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Food is one of the best, most natural healers out there. From helping to ease nausea to taking the edge off sore throats, what we eat should always form part of a healthy living plan. Which is what makes ‘How to Eat to Beat Disease’, a new book by William Li, M.D., so exciting. The book provides a science-backed approach to ‘food as medicine’, sharing the research behind over 200 health-enhancing foods.

Some of these can be great natural immune boosters to add to your plate this cold and flu season:

1. Mushrooms

White button mushrooms are a good source of bioactives, including beta-glucan, an immune-stimulating dietary fibre. Researchers at the University of Western Sydney in Australia studied 20 healthy volunteers who were assigned to eat either a regular diet or a regular diet plus white button mushrooms. The mushroom-eating participants ate 100 grams of blanched mushrooms per day, roughly equivalent to 1.3 cups of mushrooms for one week. As a test of whether the mushrooms affected immune function, the researchers measured the levels of two antibodies (IgA and IgG) in the subjects’ saliva. More antibodies are produced in the saliva after immune activation. The researchers found a steady increase in IgA levels in the participants, with a 55% increase after one week of mushroom consumption and a continued rise to 58% above baseline levels up to two weeks after finishing the mushrooms. Eating the mushrooms helped activate the gut, which stimulated the immune system to produce the antibodies. The antibodies then circulated to the mucus membranes, where they were secreted in saliva.

2. Aged Garlic

Garlic is known as having antiseptic, antibacterial, and antifungal properties. Garlic can boost the immune system, which means it can help to effectively ward off and combat viruses and other microorganisms.

It turns out the Ancient Greeks, who used garlic to strengthen athletes and soldiers and as a component of healing tonics, were onto something. Aged garlic has shown to be a beneficial dietary supplement and is thought to retain potent bio-actives, such as apigenin, that can influence the immune system.

Researchers at the University of Florida in Gainesville studied the effect of aged garlic on the immune systems of 120 healthy men and women in their mid-20s and early 30s during the cold and flu season. Two groups received either an aged garlic extract or a placebo for 90 days and had their blood drawn for analysis of immune response. The subjects were instructed to keep a daily illness diary to log any symptoms of being sick, such as runny nose, head congestion, sore throat, cough, fever, or body aches, and to record if they became ill enough to miss school or work.

At the end of the study, the group who consumed aged garlic extract had significantly more immune T-cells and natural killer (NK) cells circulating in their bloodstream than the group taking the placebo. Remarkably, the T-cells resulting from the aged garlic were supercharged and could replicate themselves eight times faster than in people receiving the placebo. The NK cells, too, were enhanced by garlic. They were said to be 30% more activated than similar cells in people on the placebo.

3. Broccoli Sprouts

Broccoli contains sulforaphanes – which are considered potent bio-actives. Sulforaphanes activate the immune system, and, remarkably, broccoli sprouts contain up to 100 times more sulforaphane than regular full-grown broccoli. You can really taste the broccoli flavour when you chew them thoroughly. The chewing is crucial because it ruptures the plant cell walls to release an enzyme called myrosinase. This enzyme is essential because it purportedly converts the sulforaphane, which is naturally inactive in the plant, to its active form in your mouth. Activated sulforaphane can affect the cells in your body.

Researchers at the University of North Carolina at Chapel Hill, Stanford University, and the University Children’s Hospital of Basel, Switzerland, studied the impact of eating broccoli sprouts on the immune system by conducting a clinical trial involving the ‘flu vaccine. They wanted to know if the sprouts could help the body boost its response after vaccination. The scientists enrolled 29 healthy volunteers in their late 20s and gave them either 2 cups of broccoli sprouts blended into a shake or a placebo shake to drink each day for four days. The volunteers received a nasal spray ‘flu vaccine on the second day after starting to drink the shake. The vaccine delivered a live but weakened flu virus into the mucus membrane in the nose.

The results showed that volunteers who drank the broccoli sprout shake had 22 times more NK T-cells in their blood compared to those who drank the placebo shake. Their NK cells also had more killing power. The proof in the pudding was that broccoli sprout shake drinkers also had less ‘flu virus remaining in the cells of their nose, indicating that their bodies had cleared the invaders more effectively. Eating broccoli sprouts can boost your immune defence against the ‘flu virus.

4. Extra Virgin Olive Oil

The question “Does olive oil boost immunity?” has probably never crossed your mind, but as we know, extra virgin olive oil is a critical component of the Mediterranean diet, and the bio-actives it contains, such as hydroxytyrosol, oleocanthal, and oleic acid, are said to enhance the immune system.

Researchers at Tufts University, the University of Massachusetts, and the Institute for Food Science and Technology and Nutrition in Spain designed a clinical study to see if replacing the oil (butter and corn oil) found in the typical American diet with extra virgin olive oil would improve a person’s immune response. The researchers selected 41 overweight or obese volunteers over the age of 65 who ate an unhealthy diet that was high in saturated fat and refined and processed grains and low in dietary fibre. The researchers then gave all the subjects a bottle of oil and spread. One group received extra virgin olive oil from Spain in liquid and spreadable form while the other received a mix of corn and soybean oil as well as a butter spread. For three months, the participants continued to eat a typical American diet but used only their assigned oil and spread. Both groups consumed on average about 3 tablespoons of oil per day. Blood analysis showed that the immune T-cells in the olive oil group increased their ability to become activated and expand in number by 53%. The same immune cells in the group eating corn-soy oil and butter had no change.

Olive oil also helps reduce the body’s reaction to allergens. The bioactive hydroxy-tyrosol found in extra virgin olive oil could help immune cells make interleukin-10, which can assist in calming inflammation. These combined effects show that substituting extra virgin olive oil for other cooking oils used in a typical American diet could possibly have both immune-boosting and anti-inflammatory health benefits.

Importantly, not all olive oils contain the same amount of hydroxy-tyrosol. A study from the Instituto de la Grasa in Spain compared the polyphenols found in four types of Spanish extra-virgin olive oils made from olive mono-varietals (Arbequina, Hojiblanca, Manzanilla, Picual). The highest levels of hydroxytyrosol were present in the oil produced from Picual olives.

5. Ellagic Acid

Many popular foods contain ellagic acid, a bioactive with health-defence-activating properties.

Chestnuts, blackberries, black raspberries, walnuts, and pomegranate have among the highest levels. Ellagic acid has antiangiogenic effects that could possibly starve tumours. But when it comes to immunity, ellagic acid can assist immune cells by improving their ability to assist in detecting and destroying cancer cells.

And if you still fall ill this winter, despite eating all the immune-boosting foods and knocking back ginger shots like you did back in college, consider the Releaf Cough and Cold Range.



In the range, you’ll find Releaf Cough and Cold Effervescent, which comes in a pleasant citrus flavour and provides a unique combination that includes MSM to help relieve symptoms of colds and hay fever, such as a runny nose, cough, pain and inflammation.

The range also includes Releaf Cough and Cold Syrup, which contains Hedera helix to help relieve a productive cough and tight chest, as well as Pelargonium, shown to assist in significantly reducing the severity of symptoms of the common cold and shorten its duration. (1)



Releaf Pharma believes all treatment of illness should begin with your doctor’s opinion.

The views expressed in this editorial content are gathered from outside sources which can be cross-referenced here:

Eat to Beat Disease: The New Science of How Your Body Can Heal Itself