Lectins are proteins that bind to carbohydrates and are found in plant foods like beans, legumes, and wheat. In their active form, lectins can withstand acidic environments in the body, making them hard to break down and digest. Animal studies suggest that lectins can block the absorption of minerals like calcium and iron, impact growth and diversity in the gut, and exacerbate inflammation. As a result, lectins have earned the title "antinutrient," and fad diets have capitalized on these undesirable effects. [1]
How do lectins impact human health? While it's true that active lectins can have antinutrient-like properties, the actions of lectin in the body are more complicated. What fad diets don't tell you is that you'd have to eat lectins in-tact and in massive amounts actually to impair digestion and absorption of key nutrients. Lectin-containing foods are rarely consumed raw: we cook wheat and soak beans before eating. Because lectins are water-soluble, soaking or cooking these foods in water minimizes most, if not all, lectin activity. What's more, lectin-containing foods often contain fiber and other health-promoting nutrients like antioxidants that help mitigate cell damage and control the body’s glucose response. [1]
Key takeaway: Lectins should not be feared! Cooking foods like beans, legumes, and wheat deactivates lectins, reducing the "antinutrient" activity.
Since ancient times, apple cider vinegar has been used as a cure for pain and wounds. It has recently been reclaimed by the health industry as a way to curb appetite and improve digestion. Apple cider vinegar is apple juice with added yeast, which ferments the sugar into alcohol and then to acetic acid. The yeast is an added probiotic, and because we know that probiotics diversify and enrich the gut, apple cider vinegar earned a reputation for regulating digestion. But does scientific literature support the use of apple cider vinegar for gut health?
Despite being used for centuries, the research on apple cider vinegar is primarily in animals. A study conducted in rats found that an apple cider vinegar supplement significantly lowered BMI and reduced levels of two strains of "bad" gut bacteria, Firmicutes enterobacteriaceae and Clostridium, in both the colon and feces. Reducing Firmicutes promotes good gut health, as these are gut bacteria associated with impaired glucose and lipid metabolism. While the evidence is promising, research on the impact of apple cider vinegar and gut health in humans is warranted.
A review of small trials found that the addition of apple cider vinegar to meals helped to control blood glucose and insulin sensitivity in participants with Type II Diabetes. [2] Another study looked at the impact of apple cider vinegar and caloric restriction compared to caloric restriction alone in metabolically healthy participants who were overweight or obese. Both groups saw improvements in BMI, LDL, HDL, and total cholesterol over 12 weeks. However, there were no significant differences between the two groups, meaning the science can't tease out whether the positive health benefits result from the apple cider vinegar or the caloric restriction.
Key Takeaway: The impact of apple cider vinegar on gut health, bloating, and digestion has yet to be determined. Animal studies and small trials show that apple cider vinegar may potentially impact fasting glucose control, but further evidence is warranted.
Another food marketed for gut health is bone broth. Bone broth is made by simmering animals' bones and connective tissue in water, creating a broth that is then cooled and drunk. The primary structural protein in the bone and tissue is collagen. When cooked down, collagen becomes gelatin which contains essential amino acids, the building blocks of proteins. [3] Specific amino acids can benefit the gut, so what does the research say?
One measure of good gut health is intestinal permeability, the ease at which substances can pass through the gut's wall. When the gut lining becomes loose or permeable, substances can pass through it more quickly, leaving the gut susceptible to harmful bacteria. Interestingly, the amino acid glutamine plays a crucial role in maintaining the integrity of the intestinal barrier, making glutamine-containing foods and supplements attractive for those looking to improve gut health. [4] Bone broth often contains glutamine and may, therefore, elicit benefits in the gut.
Bone broth also contains collagen, which may play a role in injury prevention, as it is a key component of connective tissues like tendons and ligaments. Fortunately, we can get collagen from the diet—eating or drinking collagen-containing foods can help support the synthesis of new collagen in the body.[5]
It's important to note that, while bone broth does show promising preliminary results for gut health and injury prevention, further research is warranted. At this time, standardized research on bone broth is still difficult, as bone broth recipes are highly variable.
Key Takeaway: Bone broth can contain amino acids that improve the gut lining and improve collagen production in the body, but further research and recipe standardization is warranted.
While on the topic of collagen, research has shown that collagen supplements can promote joint health in athletes. Various studies found that collagen supplements promoted pain reduction in athletes experiencing joint pain, improved knee joint extension in healthy subjects, and extended the length of pain-free exercise.[6,7] Other studies found that collagen supplementation helped to improve indicators of athletic performance after strenuous exercise.
Key takeaway: Based on current research, we recommend collagen supplements to active individuals experiencing joint pain.
The multi-trillion-dollar beauty industry is now in the business of selling vitamin and mineral-rich supplements with bold cosmetic claims. One prevalent and heavily marketed supplement aimed at improving consumers' hair, skin, and nails is high-dose biotin. Biotin is a water-soluble B-vitamin and is an essential cofactor for several enzymes involved in the breakdown of fatty acids, amino acids, and gluconeogenesis.[9] It is often marketed as a vitamin that can strengthen and lengthen hair and nails. But what does the evidence say about biotin supplements and potential health impacts?
Biotin deficiency, which is very rare, is linked to alopecia (hair loss) and dermatitis (skin irritation).[10] Supplementation in biotin-deficient people may improve hair and skin outcomes. Case reviews studying biotin supplements' impact on hair and nail changes found that biotin supplements helped 18 people with underlying skin and nail issues (brittle nail syndrome, etc.) improve their hair and nails.[11] But in people who do not have an underlying deficiency, there is little scientific evidence to support the impact of biotin supplementation on hair, skin, and nails.
Although biotin is water-soluble and is therefore not readily stored in the body, high-dose supplements can still come with side effects. [12] Studies show that a biotin supplement may affect the following biomarkers: vitamin D, cortisol, ferritin, folate, vitamin B12, hsCRP, DHEAS, and testosterone. If you choose to take a biotin supplement, InsideTracker recommends stopping supplementation at least 72 hours before a blood draw to ensure accurate test results.[13,14]
Key takeaway: Biotin supplements likely only impact the hair and nails of those with severe biotin deficiencies and may alter your other biomarker levels. There is limited evidence on biotin's influence on hair and nails despite its commercial popularity.
Resources:
[1] https://pubmed.ncbi.nlm.nih.gov/31293334/
[2] https://pubmed.ncbi.nlm.nih.gov/14694010/
[3] https://pubmed.ncbi.nlm.nih.gov/28702900/
[4] https://pubmed.ncbi.nlm.nih.gov/27749689/
[5] https://pubmed.ncbi.nlm.nih.gov/29893587/
[6] https://pubmed.ncbi.nlm.nih.gov/18416885/
[7] https://pubmed.ncbi.nlm.nih.gov/24153020/
[8] https://pubmed.ncbi.nlm.nih.gov/30783776/
[9] https://pubmed.ncbi.nlm.nih.gov/28628687/
[10] https://pubmed.ncbi.nlm.nih.gov/31144371/
[11] https://pubmed.ncbi.nlm.nih.gov/28879195/
[12] https://pubmed.ncbi.nlm.nih.gov/29438761/
[13] https://pubmed.ncbi.nlm.nih.gov/28534685/