and milk content rather than cocoa itself. The evidence isn't strong enough to call chocolate a cause.

Rosacea triggers

Rosacea, a common condition that causes facial redness and flushing, has the clearest food triggers of any skin condition. In surveys by the National Rosacea Society, the most frequently reported triggers were alcohol (especially red wine), spicy foods, hot drinks and foods containing cinnamaldehyde, such as tomatoes, citrus and chocolate. Triggers vary a great deal between people, so a symptom diary is the usual way to identify your own.

Eczema and food allergy in children

Children with moderate to severe eczema are more likely to have food allergies, and parents often try cutting out foods to calm flares. Pediatric and allergy organizations advise against broad elimination diets without testing. They rarely clear eczema on their own, can lead to poor growth in young children, and in some cases removing a food a child was tolerating can increase the risk of developing a true allergy to it later. If you suspect a food allergy, an allergist can test for it properly.

Sugar and skin aging

Sugar molecules can bind to collagen and elastin in a process called glycation, producing compounds known as advanced glycation end products. These make collagen stiffer and are thought to contribute to sagging and wrinkles over decades. The process is best documented in people with poorly controlled diabetes, and it is one more reason to keep added sugar moderate, though sun exposure remains the far bigger cause of visible skin aging.

A practical approach

If you suspect a food is affecting your skin, change one thing at a time and keep it up for at least six to eight weeks, since skin takes that long to show a difference. Taking photos in the same light at the start and end is more reliable than memory. Persistent acne, eczema or rashes are worth seeing a dermatologist about, because effective treatments exist and diet alone rarely solves them.