Did you know that guava and tomato are just two of the lycopene-rich fruits and vegetables that can protect your brain and reduce your risks for cancer, heart disease and bone fractures?

Lycopene, the pigment in red fruits and vegetables like pink guava and tomatoes, is an important dietary tool scientists are currently taunting in the prevention and suppression of neurodegenerative diseases. Past research has also shown lycopene to have antioxidant properties, which are effective in fighting other diseases such as cancer, precursors to heart diseases and bone conditions.

Neurodegenerative Disease

Lycopene demonstrated antioxidant properties in protecting the neural system in vitro and the consumption of lycopene-rich fruits and vegetables is recommended as a preventive strategy for neurodegenerative diseases.^[i]

In addition to suppressing oxidative stress and inflammation in the brain, lycopene restores changes associated with neurodegenerative disorders, epileptic conditions, aging, brain hemorrhages, spinal cord injury and neuropathy and prevents proteinopathies, neuroinflammation, apoptosis, cerebral edema and synaptic dysfunction in the brain.^[ii]

Lycopene also ameliorated neuroinflammation, oxidative stress, amyloid genesis and memory loss in an Alzheimer's-induced mice model, through mediating cell signaling pathways (MAPKs, NFκB and Nrf2) related to inflammation, and thus could be effective in preventing Alzheimer's disease.^[iii]

In their in vitro study of mice, researchers found lycopene to be effective in reducing oxidative stress, which is considered a major cause of Alzheimer's disease, by reducing cell apoptosis through activation of the PI3K/Akt pathway.^[iv]

Researchers studied 6,958 participants aged older than 50 years to assess the impact of carotenoids on mortality risk from Alzheimer's. High levels of lycopene, lutein and zeaxanthin were found to lower the risk of Alzheimer's mortality.^[v] In an Alzheimer's-induced mice study, oxidative stress biomarkers were measured with two treatments --lycopene and lycopene combined with vitamin E.

The combination was synergistic in significantly decreasing memory impairments and improved three oxidative stress markers for Alzheimer's.^[vi] In a rat study, researchers demonstrated that lycopene, a natural carotenoid, lowered aluminum-induced hippocampal lesions by inhibiting oxidative stress-mediated inflammation and apoptosis in the brain.^[vii]

Similarly, lycopene was found to be very effective against age-induced cognitive impairment, memory loss and cognitive defects while reversing age-associated neuronal damage and synaptic dysfunction in brain synapses by mitigating oxidative stress and inflammation markers in a mouse model.^[viii]

Cancer Risk

Twenty-six studies of 563,299 participants with 17,517 documented cases of prostate cancer were meta-analyzed, showing that higher lycopene intake (between 9 milligrams (mg) and 21 mg per day) reduced the incidence of prostate cancer.  The prostate cancer risk declined 18% with increasing consumption of lycopene (intake of tomatoes and watermelon) in a study of 404 participants.^[ix]

In addition, researchers have found lycopene-rich foods like tomatoes to be positive for a variety of other cancers. In a meta-analysis including 15 studies of 644 animals, lycopene supplementation significantly reduced the incidence, number and growth of liver cancer.^[x]

In their comprehensive review of the literature, scientists attested to tomato lycopene's preventive action against the formation and development of lung cancer as well.^[xi] Lycopene supplementation in lung and liver tumor-induced mice reduced experimental tumor metastasis in vivo by decreasing tumor invasion, proliferation and angiogenesis.^[xii]

In a pooled analysis of 21 studies, the group that consumed the most tomato products had the lowest risk for gastric cancer.^[xiii] In a study of U.S. adults, tomato (86% lower risk) and lycopene (79% lower risk) intake was inversely related to all cancer deaths.^[xiv]

Guava leaf extract has been shown to have a strong anticancer effect by preventing and stopping the growth of cancerous cells in in-vitro studies of animal induced cancers.^{[xv], [xvi]}

Cardiovascular Disease Risk

In a meta-analysis of 14 studies, high dietary lycopene was significantly associated with low risk for cardiovascular disease, stroke and coronary heart disease.^[xvii] Similarly, in an overview of 23,935 patients, mortality from coronary heart disease and cerebrovascular disease was significantly lower for those who had high tomato and lycopene intake, illustrating their cardioprotective abilities.^[xviii]

A systematic review and meta-analysis of 21 studies showed that increasing the intake of tomatoes and lycopene products has positive effects on blood lipids, blood pressure and endothelial function, which make them valuable nutritional strategies to fight cardiovascular diseases.^[1]

In a human study of 142 patients with cardiovascular disease, lycopene supplementation (7 mg per day) for four weeks increased serum lycopene levels more than four times, significantly improved tissue oxygenation and blood flow and reduced inflammatory oxidative damage markers threefold and oxidized lipid levels fivefold.^[xix] Tomato juice (338 mg per day) treatment for 20 days also reduced inflammation (an underlying risk factor for cardiovascular disease and diabetes) in a controlled trial of 106 overweight and obese females.^[xx]

Guava consumption was shown to have significant effects on heart health risk in 120 patients with high blood pressure Specifically, the study found a 9.9% net decrease in total cholesterol, 7.7% decrease in triglycerides and blood pressure lowered (systolic by 9 points and diastolic by 8 points) with an 8% net increase in high-density lipoprotein cholesterol after 12 weeks of guava fruit treatment.^[xxi]

Bone Health

In another study, 370 men and 576 women (70 to 80 years of age) from the Framingham Osteoporosis Study completed a food frequency questionnaire in 1988 to 1989 and were followed  for 17 years for bone fractures.

Results showed that subjects with higher lycopene intake had significantly lower risk of hip and nonvertebral fractures.^[xxii] Tomato and tomato products, as rich sources of lycopene, have been shown to decrease bone loss, which significantly lowers risk for fractures in vivo and in vitro studies of postmenopausal women.^[xxiii]

In vitro and clinical studies of osteoblast cells found the intake of a lycopene-rich tomato sauce (5 mg and 10 mg) in 39 postmenopausal women resulted in no significant bone density loss with the treatment and better bone turnover results compared to those in the non-tomato sauce control group, showing that tomato sauce can be used to lower risk of bone loss and to prevent osteoporosis.^[xxiv]

Top 12 Lycopene Food Sources

So which fruits and veggies are reliable lycopene sources? Boost your lycopene levels by increasing your consumption of the top foods found in Table 1.^[xxv] Although there is no daily minimum requirement for lycopene, sources suggest consuming from 8 mg to 21 mg per day for optimal health.^[xxvi]

Table 1. Top Fruits and Vegetables Highest in Lycopene (By Milligrams Per Cup)

Sensitivities to Nightshade Vegetables

Some people may experience chronic pain and inflammation from a sensitivity to foods called “nightshade” vegetables. That is because they can contain glycoalkaloids such as solanine in potato and eggplant,^[xxix] tomatine in tomato and capsaicin in garden peppers as well as wheat lectin or chitin-binding lectins found in tomatoes^[xxx] and red pepper.

Reactions should be monitored for their effect on the digestive system and arthritic symptoms, and triggering foods should be avoided completely if the sensitivity continues or slowly brought back into the diet one by one if tolerated.^[xxxi] Pesticide-treated and genetically modified (GMO) foods are the most problematic and buying non-GMO and organic nightshade vegetables is essential.

Lycopene gives fruits and vegetables, like tomatoes, guavas, watermelon and red bell peppers, their reddish hues and packs a punch for its neuroprotective, anticancer, bone protective and heart healthy properties. To read more about the impact of guavas and tomatoes on your health, see GreenMedInfo.com's research database on lycopene.