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You may have a rock-solid regimen of vitamins, minerals, herbs and other supplements. But certain foods and nutrients can diminish (or enhance) absorption, and some combinations can be downright dangerous—so how you’re taking your supplements may be as important as what you’re taking. Here are 6 simple ways to optimize your supplement routine.

1. Don’t take multis with your morning coffee

The caffeine in coffee (or tea, for that matter) inhibits vitamin D receptors in the body, lessening absorption and impacting vitamin D’s bone-building and immune-boosting benefits. That morning coffee also blunts calcium uptake and, in high quantities, can deplete the bones of minerals.

Because caffeine acts as a diuretic that increases blood flow through the kidneys, water-soluble vitamins such as B and C can be transferred into urine before they’ve had a chance to be absorbed into the bloodstream. Plus, coffee’s laxative effects speed transit time through the intestines, which also decreases time during which nutrients can be fully assimilated.

Best advice: Drink your coffee or tea before breakfast, then take multis about 15 minutes after eating, when there’s still enough food in your stomach to prevent stomach upset and enhance absorption of fat-soluble nutrients such as vitamin D and K.

2. Take a separate calcium supplement

Don’t count on a multi to fulfill your calcium needs. Because calcium (and magnesium) are required in higher quantities than vitamins and other nutrients, most multis don’t contain enough to meet your daily needs. Plus calcium and other minerals, like magnesium, compete for absorption in the body when taken together. That said, you do need both for bone health—magnesium helps guide calcium into bones, not soft tissue, and too much calcium with too little magnesium can contribute to calcification of the arteries, increasing the risk of heart disease.

But while it’s true that you likely need more calcium, don’t take too much. Studies suggest that high levels of calcium from supplements may increase plaque buildup in the arteries, increasing the risk of cardiovascular disease.

Best advice: To maximize benefits and decrease risk, take calcium and magnesium supplements separately, with at least 2 hours between (take calcium with breakfast and lunch, and magnesium with dinner.) Bonus: Taking magnesium before bed enhances sleep and promotes regularity.

3. Don’t take vitamin D with vitamin A

High levels of vitamin A can interfere with your body’s uptake of vitamin D, which is why most multis include a higher percentage of vitamin D than vitamin A to make up for potential deficits. On the other hand, do take vitamin D with vitamin K, especially if you’re using a calcium supplement. Research suggests that taking vitamin K enhances D’s bone-building benefits—and if you’re low in vitamin K, supplementing with vitamin D and calcium can even be harmful.

When you take your D is important, too. A meal that contains fat improves vitamin D absorption and can increase blood levels by as much as 50 percent. But if you eat late, don’t take D with dinner. It can interfere with melatonin production and disrupt sleep.

Best advice: Studies suggest that low doses of vitamin D (less than 400 IUs per day) don’t prevent fractures, but ultra-high doses can prompt excess calcium absorption, increasing the risk of heart attack and stroke. In general, 600 IUs of vitamin D per day should be enough, although you’ll want to take more if you have dark skin or live in a northern climate.

4. Take probiotics on an empty stomach (with some exceptions)

Because harsh stomach acids can destroy probiotics, they’re best taken on an empty stomach. Some studies suggest that probiotics survive in the largest numbers when taken 30 minutes before a meal that contains some fat (which buffers stomach acids and helps probiotics survive to reach the intestines). Other research suggests that food buffers stomach acid and improves probiotic survival (and probiotics were traditionally taken through cultured foods such as yogurt or sauerkraut).

Ultimately, it may depend in part on the strain. Some probiotics (those with Lactobacillus or Bifidobacteria strains) are best taken about 30 minutes before meals, while other strains, such as Saccharomyces boulardiiCan be taken with or without food.

Best advice: Consistency is really the key. Research suggests that regularly taking probiotics positively impacts gut bacteria, whether they’re taken with or without food. If you do take your probiotic with a meal, remember that some foods, such as oatmeal and low-fat milk, promote probiotic survival through the digestive process. Be wary of probiotics with added prebiotics—they can cause gas, bloating, diarrhea, and significant digestive distress in some people.

5. Don’t take iron with green tea

Green tea is high in compounds that can dramatically reduce iron’s bioavailability, and some research suggests that drinking large amounts of green tea can lead to iron-deficiency anemia. Tannins and polyphenols in coffee and tea also bind with iron and inhibit its absorption, and even herbal teas, such as peppermint and chamomile, can impact iron.

Other minerals, including calcium, magnesium, zinc, and copper, compete with iron, which reduces its availability. High doses of vitamin E can also interfere with iron.

Also impacting iron uptake: phytates and fiber in whole grains, legumes, and nuts; oxalates in chocolate, black tea, and dark leafy greens; and calcium and phosphorous in milk, yogurt, and cheese. And eggs contain a compound that can reduce iron absorption by as much as 28 percent.

Best advice: Unless you have a sensitive system, take your iron supplement an hour before or two hours after eating. And wash it down with orange juice—vitamin C dramatically enhances the absorption of iron supplements.

6. If you’re taking fish oil, skip the ginkgo

Fish oil and omega-3 supplements can interact with Ginkgo biloba and other blood-thinning herbs, increasing the risk of bleeding. Fish oil can also amplify the effects of blood-pressure drugs, dropping blood pressure precipitously.

Similarly, St. John’s wort combined with some antidepressants or migraine medications can lead to harmful increases in serotonin levels. St. John’s wort can also magnify the effects of sleep supplements or those with sedative actions, including melatonin.

Best advice: It’s probably better to get omega-3s from food, if possible. Some research suggests that omega-3 fatty acid supplements had little to no effect on reducing heart attacks, strokes, or deaths from heart disease, while high levels of dietary omega-3s are linked with cardiovascular protection.

Don’t Be Fooled by the USP Seal

A USP (United States Pharmacopeia) designation on supplement labels means that certain standards of quality have been met—eg, disintegration, dissolution, strength, and purity. While this can be a good thing, it doesn’t guarantee a high-quality supplement. For example, many cheap, chain-store brands bear the USP seal, but they contain inferior forms of key nutrients such as poorly absorbed calcium and synthetic vitamin E (dL-alpha tocopherol rather than d-alpha tocopherol). Supplement formulation has taken a quantum leap over the past decade or so, raising the bar when it comes to true quality. Newer designations that really make a difference include:

• GMP Certified
• UL Certified
• Third-Party Verification and/or Testing
• Non-GMO Project Verified
• USDA Organic
• B Corp
• Molecularly Distilled (omega-3 fats)

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