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Why Vitamin D is Critical for Your Immune Health

Vitamin D is the “most critical daily nutrient to your immune health.”


Do you find yourself constantly catching cold after cold? Just one severe cold or flu virus can ruin an entire vacation or special event, not to mention the missed time at work. It’s time to find something to strengthen your immune system that really works. In this video, Dr. Nancy Lin, Ph.D., explains what you need to stay healthy and virus-free no matter what the season.

Video Highlights

  • 0:42: The Real Reasons You Catch a Cold or Flu
  • 3:17: Why Traditional Vitamin D Supplements Don’t Work
  • 4:47: Three Must-Haves in Your Vitamin D Supplement
  • 5:53: Vitamin D3 from Animals vs. Plants
  • 9:01: Dr. Nancy’s Preferred Vitamin D3
  • 9:52: Tips to Boost Immunity

The Real Reasons You Catch a Cold or Flu

Woman blowing nose


Most people catch viruses in the winter and not in the summer. Contrary to popular belief, the cold weather is not the reason. Being cold does not make you sick, nor does it create more flu viruses. It really comes down to these three things:

1. Cold, Dry Weather Allows Viruses to Survive Longer

The very name “influenza” is an Italian word that originated in the mid-18th century as “influenza de freddo,” which means “influence of the cold.”

2. Close Indoor Contact Makes it Easier to Transfer Germs

During the winter, you’re more likely to spend time indoors with your friends or family. We’re also not eating as well, sitting around more, exercising less, not getting enough sleep and usually under a lot of stress. Each of these contributes to a weakened immune system. When your defense system is depleted,  bacteria, viruses and toxins can easily overwhelm your body and cause you to get sick.

3. Vitamin D Deficiency

When it comes to immunity, people almost always immediately think of Vitamin C, but most people easily get enough Vitamin C from their diet or from a multi-vitamin. However, almost everyone is deficient in Vitamin D. Known as the sunshine vitamin, the body produces Vitamin D when your skin is exposed to bright sunlight for 30 minutes or more each day without sunscreen. Many people assume they get this much exposure during the summer, but you probably get less than you think. Plus, spending time outside during the summer months without wearing sunscreen is highly discouraged.

Unlike Vitamin C, Vitamin D is not commonly found in large amounts in food. It’s virtually impossible to get enough Vitamin D from diet alone. In fact, Americans get less than eight percent of the Vitamin D they need from food.

Three Must-Haves in Your Vitamin D Supplement

Fresh fruits and vegetables

1. Choose Only Vitamin D3

It’s important to choose the right type of Vitamin D supplement. There are two forms of Vitamin D: Vitamin D2 and Vitamin D3. Always choose Vitamin D3, which is the fully active form of Vitamin D and is virtually identical to what the body naturally produces by exposure to sunlight. It’s also highly bioavailable, which means it’s easily absorbed by the body and considered superior to other forms of Vitamin D. However, Vitamin D2 is mainly what they add to fortified milk, bread and other food and drinks, so consumers often believe they are getting added Vitamin D. But, beware, Vitamin D2’s bioavailability to the body is so poor that the American Journal of Nutrition stated, “Vitamin D2 is not suitable for fortification or supplementation.” If you see Vitamin D2 on the label, stay away!

Vitamin D3 from Animals vs. Plants

With Vitamin D3 supplements, you need to choose its source: animals or plants. The dirty little secret of the supplement industry is that animal-based Vitamin D3 comes from what’s called sheep grease. Sheep secrete it from their glands to help protect their wool coats from the environment by making them water-resistant. This sheep-secreted gland grease also contains Vitamin D. In fact, 99% of Vitamin D in stores comes from sheep grease because it’s so cheap.

The Vitamin D is extracted from sheep’s wool by squeezing it and rolling the wool until it secretes a yellow, waxy and stinky substance called sheep grease. This is the same stuff they use to put on shoes to help keep them water-resistant. The sheep grease is then heavily processed and concentrated with synthetic chemicals to create synthetic Vitamin D3.

Up until recently, all the plant-based forms of Vitamin D mainly came from mushrooms and only provided Vitamin D2, the inferior version. But now, they’ve discovered not only a natural Vitamin D3 source from plants, it’s also the most available form of Vitamin D3 anywhere. It’s from a plant called lichen and is easily and sustainably farmed. It also doesn’t involve animal cruelty or potentially undesirable contaminants—and it’s completely vegan!

2. Take 5,000 IU of Vitamin D3 Daily in Fall, Winter and Spring

After much debate, the studies are showing that 5,000 IU, especially as you age and have more difficulty absorbing vitamins, is what you should be taking daily. Dr. John Cannell, President of the Vitamin D Council, which is a nonprofit group that studies all things Vitamin D, also recommends 5,000 IU a day. At this level, even a severely deficient individual can get back to healthy immune-optimal Vitamin D levels in just a few months.

3. Vitamin D3 Must be Taken with Vitamin K2

Always look for formulas with both Vitamin D3 and Vitamin K2. Any good doctor or nutritionist will tell you not to take a Vitamin D3 supplement without Vitamin K2, because it balances the action of Vitamin D3, resulting in greater bone, heart and immune health benefits. It also ensures that calcium is kept in the bones and not in the arteries, where it has the potential to calcify and cause disease.

Why Traditional Vitamin D Supplements Don’t Work

Even the most potent multivitamin only provides 20% or less of the Vitamin D you need during the winter. You’ve probably heard that Vitamin D is important for strong bones as you age, but new research has revealed that Vitamin D plays an even bigger role when it comes to your immune health. Vitamin D directly affects more than 2,000 genes in your body, helping to regulate virtually your entire immune and neuromuscular system while fighting off infections and more. That’s why for more than a decade, healthcare experts have suggested taking Vitamin D daily.

However, something seems to be alarmingly wrong. How is it that so many people are taking Vitamin D across the US, yet the rate of Vitamin D deficiency over the past 10 years has not really changed? It’s estimated that 75% of Americans are Vitamin D deficient and at-risk with chronically weakened immune systems.

Smarter Nutrition Vitamin D3 Works Because It’s Not A Traditional Supplement

Unlike those Vitamin D pills that utilize ingredients excreted from sheep's glands, Smarter Nutrition’s Vitamin D3comes from lichen, the most premium plant source of active Vitamin D3. Not only is it sustainably sourced; it’s naturally free from contaminants and undesirable animal byproducts. Encapsulated in a veggie softgel, Smarter Nutrition Vitamin D3 is formulated with organic extra virgin coconut oil for faster bioavailability and Vitamin K2 to protect your body and enhance the benefits of Vitamin D3.

Dr. Nancy prefers Smarter Vitamin D3 because it checks all the boxes and more:

  • 5,000 IU of premium plant-based Vitamin D3
  • Premium Vitamin K2 complex to increase effectiveness and keeps calcium in bones
  • Vegetarian softgel with extra virgin coconut oil for better absorption
  • Clean-formula without chemical coatings or fillers
  • Non-GMO
  • Vegan
  • Gluten-free

Tips to Boost Immunity

Green juice with Boost Your Immune System written on napkin

In addition to taking Smarter Nutrition Vitamin D3, Dr. Nancy provided 10 more ways to boost your immunity.

1. Try Mushroom Tea

Several studies have shown that Chaga or Reishi mushrooms help activate immune cells and lower inflammation so your body can better fight infection. They’re best taken in tea form.

2. Sing or Listen to Music

Both singing and listening to music for 30 minutes are linked to lower cortisol levels. When stress hormones like cortisol are elevated, they can suppress immune function; music can counteract that.

3. Laugh More

The happier, more positive you are, the more likely you are to eat right and be less stressed. Laughter can boost your immune system along with your mood. Laughter releases dopamine and other feel good chemicals in the brain, all of which can decrease stress.

4. Eat Organic Whole Grains

Beta glucans are fibers deep inside certain whole grains that strengthen white blood cell activity to kick out unwanted viruses. Plus, oats are a prebiotic, meaning they stimulate the good bacteria living in your gut where your immune system largely lives.

5. Get Enough Sleep

One reason getting enough sleep is so important is that the body releases cytokines during extended periods of sleep. Cytokines are a type of protein, which help the body fight off infection by regulating the immune system.

6. Limit Alcohol Consumption

New research shows that drinking alcohol can damage the body’s dendritic cells, which are important components of the immune system. An increase in alcohol consumption over time can increase a person’s exposure to bacterial and viral infections. Plus, alcohol is loaded with sugar, which suppresses the immune system.

7. Eat Citrus Fruits

Chock-full of benefits, citrus fruits are a great and delicious way to get your daily dose of Vitamin C. Vitamin C helps to increase the production of white blood cells. Because your body doesn’t produce Vitamin C on its own, you need to get it from food or a multivitamin. Organic strawberries, grapefruit, oranges, lemons, limes and tangerines are all excellent sources.

8. Load Up on Garlic

Allicin, a sulfur-containing compound found in ground garlic, contains powerful immune boosting properties and it’s easy to add to so many dishes.

9. Move Your Body

Movement of any kind helps to reduce inflammation, disease and stress. It also accelerates circulation of disease-fighting white blood cells needed for a healthy immune system.

10. Wash Your Hands

Always wash your hands with soap and water. It seems obvious, but many people skip this step. Sing the “Happy Birthday” song in your head (or aloud) for the full duration of the wash.

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