While in school in my dermatology lectures, we didn’t spend much time on the connection / correlation between diet and skincare. And that’s because the literature is relatively scant if you’re singularly looking for double-blind, randomized controlled study (the gold standard in the land of researchville). More on that here. One of the main reasons for lack of research into nutrition and acne is the high cost of appropriate studies, since, unlike for medications, the expected efficacy is low and there is a lack of options for increasing the price of foods to finance research. ( 2 )
So it is not currently possible to set out evidence-based nutritional recommendations in many cases because “no level A articles (double‐blind, comparative, randomized clinical studies) have been published. The information collected and reviewed in this study has therefore been exclusively reported through level B (randomized studies with serious limitations or a low number of cases) and level C (case–control or cohort studies) papers, only.” ( 3 )
So it’s quite difficult to definitively say one way or the other if there is a causative link between poor diet and poor skin. But there is enough research available to at least say with certainty that nutrition can influence skin to some degree. The specific degree is just difficult to quantify.
For the sake of simplicity, I’m looking at nutrition and acne, though many of the nutrients needed for clear skin also affect things like skin dryness and eczema, so the conclusions can extend to skincare issues beyond simply acne. I used a variety of different resources, most notably a textbook from my Master’s program (Nutritional Medicine by Alan Gaby, MD.) as well as some systematic review studies (mostly because I didn’t want to sift through ALL the research, as there are just so many studies), as well as a densely researched e-book from a trusted source (Chris Kresser’s ebook on nutrients for skin health – so good and a free download! Highly recommend.).
Let’s crack on!
Before talking about dietary factors that may influence to skincare troubles, let’s start the various contributors to acne. They include, “tissue inflammation, lugging of hair follicles as result of epidermal hyper-proliferation, and hormonal imbalances” ( 1 ). Different external and internal factors, including air pollution, aggressive skincare products, medication, mechanical, hormonal and familial factors and, more recently, lifestyle and stress, can also be causative agents of acne ( 3 ).
The conventional treatments are pretty widespread and range from topical treatments (retinoids, antibiotics, benzoyl peroxide) to systemic medications (antibiotics, oral contraceptive pills, and isotretinoin aka acutane) ( 1 ).
Throughout the research, there were some patterns of nutrition that may contribute to the prevalence of acne:
Possible acne contributors
again emphasis on the correlation, not causation
- in one study, 52 patients were assigned to consume their usual diet or to restrict sugar intake by eliminating soft drinks, candy and cake, and limiting sugar in coffee or tea to 2tsp per day. After follow up of 1 month, substantial improvement or complete clearing of lesion was seen in 84% of those consuming the low-sugar diet and 74% of those in control group. Suggests reducing sugar intake may be beneficial ( 1 )
- Another study showed that a low‐glycemic‐load diet (aka low in sugar) improved acne severity and insulin sensitivity. ( 3 )
Food allergy / sensitivity
- acne exacerbation could result from allergic reactions or from effects of biologically active substances in certain foods (ie hormones in cow’s milk and possibly amines or other chemicals in chocolate). Adult onset acne responds more frequently to food elimination than acne that began during teen years. Common symptom-evoking foods include: chocolate, milk, tomatoes, oranges, nuts, wheat, pork ( 1 ). Find details about elimination diets here.
Milk / dairy
- in an observational study of 47,355 women participating in nurses health study II, consumption of higher amounts of cow’s milk during high school was associated with increased incidence of severe teenage acne. After adjustment for potential confounding variables, the incidence of severe acne was 22% higher in those consuming greatest amount of milk than in those consuming least amount. The idea behind this is milk from pregnant cows (75-90% of milk on the market) contains progesterone, 5 alpha-reduced steroids, and other steroid hormones. These hormones can be metabolized in the human body to dihydrotestosterone which can promote the development of acne. In addition, cow’s milk may contain substantial amounts of iodine, mainly from the use of disinfectants to clean the cows’ udder and milk equipment from fortification of animal feed with iodine. Excessive iodine intake can trigger or exacerbate acne. ( 1 )
- In this study, acne was positively associated with milk, particularly skimmed milk. Skimmed milk was associated with higher plasma IGF‐1 levels.IGF‐1 stimulates the synthesis of androgens in both ovarian and testicular tissues and inhibits hepatic synthesis of sex hormone‐binding globulin resulting in increased bioavailability of androgen. The authors hypothesized that dairy products influence acne through hormonal mediators by increasing plasma insulin‐like growth factor (IGF)‐1 levels. This may be due to skimmed milk processing. In addition, skimmed milk may be more acnegenic because, in comparison with whole milk, it contains less estrogen, which is known to reduce acne. Another study paralleled these findings, reporting that skimmed milk rather than full‐fat milk triggers acne ( 3 ).
- In general, industrial cow’s milk has been reported to be spiked with anabolic steroids and other growth factors, such as progesterone, a testosterone precursor. Testosterone precursors and 5α‐reduced molecules are thought to contribute to the comedogenicity of milk by stimulating sebum production and hyperkeratinization of the pilosebaceous unit. ( 3 ).
- Furthermore, the majority of the milk and dairy products consumed in the United States come from pregnant cows. Hormones clearly play a role in acne, as sebum production may be influenced by androgens and hormonal mediators, such as sex hormone binding globulin (SHBG) and insulin like growth factor-I (IGF-I), all of which may be influenced by dietary factors. ( 4 )
- In sum, researchers concluded that there was an association between drinking milk and acne. However these studies had limitations because the questionnaire required self-assessment of acne and was based on memory of food intake. This can be difficult and subjective since recalling what one ate days ago can be difficult. Also an association between drinking milk and acne means that more validated and well-designed studies are needed to prove if there is an association or a cause. ( 4 )
The western diet
- ecological studies suggest that the incidence of acne is low in non‐Western societies and increases with the adoption of a Western diet, characterized by a high intake of dairy products, hyperglycemic food and free fatty acids ( 3 )
- The ratio of omega-6 to omega-3 fatty acids in Western diets is commonly at least 10 to 1, compared with ratios of 4 to 1 in Japan and 2 to 1 in hunter- gatherer populations. This high ratio of omega-6 to omega-3 fatty acids in our modern diet likely plays a role in the prevalence of inflammatory skin conditions such as acne, psoriasis, and rosacea. ( 6 )
- Acne is a rare condition in non‐Westernized societies with higher ratios of omega‐3 to omega‐6 polyunsaturated fatty acids from dietary intake. Conversely, populations in Papua New Guinea and Inuits, who have no milk or cereal intake, do not develop acne. ( 3 ) A Western diet is not only deprived of omega- 3s but is also a diet rich in refined carbohydrates. One study found that individuals with acne consumed significantly less fish and more junk food than the control individuals. ( 3 )
- One studyfound an association between high-glycemic-index foods and longer acne duration, whereas two randomized controlled trialsassociated low-glycemic-index diet with reduced acne risk. ( 4 )
- Regular fish consumption and vegetable consumption have been reported to reduce acne. ( 3 )
- a palaeontological nutrition regimen, consisting of fish, vegetables and fruits with a low glycemic, lipid and trans‐fatty acid load, may help to reduce the risk of acne. ( 3 )
Androgens, including testosterone, are an important acne trigger and are present in both men and women.After alcohol consumption, some alcohol is secreted through the sweat, thus possibly acting as a nutritive for Cutibacterium acnes, the bacteria that is most commonly associated with acne. Furthermore, alcohol may worsen acne by influencing the immune system. Frequent and long‐term alcohol use is known to suppress the immune system, which in turn allows bacteria to grow and multiply, leading to an unbalanced skin microbiota and to acne. And chronic consumption of alcohol has been suggested to increase cytokine release which may influence acne. ( 3 )
Some studies report that caloric restriction can change sebum composition. However it is unknown if this could relate to the pathological condition of acne. ( 4 )
In one study, subjects had a higher mean grade of acne severity and mean perceived stress score during examinations. Increased acne severity was significantly associated with increased stress levels, while self-assessed change in diet quality was the only other significant association. Patients with acne may experience worsening of the symptoms during examinations. Furthermore, changes in acne severity correlate highly with increasing stress, suggesting that emotional stress from external sources may have a significant influence on acne. ( 5 )
HAPPY SKIN NUTRIENTS
- One study found that consumption of fish was associated with a protective effect against moderate‐to‐severe acne. This inverse association between fish consumption and acne severity may be due to the fact that fish contains high levels of omega-3 fatty acids, which acts as a competitive inhibitor of the inflammatory arachidonic acid (AA) conversion to inflammatory mediators, prostaglandin E2 and leukotriene B4, thereby reducing inflammation in acne. ( 3 )
- Another studyprovided some evidence that fish oil supplements may improve overall acne severity, especially of moderate‐to‐severe acne. ( 3 )
- Several studies have suggested that inflammatory markers correlate with an increase of the omega-6/omega-3 ratio. The Omega-6 fatty acids are thought to induce more pro-inflammatory mediators and have been associated with the development of inflammatory acne.Conversely, intake of high levels of omega-3 fatty acids is associated with decreases in inflammatory factors. ( 4 ) High levels of omega-3 fatty acids have been shown to decrease inflammation, and may reduce the risk of acne and other skin problems by decreasing insulin-like growth factor (IGF-1) and preventing hyper-keratinization of sebaceous follicles.( 6 )
- In sum, consuming foods rich in omega-3 fatty acids may lead to smoother, younger-looking skin with a visible reduction in inflammatory skin conditions like acne and psoriasis. These fats can be found in cold water fatty fish such as sardines, salmon, mackerel, tuna, anchovies, and black cod, among many others. ( 6 )
- Vitamin A influences the physiology of the skin by promoting epidermal differentiation, modulating dermal growth factors, inhibiting sebaceous gland activity, and suppressing androgen formation. ( 6 )Vitamin A deficiency causes abnormal visual adaptation to darkness but also dramatically affects the cutaneous biology as dry skin, dry hair and broken fingernails are among the first manifestations of vitamin A deficiency. ( 4 )
- Lack of vitamin A causes the skin to become keratinized and scaly, and mucus secretion is suppressed. Rough, dry skin is a common sign of vitamin A deficiency ( 6 )
- The most vitamin A-rich foods are liver and cod liver oil, but other sources include: kidney, cream and butter from pastured cows, and egg yolks from pastured chickens. Liver is also an incredible source of vitamin A if you can stomach it. ( 6 )
- Increasing the amount of vitamin C in the diet can contribute to improved skin health and faster healing. Some studies report that diets high in vitamin C are associated with better skin appearance and less skin wrinkling, and are correlated with a decreased level of dry skin. The highest sources of vitamin C include bell peppers, guava, dark leafy greens, broccoli, brussels sprouts, kiwi, citrus fruits, and strawberries. As well as herbs like cilantro, chives, thyme, basil and parsley are also high in vitamin C. ( 6 )
- Vitamin D’s critical importance for the skin and consequently for the human body’s endocrine system is demonstrated by the fact that the skin is both the site of synthesis of vitamin D active metabolites. In fact, vitamin D analogues have been developed for the treatment of psoriasis which is characterized as an aggressive hyperproliferative skin disease. ( 4 )
- Vitamin E is a potent anti-inflammatory agent, defending the skin against free radicals and reactive oxygen species that would otherwise cause damage. Adequate levels of this vitamin in the skin may prevent inflammatory damage from sun exposure, helping to reduce the aging and skin cancer risk from excessive UV radiation. ( 6 )
- Whole food sources of vitamin E include spinach, turnip greens, chard, sunflower seeds, almonds, bell peppers, asparagus, collards, kale, broccoli, and brussels sprouts. Olive oil contains a moderate amount of vitamin E as well. It is important to eat these foods with plenty of fat to boost the absorption of vitamin E, which is a fat-soluble vitamin. ( 6 )
- assists in the proper structure of proteins and cell membranes, improves wound healing, has anti-inflammatory effects, and protects against UV radiation.( 6 )
- Dietary sources of zinc are best absorbed from animal sources, where it is not bound to phytates as in plant sources. Organs such as kidney and liver, red meat such as beef and lamb, and seafood such as oysters, scallops, and other shellfish are the highest animal sources of zinc. Plant foods such as pumpkin seeds and other nuts can also be high in zinc as well, but are less bioavailable. ( 6 )
- While true biotin deficiency is rare, consuming adequate amounts of biotin can help prevent problems with dry skin and seborrheic dermatitis. The best sources of biotin are egg yolks and liver, and other good sources include swiss chard, romaine lettuce, almonds, and walnuts. ( 6 )
- Sulfur is necessary for collagen synthesis, which gives the skin its structure and strength. Getting enough sulfur in your diet can help maintain collagen production and keep your skin looking firm. Sulfur is abundant and bioavailable in animal foods such as egg yolks, meat, poultry, and fish. It’s also found in plant foods, including: garlic, onions, brussels sprouts, asparagus, and kale. Fermentation may make this sulfur more bioavailable, so foods like sauerkraut and other fermented crucifers are excellent sources of sulfur ( 6 )
- deficiency in silica could result in reduced skin elasticity and wound healing due to its role in collagen and GAG formation. Food sources of silica include leeks, green beans, garbanzo beans, strawberries, cucumber, mango, celery, asparagus and rhubarb. ( 6 )
- is likely beneficial for preventing wrinkling and premature aging. Adequate dietary vitamin K2 prevents calcification of our skin’s elastin, the protein that gives skin the ability to spring back, smoothing out lines and wrinkles. Great sources of vitamin K2 include butter and other high fat dairy products from grass-fed cows, egg yolks, liver, and natto. Fermented foods such as sauerkraut and cheese are also quite high in vitamin K2 due to the production of this vitamin by bacteria. ( 6 )
- Patients with acne have been shown to have low levels of blood selenium, as well as low levels of selenium-dependent glutathione activity. Clinical research has shown that selenium supplementation, along with vitamin E, improves the appearance of acne while simultaneously increasing glutathione activity in those patients with lower levels. It’s best to get your selenium from food, and the richest sources of this trace element are organ meats and seafood, followed by muscle meats. Fish such as cod, tuna, halibut, sardines, and salmon are excellent sources, along with liver and meats like beef, turkey, and lamb. Brazil nuts are also a rich in selenium, and just two brazil nuts a day will give you the 200 micrograms necessary for an adequate intake. ( 6 )
- The ability of the gut microbiota and oral probiotics to influence systemic inflammation, oxidative stress, glycemic control, and tissue lipid content, may have important implications in skin conditions such as acne, rosacea, atopic dermatitis, and psoriasis. Recent studies have shown that orally consumed pre and probiotics can reduce systemic markers of inflammation and oxidative stress, which may help reduce inflammatory acne and other skin conditions. Include fermented foods such as sauerkraut, kimchi, yogurt, and kefir in your regular diet. ( 6 )
- Probiotics: Another line of evidence suggesting a connection between the gut and skin is the observation that probiotics improve skin conditions. Oral probiotics have been shown to decrease lipopolysaccharide, improve intestinal barrier function and reduce inflammation. Oral probiotics can also regulate the release of pro-inflammatory cytokines within the skin. ( 6 )
- Check out this post for a more thorough investigation and explanation of gut health.
Not proven / conflicting results in literature
- Chocolate: No well- designed study has been performed to address the belief still deep-rooted in the population that chocolate has an adverse effect on acne. ( 2 )
- Some sources report that 99% dark chocolate, when consumed in normal amounts for 4 weeks, exacerbated acne in male subjects with acne‐prone skin, potentially due to the presence of saturated fatty acids. However, this study used a food frequency questionnaire as the method of data collection. And was performed in a group of 25 year old men without controlling for other dietary factors. ( 3 )
- Another study on the impact of chocolate bars and jelly beans and the worsening or onset of acne showed that chocolate bar intake resulted in a worsening of acne. However, the chocolate was administered as a chocolate bar also containing sugar and milk: both are considered as potentially playing a role in acne. ( 3 )
- Coffee / caffeine: To date, there is no clinical evidence that products containing coffee or caffeine cause or worsen acne. ( 3 )
- Chocolate: No well- designed study has been performed to address the belief still deep-rooted in the population that chocolate has an adverse effect on acne. ( 2 )
( 1 ) Gaby, A. (2011). Nutritional Medicine. Textbook.
( 2 ) Fiedler, F., Stangl, G.I., Fiedler, E., & Taube, K-M. (2017). Acne and nutrition: A systematic review. Acta Derm Venereol 2017; 97: 7–9. Doi: 10.2340/00015555-2450
( 3 ) Claudel, J.P., Auffret, N., Leccia, M.T., Poli, F., & Dreno, B. (2018). Acen aand nutrition: hypotheses, myths, and facts. Journal of the European Academy of Dermatology and Venereology, 32(10, 1631-1637.
( 4 ) Pappas, A. (2009). The relationship of diet and acne. Dermato-Endocrinology, 5. 262-267.
( 5 ) Chiu, A., Chon, S.Y., Kimball. A.B. (2003). The response of skin disease to stress. JAMA Dermatology, 139(7), 897-900.
( 6 ) Kresser, C. Nutrition for healthy skin. E-book.