The 10 best vitamins and supplements to consider for optimal metabolic health

Discover the vitamins, minerals, and supplements that research shows may help improve metabolic health. Plus: the ones you can probably skip.

WRITTEN BY

Stephanie Eckelkamp

REVIEWED BY

Dr. Ami Kapadia

UPDATED: 27 Sep 2023

PUBLISHED: 16 Sep 2022

🕗 10 MIN READ

Optimal metabolic health requires more than watching your carbohydrate intake or getting enough protein and fat to support stable blood sugar. Yes, minding these macronutrients is essential, but many other nutrients and nutrient-like substances found in food—such as  micronutrients (vitamins and minerals), antioxidant phytochemicals, omega-3 fatty acids, fiber, and probiotic bacteria—are unsung workhorses when it comes to supporting the body’s vital metabolic processes.

In the right quantities, these substances give your body the tools it needs to thrive on a cellular level. From a metabolic standpoint, they may help metabolize macronutrients, deliver energy to cells, regulate glucose, manage insulin production, reduce inflammation, and more. But when you fall short, these processes can be disrupted, increasing your risk for poor metabolic health and a range of related chronic diseases. For example, specific vitamin and mineral deficiencies have been associated with obesity, diabetes, cardiovascular disease, and metabolic syndrome. 

According to surveys, a large percentage of Americans’ diets are deficient in critical micronutrients—94% don’t get enough Vitamin D, 53% don’t get enough magnesium, 44% don’t get enough calcium. For some people, diets that contain a lot of processed foods and lack a diversity of fruits and vegetables can cause deficiencies. Even those who eat a healthy diet of whole or minimally processed foods (with an emphasis on a variety of colorful plants) can still come up short on certain nutrients because of declining soil quality and inadequate nutrient absorption.  

What’s more, for many vitamins, the RDA (average daily level of intake sufficient to meet the nutrient requirements of 97–98% of healthy individuals) isn’t necessarily the amount that will ensure optimal health in the average person or those dealing with suboptimal health or certain health conditions.

Knowing this, it’s easy to see how certain dietary supplements could be beneficial. But what should you supplement with? While recommendations vary by person and should ideally be guided by a healthcare provider and appropriate lab testing, certain vitamins and supplements tend to be more beneficial than others.

Use this guide to learn which vitamins and micronutrients are difficult to get through your diet and are best consumed as supplements and how to choose a good brand and take it safely.  

The Best Vitamins and Supplements to Consider for Metabolic Health 

These vitamins and supplements support metabolic health in a variety of ways. Remember, several may also be present at appropriate doses in your current multivitamin-multimineral supplement—so double check.  

1. Alpha-lipoic acid

Metabolic benefits: Alpha-lipoic acid (ALA) is an antioxidant compound produced in the mitochondria (or energy production centers) of cells, where it assists enzymes in glucose metabolism and energy production—but poor dietary and lifestyle habits, as well as exposure to environmental chemicals and pollutants, may increase a person’s demand, making supplements potentially beneficial. As an antioxidant, ALA helps combat oxidative stress by neutralizing harmful free radicals in the body that might otherwise damage cells and contribute to inflammation, insulin resistance, diabetes, diabetic neuropathy (nerve damage), and overall metabolic dysfunction. ALA has even been shown to help restore levels of another potent antioxidant within cells called glutathione, which normally declines with age. Research also suggests that ALA may have insulin-like effects and improve glucose uptake by muscle and fat cells from the bloodstream, lowering blood sugar levels.  

One meta-analysis of 24 studies found that ALA supplementation among patients with metabolic diseases helped lower fasting blood glucose, insulin levels, insulin resistance, hemoglobin A1C levels (a measure of your average blood sugar over 3 months), triglycerides, and LDL cholesterol. Other studies suggest that supplementing with 600 mg daily may reduce neuropathy symptoms (e.g., loss of sensation) among type 2 diabetes patients. 

How much do you need? There’s no official recommended dose for ALA, but if you choose to supplement, the Linus Pauling Institute recommends 200 to 400 mg daily for generally healthy people. Higher doses of up to 600 mg per day may also be effective for improving metabolic markers such as insulin sensitivity, or how efficiently your body processes glucose, as well as diabetic neuropathy. Research suggests higher daily doses of up to 2,400 mg are unlikely to cause harm but don’t deliver added benefits. 

Special considerations: Because food interferes with ALA absorption, take the supplements on an empty stomach, before or between meals. Also, despite its general safety, experts advise consulting your doctor before taking ALA if you consume excessive alcohol, or have diabetes, liver disease, a thyroid disorder, or thiamine deficiency. 

2. Vitamin D

Metabolic benefit: Vitamin D receptors are found in nearly all cells in the body, which means this essential nutrient has incredibly widespread effects on health, including metabolic processes. Specifically, vitamin D appears to have anti-inflammatory effects throughout the body, including on pancreatic beta cells that produce insulin, so it may support normal insulin production. Low vitamin D levels have been associated with obesity, insulin resistance, heart disease, and diabetes. 

But many of us come up short, mainly because we don’t get enough exposure to sunlight, which is one of the biggest drivers for our body making the vitamin D it needs. 

Supplementing with vitamin D appears to be beneficial for blood sugar control and reducing Type 2 diabetes risk. A meta-analysis of 28 studies showed that vitamin D supplementation lowered fasting blood glucose in non-overweight people, those with “insufficient” vitamin D levels, and those with prediabetes. Vitamin D reduced Type 2 diabetes risk when supplemented without calcium in overweight individuals and those with prediabetes. Another meta-analysis of 19 studies found that people with Type 2 diabetes who were supplemented with vitamin D experienced a decline in HbA1c (a 3-month average of blood glucose levels), insulin resistance, and insulin levels.

How much do you need? The recommended dietary allowance (RDA) for vitamin D is 600 IU (or 15 mcg) per day for adults under age 70 and 800 IU (or 20 mcg) per day for adults over age 70. But these doses may be low for optimal health. Many experts believe blood levels of vitamin D should fall in the 30-50 ng/mL range—and to hit this mark, you’d likely need 1,500–2,000 IU of vitamin D per day. Additionally, some benefits of vitamin D, such as reduced diabetes risk, appear to kick in around 2,000 IU per day. 

Special considerations: Choose vitamin D3, which is more effective at raising your levels than vitamin D2. Because vitamin D is fat-soluble, it should be taken with a fat-containing meal or snack to boost absorption. At the doses mentioned above, vitamin D is quite safe for most individuals, but it may interfere with a few medications, such as statins and corticosteroids.  

3. B-complex vitamins

Metabolic benefits: B vitamins play a vital role in metabolism, including breaking down carbohydrates into sugars, including glucose, and helping the body use fats and proteins. So a daily B-complex, which provides all eight B vitamins, may be an efficient way to support metabolic health (particularly for pregnant individuals, vegans, older adults, and people with digestive conditions such as celiac and Crohn’s disease—all of whom may struggle to obtain or absorb adequate B vitamins from dietary sources). The following are included in a B-complex: thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7), folate (B9), and cobalamin (B12). Here are a few ways they impact metabolic health:

• Vitamin B6 plays an important role in reactions that regulate glucose, fat, and protein metabolism, and higher B6 levels have been associated with reduced risk of Type 2 diabetes. Additionally, animal research suggests vitamin B6 may lower blood glucose levels and combat oxidative stress and its associated cellular damage.
• Low levels of folate and vitamin B12 have been associated with cellular inflammation and increased synthesis of fat and an amino acid called homocysteine. High levels of homocysteine, in turn, are linked to atherosclerosis and cardiovascular disease, insulin resistance, and Type 2 diabetes. Supplementing with folate, vitamin B12, and B-complex supplements has been shown to effectively lower homocysteine, helping prevent metabolic dysfunction. Folate supplements may also improve fasting glucose and insulin resistance.

How much do you need? The RDAs for each B vitamin vary; some are slightly higher for men. Here’s how the daily dose breaks down for each: 

• B1 (1.1-1.2 mg) 
• B2 (1.1-1.3 mg) 
• B3 (14-16 mg,
• B5 (5 mg) 
• B6 (1.3 mg) 
• B7 (30 mcg) 
• B9 (400 mcg – if from food, not supplement) 
• B12 (2.4 mcg) 

B-complex supplements often exceed these amounts significantly. However, because B vitamins are water-soluble, many of them are not stored in the body, and you’ll excrete what you don’t need when you pee. That means supplements containing doses higher than the RDA are unlikely to cause problems. However, it is important to know that there have been cases of neuropathy (weakness, numbness, or pain) with excessive doses of vitamin B6, so we recommend consulting a physician before taking more than the amounts in a B-complex.

People on plant-based diets, in particular, may benefit from a B complex, including B12, since B12 is predominantly obtained from animal products.

4. Curcumin

Metabolic benefits: At their core, metabolic diseases are inflammatory diseases. For example, inflammation contributes to insulin resistance (which can lead to diabetes) and blood vessel damage (which ups your risk for cardiovascular disease). Fortunately, curcumin—the compound that gives turmeric its golden hue—is an anti-inflammatory and antioxidant powerhouse that reduces inflammation and oxidative stress (which can trigger even more inflammation and metabolic damage) at the cellular level. Curcumin has been shown to upregulate the NRF2 pathway, which is responsible for activating genes that boost our body’s antioxidant defenses, and it downregulates the NF-κB pathway, which turns on pro-inflammatory genes. 

Curcumin may also play a role in protecting pancreatic beta cells (the cells that release insulin) and regulating fat metabolism. In one study, taking 300 mg of a curcumin supplement per day for three months significantly reduced fasting blood glucose, insulin resistance, and HbA1c, as well as triglycerides and free fatty acids in the blood of overweight and obese Type 2 diabetes patients.

How much do you need? There’s no official recommended dose for curcumin, but many supplements are dosed at 500 mg per day, which appears to be safe; one study found that 500mg three times a day was safe and effective for pain-reducing benefits. Opt for curcumin supplements standardized to contain 95% curcuminoids and consider options featuring black pepper extract to boost absorption. Compared to supplements containing isolated curcuminoids, ground turmeric is far less potent. 

Special considerations: Curcumin is fat-soluble, so consider taking it with a fat-containing meal or snack to boost absorption. While curcumin is generally safe, it does have antiplatelet effects, so it can thin the blood and amplify the effects of drugs like aspirin and warfarin. It may also interfere with iron absorption and cause problems for people who are borderline iron deficient. 

5. Magnesium

Metabolic benefits: Magnesium is an essential mineral that activates enzymes needed for hundreds of biochemical reactions in the body—including the enzymes that metabolize vitamin D. Research also suggests magnesium plays a vital role in improving insulin sensitivity, which allows your body to process glucose efficiently. It appears to do this by enabling the cascade of glucose-metabolizing processes triggered by insulin binding to its receptor and by helping increase glucose transporter proteins, which help move glucose from the bloodstream into cells where it can be used for energy or storage. Magnesium may also help counter low-grade inflammation, a factor in metabolic diseases like diabetes.

One randomized controlled trial found that taking 250 mg of magnesium per day for three months helped lower HbA1c and insulin resistance among people with Type 2 diabetes; and, according to a meta-analysis of five studies, a person’s overall risk of metabolic syndrome decreased 17% for every additional 100 mg of magnesium per day (up to about 420 mg per day).

How much do you need? The RDA for magnesium is 400-420 mg per day for men and 310-320 mg per day for women, but around 50% of Americans may not be hitting the mark due in part to increased consumption of processed foods and decreased consumption of vegetables and other magnesium-rich whole foods. There are several varieties of magnesium supplements: Magnesium glycinate, magnesium citrate, magnesium lactate, magnesium chloride, magnesium threonate, and magnesium aspartate are generally well absorbed, while magnesium sulfate and oxide may not be as bioavailable. 

Special considerations: If you have any form of kidney disease, we recommend consulting with your physician before taking a magnesium supplement. Otherwise, magnesium is considered safe, but high doses of certain forms (magnesium carbonate, chloride, gluconate, and oxide) may cause diarrhea and cramping. Supplements may also interfere with certain antibiotics and osteoporosis medications.

6. Omega-3 or fish oil

Metabolic benefit: Omega-3 fatty acids are essential polyunsaturated fatty acids (PUFAs) that are incorporated into the cellular membranes of every tissue in the body, where they enhance cellular communication, influence gene expression, and help build the cell’s structure. Among their many benefits: Omega-3s have anti-inflammatory effects (acting, in part, by downregulating the pro-inflammatory NF-κB pathway and reducing the secretion of several proinflammatory molecules, including cytokines), and they have been associated with several favorable metabolic changes, such as a reduction in triglycerides, blood pressure, and body fat levels, as well as improved insulin sensitivity. 

There are three primary omega-3 fatty acids: eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and alpha-linoleic acid (ALA). EPA and DHA from sources such as fatty fish and algae are considered long-chain fatty acids, which can be used directly by your body—they’re also the ones most commonly associated with omega-3’s health benefits. ALA is a short-chain fatty acid found in certain plant foods that can be converted into EPA and DHA in the body, but its conversion rate is low (less than 15%), so it is likely less efficient for promoting certain benefits. 

While omega-3 fatty acids are found in foods such as fish (like salmon and mackerel), walnuts, and flaxseeds, research shows that Americans are not consuming enough of certain omega-3s through diet alone. That’s where supplements can help.

Increasing omega-3 levels via supplements may be particularly beneficial for people already at a metabolic disadvantage. In one study of overweight middle-aged men, those with the highest blood levels of omega-3s had lower levels of the inflammatory marker CRP, fewer free fatty acids (substances that can cause insulin resistance) in the blood, and better insulin sensitivity compared to men with the lowest levels of omega-3s. 

How much do you need? Women need around 1,100 mg of ALA omega-3s daily, while men need about 1,600 mg daily. The Dietary Guidelines for Americans recommend at least 250 mg of combined DHA/EPA per day—but Levels Health advisor Dr. Mark Hyman, MD, recommends 2,000 mg of EPA/DHA per day split into two doses.

Special considerations: The conversion rate of ALA to EPA and DHA in the body is poor, so supplements containing EPA and DHA, such as fish oil or algae oil, are your best bet and may be better for inflammation. Look for supplements that have undergone molecular distillation, which removes heavy metals and other contaminants that fish can absorb. 

7. Selenium 

Metabolic benefit: Selenium is an essential trace mineral that supports normal thyroid function and packs an antioxidant punch, both of which are crucial for optimal metabolic health. Within the body, selenium is incorporated into the structure of specific proteins, creating around two dozen selenoproteins, which influence various processes. For example, several selenoproteins help neutralize free radicals and protect cells from the oxidative damage that often underlies insulin resistance and metabolic dysfunction. In animal studies, selenium has also been shown to mimic insulin, helping transport glucose from the bloodstream into the body’s cells, where it can be used for energy or storage. Selenium content of food can vary by region depending on soil quality. In general, U.S. soil contains enough selenium for most individuals to meet the RDA of 55 mcg—however, some research suggests there may be metabolic benefits of supplementing with additional selenium (though other studies show a link between high selenium and Type 2 diabetes).

Selenium is also found in high concentrations in the thyroid, a gland that produces hormones T3 and T4 that regulate cellular metabolism throughout the body; as a result, thyroid hormones regulate things like body weight, temperature, and organ function. Selenium exerts a protective effect on the thyroid by helping neutralize the many free radicals generated during thyroid hormone production. This means too little selenium may contribute to thyroid hormone imbalances and thyroid disorders that compromise metabolic function. The good news: According to a literature review, taking 200 mcg of selenium per day may help prevent thyroid disorders such as postpartum thyroiditis and improve symptoms and quality of life among those with Hashimoto’s and Grave’s disease. 

How much should you take? The RDA for selenium is 55 mcg per day for adults. Research on higher amounts is mixed, but some studies suggest that 200 mcg per day may support optimal thyroid and metabolic health. Because excess selenium may cause nervous system abnormalities, hair loss, skin lesions, and other side effects, it’s best not to exceed 400 mcg per day.

Special considerations: Early signs of excess selenium intake include a metallic taste in the mouth and garlic breath. If you notice either of these, you most likely need a lower dose. If you don’t want to take another pill, “supplementing” with 2 to 3 Brazil nuts daily will help you hit the 200 mcg mark. Each nut contains 68-91 mcg of selenium.  

8. Zinc

Metabolic benefit: Zinc is an essential mineral that activates enzymes needed for hundreds of vital biochemical reactions in the body, including those that regulate vitamin D activation and thyroid function. Zinc also serves as an antioxidant by influencing enzymes that neutralize free radicals or reactive oxygen species that might otherwise trigger cellular damage and insulin resistance. Found in high amounts in pancreatic beta cells (insulin-secreting cells), zinc is vital for the proper synthesis, storage, and release of insulin—the hormone that helps transport glucose from the bloodstream into cells where it can be used for energy or storage. 

Zinc deficiency, while somewhat rare in the U.S. (it’s more common if you have a chronic illness, gastrointestinal disorder, poor diet, or don’t eat meat), is a risk factor for obesity and diabetes—but supplements may help. A meta-analysis of 32 interventional studies found that zinc supplementation significantly reduced fasting blood glucose, HbA1c, and inflammatory markers among people with Type 2 diabetes or at risk for diabetes. More recently, another meta-analysis of 27 studies found that low dose daily zinc supplementation” taken for more than 3 months showed the greatest benefit for reducing diabetes and cardiovascular disease risk factors, significantly improving fasting blood glucose, insulin resistance, triglycerides, total cholesterol, and LDL cholesterol. 

How much should you take? The RDA for zinc is 8 mg daily for women and 11 mg daily for men. You can supplement with a bit more than this, but the beneficial cap for metabolic benefits may be around 25 mg per day. Studies have also shown that excessive zinc intake may lead to elevated HbA1c and high blood pressure, so stay below the upper limit of 40 mg per day unless your healthcare provider suggests otherwise. 

Special considerations: Zinc may interfere with a few medications, including certain antibiotics. Zinc can also impact copper absorption, so long-term zinc supplementation should include copper (some products combine the two). 

9. Vitamin C 

Metabolic benefit: Vitamin C is often touted for its immune benefits, but it’s also an important antioxidant that limits the damaging effects of free radicals that promote oxidative damage, inflammation, and metabolic dysfunction. In addition, it helps regenerate other antioxidants, like vitamin E, in the body. In one study, supplementing with 1,000 mg of vitamin C per day significantly reduced fasting blood glucose, along with the inflammatory proteins interleukin-6 and CRP, in obese patients with diabetes or high blood pressure. While overt vitamin C deficiency is rare, someone may experience inadequate intake if they get a limited variety of fruits and vegetables or have certain gastrointestinal conditions.  

Vitamin C may also help counter the effects of certain chemicals collectively dubbed “obesogens.” These chemicals—including a variety of persistent organic pollutants (POPs) such as flame retardants and pesticides—are widespread in food, drinking water, and soil and appear to have pro-inflammatory and hormone-disrupting effects on the body that impact a range of cellular processes and may predispose people to weight gain, metabolic syndrome, insulin resistance, and Type 2 diabetes. In one small study, researchers measured blood levels of three classes of POPs in 15 healthy women, both before and after supplementing with 1,000 mg of vitamin C per day for two months. The result: Several chemicals classified as organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were significantly reduced after vitamin C supplementation. 

Research suggests that vitamin C might help lower levels of uric acid (a natural waste product from the digestion of foods) in the body. In a meta-analysis of 16 studies, supplementing with vitamin C at doses ranging from 200-2,000 mg per day was associated with significant reductions in uric acid levels among people under 65. The researchers noted, however, that there was no significant difference between the lower and higher doses, suggesting that more isn’t necessarily better.

How much should you take? The RDA for vitamin C is 75 mg per day for women and 90 mg per day for men. However, the research above suggests that higher doses, ranging from 200-1,000 mg per day, are likely safe and may offer metabolic benefits. 

Special considerations:  For those with kidney stones or who are predisposed to forming stones, we recommend speaking with your physician before considering taking vitamin C, as there is a potential risk that it can contribute to developing certain types of stones. For most people, vitamin C is relatively safe and has a low risk for toxicity and side effects if you stay under the upper limit of 2,000 mg daily. If you consume too much, you may experience gastrointestinal distress, such as diarrhea, nausea, and cramping.

10. CoQ10

Metabolic benefit: Coenzyme Q10 (CoQ10) is a powerful antioxidant found in cells throughout the body, most abundantly in the heart, liver, and kidneys. It’s vital for energy production and serves as an essential component of the electron transport chain—a series of reactions within the mitochondria of cells that synthesize energy in the form of ATP. As an antioxidant, CoQ10 also helps neutralize free radicals that might otherwise contribute to metabolically damaging oxidative stress. Conditions such as atherosclerosis, nonalcoholic fatty liver disease (NAFLD), and metabolic syndrome are characterized by increased inflammation and oxidative stress—which is why boosting CoQ10 levels via supplementation may be beneficial. CoQ10 levels also start falling around age 20 and may be as little as half (in certain parts of the body) by 80.  

Supplementing with CoQ10 appears beneficial and has been associated with improvements in several metabolic biomarkers. In one study, supplementing with 100 mg of CoQ10 per day for 12 weeks was associated with reductions in fasting blood glucose, insulin resistance, and LDL cholesterol and increased HDL cholesterol among women with Type 2 diabetes. And another study found that supplementing with 100 mg per day for four weeks significantly improved waist circumference and markers of oxidative stress among people with NAFLD. CoQ10 supplementation has also been shown to improve blood glucose levels and insulin resistance among women with polycystic ovarian syndrome (PCOS)—a condition associated with insulin resistance, weight gain, and increased risk of Type 2 diabetes. 

How much should you take? There’s no official recommended dose for CoQ10, but experts often recommend 30-200 mg per day in the form of gel capsules, which tend to be better absorbed. Higher doses up to 400 mg per day also appear safe but may not be necessary. 

Special considerations: CoQ10 is fat-soluble, so take supplements with a fat-containing meal or snack to boost absorption. CoQ10 is relatively safe, and no serious side effects have been reported; however, some people may have mild side effects such as digestive upset and insomnia. It may also interfere with medications like insulin or blood-thinning drugs like warfarin. 

How to Stay Safe with Any Vitamin or Supplement

While all the supplements above have the potential to support metabolic health, they’re not necessarily right for you. That’s because you may be getting more than enough of several of these nutrients through your diet—so supplementation would simply be a waste of money. Additionally, certain supplements and medication combos can be problematic or require you to carefully time your doses (for example, magnesium and antibiotics).

For these reasons, supplementation should be personalized. Start by talking to your healthcare provider about your current health, diet, and lifestyle to help determine which of the above supplements (or others) may be appropriate. Providing them with an up-to-date list of the prescriptions, over-the-counter drugs, vitamins, and supplements you’re already taking is essential for spotting potential interactions. 

To further hone your ideal supplement lineup, consider seeking a functional medicine physician or dietitian who can order appropriate nutrient lab testing to see where you may be lacking. For example, some practitioners use the NutrEval FMV test by Genova Diagnostics, which tests a variety of blood and urine biomarkers, and assesses the body’s needs for antioxidants, vitamins, minerals, essential fatty acids, and more.

Once you know what vitamins and supplements you want to take, your next goal is to pick a high-quality, reputable brand. This is important because research shows that several low-quality supplements have been contaminated or adulterated with harmful bacteria, fungi, heavy metals, and even prescription drugs. Unlike medications, the Food & Drug Administration (FDA) does not regulate vitamins and other supplements for safety and effectiveness before being marketed to the public. The FDA typically only investigates and removes supplements after complaints from customers or healthcare professionals are made. And although FDA regulations state that supplement manufacturers must follow current good manufacturing practices to ensure the quality of their product, there’s very little oversight on this. 

To find a good supplement, ask for brand recommendations from a healthcare provider who is knowledgeable about supplements; ideally, seek out supplements that have been third-party tested by an independent organization such as NSF International or U.S. Pharmacopeial Convention (USP). Third-party testing doesn’t guarantee a supplement will be safe or effective for everyone, but it ensures that the supplement contains the ingredients listed on the label in the correct quantities and does not contain unsafe levels of harmful contaminants. Scan bottles for USP or NSF seals, or search the manufacturer’s website for testing information. 

Some highly-rated, well-established brands that offer third-party testing on all or some of their products include Pure Encapsulations, Thorne Research, and Integrative Therapeutics. Additionally, CVS recently became the first national retailer to require third-party testing for all vitamins and supplements sold in its stores and online. 

5 Vitamins and Supplements You May Want to Skip

Supplementing these nutrients and compounds generally isn’t the best way to reap their metabolic benefits. Here’s why, plus what to do instead. 

Calcium

Low calcium levels have been associated with impaired insulin release, while other studies show an association with less insulin resistance. Calcium supplementation doesn’t have clear benefits—it may even cause harm. A study analyzing health data over 10 years found an association between calcium supplements and plaque buildup in the arteries. Aim for 1,000 mg of calcium per day (or 1,200 mg for women over 50) from food sources such as dairy products, sardines (with bones), almonds, tahini, and dark leafy greens (cooked to reduce oxalates, which can inhibit calcium absorption).   

Fiber

Fiber mostly passes through the digestive system intact—this slows the absorption of sugars from carbohydrate-containing foods into the bloodstream, which buffers spikes and dips in blood glucose. Fiber is also fermented by your gut bacteria, producing beneficial metabolites called short-chain fatty acids that are associated with improved insulin sensitivity, weight regulation, and decreased inflammation. But skip fiber supplements, which may contain sugar and artificial colors and flavors. Fiber from whole plants is far superior. To promote stable blood sugar and feed gut bacteria, aim for 30-50 grams of fiber per day from sources like chia seeds, flax seeds, avocados, beans and lentils, and berries. 

Green tea extract

Forget the claims that green tea extract supplements can boost metabolism, fat burning, and weight loss—their true benefits are relatively modest and they have the potential to be dangerous. They’ve been associated with liver damage, nausea, vomiting, diarrhea, dizziness, tremors, and confusion in adults and children. The good news: Sipping green tea offers real benefits without side effects. Drinking six cups of brewed green tea per day has been associated with a reduced risk of developing Type 2 diabetes, and a meta-analysis showed that green tea consumption might reduce fasting glucose and HbA1c. These effects are likely due to the antioxidant activity of polyphenols in green tea, according to Levels Health advisor Sara Gottfried, MD. 

Melatonin

Melatonin is a hormone naturally secreted by the pineal gland in the brain that stimulates sleepiness and regulates circadian rhythms. In addition to helping you get enough sleep (crucial for maintaining balanced blood sugar), melatonin also functions as an antioxidant and possesses anti-inflammatory properties, which help counter oxidative stress and damage that can lead to insulin resistance and overall metabolic dysfunction. But instead of taking melatonin supplements—many of which are dosed unnecessarily high, around 3 to 5 mg, when the research suggests 0.3 to 0.5 mg is adequate—support your brain’s natural melatonin production by dimming the lights, minimizing screen time, and popping on a pair of blue-light-blocking glasses after the sun sets. 

Probiotics

Promising new research suggests that probiotic supplements containing a bacterial strain called Akkermansia muciniphila may improve insulin sensitivity, abnormally high insulin levels, and total cholesterol in overweight or obese insulin-resistant individuals. However, according to Dr. Gottfried, we’re still in the early days of knowing when and how to use probiotic supplements for maximum benefit, and current research suggests that consuming probiotic-rich fermented foods may be a better option. In one study, people with prediabetes who ate kimchi, a fermented cabbage dish, increased insulin sensitivity, decreased insulin resistance, reduced blood pressure, and improved glucose tolerance. Get your fill of naturally occurring probiotics by eating fermented foods like kimchi, sauerkraut, kvass, kefir, and unsweetened yogurt.